An aqueous colloidal silver solution stabilized with carbonate ions

A method has been developed for the preparation of a stable “pure” silver hydrosol containing nanoparticles with an average size of 10 nm and stabilizing carbonate ions. The method consists in the photochemical reduction of silver ions with oxalate ions, which simultaneously generate carbonate ions. Optical spectroscopy, electron microscopy, and dynamic light scattering are used to study the hydrosol     

Formation of colloidal silver nanoparticles stabilized by Na+-poly(gamma-glutamic acid)-silver nitrate complex via chemical reduction process

Macromolecular and polyanionic Na⁺–poly(γ-glutamic acid) (PGA) silver nitrate complex acted as both a metal ion provider and a particle protector to fabricate nanosized silver colloids under chemical reduction by dextrose. The formation and size of particles have been characterized from transmission electron microscopy (TEM), dynamic light scattering analysis and UV–vis spectrophotometer. The results showed that the average particle size was 17.2 ± 3.4 to 37.3 ± 5.5 nm, apparently depending on the complex concentration. It was found that the rate constant and conversion of silver nanoparticles were proportional to the concentration of PGA. The growth mechanism of nanosized silver colloid was fully discussed. In addition, the in vitro cytotoxicity evaluated by L929 fibroblasts proliferation and antibacterial activity against Gram-positive strain (methicillin-resistant S. aureus (MRSA)) and Gram-negative strain (P. aeruginosa) bacteria have been assessed.     

ESR-spectrum of silver atoms stabilized in gamma-irradiated aluminium silicate modified by nickel

ESR technique was used to study the effect of conditions chosen to prepare samples to obtain and stabilize silver atoms forming under the action of⁶⁰Co -irradiation at 77 K in aluminium silicate modified by nickel and containing silver ions. The use of¹⁰⁹Ag isotope made it possible to detect two types of silver atoms Ag_I and Ag_II in -irradiated aluminium silicate modified by nickel and containing silver ions introduced by various techniques. The parameters of the ESR-spectrum of the silver particles under study have been determined and their thermal stability has been investigated.     

Colloidal silver nanoparticles stabilized by a water-soluble triosmium cluster

Silver nanoparticles stabilized by the water soluble triosmium cluster Os₃(μ-H)(CO)₁₀S(CH₂)₁₀COO]Na were prepared by both photochemical and chemical reduction of silver nitrate. The silver nanoparticles were characterized by UV-Vis spectroscopy and high resolution TEM. The particles obtained by chemical reduction showed remarkable stability.     

Development of catalytically active silver colloid nanoparticles stabilized by dextran

Colloidal silver nanoparticles (Ag-NPs) with a mean diameter of 6.1 nm and a narrow size distribution were prepared by reduction of the correspondent metal salt with injection of NaBH(4), in the presence of dextran, and characterized by UV-vis, TEM, and DLS. The concentration of all reactants involved in the formation of the nanoparticles was optimized with the use of a new multivariate method, which revealed a significant reduction in the number of experiments when compared with the vast majority of univariate methods described in the literature. The Ag-NPs-dextran composite was able to efficiently catalyze the p-nitrophenol reduction in water by NaBH(4) with a rate constant normalized to the surface area of the nanoparticles per unit volume (k(1)) of 1.41 s(-1) m(-2) L, which is higher than values ever reported for Ag-NPs catalytic systems.     

Gamma radiation induced synthesis of gold nanoparticles in aqueous polyvinyl pyrrolidone solution and its application for hydrogen peroxide estimation

Gold nanoparticles (Au nps) have been synthesized in aqueous solution of polyvinyl pyrrolidone (PVP) by gamma radiolysis from HAuCl₄·3H₂O precursor and in presence of small concentrations of Ag⁺, 2-propanol and acetone. The effect of different experimental parameters, such as concentration of reactant, molecular weight of PVP on nanoparticle formation was studied. TEM image confirmed that spherical Au nps were formed when PVP of molecular weight 360,000 Da was used as capping agent. H₂O₂ is a reactant in the enzyme catalyzed reaction of o-phenylene diamine (o-PDA). The reaction product has a weak absorption in the yellow region of the spectrum. When this product interacts with Au nps, it leads to enhancement of the absorption peak. The nanoparticles synthesized by radiation method were used for estimation of H₂O₂. The absorbance value of this peak at λ_max was observed to change with H₂O₂ concentration, which was monitored for estimation of H₂O₂. The response is linear in the range of 2.5×10⁻⁶ mol dm⁻³ to 2×10⁻⁴ mol dm⁻³ and 1×10⁻⁷ mol dm⁻³ to 3×10⁻⁶ mol dm⁻³ H₂O₂ in two separate sets of experimental parameters with detection limit 1×10⁻⁷ mol dm⁻³.     

Photochemical synthesis of silver nanoparticles in polyvinyl alcohol matrices

Photochemical synthesis was used to obtain silver nanoparticles in a polymer matrix. The structural and optical properties of the composite material were studied by electron and IR spectroscopy, X-ray diffraction, and electron microscopy. The chemical reactions in polyvinyl alcohol in the preparation of the nanoparticles were studied.     

Synthesis and physicochemical properties of silver nanoparticles stabilized by acid gelatin

Silver nanoparticles were synthesized by the reduction of silver nitrate with sodium borohydride at widely varied concentrations of the starting reagents. A physicochemical study of the synthesized nanosystems was carried out. The stabilizing ability of acid gelatin in the systems under study was considered. The stability diagram in the coordinates initial concentration of silver nitrate-concentration of gelatin was constructed.     

Synthesis of colloidal silver nanoparticles for printed electronics

Colloidal silver particles were successfully prepared by wet chemical synthesis. The pure single phase of silver was confirmed by X-ray diffraction. Transmission electron microscope categorized that the diameters of particles were 100 and 20 nm, depending on the molecular weight of the PVP stabilizer. A schematic drawing model was used to predict the packing efficiency of 1:1 wt% of two mixtures. The mixture of silver solution was deposited as a thin solid film by a desktop inkjet printer. Scanning electron microscope showed that two different sizes of silver particles give higher densely packed structure than the film of single particle size. When a 0–20 V voltage was applied, the current density reached was 0.10 J/cm², suggesting that the silver film has potential to be applied as a cathode layer in organic light emitting diode (OLED) devices.     

Preparation of silver nanoparticles in solution from a silver salt by laser irradiation

A new method is proposed for the fabrication of a well-defined size and shape distribution of silver nanoparticles in solution; the method employs direct laser irradiation of an aqueous solution containing a silver salt and a surfactant in the absence of reducing agents.     

Influence of polyvinyl pyrrolidone on the dispersion of multi-walled carbon nanotubes in aqueous solution

The sonication-driven suspensions of multi-walled carbon nanotubes (MWNTs) were prepared using the polyvinyl pyrrolidone as a dispersant. UV-visible absorbency, surface tension, zeta potential, adsorption isotherm and transmission electron microscopy, were used to characterize the homogeneity and stability of MWNTs suspensions with different concentrations of polyvinyl pyrrolidone. All results show that the optimum concentration of polyvinyl pyrrolidone in suspension is 0.5 g/L.     

Photocatalytic synthesis of silver nanoparticles stabilized by TiO2 nanorods: a semiconductor/metal nanocomposite in homogeneous nonpolar solution

A novel colloidal approach toward semiconductor/metal nanocomposites is presented. Organic-soluble anatase TiO(2) nanorods are used for the first time to stabilize Ag nanoparticles in optically clear nonpolar solutions in the absence of specific ligands for silver. Metallic silver is generated upon UV illumination of deaerated TiO(2) solutions containing AgNO(3). The Ag nanoparticles can be obtained in different size-morphological regimes as a function of the irradiation time, due to light-induced photofragmentation and ripening processes. A mechanism for the colloidal stabilization of the silver nanoparticles is tentatively suggested, which regards the TiO(2) nanorods as inorganic stabilizers, thus acting in the same manner as conventional surfactant molecules. The proposed photocatalytic approach offers a convenient method for producing TiO(2)/Ag nanocomposite systems with a certain control over the metal particle size without the use of surfactants and/or additives. Stable colloidal TiO(2)-nanorod-stabilized Ag nanoparticles can be potentially available for a number of applications that require "clean" metal surfaces, such as homogeneous organic catalysis, photocatalysis, and sensing devices.     

Electrochemical synthesis of silver nanoparticles in solution

Silver nanoparticles in the bulk solution were obtained by the potentiostatic electrolysis in undivided cell using silver anode at the potential of the mediator reduction (tetraviologen calix[4]resorcine) at room temperature in DMF/0.1 M Bu₄NPF₆ media. The metal nanoparticles aggregate to form larger particles eventually.     

Optical absorbance of colloidal suspensions of silver polyhedral nanoparticles

The optical absorption of colloidal suspensions made of silver nanoparticles with polyhedral shapes is studied experimentally and theoretically. The influence of the shape on the optical response is investigated by comparing the measured absorbance with theoretical results for icosahedral, decahedral, and cuboctahedral silver nanoparticles. The theoretical spectra are obtained within the discrete dipole approximation. We find that colloidal suspensions of silver nanoparticles with a small dispersion of size distribution show very few structural shapes.     

Biosynthesis of silver nanoparticles by filamentous cyanobacteria from a silver(I) nitrate complex

The biosynthesis of silver nanoparticles has been successfully conducted using Plectonema boryanum UTEX 485, a filamentous cyanobacterium, reacted with aqueous AgNO3 solutions (approximately 560 mg/L Ag) at 25-100 degrees C for up to 28 days. The interaction of cyanobacteria with aqueous AgNO3 promoted the precipitation of spherical silver nanoparticles and octahedral (111) silver platelets (of up to 200 nm) in solutions. The mechanisms of silver nanoparticles via cyanobacteria could involve metabolic processes from the utilization of nitrate at 25 degrees C and also organics released from the dead cyanobacteria at 25-100 degrees C.     

Absorption spectra of large colloidal silver particles in aqueous solution

Calculations of the optical absorption spectra of spherical particles of silver with a radius (r) of 10 to 80 nm in water were performed. The single intense absorption band for small particles (r=10 nm) with a maximum at about 395 nm is gradually broadened and shifted to the long-wave region with an increase in the particle size (to 435 nm atr=40 nm). In the case of large particles, the band splits into several components absorbing light in the visible spectral region. The results are in good agreement with the optical characteristics of colloidal solutions of silver obtained upon radiochemical reduction of Ag⁺ ions in aqueous solution. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 201–203, January, 1997.     

Silver nanoparticles stabilized by crosslinked poly(vinyl pyrrolidone) and its application for facilitated olefin transport

Positively polarized silver nanoparticles by poly(vinyl pyrrolidone) (PVP) have been demonstrated for use as stable olefin carriers for facilitated olefin transport membranes. The formation and size of silver nanoparticles stabilized by PVP were monitored using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Nanocomposite membranes consisting of polymer and silver nanoparticles stabilized by PVP exhibited the high separation performance for olefin/paraffin mixtures. X-ray photoelectron spectroscopy (XPS) showed that silver nanoparticles stabilized by PVP exhibited a high positive polarity, resulting in the reversible interaction between the surface of silver nanoparticles and olefin molecules.     

Radiation-induced polymerization of isoprene in aqueous solution of silver nitrate

The rate of radiation-induced polymerization of isoprene in aqueous solution of silver nitrate is 20–50 times as fast as the rate of radiation-induced polymerization of pure isoprene. The formation of a 1:2 complex of isoprene and silver nitrate was confirmed spectrometrically, and this complex seems to polymerize by attack of an active species. The equilibrium constant K_f and the extinction coefficient E of the complex were estimated to be 0.18 and 1.4, respectively. The polymerization mechanism was concluded to be a radical one, based on the effects of inhibitors. The polyisoprene obtained had a crosslinked structure, was insoluble, and did not give a distinct melting point. The 1,2 structure was the predominant polyisoprene configuration. This was interpreted on the basis of the frontier electron density of isoprene.