X-ray analysis of α-, β-, and γ-phase Ag–Hg alloy films produced on polymer substrates by casting polyacrylamide–AgNO3 aqueous solution in Hg atmosphere

It is reported that, by dropping Hg metal on the wet α-phase Ag–Hg alloy film formed on the cast polyacrylamide–AgNO₃ aqueous solution, the α phase of fcc structure can be converted into other phases that contain more Hg. The X-ray analysis of these phases reveals that they are the β phase of hexagonal structure and the γ phase of bcc structure. It is also shown that the lattice constant of the α phase can be controlled to some extent by pH of the aqueous solution of PAAm from which the alloy film is formed.     

Alloy formation during the electrochemical growth of a Ag-Cd ultrathin film on Au(1 1 1)

The electrodeposition of a Ag/Cd ultrathin film on a Au(1 1 1) surface and the formation of a surface alloy during this process have been studied using classical electrochemical techniques and in situ Scanning Tunneling Microscopy (STM). The films were obtained from separate electrolytes containing Ag⁺ or Cd²⁺ ions and from a multicomponent solution containing both ions. First, the polarization conditions were adjusted in order to form a Ag film by overpotential deposition. Afterwards, a Cd monolayer was formed onto this Au(1 1 1)/Ag modified surface by underpotential deposition. The voltammetric behavior of the Cd UPD and the in situ STM images indicated that the ultrathin Ag films were uniformly deposited and epitaxially oriented with respect to the Au(1 1 1) surface. Long time polarization experiments showed that a significant Ag-Cd surface alloying accompanied the formation of the Cd monolayer on the Au(1 1 1)/Ag modified surface, independent of the Ag film thickness. In the case of an extremely thin Ag layer (1 Ag ML) the STM images and long time polarization experiments revealed a solid state diffusion process of Cd, Ag, and Au atoms which can be responsible for the formation of different Ag-Cd or Au-Ag-Cd alloy phases.     

Silver deposition from its nitrate solutions by hydrogenated palladium

The currentless deposition of Ag⁺ cations from silver nitrate solutions has been found on the surface of hydrogenated Pd (Pd?H). This process has been shown to proceed via a chemico-catalytic mechanism. It has been demonstrated that the major fraction of silver deposited onto the Pd-H system from the nitrate solutions in the first 0.5–1 h of holding in the solution. A minimal size of silver crystallites (26–40 nm) was found when deposited from the diluted nitrate solutions that contain 0.32–2.5 g/L of Ag. The study has revealed that the currentless Ag deposition on the Pd–H surface is accompanied by the formation of the colloid phase of Ag crystallites. It has been established that the Pd–H system could purify solutions of Ag⁺ when the amount of hydrogen in Pd exceeded the amount of Ag⁺ in the solution.     

Reaction of Ozone with Ag(I)—Mechanistic Considerations

Ozone reacts slowly with Ag⁺ (circumneutral pH, k = (11 ± 3) × 10^?2 M^?1 s^?1). After some time, ozone decay kinetics may suddenly become faster with the concomitant formation of silver sol. As primary process, an O-transfer from O₃ to Ag(I) is suggested, whereby Ag(III) is formed [Ag⁺ + O₃ + 2 H₂O → Ag(OH)₃ + O₂ + H⁺]. This conproportionates with Ag(I), which is in large excess, leading to Ag(II) [Ag⁺ + Ag(OH)₃ ? 2 Ag(OH)⁺ + HO^?]. Further, Ag(II) reacts with ozone in a high exergonic reaction [Ag(OH)⁺ + O₃ → Ag + 2 O₂ + H⁺], where ozone acts as a reducing agent. Thereby, a single silver atom, Ag, is formed that can be oxidized by O₂ and O₃ or can aggregate to a silver sol. Aggregation slows down the rate of oxidation. When Ag⁺ is complexed by acetate ions, ozone decay and silver sol formation are speeded up by enhancing Ag(II) formation [Ag(I)acetate + O₃ → Ag(III)acetate → Ag(II) + CO₂ + ?CH₃]. In the presence of oxalate, the formed complex reacts faster with ozone than Ag⁺, and Ag(III)oxalate decarboxylates rapidly [Ag(I)oxalate + O₃ → Ag(III)oxalate → Ag⁺ + 2 CO₂]. This enhances ozone decay but prevents silver sol formation. Quantum chemical calculations have been carried out for substantiating mechanistic suggestions.     

Preparation of Ag nanoparticles in the presence of low generational poly(ester‐amine) dendrimers

Stable Ag nanoparticles of 10–20 nm were prepared by reduction of AgNO₃ with NaBH₄ in water solution in the presence of low generational hydroxyl‐ terminated poly(ester‐amine) dendrimer G1.0 (OH)₁₆ and amino‐terminated poly(ester‐amine) dendrimer G1.5 (NH₂)₈ by optimizing preparation conditions. UV–vis absorption spectra and transmission electron microscopy were adopted to characterize absorption properties of Ag⁺/dendrimer complex, Ag/dendrimer nanocomposite aqueous solutions, and the morphology of the formed Ag nanoparticles, respectively. The results showed that the size of the Ag particles increased with Ag⁺/dendrimer molar ratio, and the size of Ag nanoparticles in Ag/G1.0 (OH)₁₆ system was larger than that of Ag nanoparticles in Ag/G1.5 (NH₂)₈ system, while the polydispersities of two systems were similar. Moreover, the Ag/G1.5 (NH₂)₈ nanocomposite system was more stable than the Ag/G1.0 (OH)₁₆ one. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 422–426, 2007     

Ag/Ag2S–TiO2 composite film formed using dual phase Ag/Ag2O layer as a sulfurized layer for enhanced photocatalytic activity

The Ag/Ag₂S–TiO₂ composite films were synthesized through vulcanizing sputtering Ag/Ag₂O dural-phase template capping layer on the TiO₂ film. After hydrothermal vulcanization using thiourea as a sulfur precursor, the initially decorated Ag₂O layer transformed into the Ag₂S. The surface morphology of the continuous block structure of the Ag/Ag₂S composite layer gradually shrinks to form irregular island grains dispersed on the surface of the composite film, with vulcanization reaction duration increased from one to 3 h. The light absorption ability of the Ag/Ag₂S–TiO₂ composite film was enhanced substantially compared to the TiO₂ film because of the surface plasmon resonance effect from the Ag particles and the narrow energy band of the Ag₂S. Among various surface morphologies of the Ag/Ag₂S–TiO₂ composite films, the irregular island Ag/Ag₂S grains-decorated TiO₂ composite film presents superior photoelectrochemical and photocatalytic degradation performances than the composite films consisting of continuous block and spider-web structure of the Ag/Ag₂S decorated layers. The synergistic effects of surface plasmon resonance, Ag pathway between the semiconductors, and Z-scheme charge transfer mechanism explain the high-efficiency photocatalytic activity of the Ag/Ag₂S–TiO₂ composite films.     

Selective preparation of Ag species on photoluminescence of Sm3+ in borosilicate glass via Ag+-Na+ ion exchange

Photoluminescence (PL) of rare earth ion-doped glasses could be enhanced by diverse Ag species such as Ag⁺ ions, Ag⁺-Ag⁺ pairs, Ag nano-clusters (NCs), and Ag nanoparticles (NPs). Selective preparation of silver species in rare earth ion-doped glasses is a crucial step to obtain the luminescence enhancement of rare earth ions caused by the different silver species. In this work, Ag⁺ ions and Ag NCs were selectively prepared in the Sm³⁺-doped borosilicate glass via the Ag⁺-Na⁺ ion exchange. The influence of AgNO₃/NaNO₃ ratio in the molten salt on the Ag existing states was investigated. The results demonstrate that the isolated Ag⁺ ions exist in the Sm³⁺-doped borosilicate glass when the ratio of AgNO₃/NaNO₃ is 1/1000. The Ag NCs are formed in the Sm³⁺-doped borosilicate glass when the AgNO₃/NaNO₃ ratio is 1/10. The influence of Ag⁺ ions or Ag NCs on the PL of Sm³⁺ was systematically investigated. The results show that the PL of Sm³⁺ was enhanced by the energy transfer from Ag⁺ ions or Ag NCs to Sm³⁺.     

A mononuclear complex of norfloxacin with silver(I) and its properties

Reaction of norfloxacin (H-Norf) with AgNO₃ yields an unusual mononuclear complex [Ag(H-Norf)₂]NO₃ (1) in which the local coordination environment around Ag⁺ ion is approximately linear with a N–Ag–N angle of 162.1(2)°. Larger concentration of Ag⁺ ions was found in water solution of 1. The unique bonding in 1 may lead to the readily release of Ag⁺ ion from 1, and leads to better antibacterial action in topical burn treatments. Strong blue fluorescent emission of 1 was also observed.     

Electrodeposition of Ag and Pd on a reconstructed Au(1 1 1) electrode surface studied by in situ scanning tunneling microscopy

Electrochemical deposition of Ag and potential-induced structural change of the deposited Ag layer on a reconstructed surface of Au(1 1 1) electrode were followed by in situ scanning tunneling microscope (STM). A uniform Ag monolayer was formed on a reconstructed Au(1 1 1) surface in a 50-mM H₂SO₄ solution at +0.3 V (vs. Ag/AgCl) after adding a solution containing Ag₂SO₄ so that the concentration of Ag⁺ in the STM cell became ca. 2 μM. No characteristic height corrugation such as the Au reconstruction was observed on the surface, indicating that the lifting of the substrate Au reconstruction occurred by Ag deposition. The formed Ag monolayer was converted to a net-like shaped Ag nano-pattern of biatomic height when the potential was stepped from +0.3 to −0.2 V in the solution containing 2 μM Ag⁺. This result indicates that the substrate Au(1 1 1)-(1 × 1) surface was converted to the reconstructed surface even in the presence of Ag adlayer. Quite different structure was observed for Pd deposition on a reconstructed surface of Au(1 1 1) electrode at +0.3 V and the origin for this difference between Ag and Pd deposition is discussed.     

Infusion of Ag‐Ion from Aqueous Solution into Solid Calcium Phosphate of Hydroxyapatite (HA) Crystal Structure

In contrast to extensive literature concerning Ag incorporation in hydroxyapatite, HA, while the phosphate approximated to stoichiometry of Ca₁₀(PO₄)₆(OH)₂, with added Ag has been precipitating from an aqueous solution, the paper presents Ag incorporation through Ag ion infusion from AgNO₃ solution into solid HA pressed in pellet and ignited at 800°C. After Ag ions infused into the HA‐solid (crossed the interfacial solution‐solid boundary), they diffused across the crystal structure to a depth of time‐dependent several mm. The path of Ag diffusion in the solid HA was recorded using SEM‐EDS point analyses of Ag, Ca, P, EDS‐linear analyses of those elements, and elemental mapping. Time‐dependent concentrations of Ag⁺, Ca²⁺, and PO₄^3? in AgNO₃ solutions were also analyzed. The appearance of Ag in the crystalline HA with simultaneous local depletion in Ca and phosphate recorded as P, observed by EDS with simultaneous appearance of Ca²⁺ and PO₄^3? ions and a decrease in Ag⁺ concentration in AgNO₃ solution led the authors to a conclusion that Ag⁺ for Ca²⁺ substitution supported by PO₄^3? charge balancing in the crystalline HA was in process. The HA particles in the section of the pellet without Ag had a uniform shape and size approximated to 300–400 nm. SEM image of the HA solid section, where Ag ions appeared was characterized by irregular aggregates of smaller crystals with sporadically present large, shaped in prism blocks identified by the XRD as Ag₃PO₄.     

Preparation and Characterization of Silver‐Doped Cu(In,Ga)Se2 Films via Nonvacuum Solution Process

Cu(In,Ga)Se₂ films doped with different contents of silver ions (Ag⁺) were successfully prepared using nonvacuum spin coating followed by selenization at elevated temperatures. Increasing the Ag⁺ ion content increased the lattice parameters of the chalcopyrite structure, and shifted the A1 mode in the Raman signals to low frequencies. The band gaps of the prepared (Ag,Cu)(In,Ga)Se₂ (ACIGS) films were considerably increased, thereby increasing the open‐circuit voltage (V_oc) of the solar cells. As Ag⁺ ion content increased, the microstructures of ACIGS films became densified because the formed (Cu,Ag)₂In alloy phase with a low melting point facilitated liquid‐phase sintering. The evaporation of selenium species was correspondingly suppressed in the films during selenization, thereby reducing the selenium vacancies. The improvement in the microstructures and the defects of ACIGS films increased short‐circuit current (J_sc) and fill factor of the solar cells. The spectral response of the solar cells was also enhanced remarkably. This study demonstrated that incorporation of Ag⁺ ions into Cu(In,Ga)Se₂ films substantially improved the efficiency of the solar cells.     

Electrochemical window of molten LiCl-KCl-CaCl2 and the Ag/Ag reference electrode

The electrochemical window of an LiCl-KCl-CaCl₂ eutectic melt (52.3:11.6:36.1 mol%) was determined by cyclic voltammetry and open-circuit potentiometry at 723-873 K. The reaction at the anodic limit was confirmed to be Cl₂ gas evolution. The reaction at the cathodic limit was found to be a liquid Ca-Li alloy formation on the basis of ICP analysis of the deposits. An Ag⁺/Ag reference electrode separated with a Pyrex membrane showed good stability for more than 1 week. The standard electrode potential of Ag⁺/Ag was determined in the temperature range of 723-823 K by measuring the potential of a silver electrode in different concentrations of Ag⁺ ions.     

Comparative investigation of plain and silver impregnated activated carbons for the removal of cyanide from basic aqueous solutions in the batch process

Purolite AC-20 and Norit RB 0.8CC activated carbons impregnated with AgNO₃ were used for the removal of CN^– and Ag–CN complex from model wastewater. The formed Ag⁰ centers were approved by scanning electron microscopy micrographs and X-ray powder diffraction data. The degree of Ag⁰ participating in CN^– sorption varied from 100 to 45% on AC-20/Ag and from 100 to 73% on RB 0.8CC/Ag, by varying [CN^–]/[Ag] in the initial solution from 2.0 to 19.2. The Freundlich isotherm and Fleming kinetic models were consistent with the experimental data. The K_F values for the CN^– adsorption on AC-20/Ag and RB 0.8CC/Ag increased by a factor of 1.2 and 1.5, but they lowered for Ag–CN adsorption by a factor of 4.1 and 2.1, respectively, as compared to that of plain activated carbons. The removal of 90% cyanides is appropriate by combining two batches from activated carbon: impregnated, mainly for the removal of CN^–, and plain, removing the rest of Ag–CN.     

Ag and Si Codoped Phosphate Glasses: Plasmonic Nanocomposites with Enhanced UV Transparency

The use of silicon powder to produce plasmonic Ag nanocomposite phosphate glasses which also exhibit improved transparency in the ultraviolet (UV) is proposed. Ag₂O/Si codoped glasses were prepared in a barium‐phosphate matrix by a simple melt‐quench method in ambient atmosphere. The as‐prepared glasses exhibit enhanced UV transparency, whereby the surface plasmon resonance of Ag nanoparticles (NPs) is manifested for the glasses with higher Ag₂O contents. ³¹P nuclear magnetic resonance spectroscopy is consistent with the formation of P–O–Si bonds, thus suggesting their possible role on the improved UV light transmission. Consequently, a model was presented accounting for the influence of silicon on the polymerization of the phosphate network concomitant with the creation of highly reactive oxygen species. Further exploiting the proposed reactive species, a real‐time spectroscopic study of the plasmonic response of Ag NPs in Ag/Si codoped glass samples was carried out during an in situ thermal processing. The temperature dependence of the Ag particle precipitation was studied in the 400°C–430°C range, from which an Arrhenius‐type plot allowed for estimating the activation energy of the process at 3.42 (±0.38) eV. Ultimately, the vanishing of the luminescence ascribed to Ag⁺ ions was observed in a heat‐treated sample, consistent with the high reactivity acquired by the glass matrix. Silicon thus appears promising for producing UV transparent glasses for high‐performance optics and for the reduction of Ag⁺ ions to produce Ag nanocomposites valuable for photonic (nanoplasmonic) applications.     

STM tip-induced local electrochemical dissolution of silver

Local dissolution/deposition processes under in situ scanning tunneling microscopy (STM) imaging conditions are studied in the systems Ag(111)/Ag⁺, ClO₄⁻ and Ag(111)/Ag⁺, SO₄²⁻. The results show that in both systems the local kinetics of these processes strongly depend on the polarization conditions. At STM-tip potentials more positive than the Ag/Ag⁺ equilibrium potential, a local dissolution of the Ag(111) substrate is observed even at cathodic substrate overpotentials at which the overall substrate current density is cathodic. This tip-induced Ag dissolution is in agreement with results obtained recently in the system Cu(111)/Cu²⁺. The enhanced local Ag dissolution is explained by a reduced Ag⁺ concentration underneath the STM tip promoted by both an electrostatic repulsion of Ag⁺ and a reduction of the mass transport due to the shielding effect of the tip. The possibility for a preparation of negative Ag nanostructures by STM tip-induced electrochemical dissolution is demonstrated.     

Growth of hexagonal polyaniline fibers with polyacrylamide pendants

A new concept of synthesizing hexagonal polyaniline (PANi) fibers with polyacrylamide (PAAm) pendants in PAAm oligomer (oligo‐PAAm) colloid is proposed. The size and morphology of the composite fibers can be controlled by adjusting the synthesis conditions. A possible growth mechanism of the PANi microstructures based on typical PAAm–crystals interactions in a mild aqueous solution is proposed. The amide ligands decorated oligo‐PAAm chains are able to coordinate with –C₆H₄–NH⁺C₆H₄NH⁺–C₆H₄–NH–C₆H₄–NH– sections, leading to a lower surface energy and growth along c‐directions to form fibriform morphology. The fibers have uniform diameter ranging from 200 to 400 μm, and length varying from several millimeters to 6 cm. Fourier transform infrared measurement indicates that the fiber exhibits a main PANi chain with PAAm pendants, and ultraviolet–visible spectra reveal that the PANi is in high conductive emeraldine state. Acrylamide feed significantly affects the morphology, however, the conductivity and yield of the fiber depend on hydrochloric acid and potassium peroxydisulfate concentrations in the preparation process. The hexagonal composite fibers show an electrical conductivity of 2.2 S·cm⁻¹ and yield of higher than 95%. Polymer‐directed crystal growth may provide promising routes to rational synthesis of various ordered organic materials with complex form and structural specialization. POLYM. COMPOS., 35:253–262, 2014. © 2013 Society of Plastics Engineers     

Photothermal,photocatalytic, and anti-bacterial Ti-Ag-O nanoporous powders for interfacial solar driven water evaporation

Interfacial solar driven water evaporation is an attractive and green method to alleviate the scarcity of clean and fresh water, and tremendous efforts have been devoted to prepare efficient photothermal materials. However, the practical condition for interfacial solar driven water evaporation is complex, increasing contamination by pollutants and bacterial can inactive the photothermal materials. Herein, to address this problem, Ti-Ag-O nanoporous powders, which possess photothermal, photocatalytic and anti-bacterial properties, were prepared by TiAg alloy anodization and subsequent laser irradiation method. It was found that metallic Ag nanoparticles, which were mainly formed by TiAg alloy anodization, will be oxidized into Ag₂O nanoparticles after laser irradiation. Through this laser induced transformation, the surface wettability of Ti-Ag-O powders can be improved for the hydrophilicity nature of Ag₂O, and the Ti-Ag-O powders with Ti90Ag10 alloy anodization and subsequent laser irradiation for 10 min showed the highest water evaporation rate (2.27 kg m^?2 h^?1). Meanwhile, this Ti-Ag-O powders also showed the highest photocatalytic property due to the junction between TiO₂ and Ag₂O. Moreover, the diffusion inhibition test indicated that antibacterial property of this Ti-Ag-O powders was excellent for the incorporation of Ag/Ag₂O nanoparticles. The as-prepared trifunctional Ti-Ag-O nanoporous powders holds potential for the practical application of interfacial solar driven water evaporation technology, the TiAg alloy anodization and subsequent laser irradiation method could be extended to prepare other multifunctional photothermal materials.     

Comportement electrochimique et reactivite dy systeme Ag(II)/Ag(I)-bipyridine dans le carbonate de propylene—II. Etude du couple carbonate de propylene—II. Etude du couple AgII(bipy)2+/AgI(bipy)+

Due to the reactivity expected in the presence of an excess Ag⁺ with respect to the 1–2 stoichiometry (Ag-bipy), the electrochemical behaviour of the Ag(II)/Ag(I)-bipyridine system has been investigated using voltammetry and coulometry. The change in the current-potential curves has been rationalized taking into account an equilibrium between different species of Ag(I) in neutral or acidic media. Changes of the solution nature (ratio C_bipy/C_Ag) or pH actually led to the formation of reactive species.     

Synthesis and characterization of novel silver/L‐phenylalanine‐based optically active polyacrylate nanocomposite

Novel bioactive and optically active poly(N‐acryloyl‐L ‐phenylalanine) (PAPA) was synthesized by atom transfer radical polymerization. PAPA‐silver (Ag) nanocomposites have been successfully prepared via in situ reducing Ag⁺ ions anchored in the polymer chain using hydrazine hydrate as reducing agent in an aqueous medium. By controlling of the amount of Ag⁺ ions introduced, we have produced an organic/inorganic nanocomposite containing Ag nanoparticles with well controlled size. Nanocomposites were characterized by X‐ray diffraction (XRD), UV–Vis spectrophotometry, transmission electron microscopy, and Fourier transform infrared. XRD pattern showed presence of Ag nanoparticles. The PAPA/Ag nanocomposites with 1 : 10 silver nitrate (AgNO₃) : PAPA ratio revealed the presence of well‐dispersed Ag nanoparticles in the polymer matrix. All of these Ag nanoparticles formed are spherical and more than 80% of them are in the range of 15–25 nm. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Comparative investigation of antibacterial yet biocompatible Ag-doped multicomponent coatings obtained by pulsed electrospark deposition and its combination with ion implantation

The aim of this work is to obtain antibacterial yet biocompatible coatings using pulsed electrospark deposition (PED). For this purpose new composite electrodes were fabricated from reaction mixtures Ti–C–20%Fe-10%Ca₃(PO₄)₂–3.4%Mg–X%Ag with different amount of antibacterial component (X = 0, 0.5, 1.0, 1.5 and 2.0 at% of Ag) using self-propagating high-temperature synthesis method. The electrodes consisted of TiC grains surrounded by TiFe₂ and TiFeP intermetallic matrix, CaO and MgO inclusions, and Ag-based phase. The influence of Ag content on the electrode mass transfer kinetics was studied by comparing the total substrate weight gain and electrode mass loss during PED. The structure, elemental composition, and surface roughness of coatings were studied by means of X-ray diffraction, scanning electron microscopy, and optical profilometry. The coatings were characterized in terms of Ag⁺ ion release, mechanical and electrochemical properties, as well as biocompatibility. The antibacterial characteristics of Ag-doped PED coatings were compared with those obtained by PED using Ag-free electrode and then implanted with Ag⁺ ions. The results indicated that an increase in the Ag content in electrode leads to a decrease in electrode erosion and substrate weight gain, but the efficiency of the PED process increases. Doping with a small amount of Ag (≤ 1 at%) resulted in 100% antibacterial effect against both gram-positive S. aureus and gram-negative E. сoli bacteria. In addition, the dynamics of МС3Т3-Е1 cell proliferation on the surface of PED coatings with 0.6–0.7 at% of Ag was similar to that in control samples, hereby indicating their biocompatibility. The coating biological characteristics were discussed based on the results of Ag⁺ ion release and electrochemical tests.