Aqueous Solution Of Silver Research Articles

Direct Ion Exchange Self‐Metallization: A Novel and Efficient Route for the Preparation of Double‐Surface‐Silvered Polyimide Films

AbstractSummary: Silvered polyimide films have been fabricated by direct ion exchange of a damp‐dry poly(amic acid) film with an aqueous silver solution such as silver nitrate. Thermal curing of the silver(I)‐containing films under tension leads to cycloimidization of the poly(amic acid) into polyimide with a concomitant silver(I) reduction and aggregation at both film sides to give reflective and conductive double‐surface‐silvered polyimide films. The metallized films retain the essential properties of the parent polyimide.Surface morphology of the prepared double‐surface‐silvered polyimide films.magnified imageSurface morphology of the prepared double‐surface‐silvered polyimide films.

Synthesis of silver nanoparticles with flake-like shapes

Flake-like silver nanoparticles have been synthesized in large quantity by simply aging the aqueous solution of silver and urotropine in the presence of poly-(vinylpyrrolidone) (PVP). Silver nanoflakes of different shapes from circular to polygonal could be obtained in different reaction stages. PVP molecules play an important role in the anisotropic growth of silver nanoflakes. The as-synthesized silver colloidal solution remained stable for at least 1 month. Electron diffraction analysis showed that the nanoflakes are well crystallized. The UV-VIS absorption properties have also been studied.

Photochemical deposition of SERS active silver nanoparticles on silica gel

Silver nanoparticles with an average size of nearly ∼15±3 nm were deposited onto the commercial silica gel matrix using aqueous solution of silver(I) gelatin complex. Silver(I) gelatin impregnated solid silica gel matrix has been found to produce silver particles with UV-light. The photoproduced silver nanoparticles remained very active for a long time. The surface characterization of the particles with transmission electron microscopy (TEM), energy-dispersive X-ray analysis (EDAX) and thermal analysis corroborated the presence of silver nanoparticles on silica surfaces. The resulting silver nanoparticles could easily be leached out from silica gel into an aqueous phase for indirect characterization of the nanoparticles by UV-Vis spectrophotometry. Anchoring of silver nanoparticles on silica gel helped to obtain surface enhanced Raman scattering (SERS) spectra, which was otherwise not possible in solution phase. The solid matrix served as a better catalyst for nitrophenol reduction than the simple silver nanoparticles in aqueous phase.

Studies of electrochemical quantized capacitance charging of surface ensembles of silver nanoparticles

CTAB-stabilized silver nanoparticles were synthesized by NaBH 4 reduction. The as-prepared nanoparticles can be self-assembled on 3-mercaptopropionic acid (MPA) modified gold electrode, which was supported strongly by XPS measurements. Exceptional long-term stability of the as-prepared colloidal silver aqueous solution and the desorption of silver nanoparticle ensemble on MPA after alcohol rinsing proved that these CTAB molecules adsorbed on silver core formed interdigitated bilayer structure. DPV and differential capacitance measurements were performed to characterize the as-prepared silver nanoparticle ensemble, and the interesting quantized capacitance charging behaviors were observed.

Surface‐enhanced Raman scattering of CO2 dissolved in aqueous colloidal solutions of silver and gold

AbstractThe observation of surface‐enhanced Raman scatterings (SERS) from CO2 molecules dissolved in aqueous solutions of silver and gold colloids measured with 850 nm near‐IR excitation is reported. Different types of surface enhancement and surface‐enhanced Raman spectra were observed. The SERS spectrum of CO2 on colloidal gold is in good agreement with the spectrum of CO2 dissolved in water. Two different types of SERS spectra were found for CO2 on colloidal silver. They can be assigned to physisorbed and/or weakly chemisorbed CO2 molecules and to strongly bonded CO2 ‐ negatively charged surface radicals, respectively. The enhancement factor for the stretching mode of carbon dioxide is estimated to be of the order of 102−104, depending on the kinds of metal and types of adsorption, which demonstrates that SERS on colloidal silver or gold particles in solution offers possibilities for detecting CO2 dissolved in liquids at low concentrations.

REACTION KINETICS OF POLYSTYRENE-BASED PHOSPHINIC ACID ION EXCHANGE/REDOX RESINS WITH METAL IONS

ABSTRACT The ion exchange/redox kinetics displayed by the phosphinic acid polymer with aqueous solutions of silver and mercury is presented as a function of reaction temperature (6° to 45° C) and solution pH (0 to 5). The network variables studied include the crosslink level and macroporosity. At each pH, increasing the temperature leads to a more rapid approach to equilibrium. The amount complexed at equilibrium is lowest at pH Q relative to the higher pH solutions due to increased H+ competition for ligating sites. Metal ion reduction, rather than ion exchange, is the dominant component at equilibrium. Matrix rigidity and macroporosity do not affect Ag(I) kinetics. The rate of Hg(II) sorption is much faster than for Ag(I). Macroporosity is an important variable with mercury: macroporous resins complex more than twice the amount found with gels at 15 minutes contact. It is proposed that Ag kinetics are limited by a slow redox reaction while the Hg kinetics are diffusion-limited due to a fast redox reacti...

Elektrochemische Synthese und Kristallstrukturen dreier neuer Clathrate HgAg 6O 8ClO 4, HgAg 6O 8NO 3 und Hg 2Ag 18O 33H 22(ClO 4) 4

For the first time deposition of mercury-containing oxidic phases by electrocrystallization was achieved. Depending on the concentrations, the anodic oxidation of aqueous solutions of silver and mercury nitrates or perchlorates yielded HgAg 6O 8NO 3, HgAg 6O 8ClO 4 or Hg 2Ag 18O 33H 22(ClO 4) 4. The crystal structures were determined by means of single-crystal diffractometer data (HgAg 6O 8NO 3: Fm 3m ; a=9.953(1) A ̊ ; Z=4; Hg 2Ag 18O 33H 22(ClO 4) 4: Fd 3m ; a=20.231(2) A ̊ ; Z=8). HgAg 6O 8ClO 4 in which a=10.045(1) A ̊ crystallizes isostructurally with HgAg 6O 8NO 3. Both structures show a close relationship to the clathrate type of compound Ag 7O 8X. Silver(II)- and silver(III)-atoms are indistinguishable since they share the same crystallographic position.

Heterocyclic dithiophosphates as analytical reagents: Indirect extraction-spectrophotometric determination of silver in copper concentrates and ores

The proposed method is based on the exchange reaction between the complex of copper(II) with 4,7-dimethyl-2-thiol-2-thion-1,3,2-dioxophosphorinan (DOPh III) in toluene and an aqueous solution of silver(I). The decrease in the absorbance of the Cu(DOPh III) 2 solution is proportional to the silver(I) concentration for 5–90 μg of silver in 5 ml of toluene extract and 5–30 μg in 10 ml of toluene extract. The method is applied to the determination of silver in copper concentrates and ores.

A pulse radiolysis study of the process of the colloidal metal formation in aqueous solutions

The pulse radiolysis method was used for the study of the intermediate stage of the process of the colloidal metal formation in aqueous solutions of silver, lead, mercury and of other metals. It was shown, that during radiation-chemical reduction of metal ions at the intermediate stages there appeared clusters of various degrees of complexity, the coagulation of the latter led to the formation of small metal particles. The nature of some clusters was established, the absorption bands of colloidal solutions of the above metals and the time range of some intermediate stages of the metal nucleation process were determined.

Spectrophotometric investigation of equilibria between silver(II) and 2,2′-bipyridine

A spectrophotometric study has been made of an aqueous solution of silver(II) containing nitric acid and an excess of 2,2′-bipyridine over the wavelength range 350–550 nm. The data are consistent with the existence of only two complexes related by the equilibrium [Ag(bipy)2]2++ H+⇌[Ag(bipy)]2++ Hbipy+. At I= 1.00 mol dm–3 and at 25 °C, Kh for this equilibrium is found to be (3.3 ± 0.5)× 10–3. From the variation of Kh with temperature the values for the enthalpy and entropy of the above reaction are found to be 11.5 ± 2.6 kJ mol–1 and –9 ± 10 J K–1 mol–1 respectively.

Suppression of connective tissue impregnation in a silver technique for demonstrating nerve fibers.

A tissue pretreatment is introduced which effectively suppresses the silver impregnation of connective tissue and nonspecific background elements in peripheral nerve. The result is a selective impregnation of nerve fibers. The procedure utilizes fresh frozen sections and can be used with the Holmes (1947) or Bodian (1936) techniques. Fresh frozen sections are cut at 10 microns, mounted on slides and air dried for 5 minutes. They are fixed for 30 minutes in formol-sublimate (10% formalin saturated with mercuric chloride) and then placed into 0.5% iodine in 70% alcohol for 5 minutes followed by bleaching in 2.5% sodium thiosulfate for 2 minutes. After washing in running tap water for 10 minutes and a brief rinse in distilled water, impregnation is accomplished by the Holmes (1947) or Bodian (1936) procedure beginning with the step containing the aqueous silver solution. The results show an absence of impregnation of connective tissue and nonspecific background. The technique is simple, rapid, and, by utilizing fresh frozen sections, can be used for other histological and histochemical purposes. Several experiments were done to determine the causes of the connective tissue and background suppression. The air drying step was omitted; the sections were fixed in formalin without mercuric chloride; and the formol-sublimate fixation time was increased. The results suggest that connective tissue impregnation is suppressed by the use of mercuric chloride in the fixative and that the background suppression is related to the short fixation time with formolsublimate.

Adsorption characteristics of traces of silver on selected surfaces

A study of materials used for the storage of dilute aqueous solutions of silver established the adsorption characteristics of Teflon, Vycor, polypropylene, polystyrene and coatings of paraffin, acrylic spray, and Tygon paint. None of these materials or coatings was found satisfactory for prolonged storage of water samples containing trace quantities of silver. As in an earlier study, it was necessary to complex the silver in the sample with sufficient sodium thiosulfate to insure less than 1 % adsorption to containers over a 30-day contact period.

Coordination compounds of substituted 1,10-Phenanthrolines and related dipyridyls. VIII. Complexes of silver and 2,9-Dimethyl-1,10-phenanthroline

Addition of 2,9-dimethyl-1,10-phenanthroline (dmp) in organic solvents to aqueous solutions of silver(1) salts yielded mono complexes represented by AgXdmp, where X = NO3, Cl, Br, I; 2X = SO4, and bis complexes Ag(dmp),Y, where Y = NO3, Cl04. Water of crystallization was present only in the sulphate. The mono complexes were empirically three-coordinate. Low solubility prevented the determination of molecular weights. Infrared spectra indicated that the polyatomic anions were covalently bound. The 1 : 1 electrolyte [Ag(dmp)(py)]ClO4 subsequently prepared seemed to be an example of three-coordination. The bis complexes were 1 : 1 electrolytes in nitrobenzene and were most likely tetrahedral.