Continuous synthesis of functional silver nanoparticles using microreactor: Effect of surfactant and process parameters (original) (raw)
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Materials
The size of silver nanoparticles plays a crucial role in their ultimate application in the medical and industrial fields, as their efficacy is enhanced by decreasing dimensions. This study presents two chemical synthesis procedures for obtaining silver particles and compares the results to a commercially available Ag-based product. The first procedure involves laboratory-based chemical reduction using D-glucose (C6H12O6) and NaOH as reducing agents, while the second approach utilizes trisodium citrate dehydrate (C6H5Na3O7·2H2O, TSC). The Ag nanoparticle suspensions were examined using FT-IR and UV-VIS spectroscopy, which indicated the formation of Ag particles. The dimensional properties were investigated using Atomic Force Microscopy (AFM) and confirmed by Dynamic Light Scattering (DLS). The results showed particle size from microparticles to nanoparticles, with a particle size of approximately 60 nm observed for the laboratory-based TSC synthesis approach.
Preparation of silver nanoparticles with controlled particle size
Procedia Chemistry, 2009
Silver colloids show different colors due to light absorption and scattering in the visible region based on plasmon resonance. The resonance wavelength depends on particle size and shape. Here we report chemical reduction methods for preparation of silver nanoparticles exhibiting multicolor in aqueous solutions. Depending on chemical conditions the obtained nanoparticles are differen In order to investigate the relationship between size, stability and color of silver colloids we obtained silver nanoparticles in aqueous solutions using different reducing agents. The effect of polyvinyl pyrrolidone (PVP) and polyvinyl alcohol (PVA) on stabilization of obtained silver colloids was investigated. We have also studied the effect of silver precursor and its concentration on the formation of stable silver colloids. UV-VIS spectrum for silver colloids contains a strong plasmon band near 410 nm, which confirms silver ions reduction to Ag° in the aqueous phase. The formation of metal silver was also confirmed by powder X-ray diffraction (XRD) analysis. The diameter size of silver nanoparticles was in the range from 5 nm to 100 nm
Size-Controlled Synthesis of Colloidal Silver Nanoparticles Based on Mechanistic Understanding
Chemistry of Materials, 2013
Metal nanoparticles have attracted much attention due to their unique properties. Size control provides an effective key to an accurate adjustment of colloidal properties. The common approach to size control is testing different sets of parameters via trial and error. The actual particle growth mechanisms, and in particular the influences of synthesis parameters on the growth process, remain a black box. As a result, precise size control is rarely achieved for most metal nanoparticles. This contribution presents an approach to size control that is based on mechanistic knowledge. It is exemplified for a common silver nanoparticle synthesis, namely, the reduction of AgClO 4 with NaBH 4 . Conducting this approach allowed a well-directed modification of this synthesis that enables, for the first time, the size-controlled production of silver nanoparticles 4−8 nm in radius without addition of any stabilization agent.
Molecular insights into sodium dodecyl sulphate mediated control of size for silver nanoparticles
Journal of Molecular Liquids, 2019
A specific condition directing the formation of silver nanoparticles (AgNPs) with narrow size-distribution in aqueous sodium dodecyl sulphate (SDS) solutions, using trisodium citrate (TSC) is investigated. The peculiar control in distribution of size for AgNPs in presence of 35 mM (~1 wt%) aqueous SDS solution as stabilizing agent is evident. Water penetration through packed PTFE powder and dynamic surface tension measurements demonstrate formation of stable aggregates at the given condition and accordingly reduced numbers of free SDS monomers diffusing to the growing AgNP interface. The smaller size of AgNPs was also confirmed by TEM images, which illustrates mixed morphologies for the nanoparticles in an aggregated state. The NMR experiments reveal strong hydrophobic interactions between the alkyl chains of SDS molecules adsorbed on AgNPs. These results also indicate that TSC is molecularly distributed in bulk phase without binding to the SDS micellar aggregates. A plausible molecular mechanism is proposed based on diffusion of Ag + ions to the growing AgNP surface along with SDS monomers and submicellar aggregates, subsequently forming bigger size AgNPs. The narrow distribution of size for AgNP in presence of 35 mM SDS is arguably driven by the capping of stable SDS micelles or monomers around growing nuclei and restricted number of SDS monomers and submicellar aggregates responsible for supply of Ag + at the growing AgNP nuclei.
Establishment of optimum conditions for preparation of silver nanoparticles
Silver nanoparticles (AgNPs) with tailored characteristics are prepared using carboxymethyl chitosan (CMCs) which plays a dual role ; as a reducing agent for conversion of Ag + to Ag o and as a stabilizing agent to prevent aggregation of Ag o and / or its clusters. The preparation involves a thorough investigation into factors affecting formation of AgNPs characteristics and dependence of them on these factors. Factors studied encompass concentrations of silver nitrate and CMCs as well as pH, time and temperature of the synthesizing medium. Sophisticated tools such as FT-IR, UV-vis spectral analyses and TEM reveal major characteristics of AgNPs formed as well as size, distribution and shape of AgNPs. According to current work, the most appropriate condition of converting silver ions into AgNPs are 0.25% solution of CMCs and 6ml of 0.1N AgNO3 (0.102 g / 100 ml) and carrying out the reaction at 70 o C for 45 min at pH 11. 22
Single step morphology-controlled synthesis of silver nanoparticles
Silver nanoparticles having different size and plasmon resonances were synthesized through a single step aqueous based method. The current procedure was based on the reduction of silver ions by ascorbic acid in the presence of sodiumborohydride and trisodium citrate. Triangular colloidal nanoparticles having different plasmon resonances (and hence different size and colours) were synthesized by varying only the concentration of ascorbic acid. These nanoparticles were found to be stable without using any surfactants or polymers. This study revealed a strong correlation between particle growth and concentration of constituent chemicals. Crystallinity and phase purity of the silver samples were investigated through powder X-ray diffraction studies (XRD). Absorption spectra of various silver particles were recorded using UV/Vis/NIR spectrometer. Morphological analysis was performed using transmission electron microscopy (TEM) and average edge lengths of nanoparticles were also calculated.
Synthesis and applications of silver nanoparticles
Over the past few decades, nanoparticles of noble metals such as silver exhibited significantly distinct physical, chemical and biological properties from their bulk counterparts. Nano-size particles of less than 100 nm in diameter are currently attracting increasing attention for the wide range of new applications in various fields of industry. Such powders can exhibit properties that differ substantially from those of bulk materials, as a result of small particle dimension, high surface area, quantum confinement and other effects. Most of the unique properties of nanoparticles require not only the particles to be of nano-sized, but also the particles be dispersed without agglomeration. Discoveries in the past decade have clearly demonstrated that the electromagnetic, optical and catalytic properties of silver nanoparticles are strongly influenced by shape, size and size distribution, which are often varied by varying the synthetic methods, reducing agents and stabilizers. Accordingly, this review presents different methods of preparation silver nanoparticles and application of these nanoparticles in different fields.
Influence of Reagents on the Synthesis Process and Shape of Silver Nanoparticles
Materials
The aim of this study was to prepare the silver nanoparticles (AgNPs) via chemical reduction and analyze the impact of used reduction agents: sodium borohydride (NaBH4), trisodium citrate (TSC), polyvinylpyrrolidone (PVP), and hydrogen peroxide (H2O2) on the reduction rate of Ag+ ions to Ag0, and on nanoparticles shape. It was proven that combinations of reduction agents dramatically influence the synthesis rate of AgNPs and the color of solutions, which depends on the shape and size of nanoparticles. NaBH4, TSC, and PVP showed good reduction power. In particular, TSC proved to be a key factor influencing the shape of AgNPs. The shape of nanoparticles influences the color of colloidal solutions. Yellow solutions, where UV-vis absorbance maxima (ABSmax) are in the wavelength interval 380–420 nm, contain spherical particles with a mean size of 25 nm, whereas the blue shift of ABSmax to wavelengths higher than 750 nm indicate the presence of triangular nanoparticles (size interval 18–1...