Synthesis and Ultraviolet Visible Spectroscopy Studies of Chitosan Capped Gold Nanoparticles and Their Reactions with Analytes (original) (raw)
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Improving the performance of chitosan in the synthesis and stabilization of gold nanoparticles
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This work used chitosan polysaccharide and its graft copolymers with e-caprolactone and N-vinyl-2-pyrrolidone chains to synthesise and stabilise gold nanoparticles. The nanoparticle synthesis was performed directly by reaction of polymers with potassium tetrachloroaurate in an aqueous medium and it was demonstrated that the polymers can act as reducing and stabilizing agents. The modification of chitosan considerably affects the copolymer performance during the gold nanoparticle synthesis. Different synthetic parameters, such as the reaction time, temperature, concentration and polymer and metallic salt feed ratio, were assessed. The gold nanoparticles were characterised via UV-Vis spectroscopy, dynamic light scattering (DLS), transmission electron microscopy (TEM), and zeta potential. In general, using grafted chitosan improves the synthetic performance of gold nanoparticles over unmodified chitosan, which is reflected in the amount, size distribution and suspension stability of the obtained nanoparticles. These results are promising due to the potential technological applications of chitosan derivatives.
2013
The simple route of synthesizing gold nanoparticles via chemical reduction technique was implemented. The main focus of this study is to achieve enhanced properties of gold nanoparticles by regulating the process parameters of the synthesis. The correlation of the process parameters and resultant size of gold nanoparticles has been deliberated. The gold nanoparticles were reduced with monosodium glutamate (MSG) and further capped with chitosan to prevent agglomeration between particles. The samples were characterized with several characterization techniques. The TEM micrograph showed dispersed particles with narrow size distribution of capped gold nanoparticles with the most probable particles size distributed in the range of 16 to 18 nm. The most stable gold nanoparticles occurred after reduced with 100 mM of MSG and capped with 1g of chitosan where the SPR peaks were blue shifted as the concentration of reducing agent increases and decreasing pattern of FWHM was recorded. Gold nan...
Radiation Physics and Chemistry, 2019
Different chitosan aqueous solutions, i.e., conventional chitosan in acetic acid (CTS-HOAc) and non-derivatized water-soluble chitosan (WSCTS) were used as polymer templates for a green synthesis of gold nanoparticles (AuNPs) under gamma irradiation. Because of molecular template effect, the CTS-HOAc and WSCTS exhibited different performance for AuNPs synthesis under various irradiation doses and HAuCl 4 precursor concentrations. The AuNPs formation in WSCTS and CTS-HOAc were investigated through physical appearance, numerical color, surface plasmon resonance, particle morphologies and sizes, AuNPs-polymer interaction and crystal structure. Within the irradiation doses range of 0-50 kGy, the particle sizes of the spherical AuNPs formulated in the WSCTS and CTS-HOAc solutions were in the range of 5-25 nm and 5-80 nm, respectively. The particle size and amount of AuNPs can be controlled by balancing synthetic parameters. Compared with AuNPs in CTS-HOAc, the AuNPs in WSCTS exhibit lower toxicity and promote proliferation of human skin fibroblast cells. The different CTS solution systems played an important role for AuNPs formation under irradiation. WSCTS opens a green pathway for synthesis of AuNPs for further extended to appropriate biomedical and cosmeceutical applications.
Journal of Polymer Research, 2020
Quantitative detection of hydrogen peroxide (H 2 O 2) is reported by utilizing an optical sensor based on the Surface Plasmon Resonances (SPR) of Ag and Au nanoparticles embedded in chitosan, a biopolymer. Ag and Au nanoparticles, fabricated by chemical reduction approach, were incorporated individually in chitosan matrix by solution casting method. Subsequently, their presence in the host matrix was confirmed using UV-visible spectroscopy, X-Ray diffractometer (XRD), High Resolution Transmission Electron Microscopy (HRTEM) and Field Emission Scanning Electron Microscopy (FESEM) along with Energy Dispersive Analysis of X-Ray (EDAX) spectroscopy. Structural changes induced in chitosan with addition of varying concentration of Ag or Au nanoparticles were studied using Fourier transform infrared (FTIR) spectroscopy. Optical energy gap of chitosan decreased from 3.82 ± 0.28 eV to 1.84 ± 0.19 eV for Ag-chitosan nanocomposite (Nc) film containing 0.50 wt% Ag nanoparticle while to a value of 2.14 ± 0.08 eV for Au-chitosan Nc film containing 0.5 wt% of Au nanoparticle. A significant difference in position and intensity of SPR absorption band was observed as a function of variable concentration of H 2 O 2. The detection limit of these optical sensors is upto 0.3 μM concentration of H 2 O 2. Keywords Nanocomposite. Chitosan. Plasmon. Absorption. Sensor Highlights • Stable Ag-chitosan and Au-chitosan Nc films were fabricated. • Optical energy gap reduces to 1.84 ± 0.19 eV and 2.14 ± 0.08 eV for Agchitosan Nc film and Au-chitosan Nc film respectively as compared to 3.82 ± 0.28 eV for chitosan. • FTIR analysis confirms the strong interaction of Ag and Au nanoparticles with chitosan. • The detection limit of these optical sensors is upto 0.3 μM concentration of H 2 O 2 .
Green synthesis and stabilization of gold nanoparticles in chemically modified chitosan matrices
2011
Chitosan-N-2-methylhydroxypyridine-6-methylcorboxylate (Ch-PDC) and chitosan-N-2methylhydroxypyridine-6-methylhydroxy thiocarbohydrazide (Ch-PDC-Th) were synthesized for the first time using chitosan as precursor. Chitosan, Ch-PDC, Ch-PDC-Th were used in the synthesis of gold nanoparticles (AuNP) in aqueous medium. Chitosan and Ch-PDC-Th possess reducing properties which enabled the 'green' synthesis of AuNPs. The stabilization of the AuNPs was as a result of the thiocarbide (S C) and amine (NH 2 ) groups in the chitosan matrix. The modified chitosan, its derivatives and the resulting AuNPs were characterized by Fourier transform infrared (FTIR) spectroscopy, Ultraviolet-visible (UV-vis) spectroscopy, Raman scattering measurements, powder X-ray diffraction (PXRD) and thermo gravimetric analysis (TGA). Particle size, morphology, segregation and individuality of the AuNPs were examined by transmission electron microscope (TEM) and energy dispersion spectroscopy (EDS). An average AuNPs size of 20 nm was observed for chitosan and Ch-PDC-Th while Ch-PDC was 50 nm. In comparison, AuNPs resulting from Ch-PDC-Th precursor has the most enhanced Raman and fluorescent intensities and was stable for over 2 months.
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Science and Technology of Advanced Materials, 2005
We report a novel strategy for using gold nanoparticles capped with chitosan for sensing ions of heavy metals. Acidic anions (glutamate ions in our case) are expected to cap the nanoparticle surfaces similar to conventional methods of stabilization of gold nanoparticles by citrate ions. The polycationic nature of chitosan enables attachment of the polymer to the negatively charged gold nanoparticle surfaces through electrostatic interactions. Use of chitosan serves dual purpose of providing sufficient steric hindrance ensuring stability of the colloid and also to functionalize the nanoparticles for use as sensors. The well-documented chelating properties of chitosan and the sensitivity of the optical properties of gold nanoparticles to agglomeration have been employed to detect low concentrations of heavy metals ions (Zn 2C and Cu 2C ) in water. A comparison of the optical absorption spectra of the colloidal suspension before and after exposure to metal ions is a good indicator of the concentration of the heavy metal ions. q
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Advances in Natural Sciences: Nanoscience and Nanotechnology, 2014
Gold nanoparticles (Au-NPs) have been successfully synthesized by utilizing water soluble chitosan as reducing and stabilizing agent. The colloidal Au-NPs were characterized by UV-Vis spectroscopy and transmission electron microscopy (TEM). The results showed that the colloidal Au-NPs had a plasmon absorption band with maximum wavelength in the range of 520-526 nm and the diameters were about 8-15 nm. In addition, a new Au-NPs-modified electrode was fabricated by self-assembling Au-NPs to the surface of the L-cysteine-modified glassy carbon electrode (Au-NPs/L-Cys/GCE). The Au-NPs-modified electrode showed an excellent character for electro-catalytic oxidization of uric acid (UA) in 0.1 mol L −1 phosphate buffer solution (pH 3.2). Using differential pulse anodic stripping voltammetry (DP-ASV), a high selectivity for determination of UA has been explored for the Au-NPs-modified electrode. DP-ASV peak currents of UA increased linearly with their concentration at the range of 2.0 × 10 −6 to 4.0 × 10 −5 mol L −1 with the detection limit of 2.7 × 10 −6 mol L −1 for UA. The proposed method was applied for the detection of UA in human urine and serum samples with satisfactory results.
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In this work colloidal gold nanoparticles (GNPs) are prepared using a citrate-reduction route, in which citric acid serves as reductive agent for the gold precursor HAuCl4. We demonstrate that a temperature variation on the one hand enables to tune the reaction rate of GNP formation and on the other hand allows modifying the morphology of the resulting metal nanoparticles. The use of chitosan, a biocompatible and biodegradable polymer with a multitude of functional amino and hydroxyl groups, facilitates the simultaneous synthesis and surface modification of GNPs in one pot. The resulting GNPs, which are stabilized by a network of chitosan and ß-ketoglutaric acid units, are characterized by UV-vis spectroscopy, atomic force microscopy (AFM), transmission electron microscopy (TEM) as well as fluorescence correlation spectroscopy (FCS) and reveal an average diameter of about 10 nm at the end of the synthesis. The kinetics of GNP formation is studied by calculating