Preparation and stabilization of monodisperse colloidal gold by reduction with aminodextran (original) (raw)

A Simple and Green Method for Synthesis of Ag and Au Nanoparticles using Biopolymers and Sugars as Reducing Agent

MRS Proceedings, 2012

In this work we study the effect of different reducing agent (chitosan, starch and sugars) on to synthesis of silver (AgNPs) and gold (AuNPs) nanoparticles by reduction of silver nitrate (AgNO 3 ) and chloroauric acid (HAuCl 4 ), respectively. The plasmon absorption peak between 419 -434 nm, measured using a UV-Vis spectrophotometer indicates the existence of AgNPs, this reaction was favored by the increase of temperature with optimal results at 90°C. Synthesis of AuNPs was only obtained using chitosan as reducing agent, the use of solutions of starch and sugars allows the reduction of the gold salt present in the chloroauric acid, however the low pH of the solutions creates thermodynamic instabilities for the AuNP synthesis, due to low repulsive force for colloid stability.

“Sweet” gold nanoparticles with oligosaccharide-modified poly(ethyleneimine)

Colloid and Polymer Science, 2008

This paper is focused on the use of oligosaccharidemodified hyperbranched poly(ethyleneimines) (PEI) as reducing and stabilizing agent for the formation of gold nanoparticles. The results show that the secondary amino groups of the PEI as linear units are responsible for the reduction process, and the primary amino groups as terminal units are of relevance for the particle stabilization. With regard to the final size and shape of the gold nanoparticles formed, the amount and type (maltose or maltotriose) of oligosaccharide units and structural parameters of the PEI samples are of importance. The smallest particle size of about 2 nm is obtained from a maltose-modified PEI with an excess of linear units. The size and shape of the polymer-stabilized nanoparticles can be further tuned by changing the solute concentration, the time of heating, as well as the pH value.

Preparation and stability of gold nanoparticles

In the present study a prechosen size of gold nanoparticles prepared by chemical reduction method and has been found to be highly stable under a range of different experimental conditions explored. The gold nanoparticles have been characterized by UV–vis spectroscopy and transmission electron microscopy. The stability of citrate stabilized gold nanoparticles has been investigated as a function of pH by UV–visible absorption spectroscopy and Zeta-potentiometer and has shown good stability over the experimental methods adopted.

Size-Controlled Synthesis of Gold Nanoparticles via High-Temperature Reduction

Langmuir, 2004

Gold nanoparticles having prechosen size ranging from 5 to 110 nm have been prepared in two steps. Firstly, small spherical particles (seed) of average diameters between 5 and 20 nm were prepared by varying the ratio of gold ion concentration to stabilizer/reductant, TX-100 concentration and using UV irradiation. Secondly, 20-110 nm particles were formed by a non-iterative seed-mediated growth where small particles produced by the above irradiation technique were exploited as seeds and fresh Au(III) ions were reduced onto the surface on the seed particles by ascorbic acid. The kinetics of particle formation has also been reported. These methods were fast and showed improved monodispersity sphericity and excellent reproducibility.

Influence of Gold Content on Colloidal Structure of Gold Nanoparticles Capped with Arabinogalactan

article, 2011

We studied the nanobiocomposites obtained by reduction of gold ions with water-soluble polysaccharide arabinogalactan. The influence of the gold content on the structure of the nanocomposite colloids was investigated. The size of gold nanoparticles (AuNPs) determined by transmission electron microscopy (TEM) was found to increase with the gold content in accord with the Ostwald ripening theory. Simultaneously, the anisotropic self-assembly of AuNPs, observed by TEM and extinction spectroscopy, increased due to the oriented attachment of AuNPs. The AuNP dimers were found to be mainly responsible for both scattered light depolarization and bimodal correlation time distributions determined by dynamic light scattering (DLS). Rotational and translational diffusion coefficients obtained by DLS corresponded to the spherical form of the colloids. Comparison of colloidal hydrodynamic radii and the radii of AuNPs showed that the colloidal shell was composed from the monolayer of arabinogalactan macromolecules

Synthesis and Stabilization of Gold Nanoparticles Using Water-Soluble Synthetic and Natural Polymers

Polymers

Gold nanoparticles (AuNPs) were synthesized and stabilized using the one-pot method and growth seeding, through utilization of synthetic polymers, including poly(N-vinylpyrrolidone) (PVP), poly(ethylene glycol) (PEG), and poly(vinylcaprolactame) (PVCL), as well as natural polysaccharides, including gellan, welan, pectin, and κ-carrageenan. The absorption spectra, average hydrodynamic size, ζ-potential, and morphology of the gold nanoparticles were evaluated based on various factors, such as polymer concentration, molecular mass of polymers, temperature, and storage time. The optimal polymer concentration for stabilization of AuNPs was found to be 4.0 wt % for PVP, 0.5 wt % for gellan, and 0.2 wt % for pectin, welan, and κ-carrageenan. The values of the ζ-potential of polymer-stabilized AuNPs show that their surfaces are negatively charged. Most of the AuNPs are polydisperse particles, though very monodisperse AuNPs were detected in the presence of a 0.5 wt % gellan solution. At a co...

A Facile pH Controlled Citrate-Based Reduction Method for Gold Nanoparticle Synthesis at Room Temperature

Nanoscale research letters, 2016

The synthesis of gold nanoparticles using citrate reduction process has been revisited. A simplified room temperature approach to standard Turkevich synthesis is employed to obtain fairly monodisperse gold nanoparticles. The role of initial pH alongside the concentration ratio of reactants is explored for the size control of Au nanoparticles. The particle size distribution has been investigated using UV-vis spectroscopy and transmission electron microscope (TEM). At optimal pH of 5, gold nanoparticles obtained are highly monodisperse and spherical in shape and have narrower size distribution (sharp surface plasmon at 520 nm). For other pH conditions, particles are non-uniform and polydisperse, showing a red-shift in plasmon peak due to aggregation and large particle size distribution. The room temperature approach results in highly stable "colloidal" suspension of gold nanoparticles. The stability test through absorption spectroscopy indicates no sign of aggregation for a ...

Comparative Study on Methods for Preparation of Gold Nanoparticles

Green and Sustainable Chemistry, 2012

The gold nanoparticles were prepared in many methods, differed in reducing and dispersion agents and stability. The first solution was prepared by using potassium bitartrate as reducing agent and Polyethylene glycol as a dispersion factor. We got a solution of colloid gold with wine-red color that has been measured the particle size; it was between 50-200 nanometers. The second gold colloidal solution was prepared by using sodium citrate as a reducing agent and without adding a dispersion agent, the color of the final solution is dark grey, but this solution did not remain stable, deposition happened quickly and crystals separated from the solution. The third one was prepared by using sodium citrate as a reducing agent and the solution was heated to a certain temperature, and the color of the solution became dark red after several minutes. Either the fourth method has been prepared gold colloid solution by using potassium bitartrate as a reductant for the gold ion. We have noted that no reaction under normal conditions, while the reaction by heating the solution to high temperature, and when added poly vinyl pyrrolidone will lead to a solution of colloild gold with dark purple-red color and stable under normal conditions for a long time. We measured the particles size in this experiment; it was less than 100 nanometers. We conclude from the above that all the reducing agent needs to appropriate conditions to complete the process of reduction of gold ion, and to get the nano gold particles, therefore; these particles in the colloid solution need to dispersion factor to the survival of the particles widespread so that the solutions with certain concentrations of poly vinyl pyrrolidone can be proven in the process of stability of the gold colloid solution.

Design of Polymeric Stabilizers for Size-Controlled Synthesis of Monodisperse Gold Nanoparticles in Water

Langmuir, 2007

A new methodology is described for the one-step aqueous preparation of highly monodisperse gold nanoparticles with diameters below 5 nm using thioether-and thiol-functionalized polymer ligands. The particle size and size distribution was controlled by subtle variation of the polymer structure. It was shown that poly(acrylic acid) (PAA) and poly(methacrylic acid) (PMAA) were the most effective stabilizing polymers in the group studied and that relatively low molar mass ligands (∼2500 g/mol) gave rise to the narrowest particle size distributions. Particle uniformity and colloidal stability to changes in ionic strength and pH were strongly affected by the hydrophobicity of the ligand end group. "Multidentate" thiol-terminated ligands were produced by employing dithiols and tetrathiols as chaintransfer agents, and these ligands gave rise to particles with unprecedented control over particle size and enhanced colloidal stability. It was found throughout that dynamic light scattering (DLS) is a very useful corroboratory technique for characterization of these gold nanoparticles in addition to optical spectroscopy and TEM.