Behaviour of silver—silver malonate and silver—silver succinate electrodes in aqueous media

The silver—silver oxalate electrode has been employed by many workers^1–3 in aqueous media as the second order reference electrode, but no work seems to have been done so far on the study of the behaviour of silver—silver malonate and silver—silver succinate electrodes. The present work deals with the study of these electrodes in ionic equilibria of malonate and succinate ions in aqueous media. These electrodes, in conjunction with a saturated calomel electrode, have been employed in the poten- tiometric determination of malonate and succinate ions in aqueous media. In additon, the effect of the added salts, such as, potassium nitrate and sucrose on the behaviour of these electrodes has also been examined in this media.     

Gravimetric determination of silver as silver chromate

Summary Gravimetric estimation of silver, based upon its quantitative precipitation as normal silver chromate, Ag₂CrO₄, is described.     

Recovery of silver from silver chloride residues

A new chemical process for recovering silver metal from waste silver chloride residues is described. The silver chloride is digested in an oxidizing mixture before complexation with ammonia. High-purity free silver metal is precipitated from solution by the addition of ascorbic acid as the reducing agent.     

Perfluorocarbon-stabilized silver nanoparticles manufactured from layered silver carboxylates

Perfluorocarboxylate-stabilized silver nanoparticles have been prepared uniformly via the thermal decomposition of layered silver perfluorocarboxylates (AgCO2(CF2)nCF3, n = 10, 12, 14 and 16).     

Development kinetics of silver clusters on silver halides

Silver nuclei are produced by pulse radiolysis at the surface of AgCl nanocrystallites in the presence of an electron donor, the methyl viologen, which induces the growth of silver nuclei. The experimental results observed on the increase of the silver atom concentration and on the decay of the donor concentration during this process, which is similar to the photographic development by an electron donor, are compared with the kinetics obtained from numerical simulation. The model assumes that the formation of silver clusters with a supercritical nuclearity is required before the start of an electron transfer reaction from the two reduced forms of the donor methyl viologen to the silver clusters. The reaction is controlled by the access of the donor to the surface sites of the AgCl crystallite. The rate constant values of the successive steps of the mechanism are derived from the adjustment of calculated kinetics to experimental signals under various conditions, using a single set of parameters which are fairly suitable under all conditions studied.     

Standard potentials of the silver—silver tungstate,silver—silver phosphate,and silver—silver arsenate electrodes in water—dioxane and water—urea mixtures and related thermodynamic functions

The standard potentials of the silver—silver tungstate, silver—silver phosphate and silver—silver arsenate electrodes in four different compositions of water—dioxane and water—urea mixtures at seven different temperatures from 5 to 35°C have been determined from EMF measurements of cells of the type Ag(s), AgCl(s), NaCl(c)//Na_xZ(c/x), Ag_xZ(s), Ag(s), where x is 2 or 3, and Z is WO₄, PO₄ or AsO₄. These values have been used to evaluate the transfer thermodynamic quantities accompanying the transfer of 1 g ion of WO^2?₄. PO^3?₄ or AsO^3?₄ ion from the standard state in water to the standard state in water—dioxane or water—urea mixtures.     

Preconcentration of silver as silver xanthate on activated carbon

Silver from aqueous solution was preconcentrated by adsorption on activated carbon as silver xanthate. Factors influencing the adsorption of silver have been studied. Optimum conditions for the preconcentration of silver have been established.     

Study of the silver selenide—silver telluride system

The system Ag₂TeAg₂Se was investigated by DTA, X-ray diffraction and microstructural analysis within the composition interval from 0 to 100% Ag₂Te. Samples obtained after heating at 500°C for 720 h were studied.The high-temperature polymorphs form a continuous solid solution with a minimum at 35% Ag₂ Te and 835°C. At low temperatures solid-phase transformations take place. The break-down of the solid solution proceeds eutectoidally at about 110°C on the Ag₂Te side peritectoidally at about 150°C on the Ag₂Se side. The system Ag₂TeAg₂Se is rather complex.     

Photo-induced chemical reduction of silver bromide to silver nanoparticles

This paper discusses the experimental results of the production of nanocolloidal silver using photoreduction method. Ultrafine crystalline gelatine-stabilised aqueous suspensions of silver bromide were used as a substrate for the synthesis of silver nanoparticles (Ag NPs). The influences of the reductant to substrate molar ratio, the medium’s pH, the type of the source of actinic radiation and the time of exposure to the efficient production of the Ag NPs were studied. A typical reaction was suggested, which involves the photo-induced reduction of silver bromide nanocrystals in the presence of ascorbic acid under specified physicochemical conditions. The properties of resultant silver particles were examined using UV-Vis spectroscopy and Dynamic Light Scattering (DLS). In addition, Transmission Electron Microscopy (TEM) was used for imaging the silver nanoparticle suspensions.      

Non-isothermal decomposition of silver maleate dihydrate and anhydrous silver fumarate

The non-isothermal decompositions of silver maleate dihydrate (C₄H₂O₄Ag₂2H₂O) and anhydrous silver fumarate (C₄H₂O₄Ag₂) were studied up to 500°C, in a dynamic atmosphere of air, by means of TG and DTA measurements. Both compounds showed some sublimation (at 120°C for silver maleate and at 180°C for silver fumarate) prior to the onset of decomposition (at 170°C for silver maleate and at 280°C for silver fumarate). The gaseous decomposition products of both compounds were found, using IR spectroscopy, to be dominated by maleic anhydride and CO₂. Minor proportions of ethylene, ethyl alcohol, acetone, methane and isobutene were also identified. Metallic silver was the final solid product, as identified by X-ray diffractometry. NMR analysis was used to monitor the isomerization of the maleate radical into the more stable fumarate above 230°C. Kinetic parameters (E _a and lnA) were calculated from the effect of heating rate, (2, 5, 10, and 20 deg min^?1) on the DTA measurements. A mechanism is suggested for the decomposition pathways of these compounds, on basis of the results obtained and, also, on similarities with analogous systems.     

Dithiocarbamate-capped silver nanoparticles

Nanometer-sized silver particles were synthesized by using didecylamine dithiocarbamates as the protecting ligands. With control of the initial ligand-metal feed ratios, the core diameter of the resulting particles was found to vary from about 5 to 2.5 nm, as determined by transmission electron microscopic measurements. The core size dispersity was also found to decrease with increasing feed ratio. In UV-visible spectroscopic studies, the particle surface plasmon resonance peak diminished in intensity as the particle core size decreased, whereas in electrochemical measurements, smaller sized particles gave rise to well-defined quantized charging voltammetric features, in contrast to the featureless responses with the larger particles. Such single electron-transfer behaviors were consistent with those observed in STM measurements involving individual nanoparticles. Overall, this study provides an effective approach to the synthesis of stable nanometer-sized silver nanoparticles with interesting electronic and electrochemical properties.     

Novel silver nanostructures from silver mirror reaction on reactive substrates

Novel silver clusters have been prepared by simply carrying out the silver mirror reaction on certain reactive substrates. Leaflike fractal silver microstructures and perpendicularly aligned silver nanosheets were produced on a commercially available copper foil and sandpaper-rubbed copper foil, respectively. The surface features of copper foils and the chemical state of Cu atoms play important roles in regulating the morphological structures of the resulting silver clusters. Silver nanoclusters with various morphologies ranging from the leaflike to flowerlike hierarchical structures can be produced from the silver mirror reaction on commercially available copper foils after being treated with a dilute aqueous HCl solution under different conditions. The aqueous solution of silver nanosheets shows an optical absorption spectrum with a broad light-scattering peak at about 350 nm, compared to a corresponding surface plasmon absorption band around 430 nm for silver nanoparticles from the conventional silver mirror reaction on glass.     

Solvent-adaptable silver nanoparticles

A simple and efficient way of obtaining silver nanoparticles that are dispersible both in organic and in aqueous solvents using a single capping agent is described. The silver nanoparticles are initially prepared in water in the presence of aerosol OT [sodium bis(2-ethylhexyl)-sulfosuccinate, AOT]. Thereafter, transfer of the AOT-capped silver nanoparticles to an organic phase is induced by the addition of a small amount of orthophosphoric acid during shaking of the biphasic mixture. The AOT-stabilized silver nanoparticles could be separated out from the organic phase in the form of a powder. The hydrophobic nanoparticles thus prepared are stable and are readily resuspended in a variety of other polar (including water) and nonpolar solvents without further surface treatment. The amphiphatic nature of the silver surface is brought about by a small orientational change in the AOT monolayer on the silver surface in response to the polarity of the solvent.     

Synthesis of silver (II) oxide by oxidation of silver or silver oxide by means of ozone

The oxidation by ozone of a suspension of silver or silver oxide in an aqueous solution of sodium hydroxide is described. It has been shown that the oxidation proceeds in two steps:Ag^O₃→Ag₂O^O₃→AgO.The experimental results are in good agreement with a mechanism of dissolution and precipitation. The silver (II) oxide obtained has remarkable properties of stability in alkaline solution and of reducibility to metallic silver. These special properties are probably due to the large size of the particles.     

Vibrational spectroscopy of silver perchlorate and silver trifluoromethanesulfonate solutions in acrylonitrile

Solutions of silver trifluoromethanesulfonate (“triflate”) and silver perchlorate in acrylonitrile, over a range of concentrations between 0.5 and 4 mol.kg^-1 have been analyzed by dispersive infrared and Fourier-transform Raman spectroscopy. The spectral regions studied include the solvent v(C≡N) fundamental and several anion internal modes. The silver ion solvation number in the infinite dilution limit is 3 in both systems. This number falls when the salt concentration is increased because of the ionic pairing, which is slightly more intense for silver perchlorate solutions, with a calculated spectroscopic association constant 0.23 ±0.08 kg-mol^-1. For silver triflate solutions, the spectroscopic association constant is 0.17±0.05 kg-mol^-1. In both cases, the ionic pair structure is bidentate and silver ion preserves two molecules of acrylonitrile in its first solvation shell.