Chemically Tuning the Localized Surface Plasmon Resonances of Gold Nanostructure Arrays (original) (raw)
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Mechanically Tuning the Localized Surface Plasmon Resonances of Gold Nanostructure Arrays
2012
We report the fabrication of metal nanostructures on a polydimethylsiloxane (PDMS) substrate by transferring polystyrene beads onto PDMS substrate followed by metal deposition. Experimentally tuning the plasmon resonance of the metal nanostructures was demonstrated by stretching the patterned PDMS substrate. The distance between adjacent nanodisks affects the coupling between the disks, leading to a repeatable and reversible shift in the spectrum. The device can be valuable in many applications such as bio/chemical sensing, reconfigurable optics, and the study of coupled resonances.
Geometrical effects on the surface plasmonic resonance by highly ordered Au nanostructures
Journal of Physics and Chemistry of Solids, 2018
Three differently shaped and highly ordered Au nanostructures were fabricated using an anodized aluminum oxide template and a thermal evaporator. A long-range ordered cone shape, embossed shape structure, and wave-like shape were obtained. Nanoparticles were added to the substrates with the three different shapes of ordered Au nanostructures, to verify the surface-enhanced Raman scattering by nanostructures with various shapes and gaps between structures. The simulation results showed the dependency of the Raman signal on the shape of the nanostructures, and hot-spots were found to depend largely on the distance between the structures and the wavelength of the incident light source. Thus, nanostructures can be designed to achieve various purposes by varying their shapes and the fabrication process.
Gold bulletin, 2013
Surface-enhanced Raman spectroscopy (SERS) has enormous potential for a range of applications where high sensitivity needs to be combined with good discrimination between molecular targets. However, the SERS technique has trouble finding its industrial development, as was the case with the surface plasmon resonance technology. The main reason is the difficulty to produce stable, reproducible, and highly efficient substrates for quantitative measurements. In this paper, we report a method to obtain two-dimensional regular nanopatterns of gold nanoparticles (AuNPs). The resulting patterns were evaluated by SERS. Our bottom-up strategy was divided into two steps: (a) nanopatterning of the substrate by e-beam lithography and (b) electrostatic adsorption of AuNPs on functionalized substrates. This approach enabled us to highlight the optimal conditions to obtain monolayer, rows, or ring of AuNPs, with homogeneous distribution and high density (800 AuNPs/μm 2). The nanostructure distributions on the substrates were displayed by scanning electron microscopy and atomic force microscopy images. Optical properties of our nanostructures were characterized by visible extinction spectra and by the measured enhancements of Raman scattering. Finally, we tried to demonstrate experimentally that, to observe a significant enhancement of SERS, the gold diffusers must be extremely closer. If electron beam lithography is a very attractive technique to perform reproducible SERS substrates, the realization of pattern needs a very high resolution, with distances between nanostructures probably of less than 20 nm.
Synthesis and tuning of gold nanorods with surface plasmon resonance
Optical Materials, 2017
This paper aims to achieve broad-spectrum tuning of surface plasmon resonance (SPR) with palladium nanorods. For this purpose, the finite-difference time-domain (FDTD) method was selected to simulate the optical properties of palladium nanorods. Specifically, we investigated the effects of radius, axial length, and aspect ratio of palladium nanorods on the SPR, the impacts of axial length on SPR of palladium and gold nanorods of the same size, and the influence of radius on palladium nanospheres and nanorods of the same axial length. The absorption spectra of palladium nanorods in different sizes were also analyzed. The results show that the longitudinal absorption peak of palladium nanorods can be used to tune the SPR from the visible region to the infrared region; palladium nanorods are more suitable for broad-spectrum tuning of the SPR than gold nanorods; palladium nanorods are more effective for broad-spectrum SPR tuning than palladium nanospheres; changing the size of palladium nanorods can effectively tune the SPR across a broad spectrum. The research findings shed important new light on the design of surface plasmon scales, filters, biosensors, etc.
The Journal of Physical Chemistry C, 2011
b S Supporting Information ' INTRODUCTION Some noble metal nanoparticles absorb light in the UVÀvis region when the frequency of incident photons matches the collective oscillations of the conduction band electrons of the metal, which is known as localized surface plasmon resonance (LSPR). 1À5 The result is a strong absorption band(s) or increased scattering intensity at specific wavelengths for metals like Au and Ag when monitoring the optical properties in transmission mode or reflection/dark-field mode, respectively. It is well-known that the intensity and wavelength of maximum absorbance/scattering (λ max) depends on the size, shape, and composition of the metal nanoparticles. 1,2,4,6 It also depends on the refractive index of the environment surrounding the metal. 1,4,7 If the size, shape, and composition are constant for a given nanostructure throughout an experiment, then the LSPR peak intensity and λ max are sensitive to changes in the environment, which has been exploited for sensing applications. The optical properties of a metal nanostructure functionalized with a chemical receptor change if a molecule binds to the receptor and significantly alters the refractive index of the medium directly surrounding the metal nanostructure. LSPR spectroscopy has been exploited in this way for sensing a wide variety of analytes, including metal ions, 8,9 vapor molecules, 10 polymers, 11 and biomolecules. 1,12À24 The method is especially promising for biosensing applications because it is highly sensitive, simple, low cost, and label-free. 1,17,24 Reports of LSPR sensing of biological molecules, such as DNA 20,21,23 and proteins, 1,12À19,22,24 have increased tremendously over the past few years. Englebiene and co-workers first reported on the extinction changes of Au nanoparticles in solution upon antibody binding. 25 Other examples of solution-phase measurements include biopolymer adsorption kinetics, 26 ligandprotein interactions, 27 high throughput screening of proteins, 28 pH, 29 and ascorbic acid. 29 Recently, Yu and Irudayaraj used antibody-functionalized Au nanorods of varying aspect ratio for multiplex biosensing. 30 Most of the solution examples detect proteins in the μM to nM range. There are several studies on LSPR sensing with evaporated or chemically synthesized films of metal nanostructures. Chilkoti and co-workers synthesized and assembled Au nanoparticles 17,31 and Au nanorods 15 for sensing of streptavidin. Rubinstein and co-workers evaporated discontinuous Au films for sensing of avidin and antibodies specific to IgG and hCG antigens. 14,32
Gold Nanoshells on Polystyrene Cores for Control of Surface Plasmon Resonance
Langmuir, 2005
A method is presented for synthesizing core-shell structures consisting of monodisperse polystyrene latex nanospheres as cores and gold nanoparticles as shells. Use of polystyrene spheres as the core in these structures is advantageous because they are readily available commercially in a wide range of sizes, and with dyes or other molecules doped into them. Gold nanoparticles, ranging in size from 1 to 20 nm, are prepared by reduction of a gold precursor with sodium citrate or tetrakis(hydroxymethyl)phosphonium chloride (THPC). Carboxylate-terminated polystyrene spheres are functionalized with 2-aminoethanethiol hydrochloride (AET), which forms a peptide bond with carboxylic acid groups on their surface, resulting in a thiol-terminated surface. Gold nanoparticles then bind to the thiol groups to provide up to about 50% coverage of the surface. These nanoparticles serve as seeds for growth of a continuous gold shell by reduction of additional gold precursor. The shell thickness and roughness can be controlled by the size of the nanoparticle seeds as well as by the process of their growth into a continuous shell. By variation of the relative sizes of the latex core and the thickness of the gold overlayer, the plasmon resonance of the nanoshell can be tuned to specific wavelengths across the visible and infrared range of the electromagnetic spectrum, for applications ranging from the construction of photonic crystals to biophotonics. The position and width of the plasmon resonance extinction peak are well-predicted by extended Mie scattering theory.
2012
The scientific and industrial demand for controllable thin gold (Au) film and Au nanostructures is increasing in many fields including opto-electronics, photovoltaics, MEMS devices, diagnostics, bio-molecular sensors, spectro-/microscopic surfaces and probes. In this study, a novel continuous flow electroless (CF-EL) Au plating method is developed to fabricate uniform Au thin films in ambient condition. The enhanced local mass transfer rate and continuous deposition resulting from CF-EL plating improved physical uniformity of deposited Au films and thermally transformed nanoparticles (NPs). Au films and NPs exhibited improved optical photoluminescence (PL) and surface plasmon resonance (SPR), respectively, relative to batch immersion EL (BI-EL) plating. Suggested mass transfer models of Au mole deposition are consistent with optical feature of CF-EL and BI-EL films. The prototype CF-EL plating system is upgraded an automated scalable CF-EL plating system with real-time transmission ...
Thin Solid Films, 2014
We report on a versatile method to fabricate gold nanocrown arrays on a thin gold film based on ultraviolet nanoimprint lithography and tilted evaporation technique. We realize highly ordered 2-dimensional nanocrown arrays and characterize their sizes and morphologies using scanning electron microscopy. To demonstrate an enhanced surface plasmon resonance (SPR) detection by the fabricated gold nanocrown samples, biosensing experiments are performed by measuring SPR angle shift for biotin-streptavidin interaction and bulk refractive index change of dielectric medium. We hope that the suggested plasmonic platform with a high sensitivity could be extended to a variety of biomolecular binding reactions.
High-density, uniform-sized and vertically aligned gold nanorods were grown on aluminum substrate by DC electrodeposition into modified porous anodic alumina (PAA) template. Optical reflection measurements using s-and p-polarized light showed strong surface plasmon resonances (SPRs), for both Au/PAA composites and freestanding Au nanorod arrays. By changing the aspect ratio of the Au nanorods, the angle of incidence of the polarized light, and the dielectric environment, it was possible to vary the position and the intensity of the SPR reflection minima in a reproducible and predictable manner. We successfully measured higher order transverse SPR, which proves the formation of highly uniform Au nanorods.
Plasmon resonances in near-field coupled 2D Au Nanoparticle Arrays
… 21-26, 2008, 2008
When Au nanoparticles are close proximity to each other in a regular two-dimensional array, coupling of plasmon resonances of the individual particles leads to a collective response. Such systems are of interest especially because of their potential application in analytical techniques such as Surface Enhanced Raman Spectroscopy (SERS). We used extreme ultraviolet interference lithography (EUV-IL) and a shadow evaporation technique to fabricate two-dimensional arrays of Au dots with a periodicity of 100 nm. The gap between the particles that controls the extent of coupling was varied in a range from 50 nm to below 10 nm. Optical measurements show two resonances at 520 nm and 620 nm, with the latter gaining strength as the gap is reduced. Extensive experimental theoretical investigations using a FDTD algorithm demonstrate that the low-energy resonance can be assigned as a collective surface plasmon resonance arising from the strong near-field coupling between the nanoparticles.