Reduction Rate Of Ag Research Articles

Influence of Reagents on the Synthesis Process and Shape of Silver Nanoparticles.

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 18–150 nm). A mixture of spherical, triangular, irregular, and hexagonal nanoparticles give different color, e.g., green. The formation and stability of AgNPs was tracked by UV-vis spectroscopy, size and shape by TEM techniques, and particle size distribution was studied by particle size analyzer.

Temperature-induced changes in polymer-based fractal patterns due to Ag metal aggregation

The present study throws light on the formation of silver fractal patterns when temperature treatment is given to the chitosan–AgNO3 solution for different temperatures and time periods. Temperature treatment results in both an enhanced degradation of the polymer (i.e., chitosan) and reduction rate of Ag+ ions to the silver particles. Small-sized clusters of silver particles form in the polymeric matrix, which were confirmed by ultraviolet–visible spectroscopy and scanning electron microscopy. Silver clusters aggregate giving different patterns due to the different temperature treatments. Changes in Fourier transform infrared spectra were invoked to explain the reduction of the Ag+ ions and the degradation mechanism of chitosan due to the temperature exposure. Degradation of chitosan due to temperature treatment results in a change in the viscosity. Viscosity measurements were taken by using an Ubbelohde viscometer for the chitosan–AgNO3 system as a function of storage time and temperature treatment time. A decrement in the viscosity was observed in all the cases, which confirms the degradation of chitosan both with and without complexation of salt (AgNO3). The degradation behavior of the polymer in different experimental conditions significantly modifies the aggregation patterns due to silver particles.

Synthesis of Ag Nanorods with Highly Tunable Plasmonics toward Optimal Surface‐Enhanced Raman Scattering Substrates Self‐Assembled at Interfaces

AbstractAg nanorods receive intensive attention due to the excellent plasmonic properties. However, the difficulty in synthesis of monodisperse Ag nanorods with broad aspect ratios has limited their in‐depth applications. Here, a seed‐mediated method is reported for the synthesis of Ag nanorods with lengths from 65 to 5000 nm, corresponding to aspect ratios from 2 to 156. The plasmonic resonance is tuned from visible to mid‐infrared wavelength. The synthesis protocol relies on robust Au seeds synthesized in N,N‐dimethylformamide (DMF), which induces the one‐dimensional (1D) growth of Ag atoms. To maintain symmetry breaking initiated by the Au seeds, the reduction rate of Ag+ is decreased by adding hexadecyltrimethylammonium chloride (CTAC) to form AgCl particles. The optimized conditions to prevent the homogeneous nucleation of Ag nanoparticles and residue of AgCl particles in products are identified, under which the conversion efficiency of Ag ions to Ag nanorods is evaluated about 48%. More importantly, the anisotropic Ag nanorods are self‐assembled into monolayers at interfaces with the long axis of Ag nanorods perpendicular or parallel to the interfaces, respectively. The as‐fabricated monolayers exhibit uniform and reproducible surface‐enhanced Raman scattering (SERS) activities. The optimal SERS performance is achieved from Ag nanorod monolayer with vertical orientation and the longest rod length.

Maple leaf (Acer sp.) extract mediated green process for the functionalization of ZnO powders with silver nanoparticles

The functionalization of ZnO powders with silver nanoparticles (AgNPs) through a novel maple leaf extract mediated biological process was demonstrated. Maple leaf extract was found to be a very effective bioreduction agent for the reduction of silver ions. The reduction rate of Ag+ into Ag0 was found to be much faster than other previously reported bioreduction rates and was comparable to the reduction rates obtained through chemical means. The functionalization of ZnO particles with silver nanoparticles through maple leaf extract mediated bioreduction of silver was investigated through UV–visible spectrophotometry, transmission electron microscopy (TEM), and X-ray diffraction analysis. It was found that the ZnO particles were coated with silver nanoparticles 5–20nm in diameter. The photocatalytic ability of the ZnO particles functionalized with silver nanoparticles was found to be significantly improved compared to the photocatalytic ability of the neat ZnO particles. The silver functionalized ZnO particles reached 90% degradation of the dye an hour before the neat ZnO particles.

A modified polyol process for growing Ag nanowires and nanoplates using 2-ethoxy ethanol

A modified polyol process was proposed to prepare Ag nanowires in this study. The typical reductant, ethylene glycol, was replaced with 2-ethoxy ethanol in the presence of polyvinylpyrrolidone (PVP) to grow Ag nanowires and nanoplates. The growth of Ag nanowires was monitored by the UV–Visible spectrum, which depends on the geometry-dependent surface plasmon resonances of the Ag nanowires. The crystal phase of the Ag nanostructures was identified by X-ray diffraction. Transmission electron microscopy showed that the average dimensions of the Ag nanowires were lengths of approximately 2–10 μm and diameter of 80 nm. The PVP molecules played a key role in directing the growth of the Ag nanostructures along the (111) crystal plane, and the reduction rate of Ag+ at 25 °C when 2-ethoxy ethanol was used was faster than when ethylene glycol was used, which improved the growth of the Ag nanowires. When the AgNO3-to-PVP ratio was adjusted to 2, multiple twinned particles could be observed at an initial stage of the reaction, and a higher yield of the Ag nanowires was synthesized. When the PVP drop rate was slowed, more Ag nanowires were grown. Interestingly, when the AgNO3 and PVP molecules were initially premixed, Ag nanoplates were generated, rather than nanowires, at a higher temperature in this reduction system.

Recovery of silver from silver(I)-containing solutions in bioelectrochemical reactors

A novel approach was tested for metallic silver recovery and power generation by using cathodic reduction in bioelectrochemical systems (BESs). In dual-chamber BESs (130mL volume) with acetate as electron donor on anode, both Ag+ ions and Ag(I) thiosulfate complex in catholyte were reduced on cathode. The reduction rate of Ag+ was more rapid than the Ag(I) complex as expected by energetic analysis. X-ray diffraction (XRD) analysis indicated that electrodeposits on cathodes from both catholyte were metallic silver with >91% purity. The feasibility of metallic silver recovery with the BESs was confirmed using simulated photographic wastewater and up to 95% of Ag(I) removal was achieved.

Facile shape control synthesis and optical properties of silver nanoparticles stabilized by Daxad 19 surfactant

It is known that silver (Ag) nanoparticles are attractive due to their novel and mild chemical and physical properties. In this research, anisotropic mono-dispersed silver nanoparticles are synthesized via a simple chemical reduction method and assisted by Daxad 19 surfactant. The reactant temperatures and weight ratios of the chemical constituents play a key role in controlling the hybrid shaping mechanism. The results indicate that the reduction rate of Ag + to Ag 0 nanoparticles is enhanced significantly with increasing weight ratios of Daxad 19 and AgNO 3 under controlled reactant temperature. The results show that the as-prepared silver nanoparticles are well-dispersed and uniform in size and shape. The dimensions of the particles are easily controlled. A comparison between experimental absorbance UV–visible spectra and simulated spectra from Mie's Scattering Theory is carried out. It is observed that the simulated spectrum confirms well with the optical behaviour of the experimental spectra.

In situ time-resolved XAFS analysis of silver particle formation by photoreduction in polymer solutions

Formation mechanisms of silver (Ag) particles in an aqueous ethanol solution of poly( N-vinyl-2-pyrrolidone) (PVP) by the photoreduction of AgClO 4 were investigated by using UV–Vis, transmission electron microscopy (TEM), extended X-ray absorption fine structure (XAFS), and in situ energy-dispersive X-ray absorption fine structure (in situ DXAFS) measurements. The average diameter of the Ag particles prepared in the presence and absence of benzoin as a photo-activator was estimated from TEM to be 7.4 and 5.1 nm, respectively, and their particle size distributions ranged from 2 to 15 nm. XAFS analysis indicated that metallic Ag particles were synthesized, and the reduction rate of Ag + to Ag 0, the creation of Ag 0–Ag 0 bonds and their particle growth by the association of Ag 0–Ag 0 was regulated by the metal concentration and the inclusion of benzoin. In situ DXAFS measurements were performed in real time to investigate the kinetics of Ag + reduction and Ag particle formation. During the induction period the reduction of Ag + to Ag 0 occurred, and subsequent nucleation and growth process concurrently proceeded after the induction period. The intermediate small Ag particles (C.N. smaller than about 4) were generated in the nucleation process, and grown up to larger particles (C.N.s equal to 4.5 ± 1.5) in the longer-duration photoreduction.