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⁺.     

Preparation and Characterization of Gelatin Nanofibers Containing Silver Nanoparticles

Ag nanoparticles (NPs) were synthesized in formic acid aqueous solutions through chemical reduction. Formic acid was used for a reducing agent of Ag precursor and solvent of gelatin. Silver acetate, silver tetrafluoroborate, silver nitrate, and silver phosphate were used as Ag precursors. Ag⁺ ions were reduced into Ag NPs by formic acid. The formation of Ag NPs was characterized by a UV-Vis spectrophotometer. Ag NPs were quickly generated within a few minutes in silver nitrate (AgNO₃)/formic acid solution. As the water content of formic acid aqueous solution increased, more Ag NPs were generated, at a higher rate and with greater size. When gelatin was added to the AgNO₃/formic acid solution, the Ag NPs were stabilized, resulting in smaller particles. Moreover, gelatin limits further aggregation of Ag NPs, which were effectively dispersed in solution. The amount of Ag NPs formed increased with increasing concentration of AgNO₃ and aging time. Gelatin nanofibers containing Ag NPs were fabricated by electrospinning. The average diameters of gelatin nanofibers were 166.52 ± 32.72 nm, but these decreased with the addition of AgNO₃. The average diameters of the Ag NPs in gelatin nanofibers ranged between 13 and 25 nm, which was confirmed by transmission electron microscopy (TEM).     

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     

Preparation and antibacterial activity of polyvinyl alcohol/regenerated silk fibroin composite fibers containing Ag nanoparticles

Polyvinyl alcohol (PVA)/regenerated silk fibroin (SF)/AgNO₃ composite nanofibers were prepared by electrospinning. A large number of nanoparticles containing silver were generated in situ and well‐dispersed nanoparticles were confirmed by transmission electron microscopy (TEM) intuitionally. Ultraviolet (UV)‐visible spectroscopy and X‐ray diffraction (XRD) patterns indicated that nanoparticles containing Ag were present both in blend solution and in composite nanofibers after heat treatment and after subsequent UV irradiation. By annealing the nanofibers, Ag⁺ therein was reduced so as to produce nanoparticles containing silver. By combining heat treatment with UV irradiation, Ag⁺ was transformed into Ag clusters and further oxidized into Ag₃O₄ and Ag₂O₂. Especially size of the nanoparticles increased with heat treatment and subsequent UV irradiation. This indicated that the nanoparticles containing silver could be regulated by heat treatment and UV irradiation. The antimicrobial activity of heat‐treated composite nanofibers was evaluated by Halo test method and the resultant nanofibers showed very strong antimicrobial activity. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

A novel method to prepare self‐lubricity of Si3N4/Ag composite: Microstructure,mechanical and tribological properties

Si₃N₄/Ag composites were firstly prepared through SPS technology, using Si₃N₄ and AgNO₃ as raw materials. Utilizing the coordination bonding of Ag⁺ ions with nitrogen atoms of Si₃N₄, in situ generated Ag particles about 1 μm were tightly anchored on Si₃N₄ surface, thereby preventing the outflow of silver during sintering process. Meanwhile, smaller silver particles about 20 nm were located at the grain boundaries of Si₃N₄, which effectively improved the mechanical and tribological properties of Si₃N₄‐based composites. Finally, the Si₃N₄/Ag composites reinforced by Ag particles showed a friction coefficient of 0.48 ± 0.01, wear rate of 1.79 × 10^?6 mm³ N^?1 m^?1 and fracture toughness of 7.05 ± 0.2 MPa m^1/2, respectively.     

Highly efficient and stable Ag/Ag3PO4 plasmonic photocatalyst in visible light

A highly efficient and stable photocatalyst Ag/Ag₃PO₄ was prepared by the ion-exchange process between AgNO₃ and Na₂HPO₄ and subsequently light-induced reduction route. The diffuse reflectance spectra (DRS) indicated Ag/Ag₃PO₄ had strong absorption in UV and visible-light regions. The composite showed excellent visible-light-driven photocatalytic performance. It can decompose organic dye within several minutes and still maintain a high level activity even though used five times. It is considered that this excellent performance results from the surface plasmon resonance of Ag nanoparticles and a large negative charge of PO₄^3 − ions.     

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.     

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     

Influence of tartaric acid on the electrodeposition of silver from binary water + dioxane AgNO3 solutions

Silver electrodeposits prepared from AgNO₃ solutions never give compact, smooth plates unless an organic additive, such as tartaric acid (H₂A), is used as growth inhibitor. It was shown previously that the relevant chemical entity controlling growth inhibition is the bulk concentration of a neutral associate Ag(HA) formed in the solution between Ag⁺ and tartaric monoanions HA^–. In the present work we extend this investigation to mixed water + dioxane solvent systems where the addition of dioxane, affecting the formation constant of Ag(HA), changes the bulk concentration of this associate. It was found that the associate Ag(HA) also formed in water + dioxane solvent systems is the active component in the solution governing the growth inhibition. On the concentration of this associate most of the structural features of Ag deposits (e.g., the grain size, the superficial roughness and the degree of the preferred orientation <1 1 0>) depend.     

Thioether‐Functionalized Corn Oil Biosorbents for the Removal of Mercury and Silver Ions from Aqueous Solutions

Heavy‐metal contamination is one of the most important environmental problems faced in the world, particularly in developing countries. Metals such as silver and mercury from drinking water, food, and air sources can accumulate in living organisms and present significant health concerns. Meanwhile, the demand for these metals in many industries continues to increase. In the present study, thioether‐functionalized corn oil (TFCO) from a photoinitiated thiol‐ene synthesis was utilized to remove Ag⁺ and Hg²⁺ ions from an aqueous solution. An aqueous solution containing AgNO₃ and Hg[NO₃]₂ was prepared and contacted directly with TFCO. After vortex mixing for 60 s, the experiment ran for 351 min with the aqueous phase being periodically sampled for the analysis of metal ions (M ⁿ⁺). Results showed that 88.9% of Ag⁺ and 99.6% of Hg²⁺ ions were removed from the aqueous phase by the TFCO. Mass balances indicated that the total M ⁿ⁺ concentration in the oil phase was 13.890 g kg^?1 under the conditions studied. TFCO exhibited higher selectivity for removing Hg²⁺ than for Ag⁺ ions. Analysis of the adsorption kinetics showed that a pseudosecond‐order model may be used to determine the rate of Ag⁺ ion sorption by the oil phase. The presence of the Hg²⁺ ions interfered with the adsorption of Ag⁺ ions from the aqueous solution.     

Enhanced room temperature coefficient of resistivity (RT-TCR) and broad metal-insulator transition temperature (TMI) of La0.67Ca0.33-xAgxMnO3 polycrystalline ceramics

Polycrystalline La_0.67Ca_0.33-xAg_xMnO₃ (LCAMO, x = 0, 0.06, 0.15, 0.18, and 0.24) ceramics were fabricated by conventional sol-gel route at relatively low sintering temperature of 1100 °C for 12 h. Effects of silver content (x) on crystal structure, grain size, resistivity and magnetic properties of as-prepared LCAMO specimens were investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), elemental mapping and energy dispersive spectrometry (EDS), X-ray photoelectron spectroscopy (XPS), and standard four-probe method (ρ-T). The data from XPS, XRD and EDS revealed that silver existed as Ag⁺ ions in the lattice matrix position of LCAMO ceramics. Broad metal-insulator transition temperature (T_MI) values ranging from 267.0 K (x = 0) to 302.6 K (x = 0.24) were obtained with LCAMO specimens prepared with variable Ag⁺ added contents. Peak temperature coefficient of resistivity (TCR) enhanced from 4.1% K⁻¹ at 263.2 K (for x = 0) to 10.9% K⁻¹ at 278.5 K (for x = 0.18), and reached 7.5% K⁻¹ at room-temperature (295.9 K) for x = 0.24. Meanwhile, magnetoresistance (MR) of materials reached 17.7% at room-temperature (299.2 K) for x = 0.24. Overall, these findings demonstrated that Ag doping was beneficial for improving electrical and magnetic properties of LCAMO materials. In summary, LCAMO ceramics achieved RT-TCR and MR at optimal Ag stoichiometric ratio, promising for applications in infrared bolometers or magnetic sensors.     

Studying the localized deposition of Ag nanoparticles on self-assembled monolayers by scanning electrochemical microscopy (SECM)

The local deposition of Ag nanoparticles (NPs) on ω-mercaptoalkanoic acid, HS(CH₂)_nCO₂H, (n = 2, 10) self-assembled monolayers (SAMs) by scanning electrochemical microscopy (SECM) is reported. We found that the presence of a SAM had a pronounced effect on Ag deposition. Experiments were conducted by applying different potentials to an Au(1 1 1) substrate either in the presence of a constant concentration of Ag⁺ ions in solution (bulk deposition) or by generating a flux of Ag⁺ from an Ag microelectrode that was positioned close to the Au(1 1 1) substrate (SECM deposition). SECM was used for generating a controlled flux of silver ions by anodic dissolution of an Ag microelectrode close to the SAMs modified Au(1 1 1). We found that the shape of the NPs was affected by the length of the carbon-chain of the SAM. Tetrahedral NPs were obtained on bare Au(1 1 1) surfaces while rod like and cubic Ag NPs were deposited onto 3-mercaptopropanoic acid (MPA) and 11-mercaptoundecanoic acid (MUA) SAMs, respectively. The size and shape of the deposited NPs were influenced by the deposition potential.We conclude that the shape and distribution of locally deposited Ag NPs on Au(1 1 1) can be controlled by modification of the substrate with a SAM and through controlling the Ag⁺ flux generated by SECM.     

Preparation and Characterization of Polypyrrole Silver Nanocomposites via Interfacial Polymerization

Conducting polypyrrole silver (Ppy-AgNC) nanocomposite was synthesized by an interfacial polymerization method. Ag⁺ ions from the AgNO₃ solution were taken in the formation of Ppy-AgNC. The incorporated silver was confirmed by X-ray diffraction (XRD). During the polymerization in a nitrate ion-containing solution, the impregnation leads to the formation of metallic silver. The size distribution of Ag into the polymer is confirmed by transmission electron microscopy (TEM), and proves the formation of a uniform species with spherical particles of Ag (mean diameter of 8-12 nm) branching at the border of Ppy. The thermal behavior of the material was studied by thermogravimetric measurements.     

In vitro silver ion release kinetics from nanosilver/poly(vinyl alcohol) hydrogels synthesized by gamma irradiation

A nanosilver (nano‐Ag)/poly(vinyl alcohol) (PVA) hydrogel device was synthesized with γ irradiation because it is a highly suitable tool for enhanced nano‐Ag technologies and biocompatible controlled release formulations. The amount of the Ag⁺ ions released in vitro by the nano‐Ag/PVA hydrogel device was in the antimicrobial parts per million concentration range. The modeling of the Ag⁺ ion release kinetics with the elements of the drug‐delivery paradigm revealed the best fit solution (R² > 0.99) for the Kopcha and Makoid–Banakar's pharmacokinetic dissolution models. The term A/B, derived from the Kopcha model, indicated that the nano‐Ag/PVA hydrogel was mainly an Ag⁺‐ion diffusion‐controlled device. Makoid–Banakar's parameter and the short time approximated Ag⁺‐ion diffusion constant reflected the importance of the size of the Ag nanoparticles. However, it appeared that the cell oxidation potential of the Ag nanoparticles depended on the diffusion characteristics of the fluid penetrating into the Ag/PVA nanosystem. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40321.     

Silver Electrodeposition from AgNO3 Solutions Containing Organic Additives: Electrodeposition from Binary Water–Methanol Solvent Systems in the Presence of Tartaric Acid

The electrodeposition of silver at 25 °C from AgNO₃/tartaric acid solutions in binary water–methanol solvent systems was investigated. This study shows that it is possible to obtain compact and coherent silver deposits from AgNO₃ solutions only in the presence of tartaric acid (H₂A). The relevant chemical entity controlling growth inhibition is a neutral associate Ag(HA) formed in the solution between Ag⁺ and tartaric monoanions HA^–. Most of the structural features of Ag deposits such as grain size, surface roughness and degree of the preferred orientation 1 1 0, depend on the concentration of this associate. These properties of the deposits can easily be controlled by:(a) modifying the concentration of AgNO₃ or H₂A, (b) adjusting the pH of the bulk solution by addition of HNO₃ and (c) modifying the composition of the mixed solvent system.     

Influence of tartaric acid on the electrodeposition of silver from aqueous AgNO3 solutions

Silver electrodeposition from aqueous AgNO₃ solutions never gives compact, smooth plates unless an organic additive such as tartaric acid (H₂A) is used as growth inhibitor. However, depending on the bulk pH, H₂A may exist either as a neutral molecule of H₂A or as dissociated entities such as HA⁻ or A²⁻. We have shown previously that the relevant parameter governing growth inhibition was the activity, α_HA-, of tartaric monoanions when silver was plated from a solution of constant AgNO₃ concentration. The aim of the present work is to show what happens when this concentration is no longer constant. In these conditions, the relevant parameter governing growth inhibition is proved here to be the bulk concentration of a neutral complex Ag(HA) formed in the solution between Ag⁺ and tartaric monoanions HA⁻. On this concentration depend most of the structural features of Ag deposits, e.g. their grain size, superficial roughness and even the amount of incorporated organic material.     

Novel method of preparing Ag–Hg alloy on polyacrylamide films and their structure

A novel method is proposed of preparing thin Ag–Hg alloy on PAAm film surface at room temperature: The film of interest is formed by holding PAAm aqueous solution with AgNO₃ in Hg-saturated atmosphere. Two kinds of films, one of which is a conductor and the other an insulator, can be selectively formed with pH-controlled PAAm solution by ammonia. The conducting surface is assigned to the α phase of Ag–Hg alloy by means of X-ray analysis. Potentiometric titration and IR spectral studies suggest the existence of PAAm–Ag⁺ complexes. On the basis of their structure and the oxidation and reduction potential of Ag⁺ and Hg²⁺, the mechanism of film formation is also discussed.     

Fabrication of silver-doped apatite powders from silver-substituted octacalcium phosphate powders via solid–solid phase-conversion process

The excellent biocompatibility of apatite (hydroxyapatite, HAp; carbonate apatite, CO₃Ap) materials makes them suitable candidates as bone substitutes. However, they have no antibacterial ability. Meanwhile, silver (Ag) exhibits excellent antibacterial properties across a wide antibacterial spectrum. However, soluble Ag salts exhibit cytotoxicity and poor aesthetic properties. We dope Ag into an apatite unit lattice in order for the composite material to exhibit antibacterial contact abilities while simultaneously limiting the release of Ag⁺, which is the primary cause of the unwanted color changes and cytotoxicity. When a crystal structure in which silver ions are substituted for Ca in octacalcium phosphate (OCP) (Ag-OCP) is immersed in water and/or (NH₄)₂CO₃-containing solutions, Ag-OCP is converted into an apatite containing Ag via a solid–solid phase-transformation process. The Ag contents of the apatite and precursor Ag-OCP are the same. The CO₃ content of apatite samples depends on the (NH₄)₂CO₃ concentration of the treated solutions. A single-pot, single-step treatment enables the synthesis of both Ag-containing HAp and CO₃Ap. Further, these Ag-containing HAp and CO₃Ap samples show little color change from that of the precursor Ag-OCP.     

Synthesis and intercalation of silver nanoparticles in kaolinite/DMSO complexes

Ag nanoparticles were synthesized in the interlamellar space of a layered kaolinite. Disaggregation of the lamellae of the nonswelling kaolinite was achieved by the intercalation of dimethyl sulfoxide (DMSO). The kaolinite was suspended in aqueous AgNO₃ solution and the adsorbed Ag⁺ ions were reduced on the surface of kaolinite lamellae with NaBH₄ or UV light irradiation. The silver nanoparticles formed were characterized by X-ray diffraction (XRD), small angle X-ray scattering (SAXS), and transmission electron microscopy (TEM). We studied the effects of the two reduction methods on the size and the size distribution of Ag nanoparticles and how clay mineral structure is altered as a consequence of particle formation. It was established that the size of Ag nanoparticles depends on both silver content and the reduction method. Photoreduction of silver led to the formation of relatively large Ag nanoparticles (diameter 8–14 nm).     

The highly active saddle-like Ag3PO4 photocatalyst under visible light irradiation

Saddle-like Ag₃PO₄ particles of tetrahedron structure were successfully synthesized using a co-precipitation method by mixing H₃PO₄ ethanol solution and AgNO₃ ethanol aqueous solution, where the percentage of ethanol in AgNO₃ ethanol aqueous solution was varied at 0, 50, 80, 90 and 100% (v/v). The photocatalytic performance of the synthesized samples was evaluated by photodegradation of Rhodamine B (RhB) under blue light irradiation (λ = 455 nm). The results showed that the morphology of the Ag₃PO₄ particles greatly changed depending on the ethanol content in the reaction solution. Excellent photocatalytic activity was observed at 80% (v/v) of ethanol, where the Ag₃PO₄ showed saddle-like morphology derived from the tetrahedron structure.