Kinetic study of gold nanoparticles synthesized in the presence of chitosan and citric acid (original) (raw)
Related papers
Improving the performance of chitosan in the synthesis and stabilization of gold nanoparticles
European Polymer Journal, 2015
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.
Biomacromolecules, 2011
This work describes a simple synthetic route to induce chitosan (CHI) gelation by the in situ formation of gold nanoparticles (AuNPs). AuNPs were obtained by thermal treatment (e.g., 40 and 80°C) of CHI aqueous solutions containing HAuCl 4 and in the absence of further reducing agents. The CHI hydrogels resulting after AuNP formation were submitted to unidirectional freezing and subsequent freeze-drying via ISISA (ice-segregation-induced selfassembly) process for the preparation of CHI scaffolds. The study of AuNP-CHI scaffolds by SEM and confocal fluorescence microscopy revealed a morphological structure characteristic of the hydrogel nature of the samples subjected to the ISISA process. Interestingly, not only the morphology but also the dissolution and swelling degree of the resulting CHI scaffolds were strongly influenced by the strength of the hydrogels obtained by the in situ formation of AuNP. We have also studied the catalytic activity AuNP-CHI scaffolds in the reduction of p-nitrophenol. The negligible dissolution and low swelling degree obtained in certain AuNP-CHI scaffolds allowed them to be used for more than four cycles with full preservation of the reaction kinetics.
The Scientific World Journal, 2014
Gold nanoparticles (AuNPs) had been synthesized with various molarities and weights of reducing agent, monosodium glutamate (MSG), and stabilizer chitosan, respectively. The significance of chitosan as stabilizer was distinguished through transmission electron microscopy (TEM) images and UV-Vis absorption spectra in which the interparticles distance increases whilst retaining the surface plasmon resonance (SPR) characteristics peak. The most stable AuNPs occurred for composition with the lowest (1 g) weight of chitosan. AuNPs capped with chitosan size stayed small after 1 month aging compared to bare AuNPs. The ability of chitosan capped AuNPs to uptake analyte was studied by employing amorphous carbon nanotubes (-CNT), copper oxide (Cu 2 O), and zinc sulphate (ZnSO 4) as the target material. The absorption spectra showed dramatic intensity increased and red shifted once the analyte was added to the chitosan capped AuNPs.
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.
International Journal of Biological Macromolecules, 2016
Here we report "green" synthesis of gold nanoparticles in solutions of heterocyclic chitosan derivatives (N-(4-imidazolyl)methylchitosan (IMC), N-2-(2-pyridyl)ethylchitosan (2-PEC), and N-2-(4pyridyl)ethylchitosan (4-PEC)) and show how efficiency of Au(III) binding to polymer influences the Au(III) reduction rate and the size of the gold nanoparticles formed using only the reducing power of these chitosan derivatives. Rheology measurements and 1 H NMR spectroscopy data have confirmed that cleavage of glycoside bond is a common mechanism of reducing species generation in solutions of chitosan and its N-heterocyclic derivatives. However, the emerging additional reducing species in 2-PEC and 4-PEC solutions due to vinylpyridine elimination promotes Au(III) reduction and gold nanoparticles growth despite lower efficiency of glycoside bond cleavage in pyridyl derivatives. The decrease of the average size of gold nanoparticles in the row chitosan>2-PEC>IMC supported assumption that the increase of ligand nucleophilicity and stability of Au(III)-polymer complex results in formation of smaller nanoparticles.
Surface Modification of Citrate-Reduced Colloidal Gold Nanoparticles With 2-Mercaptosuccinic Acid
Langmuir, 2003
Surface modification of citrate-reduced gold nanoparticles with 2-mercaptosuccinic acid (MSA) was carried out in the aqueous phase. This provides a way to obtain carboxylic acid functionalized gold nanoparticles with diameter above 10 nm. The influence of the protecting MSA layer on the behavior of the modified gold nanoparticles in comparison with that of the traditional citrate-reduced gold colloid was evaluated by HCl titration, cyanide etching, and seeded growth tests. The modified gold nanoparticles show an improved stability against pH changes and cyanide etching. They do show further growth, which appears to be more homogeneous than for the unmodified particles. Wingate, J. E.; Zhong, C. J.; Harris, J. E.; Vachet, R. W.; Clark, M. R.; Londono, J. D.; Green, S. J.; Stokes, J. J.; Wignall, G. D.; Glish, G. L.; Porter, M. D.; Evans, N.
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.
Optimizing a Novel Method for Synthesizing Gold Nanoparticles: Biophysical Studies
Journal of Cancer Science & Therapy, 2012
The properties of Gold Nanoparticles (GNPs) make them useful for cancer therapy, diagnostics and imaging. For the application of GNPs in therapy and drug delivery there is a great necessity to synthesize known particle size of GNPs with simple methods. This study aimed to optimize a novel simple method for synthesizing GNPs.
ACS applied materials & interfaces, 2017
A "green" two-step methodology to prepare biobased gold-chitosan nanocomposite films using chitosan and AuCl4(-) as a stabilizer and precursor, respectively, is reported. The biobased nanocomposites were prepared in situ by a wet chemical reduction method. Effects of hydrazine and l-ascorbic acid as different strength reducing agents on the characteristics of gold nanoparticles were observed. In addition, the performance of these nanocomposite films as catalytic materials was assessed. The relevance of this work underlies that the catalytic activity, conversion degree and order of the reaction of the 4-nitrophenol-sodium borohydride (4NP-NaBH4) reduction system depend on the size distribution, content and mainly to the location of gold nanoparticles in the nanocomposite films. Finally, the potential recyclability of these nanocomposite films as catalytic materials was studied.