Gold nanorods: Synthesis, characterization and applications (original) (raw)
Shape separation of gold nanorods using centrifugation
Proceedings of The National Academy of Sciences, 2009
We demonstrate the use of centrifugation for efficient separation of colloidal gold nanorods from a mixture of nanorods and nanospheres. We elucidate the hydrodynamic behavior of nanoparticles of various shapes and illustrate that the shape-dependent drag causes particles to have shape-dependent sedimentation behavior. During centrifugation, nanoparticles undergo Brownian motion under an external field and move with different sedimentation velocities dictated by their Svedberg coefficients. This effects a separation of particles of different shape and size. Our theoretical analysis and experiments demonstrate the viability of using centrifugation to shape-separate a mixture of colloidal particles.
Gold Bulletin, 2010
The intense plasmon absorption bands of gold nanorods (GNRs) with peak extinction coefficients up to 6.4×109 M−1 cm−1 as well as their expected high stability make GNRs promising candidates for the colouration of bulk materials. The comparison of the integrated absorption in the visible region of GNRs with those of commercial organic pigments shows that the colouring strength of GNRs is 4 to 8 times higher. In order to improve their stability, GNRs were encapsulated in a silica shell of around 15 nm thickness using an optimized Stöber method. The silica surface was modified with octadecylsilane to enable their dispersion in non-polar media. Different plastics were successfully coloured with a tiny quantity of bare and functionalised GNRs@SiO2. These rods were homogeneously dispersed using extrusion. The shape of the rods was effectively stabilised by the silica shell at high temperature during the extrusion process. Surprisingly, a slight modification of the rods colour was observed due to a decrease of the refractive index in the mesoporous silica shell. However, this effect is greatly limited after the functionalisation.
2009
Gold nanorods have interesting optical properties due to surface plasmon resonance effects. A variety of biomedical applications of these particles have been envisaged and feasibilities demonstrated in imaging, sensing and therapy based on the interactions of light with these particles. In order to correctly interpret experimental data, and tailor the nanorods and their environments for optimal use in these applications, simulations of the optical properties of the particles under various conditions are essential. Of the various numerical methods available, the Discrete Dipole Approximation (DDA) approach implemented in the publicly available DDSCAT code, is a powerful method that has proved popular for studying gold nanorods. However, there is as yet no universal agreement on the choice of the number of dipoles for the discretization, on the shape used to represent the nanorods and on the dielectric function of gold required for the simulations. We systematically study the influence of these parameters on simulated results. We find large variations in the position of plasmon resonance peaks, their amplitudes and shapes of the spectra depending on the choice of the parameters. We discuss these in the light of experimental optical extinction spectra of gold nanorods synthesized in our laboratory. While making some recommendations to improve accuracy of the simulation results, we show that much care should be taken and prudence applied before DDA results be used to interpret experimental data and to help characterize nanoparticles synthesized.
International Journal of Biomedical Imaging, 2007
We have synthesized and characterized gold nanoparticles (spheres and rods) with optical extinction bands within the "optical imaging window." The intense plasmon resonant driven absorption and scattering peaks of these nanoparticles make them suitable as contrast agents for optical imaging techniques. Further, we have conjugated these gold nanoparticles to a mouse monoclonal antibody specific to HER2 overexpressing SKBR3 breast carcinoma cells. The bioconjugation protocol uses noncovalent modes of binding based on a combination of electrostatic and hydrophobic interactions of the antibody and the gold surface. We discuss various aspects of the synthesis and bioconjugation protocols and the characterization results of the functionalized nanoparticles. Some proposed applications of these potential molecular probes in the field of biomedical imaging are also discussed.
Synthesis and optical properties of colloidal gold nanoparticles
Journal of Physics: Conference Series, 2009
Copper oxide nanoparticles of sizes ranging from 1 to 25 nm were synthesized using a colloid microwave-thermal method, where the average size of CuO nanoparticles can be tailored by controlled microwave treatment time. The particle size was found to significantly decrease as the microwave processing time increases and can be controlled to have narrow size distributions. Both scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to characterize the sizes of the prepared nanoparticles. The UV-visible absorption spectra of the nanoparticles are blue-shifted with the size reduction, and this is attributed to quantum-confinement (QC) effect. Furthermore, the photoluminescence spectra showed UV and visible emissions, and were red shifted with increasing particles size and excitation wavelength. While the former observation confirms the QC effect and corroborates the results of UV-visible absorption spectra, the latter one is attributed to selective near band-edge excitonic transitions associated with defect states.
Continuous flow synthesis of nanoparticles using ceramic microfluidic devices
Nanotechnology, 2010
A microfluidic system based on the low-temperature co-fired ceramics technology (LTCC) is proposed to reproducibly carry out a simple one-phase synthesis and functionalization of monodispersed gold nanoparticles. It takes advantage of the LTCC technology, offering a fast prototyping without the need to use sophisticated facilities, reducing significantly the cost and production time of microfluidic systems. Some other interesting advantages of the ceramic materials compared to glass, silicon or polymers are their versatility and chemical resistivity. The technology enables the construction of multilayered systems, which can integrate other mechanical, electronic and fluidic components in a single substrate. This approach allows rapid, easy, low cost and automated synthesis of the gold colloidal, thus it becomes a useful approach in the progression from laboratory scale to pilot-line scale processes, which is currently demanded.
Nanoribbon Plasmonic Gratings and their Anomalous Interaction with Electromagnetic Waves
Advanced Materials, 2012
One of the most promising, inexpensive methods for nanostructure fabrication is the nanosphere lithography (NSL). [ 1 -6 ] The simple concept of this technique is to self-assemble a layer (usually a monolayer) of polystyrene spheres (PS) on a fl at substrate. The layer of PS is subsequently used as a shadow mask for evaporation of thin fi lms, e.g., metallic thin fi lms. In the simplest version, NSL employs the self-assembly of a densely packed hexagonal lattice of PS and perpendicular substrate evaporation, which leads after PS removal to a honeycomb array of nano-quasi-triangles. More complicated patterns and nanoparticle shapes can be obtained if the evaporation angle is statically or dynamically modifi ed. Here, we demonstrate fabrication of nanoribbon gratings by employing NSL with a very shallow static evaporation. The PS diameter is reduced by ionic etching after the assembly and controls the grating geometry. We use this shallow angle NSL (SANSL) technique to make Au and Fe nanoribbon gratings deposited on transparent substrates.
Photothermal Properties of Gold Nanoparticles
Zeitschrift für Physikalische Chemie, 2007
This paper describes our recent time-resolved spectroscopy studies of the properties of gold particles at high laser excitation levels. In these experiments, an intense pump laser pulse rapidly heats the particle, creating very high lattice temperatures -up to the melting point of bulk gold. These high temperatures can have dramatic effects on the particle and the surroundings. The lattice temperature created is determined by observing the coherently excited the vibrational modes of the particles. The periods of these modes depend on temperature, thus, they act as an internal thermometer. We have used these experiments to provide values for the threshold temperatures for explosive boiling of the solvent surrounding the particles, and laser induced structural transformations in non-spherical particles. The results of these experiments are relevant to the use of metal nanoparticles in photothermal therapy, where laser induced heating is used to selectively kill cells.
Nanotechnology, 2008
Polymer nanocomposites containing noble metal nanoparticles are promising materials for plasmonic applications. In this paper, we report on a high-resolution negative-tone nanocomposite resist based on poly(vinyl alcohol) where silver nanoparticles and nanopatterns are simultaneously generated by electron-beam lithography. Our results indicate nanostructures with a relatively high concentration of nanoparticles and, consequently, an electromagnetic coupling among the nanoparticles. Therefore, the patternable nanocomposite described in this work may be a suitable material for future plasmonic circuitry.
Photodetection with Active Optical Antennas
Science, 2011
Nanoantennas are key optical components for light harvesting; photodiodes convert light into a current of electrons for photodetection. We show that these two distinct, independent functions can be combined into the same structure. Photons coupled into a metallic nanoantenna excite resonant plasmons, which decay into energetic, "hot" electrons injected over a potential barrier at the nanoantenna-semiconductor interface, resulting in a photocurrent. This dual-function structure is a highly compact, wavelength-resonant, and polarization-specific light detector, with a spectral response extending to energies well below the semiconductor band edge.
Building plasmonic nanostructures with DNA
Nature Nanotechnology, 2011
Plasmons are electron excitations that occur in metals and semiconductors in response to visible electromagnetic waves, resulting in the collective oscillation of conduction band electrons -a phenomenon known as plasmon resonance. Unlike a bulk metal or an extended metal surface where plasmons are free to propagate, a metal nanoparticle imposes a boundary condition that confines plasmons to a finite volume. Consequently, nanoparticles in close proximity exhibit strong near-field coupling and field enhancement effects that have profound implications in subwavelength optics applications. This serves as the foundation for the nascent field of nanoparticle plasmonics, which seeks to precisely manipulate lightmatter interactions on the nanoscale while circumventing the diffraction limit. In this section, we explore the fundamental theories describing the plasmon resonances of individual nanoparticles and systems containing numerous nanoparticles.
Intense Optical Activity from Three-Dimensional Chiral Ordering of Plasmonic Nanoantennas
Angewandte Chemie International Edition, 2011
Noble-metal nanoparticles with localized surface-plasmon resonances (LSPR) have been recently used to prepare new materials with improved optical circular dichroism. This interest stems from a wide range of applications in biology and physics, including the structural determination of proteins and DNA and the pursuit of negative refraction. Surfaceplasmon-mediated circular dichroism (SP-CD) in solution has been explored to date using small spherical metal particles, invariably resulting in moderate signals over a narrow spectral range. In contrast, we present herein a novel class of metamaterial consisting of gold nanorods (NRs) organized in three-dimensional (3D) chiral structures and yielding a record circular dichroism anisotropy factor for metal nanoparticles (> 0.02) across visible and near-infrared (Vis-NIR) wavelengths (600-900 nm). The fabrication process can be easily upscaled, as it involves the self-assembly of gold nanorods on a fiber backbone with chiral morphology. Our measurements are fully supported by theoretical modeling based on coupled dipoles, unraveling the key role of gold nanorods in the chiroptical response.
Dichroic Optical Properties of Uniaxially Oriented Gold Nanorods in Polymer Films
2014
Applications based on the optical excitation of the longitudinal surface plasmon resonance (LSPR) of gold nanorods (AuNRs) work at highest efficiency if all component AuNRs can be maximally excited, simultaneously. This can be achieved in aligned AuNR structures, such as those embedded in uniaxially stretched polymer films. Since too high heating temperatures during film stretching cause reshaping and alteration of optical properties of the rods, a maximum allowable heating temperature is determined. The alignment of the rods is quantified by an orientational order parameter of 0.92 based on a statistically significant sample, of assumed tdistributed means and obtained by scanning electron microscopy (SEM). We show that a stretched AuNRs-PVA composite film has optical properties that approach the dichroic properties of an idealized ensemble of fully aligned, identical and non-interacting AuNRs embedded in a PVA film. The idealized system is provided by FDTD simulations of a single AuNR, which we carried out using the size-and shape-adapted dielectric function of gold and the software RSOFT.
Deterministic assembly of linear gold nanorod chains as a platform for nanoscale applications
Nanoscale, 2013
We demonstrate a method to assemble gold nanorods highly deterministically into a chain formation by means of directed capillary assembly. This way we achieved straight chains consisting of end-to-end aligned gold nanorods assembled in one specific direction with well-controlled gaps of $6 nm between the individual constituents. We determined the conditions for optimum quality and yield of nanorod chain assembly by investigating the influence of template dimensions and assembly temperature. In addition, we transferred the gold nanorod chains from the assembly template onto a Si/SiO 2 target substrate, thus establishing a platform for a variety of nanoscale electronic and optical applications ranging from molecular electronics to optical and plasmonic devices. As a first example, electrical measurements are performed on contacted gold nanorod chains before and after their immersion in a solution of thiol end-capped oligophenylenevinylene molecules showing an increase in the conductance by three orders of magnitude, indicating molecular-mediated transport.
Molecular precursor-mediated tuning of gold mesostructures: Synthesis and SERRS studies
Journal of Crystal Growth, 2010
This article describes the high yield synthesis of a range of anisotropic gold mesostructures such as flowers, cubes, plates, and quasispherical mesostructures using a seed-mediated approach. These structures were formed from precursor seed nanoparticles of gold stabilized by the template, 1,2phenylenediamine (1,2-PDA). We demonstrated that control of the morphologies from mesoflowers to quasispherical structures is possible with the molecular precursors used in the synthesis of seeds. It was found that concentration of the template, 1,2-PDA added during seed preparation played an important role in the conversion of mesoflowers to quasispherical and cube-like structures. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-vis spectroscopy and energy dispersive analysis of X-rays (EDAX) were used for the determination of physical and chemical composition of the nano/mesostructures formed. The seed nanoparticles responsible for the formation of these various anisotropic structures were further characterized and analyzed using laser desorption ionization mass spectrometry (LDI MS) and TEM. We demonstrated high surface-enhanced resonance Raman scattering (SERRS) activity of the mesoflowers using crystal violet (CV) as the analyte molecule. The shapedependent SERRS activity of various meso/nanostructures was also studied. A $ 0.8 Â 10 2 decrease in the SERRS intensity was observed in quasispherical structures compared to mesoflowers. The increased SERRS activity is attributed to the unique shape and nanofeatures present on the mesoflowers, which were absent in the quasispherical mesostructures. We believe that the high SERRS activity exhibited by the mesoflowers may be utilized for developing novel sensors.
RSC Adv., 2014
By monitoring the synthesis of the Turkevich gold nanoparticles, under appropriate conditions, it was possible to probe the formation of the dicarboxyketone intermediate species, revealing their unexpected strong interaction with the gold nanoparticles. The dicarboxyketone species exhibited a contrasting spectral and kinetics behaviour in relation to citrate stabilized products, explaining several existing controversial points, such as the lack of reproducibility and variable SERS response. In these species, because of the covalent interaction, the chemical mechanisms involved in SERS predominate over the electromagnetic contribution observed for the citrate stabilized gold nanoparticles. New interesting aspects were found, such as a greater stabilization and strong SERS response observed even for the non-aggregated nanoparticles.
Prospects for Gold Nanorod Particles in Diagnostic and Therapeutic Applications
Biotechnology and Genetic Engineering Reviews, 2008
Rod-shaped gold nanoparticles ('nanorods') have recently attracted widespread attention due to their unique optical properties and facile synthesis. In particular, they can support a longitudinal surface plasmon, which results in suspensions of them having a strong extinction peak in the upper visible or near-infrared parts of the spectrum. The position of this peak can be readily tuned by controlling the shape of the rods. In addition, the surface of the nanorods can be functionalized by a very wide variety of molecules. This has led to interest in their use as selective biomarkers in biodiagnostics or for selective targeting in photothermal thearapeutics. Here, we review the recent advances in the use of gold nanorods in these applications. Additionally, the information available regarding their biocompatibility is discussed.
Tunable infrared absorption by metal nanoparticles: The case for gold rods and shells
Gold Bulletin, 2008
Nanoparticles of elements such as Au, Al or Ag have optical extinction cross-sections that considerably surpass their geometric cross-sections at certain wavelengths of light. While the absorption and scattering maxima for nanospheres of these elements are relatively insensitive to particle diameter, the surface plasmon resonance of Au nanoshells and nanorods can be readily tuned from the visible into the infrared by changing the shape of the particle. Here we compare nanoshells and nanorods in terms of their ease of synthesis, their optical properties, and their longer term technological prospects as tunable "plasmonic absorbers". While both particle types are now routinely prepared by wet chemistry, we submit that it is more convenient to prepare rods. Furthermore, the plasmon resonance and peak absorption efficiency in nanorods may be readily tuned into the infrared by an increase of their aspect ratio, whereas in nanoshells such tuning may require a decrease in shell thickness to problematic dimensions.
Spectrally selective coatings of gold nanorods on architectural glass
Journal of Nanoparticle Research, 2010
Infrared-blocking coatings on window glass can be produced by dispersing gold nanorods into a polymer coating. The spectral selectivity of the coating is controlled by the shape and aspect ratio of the nanoparticles, which are in turn determined by the conditions applied during their synthesis. Coatings of nanorods in polyvinyl alcohol were deposited onto glass and characterized in both laboratory and sun-lit conditions. Selective attenuation of the near-infrared was demonstrated with the test panels transmitting approximately one-third of the incident solar radiation and absorbing nearly two-thirds. The high absorptive cross sections of the gold nanorods suggest that they can be applied in efficacious coatings at relatively low volume fractions.
POLYMER-MODIFIED GADOLINIUM NANOPARTICLES FOR TARGETED MAGNETIC RESONANCE IMAGING AND THERAPY
Nano LIFE, 2010
Functional imaging is a novel area in radiological sciences and allows for the non-invasive assessment and visualization of speci¯c targets such as gene and protein expression, metabolic rates, and drug delivery in intact living subjects. As such, the¯eld of molecular imaging has been de¯ned as the non-invasive, quantitative, and repetitive imaging of biomolecules and biological processes in living organisms. For example, cancer cells may be genetically altered to attract molecules that alter the magnetic susceptibility, thereby permitting their identi¯cation by 263 magnetic resonance imaging. These contrast agents and/or molecular reporters are seen as essential to the task of molecular medicine to increase both sensitivity and speci¯city of imaging. Therefore, there are¯ve general principles which need to be ful¯lled in order to conduct a successful in vivo molecular imaging study: (1) selection of appropriate cellular and subcellular targets; (2) development of suitable in vivo a±nity ligands (molecular probes); (3) delivery of these probes to the target organ; (4) ampli¯cation strategies able to detect minimal target concentrations; and (5) development of imaging systems with high resolution. Although there has been a wide range of routes taken to incorporate both imaging agents and a disease-targeting moiety into diagnostic devices, arguably the most interesting of these routes employs the use of nanoparticles. Nanoscale diagnostic systems that incorporate molecular targeting agents and diagnostic imaging capabilities are emerging as the next-generation imaging agents and have the potential to dramatically improve the outcome of the imaging, diagnosis, and treatment of a wide range of diseases. The present review addresses chemical aspects in development of molecular probes based upon gadolinium nanoparticles and their potential role in translational clinical imaging and therapy.
Sensitivity-enhancement methods for surface plasmon sensors
Laser & Photonics Reviews, 2011
Surface plasmon resonance (SPR) sensors have been a mature technology for more than two decades now, however, recent investigations show continuous enhancement of their sensitivity and their lower detection limit. Together with the recent investigations in localized SPR phenomena, extraordinary optical transmission through nanoapertures in metals, and surface-enhanced spectroscopies, drastic developments are expected to revolutionize the field of optical biosensing. Sensitivity-enhancement (SE) techniques are reviewed focusing both on the physical transduction mechanisms and the system performance. In the majority of cases the SE is associated with the enhancement of the electromagnetic field overlap integral describing the interaction energy within the analyte. Other important mechanisms are the interaction between plasmons and excitons and between the analyte molecules and the metal surface. The lower detection limit can be reduced significantly if systems with high signal-to-noise ratio are used such as common-path interferometry, ellipsometry or polarimetry systems.
Identification of intracellular gold nanoparticles using surface-enhanced Raman scattering
Nanoscale, 2014
The identification of intracellular distributions of noble metal nanoparticles is of great utility for many biomedical applications. We present an effective method to distinguish intracellular from extracellular nanoparticles by selectively quenching the SERS signals from dye molecules adsorbed onto star-shaped gold nanoparticles that have not been internalized by cells.
Journal of Nanoparticle Research, 2011
We investigate the photothermal conversion and transformation of gold nanoparticles with an initial dogbone shape after dispersion in hydrated chitosan films, which is a representative model of biological tissue, and excitation by a CW diode laser for 1 min. Gold nanodogbones are observed to undergo a distinct modification above a sharp threshold of *11 W cm -2 and 110°C. Surprisingly, the very same modification is achieved up to at least 36 W cm -2 and 250°C. We use an analytical model derived from Gans theory to associate the change in color of the films with the change in shape statistics of these gold nanoparticles. This model proves both convenient and dependable. We interpret the photothermal transformation as a rearrangement of particles with a dogbone shape and an aspect ratio of 4.1 into rods with an aspect ratio of 2.5, where material from the end lobes of the dogbones may relocate to the waists of the rods. In turn, additional transitions to stable gold nanospheres may exhibit fairly slower kinetics.
A review on materials for light scattering in dye-sensitized solar cells
RSC Advances, 2014
Dye-sensitized solar cells (DSCs) offer interesting possibilities in photovoltaics which is the technology of harvesting solar photons to generate electricity. Improving the charge transport through the metal oxide film, finding dyes with better absorption both in the visible and near IR regions of the solar spectrum and fabricating innovative materials for the scattering layer are the proposed way forward for improving the efficiency of DSCs. Light scattering is employed in dye-sensitized solar cells to improve the optical absorption of the incident light. The conventional method of light scattering in DSCs is by using a separate scattering layer consisting of large particles with diameters comparable to the wavelength of the incident light. An additional over-layer on the nanocrystalline TiO 2 photoanode will encourage light scattering in DSCs especially in the red part of the solar spectrum. Different nanostructures with good dye adsorption and light scattering properties were tried as light scattering layers in DSCs. Of late, scientists have attempted to use functional materials having enhanced light scattering properties and high internal surface area as dual function materials (that is a single layer of material capable of both light absorption and scattering). This review explores theoretical aspects and materials innovation for light scattering and their application in DSCs.
Specific Near-IR Absorption Imaging of Glioblastomas Using Integrin-Targeting Gold Nanorods
Advanced Functional Materials, 2011
Molecular imaging using nanoprobes with high resolution and low toxicity is essential in early cancer detection. Here we introduce a new class of smart imaging probes employing PEGylated gold nanorods (GNRs) conjugated to cRGD for specifi c optical imaging of α v β 3 integrins from glioblastoma. GNRs exhibiting an optical resonance peak in the near-infrared (NIR) region were synthesized using the seed-mediated growth method. CTAB (cetyl trimethylammonium bromide) bilayer on the GNRs was replaced with a biocompatible stabilizer, heterobifunctional polyethyleneglycol (COOH-PEG-SH). Further, the carboxylated GNRs (PGNRs; PEG-coated GNRs) were functionalized with cRGD using EDC-NHS chemistry to formulate cRGD-conjugated GNRs (cRGD-PGNRs) for α v β 3 integrins. In order to assess the potential of the cRGD-PGNRs as a targeted imaging probe, we investigated their optical properties, biocompatibility, colloidal stability and in vitro/in vivo binding affi nities for cancer cells. Consequently, cRGD-PGNRs demonstrated excellent tumor targeting ability with no cytotoxicity, as well as suffi cient cellular uptake due to stable and prolonged blood circulation of cRGD-PGNRs.
Growth and properties of coherent twinning superlattice nanowires
Nanoscale, 2012
Although coherent twin boundaries require little energy to form in nanoscale single crystals, their influence on properties can be dramatic. In recent years, some important steps forward have been made in understanding and controlling twinning processes at the nanoscale, making possible the fabrication of nanoengineered twinning superlattices in crystalline nanowires. These advances have opened new possibilities for properties and functionalities at the atomic and quantum scales by modulating twin densities. This article presents a brief overview of recent theoretical and experimental progress in growth mechanisms and promising properties of coherent twinning superlattice nanowires with special emphasis toward cubic systems in semiconductor and metallic materials. In particular, we show how nanoscale growth twins can considerably enhance bandgap engineering and mechanical behaviour in quasi-one-dimensional materials. Opportunities for future research in this emerging area are also discussed.
Creation and luminescence of size-selected gold nanorods
Nanoscale, 2012
Fluorescent metal nanoparticles have attracted great interest in recent years for their unique properties and potential applications. Their optical behaviour depends not only on size but also on shape, and will only be useful if the morphology is stable. In this work, we produce stable size-selected gold nanorods (aspect ratio 1-2) using a size-selected cluster source and correlate their luminescence behaviour with the particle shape. Thermodynamic modelling is used to predict the preferred aspect ratio of 1.5, in agreement with the observations, and confirms that the double-icosahedron observed in experiments is significantly lower in energy than the alternatives. Using these samples a fluorescence lifetime imaging microscopy study observed two photon luminescence from nanoparticle arrays and a fast decay process (<100 ps luminescence lifetime), which are similar to those found from ligand stabilized gold nanorods under the same measurement conditions, indicating that a surface plasmon enhanced two-photon excitation process is still active at these small sizes. By further reducing the nanoparticle size, this approach has the potential to investigate size-dependent luminescence behaviour at smaller sizes than has been possible before. 9962-7356 † Electronic supplementary information (ESI) available: Electron micrographs of gold nanorods on an amorphous carbon TEM support, using scanning transmission electron microscopy with a high angle annular dark field detector, and representative intensity 3D plots. See
Mapping the structural and optical properties of anisotropic gold nanoparticles
Journal of Materials Chemistry C, 2013
The morphology and optical properties of gold nanorods are obtained using a strategic combination of theoretical and numerical techniques. Shape-dependent phase diagrams are developed, and the structural and color properties of anisotropic gold nanoparticles are predicted for two different sizes and colloidal concentrations. Calculated maps reveal an intimate relationship between size, morphology, temperature, environment, and optical properties, and confirm that the aspect ratio of the nanorod is an important factor influencing the color of the colloidal samples. When the aspect ratio value is between 1 and 5, the color of the sample changes from pink to blue and green, but if the aspect ratio is larger than 5 the colloid shows slight color variations in green-yellow hues. It is also found that although the solution is heated, at temperatures below melting point, there can be a transition in morphology but the color remains the same for a given aspect ratio, so morphological variations are unlikely to degrade the optical performance, provided the aspect ratio is preserved. We also conclude that the nanorod size plays a secondary role, in contrast to common assumption, since the color palette is quite independent of size. Color variations of samples with different refraction indices and the effect of different 'end truncations' for square nanorods are also examined in detail, both of which can modify the relationship between aspect ratio and color transition, although the overall color palette remains the same. As we will show, the theoretical results discussed here are in excellent agreement with experimental observations.
Shape-controlled Synthesis of Silver and Palladium Nanocrystals using β-Cyclodextrin
MRS Proceedings, 2012
Shape-controlled silver and palladium nanoparticles were for the first time synthesized by seed-mediated techniques in the presence of β-cyclodextrin (β-CD). Palladium and silver seeds were prepared by reduction of palladium or silver ions with sodium borohydride in the presence of sodium citrate dihydrate as a stabilizer. Seeds were then injected into a "growth" solution containing the same Pd (or Ag) precursor, ascorbic acid (as a weak reducing agent), and β-CD. Using β-cyclodextrin impacts the final morphology of silver nanoparticles through a strong capping effect slowing down the growth regime and shifting it to thermodynamiccontrolled conditions. Adjusting the β-CD/Ag molar ratio can lead to the selective formation of multiply twinned icosahedral particles presenting mainly {111} facets. On palladium, β-cyclodextrin selectively led to the controlled aggregation of primary nanoparticles into nanodendrites or multipods. After deposition on TiO 2 , these nanostructured Pd catalysts show excellent activity for the hydrogenation of cinnamaldehyde.
Monomer adsorption of indocyanine green to gold nanoparticles
Nanoscale, 2011
NIR-dye encoded gold nanoparticles (GNP) are rapidly emerging as contrast agents in many bio-imaging/sensing applications. The coding process is usually carried out without control or a clear understanding of the metal-liquid interface properties which, on the contrary, are critical in determining the type and extension of dye-metal interaction. In this paper, we investigated the effect of gold surface composition on the adsorption of Indocyanine Green (ICG) on GNP, simulating the surface conditions of gold nanorods on citrate-capped gold nanospheres. These substrates allowed a careful control of the metalliquid interface composition and, thus, detailed absorption -and fluorescence concentration studies of the effects of each individual chemical in the colloidal solution (i.e. bromide anions, Cetyl trimethylammonium ions and Ag + -ions) on the ICG-gold interaction. This study reveals the drastic effect that these experimental parameters can have on the ICG adsorption on GNP.
Gold nanorods as molecular contrast agents in photoacoustic imaging: the promises and the caveats
Contrast Media & Molecular Imaging, 2011
Rod-shaped gold nanoparticles exhibit intense and narrow absorption peaks for light in the farred and near-infrared wavelength regions, due to the excitation of longitudinal plasmons. Light absorption is followed predominantly by non-radiative de-excitation, and the released heat and subsequent temperature rise cause strong photoacoustic (optoacoustic) signals to be produced. This feature combined with the relative inertness of gold, and its favorable surface chemistry which permits affinity biomolecule coupling, has seen gold nanorods (AuNR) attracting much attention as contrast agents and molecular probes for photoacoustic imaging. In this article we provide an short overview of the current status of the use of AuNR in molecular imaging using photoacoustics.
Standing Arrays of Gold Nanorods End-Tethered with Polymer Ligands
Small, 2012
Nanomaterials with vectoral electromagnetic properties have potential applications in solar cells, plasmonic cavity resonators, light polarizers, and biosensing. Here a new, simple, solution-based method for producing nanomaterials comprising vertically aligned standing arrays of gold nanorods (NRs) end-functionalized with polymer ligands is reported. The method utilizes the side-by-side assembly of the NRs into large 2D superlattices, followed by the precipitation of the lattices on a solid substrate. The critical design rules for the self-assembly of superlattices are demonstrated, and they show the generality of the method by forming standing arrays from the NRs end-tethered with poly(N-vinylcarbazole) or with polystyrene molecules. Nanorod Arrays A. Petukhova et al. 732 www.small-
BioMed research international, 2014
Gold nanorods (GNRs) are considered one of the most promising forms of nanoparticles for nanobiotechnology; however, the problem of their toxicity is currently not resolved. We synthesised GNRs, modified with linear polyethyleneimine (PEI-GNRs), and examined their physicochemical and some biological properties in comparison with GNRs modified with BSA and spherical gold nanoparticles (sGNPs) modified with the same agents. The influence of the buffer, cell culture media, and serum on hydrodynamic diameter and zeta potential of all GNPs was studied. Simultaneously, the size, shape, and formation of a corona were examined by transmission electron microscopy (TEM). PEI-GNRs and GNPs were nontoxic for BHK-21 and HeLa cells (MTT test). Penetration of all GNPs into BHK-21, melanoma B16, and HeLa cells was examined after 30 min, 3 h, and 24 h of incubation using TEM ultrathin sections. PEI-GNRs and PEI-sGNPs demonstrated fast and active penetration into cells by caveolin-dependent and lipid...
Journal of Nanoparticle Research, 2011
Hexagonal mesostructured films containing silver ions were obtained by sol-gel method. Brij 58 was used to produce channels into the film, which house these ions. The films were exposure to UV radiation to produced silver metallic nanoparticles. The presence of the metallic nanoparticles was determined by infrared spectroscopy and optical absorption. Besides, these nanoparticles and coreshell structures of silver-silver oxide nanoparticles were identified by high-resolution transmission electronic microscopy. From these measurements, the obtained size range for silver nanoparticles was 6.1 nm. The absorption spectrum located at 440 nm was modelled and well fitted with the Gans theory considering refractive index higher than the one coming from host matrix. This index is explained because the silver oxide shell modifies the local surrounding medium of the metallic nanoparticles.
Complex Oxide-Noble Metal Conjugated Nanoparticles
Advanced Materials, 2013
The past decade has witnessed tremendous progress in the synthesis of nanoparticles (NPs) with controllable size, shape, and composition. [ 1 , 2 ] However, these NPs would unlikely meet the rising demand for the advanced breeds of building blocks for functional materials and devices. Hybrid NPs composed of multiple components usually exhibit multiple functionalities. These NPs attract tremendous research interest because of their unique properties and applications that, however, are diffi cult (or even impossible) to be achieved by single-component NPs. To date, signifi cant progress has been achieved in the synthesis of noble metal NPs with epitaxial unitary, binary domain hybrid NPs (eg., Au@Ni, Au-Fe 3 O 4 , Au-TiO 2 , and Au-CdSe) by using various synthetic methods including surface selective modifi cation, template-assisted self-assembly, phase separation, and surface-controlled nucleation and growth. However, almost all of these methods involve the use of environmentally harmful chemicals (precursor, surfactant, and solvent) and complicated synthetic procedures, which inevitably hinders the applicability of these products. Complex oxides cover a broad spectrum of intriguing functionalities due to the interplay among the lattice, charge, orbit, and spin degrees of freedom. Heterostructures containing complex oxides provide a powerful route to manipulate these degrees of freedom and offer tremendous opportunities for next-generation electronic devices. However, using conventional methods to synthesize complex oxides with small size and high crystallinity is very diffi cult (due to the extremely strict requirements of well matching reaction rates of multiple precursors), and combining them with noble metals in hybrid NP structures even presents a greater challenge. Among various complex oxides, complex oxide NPs with a spinel structure (e.g., CoFe 2 O 4 , MnFe 2 O 4 , NiFe 2 O 4 ) show remarkable optical, electronic, mechanical, thermal, and magnetic properties. [ 13 , 14 ] These properties are exploited in technological applications like ferrofl uids, biomedicine, and recording media. On the other hand, as a large family of complex oxides, perovskites (e.g., SrTiO 3 , BiFeO 3 , LaMnO 3 ) also draw wide-spread attention due to their catalytic, ferroelectric, and ferromagnetic properties, as well as their application in superconductors, thermoelectrics, and fuel cells. Nanometer-scaled perovskites even exhibit distinct properties over bulk materials, such as quantum paraelectrics and photoluminescence. In this study, a simple yet versatile strategy to synthesize complex oxide-noble metal hybrid NPs is demonstrated. As model hybrid NPs, gold-spinel heterodimer (Au-CoFe 2 O 4 ) and goldpervoskite heterodimer (Au-SrTiO 3 ) NPs were fabricated. We examined these NPs structurally and chemically by a combination of X-ray diffraction, Raman spectroscopy, synchrotron radiation X-ray absorption, and X-ray photoelectron spectroscopy. The interplay between complex oxides and noble metals is explored based on the magnetic, plasmonic, and photocatalyic behaviors of these NPs. Our study paves the way to the intriguing functionalities of complex oxide conjugation.
Synthesis and modelling of the mechanical properties of Ag, Au and Cu nanowires
Science and Technology of Advanced Materials
The recent interest to nanotechnology aims not only at device miniaturisation, but also at understanding the effects of quantised structure in materials of reduced dimensions, which exhibit different properties from their bulk counterparts. In particular, quantised metal nanowires made of silver, gold or copper have attracted much attention owing to their unique intrinsic and extrinsic length-dependent mechanical properties. Here we review the current state of art and developments in these nanowires from synthesis to mechanical properties, which make them leading contenders for next-generation nanoelectromechanical systems. We also present theories of interatomic interaction in metallic nanowires, as well as challenges in their synthesis and simulation.
Scientific Reports
We report efficient detection of alpha radiation on highly textured and vertically aligned along (002) Gallium-doped Zinc Oxide (ZnO:Ga) nanorods on a glass substrate with an average diameter ~150 ± 10 nm. Photoluminescence measurement showed near band emission 393 nm, in agreement with the bandgap value ~3.22 eV, measured by UV-Vis spectroscopy. The developed ZnO:Ga nanorod scintillator is coupled with a commercially available photomultiplier tube and 1K Multichannel Analyser to fabricate an alpha radiation detector. The performance of the alpha radiation detector is evaluated using various activities alpha radiation sources. A large pulse height spectrum is recorded by the detector for different alpha sources against the background spectrum. The calculated detection efficiency and Minimum Detectable Activity (MDA) showed that the detector is highly sensitive to alpha radiation. The repeatability and reproducibility of the performance are studied by evaluating the response of a single scintillator for numerous exposures and by studying inter-batch response variations, respectively. The response is repeatable within ±1% whereas reproducibility varies from ±20% for extremely low activity alpha sources to ±5% for high activity alpha sources. The performance of ZnO:Ga nanorod scintillator grown on glass substrate demonstrates that it can be a promising material system for the detection of alpha radiation.
Journal of Materials Science & Technology, 2014
A SiO 2 eTiO 2 template with ordered tubular mesochannels has been prepared by the solegel method. Au nanorods are deposited in the tubular mesochannels of the SiO 2 eTiO 2 template, and the shape of Au is changed from nanorods to nanospheres by ultraviolet irradiation during thermal deposition. The photocatalytic activity of mesoporous SiO 2 eTiO 2 with/without Au nanorods/nanospheres is evaluated. Deposition of Au in the mesoporous SiO 2 eTiO 2 template enhances the photocatalysis of TiO 2 . Interestingly, the sample containing Au nanorods exhibits higher photocatalytic activity than that with Au nanospheres. Photocatalysis by exciting surface plasmon resonance is not detected in the composite samples regardless of the shape of the deposited Au nanoparticles.
Nanoscale Research Letters, 2012
Nanocrystallized SiO 2 -TiO 2 with tubular mesopores was prepared via the sol-gel technique. Gold was deposited in the tubular mesopores of the nanocrystallized SiO 2 -TiO 2 . The shape of the gold was varied from one-dimensional [1-D] to zero-dimensional [0-D] nanostructures by an increase in TiO 2 content and ultraviolet [UV] irradiation during gold deposition. 1-D gold nanostructures [GNSs] were mainly obtained in the mesopores when a small amount of TiO 2 -containing mesoporous SiO 2 -TiO 2 was used as a template, whereas the use of a template containing a large amount of TiO 2 led to the formation of shorter 1-D or 0-D GNSs. UV irradiation also resulted in the formation of 0-D GNSs.
Scientific reports, 2017
Catecholamine neurotransmitters, generally including dopamine (DA), epinephrine (EP) and norepinephrine (NE) are known as substantial indicators of various neurological diseases. Simultaneous detection of these compounds and their metabolites is highly recommended in early clinical diagnosis. To this aim, in the present contribution, a high performance colorimetric sensor array has been proposed for the detection and discrimination of catecholamines based on their reducing ability to deposit silver on the surface of gold nanorods (AuNRs). The amassed silver nanoshell led to a blue shift in the longitudinal localized surface plasmon resonance (LSPR) peak of AuNRs, creating a unique pattern for each of the neurotransmitters. Hierarchical cluster analysis (HCA) and linear discriminate analysis (LDA) pattern recognition techniques were employed to identify DA, EP and NE. The proposed colorimetric array is able to differentiate among individual neurotransmitters as well as their mixtures...
Gold coated iron phosphide core–shell structures
RSC Adv.
Core-shell particles Fe 2 P@Au have been prepared beginning with Fe 2 P nanorods, nanocrosses and nanobundles prepared from the solvothermal decomposition of H 2 Fe 3 (CO) 9 (m 3 -P t Bu). Iron phosphide structures can be produced from a single-source organometallic precursor with morphological control by varying the surfactant conditions to yield fiber bundles and dumbbell-shaped bundles ranging from nanometers to microns. Derivatization of the surfaces with g-aminobutyric acid was used to attach Au nanoparticle seeds to the surface of the Fe 2 P nanoparticles followed by completion of the Au shell by reduction with formaldehyde or aqueous HAuCl 4 /CO, with the latter giving somewhat better results.
Microbubble Resonators for All-Optical Photoacoustics of Flowing Contrast Agents
Sensors
In this paper, we implement a Whispering Gallery mode microbubble resonator (MBR) as an optical transducer to detect the photoacoustic (PA) signal generated by plasmonic nanoparticles. We simulate a flow cytometry experiment by letting the nanoparticles run through the MBR during measurements and we estimate PA intensity by a Fourier analysis of the read-out signal. This method exploits the peaks associated with the MBR mechanical eigenmodes, allowing the PA response of the nanoparticles to be decoupled from the noise associated with the particle flow whilst also increasing the signal-to-noise ratio. The photostability curve of a known contrast agent is correctly reconstructed, validating the proposed analysis and proving quantitative PA detection. The experiment was run to demonstrate the feasible implementation of the MBR system in a flow cytometry application (e.g., the detection of venous thrombi or circulating tumor cells), particularly regarding wearable appliances. Indeed, th...
Large-scale, low-cost synthesis of monodispersed gold nanorods using a gemini surfactant
Nanoscale, 2015
In this work, we demonstrate that monodispersed gold nanorods (AuNRs) can be obtained in a large-scale and cost-effective way. By using an industrial grade gemini surfactant (P16-8-16), the cost of the synthesis of high-quality AuNRs can be significantly reduced by 90%. The synthesis can be scaled up to over 4 L. The aspect ratio of AuNRs can be well tuned from ∼2.4 to ∼6.3, resulting in a wide tunability of the SPR properties. Systematic studies reveal that P16-8-16 could have a dual function: it can not only act as a capping ligand to stabilize AuNRs but also it can pre-reduce Au(3+) to Au(+) by the unsaturated C[double bond, length as m-dash]C bond. Furthermore, the shape of AuNRs can be tailored from straight nanorods to "dog-bones" by simply varying the concentration of the surfactant. A mechanistic study shows that the shape change can be attributed to the presence of excess bromide ions because of the complex effect between bromide ions and gold ions. This work will...
Synthesis and modelling of gold nanostars with tunable morphology and extinction spectrum
Journal of Materials Chemistry, 2011
We present a simple seed-less synthesis procedure to fabricate stable gold nanostars (AuNSs) with tunable extinction properties from the visible up to 1800 nm, depending on the average values of core size and branch length. The experimental results are compared with data from Finite Elements Method computations by using an approximated model of the fabricated branched systems. The theoretical computations highlight the existence of hot spots located on the tips of the nanostars even up to 1800 nm wavelength, which opens the way to the improvement of IR diagnostics or chemical sensing.
Nanomaterials and Nanotechnology
A simple technique of seed-mediated growth has been successfully performed to grow anisotropy gold nanoparticles on solid substrates. The growth of the gold nanoparticles has been carried out in the presence of a binary surfactant mixture of hexadecyltrimethylammonium bromide with two different molecular weights of a capping agent, namely polyvinylpyrrolidone: 40,000 and 55,000. In this study, the effect of process parameters, growth time and molecular weight of capping agent was investigated. The growth time shows a significant impact on the shape and size of nanoparticles. The shorter growth time produced small spherical to square-like shape particles, whereas bigger particles including nanorods, nanosquares and nanotriangles were formed with longer growth time. The shape controlling agent, polyvinylpyrrolidone, was used to synthesis gold nanoparticles. It was found that monodisperse gold nanoparticles with uniform shape and size are hardly obtained when polyvinylpyrrolidone 40,00...
Tissue perfusion modelling in optical coherence tomography
BioMedical Engineering OnLine
Background Optical coherence tomography (OCT) is a well established imaging technique used in different fields of clinical medicine, preclinical research or biology. The main capability of this technique is its ability to noninvasively create images of tissue on a micrometre
Materials, 2014
In the present work, the influence of a gold nanoparticle's shape was investigated on the commercially available Evonik Aeroxide P25. By the variation of specific synthesis parameters, three differently shaped Au nanoparticles were synthetized and deposited on the surface of the chosen commercial titania. The nanoparticles and their composites' morphological and structural details were evaluated, applying different techniques such as Diffuse Reflectance Spectroscopy (DRS), X-ray Diffraction (XRD), and Transmission Electron Microscopy (TEM). The influence of the Au nanoparticles' shape was discussed by evaluating their photocatalytic efficiency on phenol and oxalic acid degradation and by investigating the H2 production efficacy of the selected composites. Major differences in
Cancer and bacterial diseases have been the most incidental diseases to date. According to the World Health Report 2018, at least every family is affected by cancer around the world. In 2012, 14.1 million people were affected by cancer, and that figure is bound to increase to 21.6 million in 2030. Medicine therefore sorts out ways of treatment using conventional methods which have been proven to have many side effects. Researchers developed photothermal and photodynamic methods to treat both cancer and bacterial diseases. ese methods pose fewer effects on the biological systems but still no perfect method has been synthesized. e review serves to explore porphyrin and gold nanorods to be used in the treatment of cancer and bacterial diseases: porphyrins as photosensitizers and gold nanorods as delivery agents. In addition, the review delves into ways of incorporating photothermal and photodynamic therapy aimed at producing a less toxic, more efficacious, and specific compound for the treatment.
Seed-Mediated Growth of Gold Nanorods: Limits of Length to Diameter Ratio Control
Journal of Nanomaterials, 2014
The effects of the seed reaction conditions on the two-step seed-mediated growth of gold nanorods and the effect of gold and reducing agent content in the growth solution were evaluated. Results indicate that the reaction conditions used to produce the seeds have a significant impact on the aspect ratio of the gold nanorods produced. Increasing the concentration of gold or the reaction temperature in the seed production step results in lower length to diameter (aspect ratio) gold rods. In addition, the amount of prepared seed added to the growth solution impacts the rod aspect ratio, with increasing amounts of seed reducing the aspect ratio. The effects of reducing agent, ascorbic acid (AA), and gold content of the growth solution on the aspect ratio of the produced rods are strongly interrelated. There exists a minimum ascorbic acid to gold concentration below which rods will not form; however, increasing the ratio above this minimum results in shorter rods being formed. Characteri...
Journal of Nanoparticle Research, 2013
Seed-mediated growth methods involving reduction of tetrachloroaurate(III) with ascorbic acid are common for the synthesis of gold nanorods. This study shows, however, that simply by appropriate choice of the reducing agent a drastic influence on the aspect ratio can be attained. Weaker reducing agents, such as dihydroxybenzene isomers (hydroquinone, catechol or resorcinol) or glucose can increase the aspect ratio of the nanorods by an order of magnitude, up to values as high as 100 (nanowires). The increase in aspect ratio is mainly a consequence of an increase in length of the particles (up to 1-3 lm). This effect is probably associated with a decrease in the reduction rate of gold(III) species by dihydroxybenzenes or glucose compared to ascorbic acid. The reduction potential of the reducing agents strongly depends on the pH value, and related effects on the dimensions of the nanoparticles are also reflected in this study. The nanorods exhibited penta-twinned nature without noteworthy defects (e.g. stacking faults and dislocations).
Nanocomposites Polarizing by Absorption: Dichroism in the Near-Infrared Region (NIR)
Materials, 2014
We describe the preparation of nanocomposites which exhibit dichroism in the near infrared region (NIR). These materials consist of crosslinked poly(dimethylsiloxane) (PDMS) and gold nanoparticles, coated with 1-dodecanethiol or tert-tetradecanethiol. The alkanethiols improve dispersibility of the gold particles, and accordingly composites were manufactured by diffusion of the particles into swollen self-supporting PDMS elastomer films. After drying, the films were exposed to solvents for one minute, stretched in wet state, dried again and annealed. This procedure led to formation of oriented linear gold particle assemblies within stretched polymer. If the aspect ratio of the particle assemblies is high, the absorption of polarized light in the NIR region is expected to depend on the angle between the polarization plane and the orientation direction of the particle assemblies, and this was observed to be the case.
APL Photonics
The tremendous impact that cardiovascular diseases have in modern society is motivating the research of novel imaging techniques that would make possible early diagnosis and, therefore, efficient treatments. Cardiovascular optical coherence tomography (CV-OCT) emerged as a result of such a demand, and it has already been used at the clinical level. Full utilization of CV-OCT requires the development of novel contrast molecular agents characterized by a large scattering efficiency in the infrared (800-1400 nm). Gold nanoparticles (GNPs) seem to be the best candidates, but their scattering properties in the infrared are hardly known. In most of the cases, scattering properties are extracted from numerical simulations. This knowledge gap here is covered by providing an experimental evaluation of the infrared scattering properties of different GNPs (nanoshells, nanostars, and nanorods). These GNPs display remarkable extinction coefficients in the first and second biological windows, including the particular CV-OCT wavelength. We use a unique combination of techniques (thermal loading experiments, infrared optical coherence tomography, infrared dark field microscopy, and optoacoustic spectroscopy) to experimentally determine the scattering efficiency at three different near-infrared wavelengths (808 nm, 980 nm, and 1280 nm), lying in the first and second biological windows. Consequently, this work determines experimentally the influence of particle morphology on the infrared scattering efficiency of GNPs and evidences the existence of remarkable discrepancies between experimental data and numerical simulations.
Straightforward synthesis of gold nanoparticles by adding water to an engineered small dendrimer
Beilstein Journal of Nanotechnology
A small water-soluble phosphorus-containing dendrimer was engineered for the complexation of gold(I) and for its reduction under mild conditions. Gold nanoparticles were obtained as colloidal suspensions simply and only when the powdered form of this dendrimer was dissolved in water, as shown by transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDX) analyses. The dendrimers acted simultaneously as mild reducers and as nanoreactors, favoring the self-assembly of gold atoms and promoting the growth and stabilization of isolated gold nanoparticles. Thus, an unprecedented method for the synthesis of colloidal suspensions of water-soluble gold nanoparticles was proposed in this work.
In vitro assessment of antibody-conjugated gold nanorods for systemic injections
Journal of Nanobiotechnology, 2014
Background: The interest for gold nanorods in biomedical optics is driven by their intense absorbance of near infrared light, their biocompatibility and their potential to reach tumors after systemic administration. Examples of applications include the photoacoustic imaging and the photothermal ablation of cancer. In spite of great current efforts, the selective delivery of gold nanorods to tumors through the bloodstream remains a formidable challenge. Their bio-conjugation with targeting units, and in particular with antibodies, is perceived as a hopeful solution, but the complexity of living organisms complicates the identification of possible obstacles along the way to tumors. Results: Here, we present a new model of gold nanorods conjugated with anti-cancer antigen 125 (CA125) antibodies, which exhibit high specificity for ovarian cancer cells. We implement a battery of tests in vitro, in order to simulate major nuisances and predict the feasibility of these particles for intravenous injections. We show that parameters like the competition of free CA125 in the bloodstream, which could saturate the probe before arriving at the tumors, the matrix effect and the interference with erythrocytes and phagocytes are uncritical. Conclusions: Although some deterioration is detectable, anti-CA125-conjugated gold nanorods retain their functional features after interaction with blood tissue and so represent a powerful candidate to hit ovarian cancer cells.
Molecules
Relevant properties of gold nanoparticles, such as stability and biocompatibility, together with their peculiar optical and electronic behavior, make them excellent candidates for medical and biological applications. This review describes the different approaches to the synthesis, surface modification, and characterization of gold nanoparticles (AuNPs) related to increasing their stability and available features useful for employment as drug delivery systems or in hyperthermia and photothermal therapy. The synthetic methods reported span from the well-known Turkevich synthesis, reduction with NaBH4 with or without citrate, seeding growth, ascorbic acid-based, green synthesis, and Brust–Schiffrin methods. Furthermore, the nanosized functionalization of the AuNP surface brought about the formation of self-assembled monolayers through the employment of polymer coatings as capping agents covalently bonded to the nanoparticles. The most common chemical–physical characterization technique...
Nanotechnology is a multidisciplinary science covering matters involving the nanoscale level that is being developed for a great variety of applications. Nanomedicine is one of these attractive and challenging uses focused on the employment of nanomaterials in medical applications such as drug delivery. However, handling these nanometric systems require defining specific parameters to establish the possible advantages and disadvantages in specific applications. This review presents the fundamental factors of nanoparticles and its microenvironment that must be considered to make an appropriate design for medical applications, mainly: (i) Interactions between nanoparticles and their biological environment, (ii) the interaction mechanisms, (iii) and the physicochemical properties of nanoparticles. On the other hand, the repercussions of the control, alter and modify these parameters in the biomedical applications. Additionally, we briefly report the implications of nanoparticles in nanomedicine and precision medicine, and provide perspectives in immunotherapy, which is opening novel applications as immune-oncology.
The Effect of Gold Nanorods Clustering on Near-Infrared Radiation Absorption
Applied Sciences
In this paper, the plasmonic resonant absorption of gold nanorods (GNRs) and GNR solutions was studied both numerically and experimentally. The heat generation in clustered GNR solutions with various concentrations was measured by exposing them to Near Infrared (NIR) light in experiment. Correspondingly, calculations based on the discrete-dipole approximation (DDA) revealed the same relationship between the maximum absorption efficiency and the nanorod orientation for the incident radiation. Additionally, both the plasmonic wavelength and the maximum absorption efficiency of a single nanorod were found to increase linearly with increasing aspect ratio (for a fixed nanorod volume). The wavelength of the surface plasmonic resonance (SPR) was found to change when the gold nanorods were closely spaced. Specifically, both a shift and a broadening of the resonance peak were attained when the distance between the nanorods was set to about 50 nm or less. The absorbance spectra of suspended ...
Glucosamine Phosphate Induces AuNPs Aggregation and Fusion into Easily Functionalizable Nanowires
Nanomaterials
The challenge to obtain plasmonic nanosystems absorbing light in the near infrared is always open because of the interest that such systems pose in applications such as nanotherapy or nanodiagnostics. Here we describe the synthesis in an aqueous solution devoid of any surfactant of Au-nanowires of controlled length and reasonably narrow dimensional distribution starting from Au-nanoparticles by taking advantage of the properties of glucosamine phosphate under aerobic conditions and substoichiometric nanoparticle passivation. Oxygen is required to enable the process where glucosamine phosphate is oxidized to glucosaminic acid phosphate and H2O2 is produced. The process leading to the nanosystems comprises nanoparticles growth, their aggregation into necklace-like aggregates, and final fusion into nanowires. The fusion requires the consumption of H2O2. The nanowires can be passivated with an organic thiol, lyophilized, and resuspended in water without losing their dimensional and opti...
Optimization of Gold Nanorod Features for the Enhanced Performance of Plasmonic Nanocavity Arrays
ACS Omega
Nanoplasmonic biosensors incorporating noble metal nanocavity arrays are widely used for the detection of various biomarkers. Gold nanorods (GNRs) have unique properties that can enhance spectroscopic detection capabilities of such nanocavity-based biosensors. However, the contribution of the physical properties of multiple GNRs to resonance enhancement of gold nanocavity arrays requires further characterization and elucidation. In this work, we study how GNR aspect ratio (AR) and surface area (SA) modify the plasmonic resonance spectrum of a gold triangular nanocavity array by both simulations and experiments. The finite integration technique (FIT) simulated the extinction spectrum of the gold nanocavity array with 300 nm periodicity onto which the GNRs of different ARs and SAs are placed. Simulations showed that matching of the GNRs longitudinal peak, which is affected by AR, to the nanocavity array's spectrum minima can optimize signal suppression and shifting. Moreover, increasing SA of the matched GNRs increased the spectral variations of the array. Experiments confirmed that GNRs conjugated to a gold triangular nanocavity array of 300 nm periodicity caused spectrum suppression and redshift. Our findings demonstrate that tailoring of the GNR AR and SA parameters to nanoplasmonic arrays has the potential to greatly improve spectral variations for enhanced plasmonic biosensing.
Photo-thermal effects in gold nanorods/DNA complexes
Micro and Nano Systems Letters, 2015
An ingenious combination of plasmonic nanomaterials and one of the most relevant biological systems, deoxyribonucleic acid (DNA) is achieved by bioconjugating gold nanorods (GNRs) with DNA via electrostatic interaction between positively charged GNRs and negatively charged short DNA. The obtained system is investigated as a function of DNA concentration by means of gel electrophoresis, zeta-potential, DNA melting and morphological analysis. It turns out that the obtained bioconjugated systems present both effective electric charge and aggregate size that are particularly amenable for gene therapy and nanomedicine applications. Finally, the effect of the localized (photothermal heating) and delocalized temperature variation on the DNA melting by performing both light induced bio-transparent optical heating experiments and a thermographic analysis is investigated, demonstrating that the developed system can be exploited for monitoring nanoscale temperature variation under optical illumination with very high sensitivity.
Polymer Coated Semiconducting Nanoparticles for Hybrid Materials
Inorganics
This paper reviews synthetic concepts for the functionalization of various inorganic nanoparticles with a shell consisting of organic polymers and possible applications of the resulting hybrid materials. A polymer coating can make inorganic nanoparticles soluble in many solvents as individual particles and not only do low molar mass solvents become suitable, but also polymers as a solid matrix. In the case of shape anisotropic particles (e.g., rods) a spontaneous self-organization (parallel orientation) of the nanoparticles can be achieved, because of the formation of lyotropic liquid crystalline phases. They offer the possibility to orient the shape of anisotropic nanoparticles macroscopically in external electric fields. At least, such hybrid materials allow semiconducting inorganic nanoparticles to be dispersed in functional polymer matrices, like films of semiconducting polymers. Thereby, the inorganic nanoparticles can be electrically connected and addressed by the polymer matr...
Plasmonic Biosensors for the Detection of Lung Cancer Biomarkers: A Review
Chemosensors
Lung cancer is the most common and deadliest cancer type globally. Its early diagnosis can guarantee a five-year survival rate. Unfortunately, application of the available diagnosis methods such as computed tomography, chest radiograph, magnetic resonance imaging (MRI), ultrasound, low-dose CT scan, bone scans, positron emission tomography (PET), and biopsy is hindered due to one or more problems, such as phenotypic properties of tumours that prevent early detection, invasiveness, expensiveness, and time consumption. Detection of lung cancer biomarkers using a biosensor is reported to solve the problems. Among biosensors, optical biosensors attract greater attention due to being ultra-sensitive, free from electromagnetic interference, capable of wide dynamic range detection, free from the requirement of a reference electrode, free from electrical hazards, highly stable, capable of multiplexing detection, and having the potential for more information content than electrical transduce...
ISRN Nanotechnology, 2012
A novel nanobiocomposite bienzymatic amperometric cholesterol biosensor, coupled with cholesterol oxidase (ChOx) and horseradish peroxidase (HRP), was developed based on the gold-nanoparticle decorated graphene-nanostructured polyaniline nanocomposite (NSPANI-AuNP-GR) film which was electrochemically deposited onto indium-tin-oxide (ITO) electrode from the nanocomposite (NSPANI-AuNP-GR) dispersion, as synthesized by in situ polymerization technique. The gold nanoparticle-decorated graphene-nanostructured polyaniline nanocomposite (NSPANI-AuNP-GR) offers an efficient electron transfer between underlining electrode and enzyme active center. The bienzymatic nanocomposite bioelectrodes ChOx-HRP/NSPANI-AuNP-GR/ITO have exhibited higher sensitivity, linearity, and lowerKmvalue than monoenzymatic bioelectrode (ChOx/NSPANI-AuNP-GR/ITO). It is inferred that bienzyme-based nanobioelectrodes offer wider linearity (35 to 500 mg/dL), higher sensitivity (0.42 μAmM−1), low km value of 0.01 mM and ...
Radiolabeled Gold Nanoparticles for Imaging and Therapy of Cancer
Materials
In the Last decades, nanotechnology has provided novel and alternative methodologies and tools in the field of medical oncology, in order to tackle the issues regarding the control and treatment of cancer in modern society. In particular, the use of gold nanoparticles (AuNPs) in radiopharmaceutical development has provided various nanometric platforms for the delivery of medically relevant radioisotopes for SPECT/PET diagnosis and/or radionuclide therapy. In this review, we intend to provide insight on the methodologies used to obtain and characterize radiolabeled AuNPs while reporting relevant examples of AuNPs developed during the last decade for applications in nuclear imaging and/or radionuclide therapy, and highlighting the most significant preclinical studies and results.
Enhancing the photothermal stability of plasmonic metal nanoplates by a core-shell architecture
2011
通讯作者地址: Zheng, NF (通讯作者),Xiamen Univ, Coll Chem & Chem Engn, State Key Lab Phys Chem Solid Surfaces, Xiamen 361005, Peoples R China 地址: 1. Xiamen Univ, Coll Chem & Chem Engn, State Key Lab Phys Chem Solid Surfaces, Xiamen 361005, Peoples R China 2. Xiamen Univ, Dept Chem, Coll Chem & Chem Engn, Xiamen 361005, Peoples R China 电子邮件地址: nfzheng@xmu.edu.cn
Collective behavior of colloids due to critical Casimir interactions
Reviews of Modern Physics, 2018
If colloidal solute particles are suspended in a solvent close to its critical point, they act as cavities in a fluctuating medium and thereby restrict and modify the fluctuation spectrum in a way which depends on their relative configuration. As a result effective, so-called critical Casimir forces (CCFs) emerge between the colloids. The range and the amplitude of CCFs depend sensitively on the temperature and the composition of the solvent as well as on the boundary conditions of the order parameter of the solvent at the particle surfaces. These remarkable, moreover universal features of the CCFs provide the possibility for an active control over the assembly of colloids. This has triggered a recent surge of experimental and theoretical interest in these phenomena. We present an overview of current research activities in this area. Various experiments demonstrate the occurrence of thermally reversible self-assembly or aggregation or even equilibrium phase transitions of colloids i...
Journal of Nanomaterials, 2015
The thermal decomposition of bis (N,N-diallyldithiocarbamato) Cd (II) in a "one-pot" synthesis in tri-n-octylphosphine oxide (TOPO) and hexadecylamine (HDA) afforded CdS (TOPO-CdS and HDA-CdS) of varying optical properties and morphologies. The influence of the ratio of the precursor concentration to the capping molecule, as a factor affecting the morphology and size of the nanoparticles, was investigated. The particles varied in shape from spheres to rods and show quantum size effects in their optical spectra with clear differences in the photoluminescence (PL) spectra. The PL spectrum of the HDA capped CdS nanoparticles has an emission maximum centred at 468, 472, and 484 nm for the precursor to HDA concentration ratio of 1 : 10, 1 : 15, and 1 : 20, respectively, while the TOPO capped nanoparticles show emission peaks at 483, 494, and 498 nm at the same concentration ratio. Powdered X-ray diffraction (p-XRD) shows the nanoparticles to be hexagonal. The crystallinity of t...
Anisotropic nanomaterials: structure, growth, assembly, and functions
Nano Reviews, 2011
Comprehensive knowledge over the shape of nanomaterials is a critical factor in designing devices with desired functions. Due to this reason, systematic efforts have been made to synthesize materials of diverse shape in the nanoscale regime. Anisotropic nanomaterials are a class of materials in which their properties are direction-dependent and more than one structural parameter is needed to describe them. Their unique and fine-tuned physical and chemical properties make them ideal candidates for devising new applications. In addition, the assembly of ordered one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) arrays of anisotropic nanoparticles brings novel properties into the resulting system, which would be entirely different from the properties of individual nanoparticles. This review presents an overview of current research in the area of anisotropic nanomaterials in general and noble metal nanoparticles in particular. We begin with an introduction to the advancements in this area followed by general aspects of the growth of anisotropic nanoparticles. Then we describe several important synthetic protocols for making anisotropic nanomaterials, followed by a summary of their assemblies, and conclude with major applications. Panikkanvalappil R. Sajanlal received his M.Sc. degree in chemistry from the University of Calicut, India, in 2004. He is currently working toward his PhD in chemistry under the supervision of Prof. T. Pradeep at the Indian Institute of Technology Madras, India. His current research focuses on the shape-controlled synthesis, characterization, and applications of anisotropic meso/nanomaterials. Theruvakkattil S. Sreeprasad received his M.Sc. degree in chemistry from the School of chemical sciences, M. G. University, India, in 2004. He is currently working toward his PhD in chemistry under the supervision of Prof. T. Pradeep at the Indian Institute of Technology Madras, India. His current research focuses on the post-synthetic tuning of size, shape, composition and properties of one and two dimensional nanosystems. Dr. Akshaya K. Samal received his M.Sc. degree in chemistry from the Sambalpur University, India and Ph. D degree in chemistry under the supervision of Prof. T. Pradeep from the Indian Institute of Technology Madras, India. His current research focuses on synthesis, characterization and properties of one dimensional nanostructures.
Graphene Oxide-Coated Gold Nanorods: Synthesis and Applications
Nanomaterials
The application of gold nanorods (AuNRs) and graphene oxide (GO) has been widely studied due to their unique properties. Although each material has its own challenges, their combination produces an exceptional material for many applications such as sensor, therapeutics, and many others. This review covers the progress made so far in the synthesis and application of GO-coated AuNRs (GO–AuNRs). Initially, it highlights different methods of synthesizing AuNRs and GO followed by two approaches (ex situ and in situ approaches) of coating AuNRs with GO. In addition, the properties of GO–AuNRs composite such as biocompatibility, photothermal profiling, and their various applications, which include photothermal therapy, theranostic, sensor, and other applications of GO–AuNRs are also discussed. The review concludes with challenges associated with GO–AuNRs and future perspectives.
Nanoparticle Interactions Guided by Shape-Dependent Hydrophobic Forces
Advanced Materials
tions, where individual NPs, their ligands, and solvents interact, the challenge is to identify the dominant forces driving the NP binding dynamics that determine the time-dependence and overall outcome of the self-assembly process. [11] The NP self-assembly is driven and controlled by many competing attractive and repulsive interactions that act between the NPs, which include van der Waals (vdW) attraction, electrostatic interaction, steric repulsion, solvation forces, such as hydrophobic force, and others. [11-13] During the self-assembly processes, attractive interactions such as vdW (between the metallic cores of NPs) and hydrophobic (between the ligated NP surfaces) forces are responsible for bringing NPs together and stabilizing them against interparticle repulsions. [14,15] In aqueous solutions, hydrophobic interactions between NPs (with hydrophobic surfaces) arise because the hydrogen bonding network between water molecules around the surface of each hydrophobic NP is interrupted, leading to an increase in the energy of these interfacial water molecules surrounding the NPs, which gives rise to an attractive force that drives the NP self-assembly. [16,17] In general, hydrophobic interactions between the NPs depend on their surface properties, sizes, and shapes. [14,18,19] During chemical synthesis, NPs are often capped with surfactant ligands to control their sizes and shapes. [20] Self-assembly of solvated nanoparticles (NPs) is governed by numerous competing interactions. However, relatively little is known about the timedependent mechanisms through which these interactions enable and guide the nanoparticle self-assembly process. Here, using in situ transmission electron microscopy imaging combined with atomistic modeling, it is shown that the forces governing the self-assembly of hydrophobic nanoparticles change with the nanoparticle shapes. By comparing how gold nanospheres, nanocubes, nanorods, and nanobipyramids assemble, it is shown that the strength of the hydrophobic interactions depends on the overlap of the hydrophobic regions of the interacting nanoparticle surfaces determined by the nanoparticle shapes. Specifically, this study reveals that, in contrast to spherical nanoparticles, where van der Waals forces play an important role, hydrophobic interactions can be more relevant for nanocubes with flat side faces, where an oriented attachment between the nanocubes is promoted by these interactions. The attachment of nanocubes is observed to proceed in two distinct pathways: nanocubes either: (i) prealign their faces before the attachment, or (ii) first connect through a misaligned (edge-to-edge) attachment, followed by a postattachment alignment of their faces. These results have important implications for understanding the interaction dynamics of NPs and provide the framework for the design of future self-assembled nanomaterials.
PLOS ONE
Macroscopically long wire-like arrangements of gold nanoparticles were obtained by controlled evaporation and partial coalescence of an aqueous colloidal solution of capped CTAB-Au nanorods onto a functionalised 3-mercaptopropyl trimethoxysilane (MPTMS) silicon substrate, using a removable, silicon wafer with a hydrophobic surface that serves as a "handrail" for the initial nanorods' linear self-assembly. The wire-like structures display a quasi-continuous pattern by thermal annealing of the gold nanorods when the solvent (i.e. water) is evaporated at temperatures rising from 20˚C to 140˚C. Formation of both single and self-replicating parallel 1D-superstructures consisting of two or even three wires is observed and explained under such conditions.
Nanomaterials, 2022
Dual probe porphyrin-gold nanorod polyelectrolyte microcapsules were developed to explore the enhancing effects of a plasmonic interface of self-assembled gold nanoparticles in the fluorescence emission from porphyrins loaded into the capsules’ core. An analysis of fluorescence lifetime imaging microscopy (FLIM) data reports a notable 105–106-fold increase in the maximum detected photon rates from diffraction-limited spots and an overall six-fold increase in fluorescence as averaged over the whole microcapsule area. Large emission enhancements were correlated with decreases in fluorescence lifetimes. The microcapsule’s design proved effective in achieving high fluorescent hybrids and may shed light on new possibilities for advanced materials imaging applications.
Controlled epitaxial growth of mesoporous silica/gold nanorod nanolollipops and nanodumb-bells
APL Materials, 2014
In this work, we describe the controlled synthesis of novel heterogeneous nanostructures comprised of mesoporous silica-coated gold nanorods (MSGNRs) in the form of core-shell nanolollipops and nanodumb-bells, using a seed-mediated sol-gel method. Although MSGNR core-shell (θ-MSGNR) structures have been reported previously by us and others, we herein discuss the first ever fabrication of MSGNR nanolollipops (ϕ-MSGNR) and nanodumb-bells ( β-MSGNR), achieved by simply controlling the aging time of gold nanorods (GNRs), the residual cetyltrimethylammonium bromide (CTAB) coating of GNRs, and the addition of dimethyl formamide during incubation, centrifugation, and sonication, respectively. Transmission electron microscopy revealed two bare GNR isoforms, with aspect ratios of approximately 4 and 6, while scanning electron microscopy was used to further elucidate the morphology of ϕ-MSGNR and β-MSGNR heterostructures. In agreement with the smaller dielectric constants afforded by incomplete silica encasement, spectroscopic studies of ϕ-MSGNR and β-MSGNR, surface plasmon resonance (SPR) bands revealed 20-40 nm blue shifts relative to the SPR of θ-MSGNR. On the basis of the attributes and applications of more conventional θ-MSGNRs, ϕ-MSGNRs and β-MSGNRs are anticipated to provide most of the utility of θ-MSGNRs, but with the additional functionalities that accompany their incorporation of both bare gold and mesoporous silica encased tips; with significant/unique implications for biomedical and catalytic applications.
Gold Nanorods Targeted to Delta Opioid Receptor: Plasmon-Resonant Contrast and Photothermal Agents
Molecular Imaging, 2008
Molecularly targeted gold nanorods were investigated for applications in both diagnostic imaging and disease treatment with cellular resolution. The nanorods were tested in two genetically engineered cell lines derived from the human colon carcinoma HCT-116, a model for studying ligand-receptor interactions. One of these lines was modified to express delta opioid receptor (dOR) and green fluorescent protein, whereas the other was receptor free and expressed a red fluorescent protein, to serve as the control. Deltorphin, a high-affinity ligand for dOR, was stably attached to the gold nanorods through a thiol-terminated linker. In a mixed population of cells, we demonstrated selective imaging and destruction of receptor-expressing cells while sparing those cells that did not express the receptor. The molecularly targeted nanorods can be used as an in vitro ligand-binding and cytotoxic treatment assay platform and could potentially be applied in vivo for diagnostic and therapeutic purposes with endoscopic technology.
A Robust Design for Cellular Vehicles of Gold Nanorods for Multimodal Imaging
Advanced Functional Materials, 2016
Ref. [82] was not included in the originally published version of this article. It should be added to the second paragraph on page 7179, which then reads as follows: "More recently, the notion to exploit the natural tropism of cells, such as tumor-associated macrophages, [35-39] T cells, [40,82] mesenchymal stem cells, [41-43] and neural stem cells, [44,45] has begun to emerge as a radical alternative." Ref.
Conceptual Developments of Aryldiazonium Salts as Modifiers for Gold Colloids and Surfaces
Langmuir, 2021
HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.
Journal of Polymer Research, 2019
Human pathogenic diseases are on the rage in the list of enfeebling diseases globally. The endless quest to salvage these drugresistant pathogens ravaging our system through various therapies still posts serious challenge. This study engaged a biogenic synthesis that is benign, facile, biocompatible, cost-effective and eco-friendly to synthesized silver nanocapsule (AgNCs) via Moringa oleifera aqueous extract under incubation control. The flavonoid-kaempferol, phenolic-chlorogenic acid and tannin components of MO acted as the potential stabilizing and reducing agent in the formation of AgNCs. The formulated AgNCs was further functionalized with PVA, PVP and PEG for biocompatibility and dispersion enhancement. Various characterization techniques were used to determine the properties of AgNCs formulated. The absorbance due to the color change was observed by the UV-Visible spectroscopy with surface plasmons resonance peak between 425 and 455 nm. The Fourier transform infrared spectroscopy (FTIR) shows the various functional group responsible for the biogenic synthesis of AgNCs. The X-ray spectroscopy analysis shows a single phase cubic structure of AgNCs formed. The Scanning electron microscopy (SEM) image shows a rod-like nanocapsule of uniform grains. The antibacterial potency of AgNCs was proven against gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli and Coliform). The AgNCs inhibited the growth of the three human pathogens with Coliform showing the highest activity to the AgNCs with a minimum inhibitory dose of 15 μg/mL. It is noteworthy that the bacterial strains show functional susceptibility to the AgNCs at lower concentrations compared to the conventional antibacterial drugs. Consequently, AgNCs serve as an enhanced substitute for the conventional antibacterial drugs in therapeutic biomedical field sequel to its pharmacodynamics against the bacterial strains.
Journal of Physics: Conference Series, 2018
The experimental conditions were investigated to fabricate gold nanowire networks (AuNNWs) by pulsed laser ablation in saline solutions. The study revealed that the production of alternative nanoparticles (or aggregates) or nanowire networks at the fundamental wavelength of a Nd:YAG laser (1064 nm) depend on the medium media surrounding Au nanoparticles during the process of synthesis. The aggregates and precipitates of the gold nanoparticles (AuNPs) in saline solutions were caused by the harsh environment of the anions with Na+ cations in the solution. The ex-situ was used for the preparation of bovine serum albumin (BSA) bio-conjugates. Enhanced colloidal stability was dramatically achieved when BSA was adsorbed onto Au nanowire networks. The optical extinction spectra of the colloids in the UV/vis region were obtained to evaluate the structure of the dispersed Au phase. Transmission electron microscopy (TEM) was applied to visualize the size and morphology of the colloidal particles. Au nanowire networks compatibility can be prepared and applied in real environments.
Modulation instability in waveguides doped with anisotropic nanoparticles
Optics Letters, 2020
The importance of interactions between processes at diverse space and time scales in biological information processing is a recurrent theme in the work of Michael Conrad (BioSystems, 1995: 35, 157-160; BioSystems, 1999: 52, 99-100). In this paper I present some results of explicit computational models that aim to capture and exploit some of the essential features of such multi-level processes. In the model formulation, I try to minimize the explicit definition of inter-level interactions, while providing the possibility of such interactions to develop. As often argued by Conrad inter-level interactions limit programmability. Indeed, we use an evolutionary process to derive the specific models. We study morphogenesis. We show that the interplay between cell adhesion and cell differentiation provides interesting mechanisms for morphogenesis. We also show that the interplay can both reduce and enhance small random fluctuations. We show that unequal cell cleavage in the early embryo-genesis reduces inter-individual variation of the morphemes developed from the same 'genome'. Our results suggest that, during evolution, the interplay between levels is exploited while it is at the same time reduced so as to give a certain primacy to inherited information.
Tuning the oriented deposition of gold nanorods on patterned substrates
Nanotechnology, 2013
The controlled patterning of anisotropic gold nanoparticles is of crucial importance for many applications related to their optical properties. In this paper, we report that gold nanorods prepared by a seed-mediated synthesis protocol (without any further functionalization) can be selectively deposited on hydrophilic parts of hydrophobic-hydrophilic contrast patterned substrates. We have seen that, when nanorods with lengths much smaller than the width of the hydrophilic stripe are used, they disperse on these stripes with random orientation and tunable uniform particle separation. However, for nanorods having lengths comparable to the width of the hydrophilic stripes, confinement-induced alignment occurs. We observe that different interactions governing the assembly forces can be modulated by controlling the concentration of assembling nanorods and the width of the hydrophilic stripes, leading to markedly different degrees of alignment. Our strategy can be replicated for other anisotropic nanoparticles to produce well-controlled patterning of these nanoentities on surfaces.
Improving in vitro biocompatibility of gold nanorods with thiol-terminated triblock copolymer
Colloid and Polymer Science, 2019
Gold nanorods (AuNRs) are usually synthesized using cetyltrimethylammonium bromide (CTAB) surfactant as a structuredirecting agent. CTAB is reported to form a tightly bound cationic bilayer on AuNR surface with the cationic trimethylammonium head group exposed to the aqueous media. However, CTAB is also known to be highly toxic in both in vitro and in vivo experiments. In this work, we investigated the cytotoxicity, colloidal stability and optical properties of AuNRs before and after substitution with thiol-terminated triblock copolymer of ethylene oxide-propylene oxide (PEO-PPO-PEO), or Pluronic F127® (PF127). For that, PF127 was first chemically functionalized with 3-mercaptopropionic acid (MPA) and further used as stabilizer for the AuNRs by replacing CTAB molecules. Unmodified PF127 was also tested and used as a control for biological experiments. Morphology of coated AuNRs was characterized by visible spectroscopy, transmission electron microscopy, zeta potential, and dynamic light scattering. We found that coating with PF127-SH guarantees both stability and biocompatibility of AuNRs for at least 45 days, besides improving cell viability when compared to the PF127-coated AuNRs, even after 72 h treatment. In addition, this new polymer coating can also provide hydrophobic domains assembled into the PPO blocks, which could be further loaded with organic active ingredients. The obtained results show the potential of this nanostructured system for future developments in multifunctional nanoplataforms for clinical applications such as drug delivery, hyperthermia, photodynamic therapy, and diagnostic imaging of cells and tissues.
Size and shape control for water-soluble magnetic cobalt nanoparticles using polymer ligands
Journal of Materials Chemistry, 2008
We report a synthesis of monodisperse water-soluble magnetic Co nanoparticles using a facile reduction method in aqueous media in the presence of alkyl thioether end-functionalized poly(methacrylic acid) (PMAA-DDT) ligands. The size and shape of the nanoparticles are both tunable by varying synthesis conditions. The size of the spherical nanoparticles can be tuned between 2-7.5 nm by changing the concentration of the polymer. Our synthesis approach also provides a route for producing much larger spherical nanoparticles of 80 nm as well as anisotropic nanorods of 15 Â 36 nm. The spherical nanoparticles are superparamagnetic at room temperature. The nanoparticles can be stable in water for up to eight weeks when 0.12 mM PMAA-DTT with molecular weight of 13500 g mol À1 is used as ligand.
A promising road with challenges: where are gold nanoparticles in translational research?
Nanomedicine, 2014
Nanoenabled technology holds great potential for health issues and biological research. Among the numerous inorganic nanoparticles that are available today, gold nanoparticles are fully developed as therapeutic and diagnostic agents both in vitro and in vivo due to their physicochemical properties. Owing to this, substantial work has been conducted in terms of developing biosensors for noninvasive and targeted tumor diagnosis and treatment. Some studies have even expanded into clinical trials. This article focuses on the fundamentals and synthesis of gold nanoparticles, as well as the latest, most promising applications in cancer research, such as molecular diagnostics, immunosensors, surface-enhanced Raman spectroscopy and bioimaging. Challenges to their further translational development are also discussed.
Nanomaterials
Photothermal application of gold nanorods (AuNRs) is widely increasing because of their good photothermal conversion efficiency (PCE) due to local surface plasmon resonance. However, the high concentration of hexadecyltrimethylammonium bromide used in the synthesis is a concern. Moreover, the mild and commonly used reducing agent-ascorbic acid does not reduce the Au(I) to A(0) entirely, resulting in a low yield of gold nanorods. Herein we report for the first time the PCE of large-scaled synthesized AuNRs using the binary surfactant seed-mediated method with hydroquinone (HQ) as the reducing agent. The temporal evolution of the optical properties and morphology was investigated by varying the Ag concentration, HQ concentration, HCl volumes, and seed solution volume. The results showed that the seed volume, HQ concentration, and HCl volume played a significant role in forming mini-AuNRs absorbing in the 800 nm region with a shape yield of 87.7%. The as-synthesized AuNRs were successf...
Nanotechnology, 2010
We present an effective, low cost protocol to reduce the toxicity of gold nanorods induced by the presence of cetyltrimethylammonium bromide (CTAB) on their lateral surface as a result of the synthesis process. Here, we use thiolated methoxy-poly(ethylene) glycol (mPEG-SH) polymer to displace most of the CTAB bilayer cap from the particle surface. The detoxification process, chemical and structural stability of as-prepared mPEG-SH-conjugated gold nanorods were characterized using a number of techniques including localized surface plasmon resonance (LSPR), transmission electron microscopy (TEM) and surface-enhanced Raman spectroscopy (SERS). In view of future applications as near-infrared (NIR) nanoheaters in localized photothermal therapy of cancer, we investigated the thermal behaviour of mPEG-SH-conjugated gold nanorods above room temperature. We found a critical temperature at around 40 • C at which the adsorbed polymer layer is susceptible to undergo conformational changes. Additionally, we believe that such plasmonic nanoprobes could act as SERS-active carriers of Raman tags for application in cellular imaging. In this sense we successfully tested them as effective SERS substrates at 785 nm laser line with p-aminothiophenol (pATP) as a tag molecule.
A seedless approach to continuous flow synthesis of gold nanorods
Chemical Communications, 2011
Preparation of stock solutions: Two stock solutions were prepared as described below: Solution 1 was comprised of 100 mM CTAB, 1 mM HAuCl 4 , and 10 mM acetylacetone. After dissolution of CTAB (36.4g/L) with stirring and gentle heating, 10 mL/L of 100 mM HAuCl 4 was added to produce an orange coloured solution with some fine orange precipitate. Solution 1 was warmed to ca. 30°C-35°C for 15 minutes to produce a transparent, deep orange solution. At this time acetylacetone (10 mM) was added with stirring at which point the solution colour changed to colourless indicating complexation of gold by acac. The low pH (ca. 3-3.5) kinetically retarded the formation of significant amounts of Au(0) until several weeks after solution preparation; with reliable results for AuNR synthesis achieved for up to 3 weeks from a given solution stored at room temperature in a cupboard. The solution temperature was maintained at 30±2°C during the RTP experiments using a hotplate-stirrer. Solution 2 was comprised of 0.1 M CTAB, 0.1 mM and 0.025 mM, 0.05 mM or 0.1 mM AgNO 3. The solution was buffered to pH 10 using 0.1 M NaHCO 3 /Na 2 CO 3. After complete dissolution of CTAB (36.4 g in 900 mL) at 30°C-35°C, 100 mL of buffer (0.5 M NaHCO 3 /0.5 M Na 2 CO 3) in 100 mM CTAB was added. Finally 0.25-1 mL/L of 100 mM AgNO 3 was added to the buffered CTAB solution. Solution 2 was found to be stable for AuNR synthesis for several weeks.
Multifunctional Gold Nanoparticles in Cancer Diagnosis and Treatment
International Journal of Nanomedicine
Cancer is the second leading cause of death in the world, behind only cardiovascular diseases, and is one of the most serious diseases threatening human health nowadays. Cancer patients' lives are being extended by the use of contemporary medical technologies, such as surgery, radiotherapy, and chemotherapy. However, these treatments are not always effective in extending cancer patients' lives. Simultaneously, these approaches are often accompanied with a series of negative consequences, such as the occurrence of adverse effects and an increased risk of relapse. As a result, the development of a novel cancer-eradication strategy is still required. The emergence of nanomedicine as a promising technology brings a new avenue for the circumvention of limitations of conventional cancer therapies. Gold nanoparticles (AuNPs), in particular, have garnered extensive attention due to their many specific advantages, including customizable size and shape, multiple and useful physicochemical properties, and ease of functionalization. Based on these characteristics, many therapeutic and diagnostic applications of AuNPs have been exploited, particularly for malignant tumors, such as drug and nucleic acid delivery, photodynamic therapy, photothermal therapy, and X-ray-based computed tomography imaging. To leverage the potential of AuNPs, these applications demand a comprehensive and in-depth overview. As a result, we discussed current achievements in AuNPs in anticancer applications in a more methodical manner in this review. Also addressed in depth are the present status of clinical trials, as well as the difficulties that may be encountered when translating some basic findings into the clinic, in order to serve as a reference for future studies.
Efficient seed-mediated method for the large-scale synthesis of Au nanorods
Journal of nanoparticle research : an interdisciplinary forum for nanoscale science and technology, 2017
Seed-mediated methods are widely followed for the synthesis of Au nanorods (NRs). However, mostly dilute concentrations of the Au precursor (HAuCl4) are used in the growth solution, which leads to a low final concentration of NRs. Attempts of increasing the concentration of NRs by simply increasing the concentration of HAuCl4, other reagents in the growth solution and seeds lead to a faster growth kinetics which is not favourable for NR growth. Herein, we demonstrate that the increase in growth kinetics for high concentrations of reagents in growth solution can be neutralised by decreasing the pH of the solution. The synthesis of the NRs can be scaled up by using higher concentrations of reagents and adding an optimum concentration of HCl in the growth solution. The concentration of HAuCl4 in the growth solution can be increased up to 5 mM, and 10-20 times more NRs can be synthesised for the same reaction volume compared to that of the conventional seed-mediated method. We have also...
Journal of Nanotheranostics
The existing diagnosis and treatment modalities have major limitations related to their precision and capability to understand several stages of disease development. A superior therapeutic system consists of a multifunctional approach in early diagnosis of the disease with a simultaneous progressive cure, using a precise medical approach towards complex treatment. These challenges can be addressed via nanotheranostics and explore suitable approaches to improve health care. Nanotechnology in combination with theranostics as an unconventional platform paved the way for developing novel strategies and modalities leading to diagnosis and therapy for complex disease conditions, ranging from acute to chronic levels. Among the metal nanoparticles, gold nanoparticles are being widely used for theranostics due to their inherent non-toxic nature and plasmonic properties. The unique optical and chemical properties of plasmonic metal nanoparticles along with theranostics have led to a promising...
Investigation of Sub-100 nm Gold Nanoparticles for Laser-Induced Thermotherapy of Cancer
Nanomaterials, 2013
Specialized gold nanostructures are of interest for the development of alternative treatment methods in medicine. Photothermal therapy combined with gene therapy that supports hyperthermia is proposed as a novel multimodal treatment method for prostate cancer. In this work, photothermal therapy using small (<100 nm) gold nanoparticles and near-infrared (NIR) laser irradiation combined with gene therapy targeting heat shock protein (HSP) 27 was investigated. A series of nanoparticles: nanoshells, nanorods, core-corona nanoparticles and hollow nanoshells, were synthesized and examined to compare their properties and suitability as photothermal agents. In vitro cellular uptake studies of the nanoparticles into prostate cancer cell lines were performed using light scattering microscopy to provide three-dimensional (3D) imaging. Small gold nanoshells (40 nm) displayed the greatest cellular uptake of the nanoparticles studied and were used in photothermal studies. Photothermal treatment of the cancer cell lines with laser irradiation at 800 nm at 4 W on a spot size of 4 mm (FWHM) for 6 or 10 min resulted in an increase in temperature of ~12 °C and decrease in cell viability of up to 70%. However, in vitro studies combining photothermal therapy with gene therapy targeting HSP27 did not result in additional sensitization of the prostate cancer cells to hyperthermia.
Optimum morphology of gold nanorods for light-induced hyperthermia
Nanoscale, 2018
Owing to their unique chemical and physical properties, colloidal gold nanoparticles have prompted a wide variety of biocompatible nano-agents for cancer imaging, diagnosis and treatment. In this context, biofunctionalized gold nanorods (AuNRs) are promising candidates for light-induced hyperthermia, to cause local and selective damage in malignant tissue. Yet, the efficacy of AuNR-based hyperthermia is highly dependent on several experimental parameters; in particular, the AuNR morphology strongly affects both physical and biological processes. In the present work, we systematically study the influence of different structural parameters like the AuNR aspect ratio, length and molecular weight on in vitro cytotoxicity, cellular uptake and heat generation efficiency. Our results enable us to identify the optimum AuNR morphology to be used for in vivo hyperthermia treatment.
Light-Induced Tuning and Reconfiguration of Nanophotonic Structures
Laser & Photonics Reviews, 2017
Interaction of light pulses of various durations and intensities with nanoscale photonic structures plays an important role in many applications of nanophotonics for high-density data storage, ultra-fast data processing, surface coloring and sensing. A design of optically tunable and reconfigurable structures made from different materials is based on many important physical effects and advances in material science, and it employs the resonant character of light interaction with nanostructures and strong field confinement at the nanoscale. Here we review the recent progress in physics of tunable and reconfigurable nanophotonic structures of different types. We start from low laser intensities that produce weak reversible changes in nanostructures, and then move to the discussion of non-reversible changes in photonic structures. We focus on three platforms based on metallic, dielectric and hybrid resonant photonic structures such as nanoantennas, nanoparticle oligomers and nanostructured metasurfaces. Main challenges and key advantages of each of the approaches focusing on applications in advanced photonic technologies are also discussed.
A comparative study of classical approaches to surface plasmon resonance of colloidal gold nanorods
Gold Bulletin, 2013
We report the errors in the evaluation of the surface plasmon resonance of gold nanorods by three classical approaches: the Gans model, the Discrete Dipole Approximation and the Surface Integral method. Using these methods, which are based on the propagation of an electromagnetic wave through a composite medium with different refractive indices, might result in an inaccurate prediction of absorption maxima. For test samples of nanorods prepared by a seed-mediated method, whose homogeneity and quality were also fully demonstrated in this study, the mismatches in the wavelengths of absorption maxima Δλ max j j between experimental and theoretical data were observed to be greater than 50 nm. In general, the observed surface plasmon resonances exhibit two distinctive bands corresponding to the transverse and longitudinal modes. The weak transverse mode was located in the region from 510 to 518 nm and varied slightly with the aspect ratio of the rods. In contrast, the longitudinal mode showed a strong dependence on aspect ratio and ranged from 658 to 768 nm. We demonstrated that the mismatches may be sufficiently reduced if the interdependence between these two modes is taken into account.
Gold nanorods and poly(amido amine) dendrimer thin film for biosensing
Journal of Solid State Electrochemistry, 2019
The use of gold nanomaterials in electrochemical biosensing has been proven to be effective either by modifying the electrodes' surface or by labeling molecules. The combination of dendrimers with gold nanomaterials is a worthwhile alternative to create a suitable environment to immobilize enzymes. In this paper, we report the development of a thin film composed of gold nanorods (AuNRs) and poly(amido amine) (PAMAM) dendrimer generation 4, which was applied for biosensing. The film was prepared by drop-casting the dispersion onto a screen-printed carbon electrode (SPCE), and tyrosinase (Tyr) enzyme was further immobilized onto the modified electrode. The direct electron transfer (DET) between the enzyme and electrode surface was verified through cyclic voltammetry (CV), yielding an apparent heterogeneous electron transfer rate constant of 0.045 s −1. Analytical curves were obtained by chronoamperometry for catechol (CAT) and dopamine (DA) with linear ranges from 2.8 to 30.3 μmol L −1 and 27.8 to 448.7 μmol L −1 , respectively, and detection limits of 1.0 μmol L −1 for CAT and 10.0 μmol L −1 for DA. The improved electrochemical properties of AuNRs-PAMAM-modified SPCE combined with the effective enzyme immobilization led to a promising electrochemical device to detect phenolic compounds.
One-Step Green Synthesis of Metallic Nanoparticles Using Sodium Alginate
Journal of Nanomaterials, 2016
Metallic nanoparticles have been focus of research because of their characteristic properties, specifically the LSPR which can have wide applications in biomedical sciences and engineering. Currently, traditional physical and chemical methods can synthesize these nanoparticles but their disadvantages such as costs, time, effectiveness, and toxicity of precursors provide a wide range of problems for the synthesis of these nanoparticles. Recently, some natural polymers and organic compounds have been used for the synthesis of nanoparticles by green methods. In this study, we synthesize copper, silver, and gold nanoparticles using sodium alginate as reducing and stabilizing agent under microwave irradiation. The LSPR for each system was observed by UV-vis spectroscopy. Particle size distribution and zeta potential demonstrate the size and stability for these nanoparticles. FESEM and TEM microscopies have shown the size and morphology of these systems correlated with UV-vis, particle si...
Non-linear finite element modelling of light-to-heat energy conversion applied to solar nanofluids
International Journal of Mechanical Sciences, 2020
In nature, physical phenomena tend to exhibit their effects simultaneously and, depending on the situation of study, their interactions cannot be neglected. For instance, nanofluids, which are composed of both fluid and nanosolids, are currently used for thermal energy storage in concentrated solar power plants and couple thermal and mechanical fields. Notice that owing to some limitations of solar collectors, fluids combined with nanoparticles are under research currently to absorb solar energy by lightto-heat conversion of energy. On this ground, the aim of the present work is to develop a numerical formulation within the finite element method (FEM) to study the light-to-heat energy conversion, phase-change and thermal stresses in nanosolids. For this purpose and in a first and good approximation, it is assumed that the light is converted into heat by the Joule heating-a non-linear term which quadratically depends on the electric field. Therefore, the set of three coupled governing equations is composed of: balance of linear momentum for the mechanical field, balance of energy for the thermal field and balance of electric current for the electric field. These equations are rewritten in a weak form, which is more amenable in the context of the FEM, and they are implemented in a numerical code. Finally, several benchmarks are presented to validate the numerical results against analytical solutions developed by the authors.
The role of particle geometry and mechanics in the biological domain
Advanced healthcare materials, 2012
Nanostructured particulate materials are expected to revolutionize diagnostics and the delivery of therapeutics for healthcare. To date, chemistry-derived solutions have been the major focus in the design of materials to control interactions with biological systems. Only recently has control over a new set of physical parameters, including size, shape, and rigidity, been explored to optimize the biological response and the in vivo performance of nanoengineered delivery vectors. This Review highlights the methods used to manipulate the physical properties of particles and the relevance of these physical properties to cellular and circulatory interactions. Finally, the importance of future work to synergistically tailor both physical and chemical properties of particulate materials is discussed, with the aim of improving control over particle interactions in the biological domain.
Efficacy of Green Synthesized Nanoparticles in Photodynamic Therapy: A Therapeutic Approach
International Journal of Molecular Sciences
Cancer is a complex and diverse disease characterized by the uncontrolled growth of abnormal cells in the body. It poses a significant global public health challenge and remains a leading cause of death. The rise in cancer cases and deaths is a significant worry, emphasizing the immediate need for increased awareness, prevention, and treatment measures. Photodynamic therapy (PDT) has emerged as a potential treatment for various types of cancer, including skin, lung, bladder, and oesophageal cancer. A key advantage of PDT is its ability to selectively target cancer cells while sparing normal cells. This is achieved by preferentially accumulating photosensitizing agents (PS) in cancer cells and precisely directing light activation to the tumour site. Consequently, PDT reduces the risk of harming surrounding healthy cells, which is a common drawback of conventional therapies such as chemotherapy and radiation therapy. The use of medicinal plants for therapeutic purposes has a long hist...
Nanoscale, 2017
In order to fully exploit structure-property relations of nanomaterials, three-dimensional (3D) characterization at the atomic scale is often required. In recent years, the resolution of electron tomography has reached the atomic scale. However, such tomography typically requires several projection images demanding substantial electron dose. A newly developed alternative circumvents this by counting the number of atoms across a single projection. These atom counts can be used to create an initial atomic model with which an energy minimization can be applied to obtain a relaxed 3D reconstruction of the nanoparticle. Here, we compare, at the atomic scale, this single projection reconstruction approach with tomography and find an excellent agreement. This new approach allows for the characterization of beam-sensitive materials or where the acquisition of a tilt series is impossible. As an example, the utility is illustrated by the 3D atomic scale characterization of a nanodumbbell on an in situ heating holder of limited tilt range.
Shape-dependent electrocatalytic activity of free gold nanoparticles toward glucose oxidation
Gold bulletin, 2013
The synthesis of shape and size-controlled free gold nanoparticles (AuNPs) was achieved by wet chemical methods. The UV-vis spectroscopy measurements and transmission electron microscopy characterizations confirmed the fine distribution in size and shape of the AuNPs. The zeta potential measurements permitted the evaluation of the stability of the AuNPs suspension. For the first time, the shape dependence on the electrocatalytic activity of these NPs is thoroughly investigated. The underpotential deposition (UPD) of lead reveals that their crystallographic facets are affected by their shape and growth process. Moreover, the glucose oxidation reaction strongly depends on the shape of AuNPs. Indeed, the gold nanocuboids (GNCs) and the spherical gold nanoparticles (GNSs) are significantly more active than the gold nanorods (GNRs) followed by the polyhedrons (GNPs). The oxidation process occurs at low potential for GNCs whereas the current densities are slightly higher for GNSs electrodes. Most importantly, the control of the shape and structure of nanomaterials is of high technological interest because of the strong correlation between these parameters and their optical, electrical and electrocatalytic properties.
Curvature sculptured growth of plasmonic nanostructures by supramolecular recognition
Physical Review Materials, 2019
Nanoscale curvature is an important and powerful tool in understanding and tailoring chemical/surface functionalities of nanostructures that dictate a host of important applications from biochemical recognitions, catalysis to spectroscopy. However, it is a critical challenge in materials chemistry to rationally shape the local nanoscale curvatures of colloidal nanoparticles during the growth owing to the constraints of their flat facets. Here we demonstrate a synthetic mechanism that could cooperatively mediate local nanoparticle surface curvature patchiness and shape symmetries during one-step colloidal growth. The idea is to tailor host-guest supramolecular recognition using fluorocarbon and hydrocarbon molecules that regulate interfacial energy during the nanoparticle growth. Such delicate regulation enables a degree of freedom in control over the local nanoparticle curvatures during the growth, resulting in intriguing plasmonic properties. More interestingly, a morphological shape transformation was induced by such curvature changes from anisotropic nanorods to isotropic nanospheres. This unique approach of the spontaneous curvature/structural transformation of plasmonic nanoparticles exploits the mutual interplay between competing supramolecules and colloidal growth. It may ultimately allow for accurate controlling nanoscale objects with varied degree of complexity that could open the door to a myriad of surface chemical, optical, and biomedical applications.
Optical and tomography studies of water-soluble gold nanoparticles on bacterial exopolysaccharides
Journal of Applied Physics, 2019
Gold nanoparticles of different shapes (spherical, rods, and prisms) aggregate when deposited onto Lactobacillus fermentum's exopolysaccharide (EPS), a set of polysaccharides excreted by the bacteria. Transmission electron microscopy studies revealed that gold nanoparticles have high affinity for EPS. UV-vis spectra of aggregated gold nanoparticles showed additional absorbance peaks at lower energies in comparison with isolated nanoparticles. In the case of gold nanoprisms, the aggregation leads to a new absorption at a very low energy centered at 1100 nm. Moreover, the EPS of L. fermentum itself produces gold aggregates from a Au(III) solution. Surface-enhanced Raman spectroscopy performances for the detection of rhodamine B of gold aggregates were drastically different. A tomography study on all samples revealed clear differences in the extension of the EPS coating on the gold nanoparticles. Only the gold aggregate in which gold interparticle surfaces were exposed to RhB showe...
Retardation of shape change of Au nanorods using photo-cross-linkable ligands
Journal of Polymer Science Part B, 2015
The thermal reshaping of gold nanorods has been slowed by grafting a diblock copolymer [P(S-b-S-N 3)] containing an outer polystyrene (PS) brush and a short, inner photocross-linkable PS-azide block. The P(S-b-S-N 3)-Au NRs were dispersed in a PS thin film and reshaping was investigated using scanning electron microscopy and UV-Vis spectroscopy. For P(S-b-S-N 3)-Au NRs in PS, the longitudinal surface plasmon resonance decreased from about 880 toward 750 nm upon annealing at 100 8C, 150 8C, and 200 8C. This blue shift increased in strength as temperature increased. However, this reshaping of P(S-b-S-N 3)-Au NRs was slower than that of Au NRs grafted with a poly(ethylene glycol) brush that was dispersed in poly(methyl methacrylate). By slowing down reshaping at elevated temperature, polymer thin film devices that heat during use (e.g., polarization dependent filters) can exhibit a longer lifetime. V
Journal of Nanomaterials, 2013
Incorporating nanoscale materials into suitable matrices is an effective route to produce nanocomposites with unique properties for practical applications. Due to the flexibility in precursor atomization and delivery, aerosol-assisted chemical vapour deposition (AACVD) process is a promising way to synthesize desired nanocomposite coatings incorporating with preformed nanoscale materials. The presence of nanoscale materials in AACVD process would significantly influence deposition mechanism and thus affect microstructure and properties of the nanocomposites. In the present work, inorganic fullerene-like tungsten disulfide (IF-WS2) has been codeposited with Cr2O3coatings using AACVD. In order to understand the codeposition process for the nanocomposite coatings, chemical reactions of the precursor and the deposition mechanism have been studied. The correlation between microstructure of the nanocomposite coatings and the codeposition mechanism in the AACVD process has been investigate...
Differential dynamic microscopy to measure the translational diffusion coefficient of nanorods
Journal of Physics: Condensed Matter, 2019
We explore differential dynamic microscopy (DDM) as a low angle scattering technique to determine the translational diffusion coefficients of gold rod shaped nanoparticles. The method is tested using five differently sized nanorods, and compared with results obtained from polarized dynamic light scattering. For the rods studied here, the method of DDM may be a more robust technique as obtaining the translational diffusion coefficient is more straightforward. Results obtained from DDM are then used as an input to fitting depolarized dynamic light scattering data for the determination of the rotational diffusion coefficient. The measured diffusion coefficients are compared with theoretical predictions based on rod sizes.
Soft Matter, 2021
Probing the rotational and translational diffusion and colloidal stability of nanorods is of significant fundamental interest with implications for many different applications. Recently R. Nixon-Luke and G. Bryant presented a method to analyze angle-dependent depolarized dynamic light scattering data allowing for the clear separation of the translational and rotational diffusion coefficients of gold nanorods in dilute suspension (R. Nixon-Luke and G. Bryant, Part. Part. Syst. Charact., 2018, 36, 1800388). In the present work we applied this analysis to gold nanorods decorated with high molecular weight, thermoresponsive poly-Nisopropylacrylamide ligands, which results in particles with lower effective aspect ratios. The temperature response of the ligand shell is studied. We precisely determine the translational and rotational diffusion coefficients over a broad range of temperatures and the results are compared to theoretical predictions. The results show that as temperature increases the ligands collapse, and the effective aspect ratio increases as the particle shape transitions from prolate spheroid at low temperatures to more cylindrical at high temperatures.
Microchimica Acta, 2017
The authors report on a robust method for the synthesis of gold nanorods (AuNRs) with tunable dimensions and longitudinal surface plasmon resonance. The method relies on seed-mediated particle growth in the presence of benzalkonium chloride (BAC) in place of the widely used surfactant cetyltrimethyl ammonium bromide (CTAB). Uniform AuNRs were obtained by particle growth in solution, and BAC is found to stabilize the AuNRs for >1 year. The SERS activity of the resulting AuNRs is essentially identical to that of CTAB-protected nanorods. The SERS activity of the BAC protected nanorods was applied to the quantitative analysis of potato virus X (PVX). The calibration plot for PVX is linear in the 10 to 750 ng⋅mL -1 concentration range, and the detection limit is 2.2 ng⋅mL -1 .
Chemical Communications, 2020
We gratefully acknowledge the Israel Energy Department for the financial support (grant no. 2028438). Experimental Section Chemicals. All chemicals were used as received. PdCl 2 (7647-10-1) was purchased from Strem Chemicals. Isopropyl-beta-D-thiogalactopyranoside (IPTG) and Kanamycin sulfate were purchased from Sigma-Aldrich. NaBH 4 (16940-66-2), yeast extract and tryptone were bought from Merck. Analytical grade chemicals such as HCl and NaOH were purchased from Bio-Lab Chemicals. Restriction and ligation enzymes and PCR reagents were purchased from New England BioLabs. DNA extraction and isolation of plasmids kits were purchased from MACHEREY-NAGEL. Bacterial strain cultivation. Bacterial cells were grown in Luria-Bertani (LB) broth (tryptone, yeast extract, NaCl [10, 5, and 5 g/liter, respectively]) at 37°C unless mentioned otherwise. Kanamycin (50 mg/liter) was added when needed. A single colony of the E. coli BL21 (DE3) containing the plasmid described above was inoculated into 5ml of LB media. The cells were grown at 37°C overnight with shaking at 1800 rpm. The next morning the overnight culture was transferred into 50ml and later into 500ml fresh medium to permit exponential growth. When the OD 600 value reached ~0.6, protein expression was induced by addition of 0.1 mM IPTG, followed by prolonged growth at either 23°C. Cells were then harvested by centrifugation at 4,500 rpm for 35min and resuspended in phosphate buffer (PB) 10mM pH=7.4. Protein Purification. The Precipitated cells were resuspended with an additional solution of fresh 20 mL PB. The lysis was performed using a Qsonica Q500-500W sonicator (Lumitron), 5 sec on, 5 sec off cycles for 20 min total time on. (1/2" probe, 40% amplitude). The cell lysate was then centrifuged twice for 20 min (10,000 rpm, 4C). The protein was purified using immobilized metal affinity chromatography (1 mL, High-affinity Ni-NTA resin, GenScript), when the supernatant was loaded on the affinity Ni-charged resin. The column was washed with 15 column volumes of wash buffer (0.1M PB, 500mM NaCl, 50mM imidazole, pH 7.4) to remove any loosely bonded proteins. Afterwards, the 6His-SP1 was eluted using 3 column volumes of elution buffer (0.1M PB, 500mM NaCl, 500mM imidazole, pH 7.4). In order to remove excess imidazole, the eluted 6His-SP1 solution was dialyzed overnight in dialysis membrane (MWCO 12-14kDa, REPLIGEN) and filtered using a 30kDa centrifuge filter (Amicon Ultra-4, Mercury) at 4,200 rpm for 20 min and 4C, then 6His-SP1 was resuspended in 0.1M
Mikrochimica Acta, 2022
The cornerstone of nanomaterial-based sensing systems is the synthesis of nanoparticles with appropriate surface functionalization that ensures their stability and determines their reactivity with organic or inorganic analytes. To accomplish these requirements, various compounds are used as additives or growth factors to regulate the properties of the synthesized nanoparticles and their reactivity with the target analytes. A different rationale is to use the target analytes as additives or growth agents to control the formation and properties of nanoparticles. The main difference is that the analyte recognition event occurs before or during the formation of nanoparticles and it is based on the reactivity of the analytes with the precursor materials of the nanoparticles (e.g., metal ions, reducing agents, and coatings). The transition from the ionic (or molecular) state of the precursor materials to ordered nanostructured assemblies is used for sensing and signal transduction for the qualitative detection and the quantitative determination of the target analytes, respectively. This review focuses on assays that are based on analyte-mediated regulation of nanoparticles' formation and differentiate them from standard nanoparticlebased assays which rely on pre-synthesized nanoparticles. Firstly, the principles of analyte-mediated nanomaterial sensors are described and then they are discussed with emphasis on the sensing strategies, the signal transduction mechanisms, and their applications. Finally, the main advantages, as well as the limitations of this approach, are discussed and compared with assays that rely on pre-synthesized nanoparticles in order to highlight the major advances accomplished with this type of nano-sensors and elucidate challenges and opportunities for further evolving new nano-sensing strategies. Analyte-mediated nanoparticle formation • Seeding growth • Enzyme-induced growth • Chemical sensors and biosensors Abbreviations * Dimosthenis L. Giokas
Spectrally-selective gold nanorod coatings for window glass
Gold Bulletin, 2006
The unique optical properties of gold nanorods, which exhibit tuneable absorption as a function of their aspect ratio, suggest that they might have potential applications in coatings for solar control on windows. Here we explore the properties of coatings produced by attaching gold nanorods to the surface of glass. Such coatings can attenuate solar radiation effectively, even at very low gold contents, but the figure-of-merit, T vis /T sol , of our experimental coatings was close to unity, indicating that they are not spectrally selective, However, calculations are presented to show how coatings comprised of a blend of rods with aspect ratios of greater than 3 can produce coatings with T vis /T sol of up to at least 1.4. The maximum value possible for perfectly spectrallyselective coating in sunlight is 2.08. Unfortunately, the practical realization of such coatings requires the further development of reliable methods to scale up the production of gold nanorods of longer aspect ratios.
Catalysts, 2021
In this study the catalytic activity of different gold and bimetallic nanoparticle solutions towards the reduction of methylene blue by sodium borohydride as a model reaction is investigated. By utilizing differently shaped gold nanoparticles, i.e., spheres, cubes, prisms and rods as well as bimetallic gold-palladium and gold-platinum core-shell nanorods, we evaluate the effect of the catalyst surface area as available gold surface area, the shape of the nanoparticles and the impact of added secondary metals in case of bimetallic nanorods. We track the reaction by UV/Vis measurements in the range of 190-850 nm every 60 s. It is assumed that the gold nanoparticles do not only act as a unit transferring electrons from sodium borohydride towards methylene blue but can promote the electron transfer upon plasmonic excitation. By testing different particle shapes, we could indeed demonstrate an effect of the particle shape by excluding the impact of surface area and/or surface ligands. All nanoparticle solutions showed a higher methylene blue turnover than their reference, whereby gold nanoprisms exhibited 100% turnover as no further methylene blue absorption peak was detected. The reaction rate constant k was also determined and revealed overall quicker reactions when gold or bimetallic nanoparticles were added as a catalyst, and again these were highest for nanoprisms. Furthermore, when comparing gold and bimetallic nanorods, it could be shown that through the addition of the catalytically active second metal platinum or palladium, the dye turnover was accelerated and degradation rate constants were higher compared to those of pure gold nanorods. The results explore the catalytic activity of nanoparticles, and assist in exploring further catalytic applications.