Silver Ion Exchange Research Articles

Unravelling the Mechanisms of Gold-Silver Core-Shell Nanostructure Formation by in Situ TEM Using an Advanced Liquid Cell Design.

The growth of silver shells on gold nanorods is investigated by in situ liquid cell transmission electron microscopy using an advanced liquid cell architecture. The design is based on microwells in which the liquid is confined between a thin Si3N4 membrane on one side and a few-layer graphene cap on the other side. A well-defined specimen thickness and an ultraflat cell top allow for the application of high-resolution TEM and the application of analytical TEM techniques on the same sample. The combination of high-resolution data with chemical information is validated by radically new insights into the growth of silver shells on cetrimonium bromide stabilized gold nanorods. It is shown that silver bromide particles already formed in the stock solution play an important role in the exchange of silver ions. The Ag shell growth can be directly correlated with the layer-by-layer dissolution of AgBr nanocrystals, which can be controlled by the electron flux density via distinctly generated chemical species in the solvent. The derived model framework is confirmed by in situ UV-vis absorption spectroscopy evaluating the blue shift in the longitudinal surface plasmon resonance of anisotropic NRs in a complementary batch experiment.

Concentration protocol of rhenium-188 perrhenate eluted from tungsten-188/rhenium-188 generator for the preparation of high-yield rhenium-188-labelled radiopharmaceuticals.

Rhenium-188 (Re) is a β, γ emitter and considered a theranostic radionuclide. It is used for bone pain palliation, treatment of unresectable hepatocellular carcinoma, skin keloids, etc. Re perrhenate is eluted from a W/Re generator in large volumes (8-14 ml) of 0.9% normal saline. Concentrating Re to 1-2 ml volume is important for high radiolabelling yield of various Re radiopharmaceuticals, especially when the generator is old. For this, ion exchange column was prepared in-house, and Re was concentrated using silver ion exchange column and QMA cartridge. Re perrhenate eluted in saline was concentrated to 1 ml with more than 99% yield.

The influence of low-temperature silver-ion exchange on the spectral-luminescent properties of fluorophosphate glasses doped with PbSe

Changes in the absorption and luminescence spectra of fluorophosphate glasses doped with PbSe caused by low-temperature Ag+–Na+ ion exchange are considered. It is found that the silver distribution gradient in a near-surface layer about 16 μm thick leads to two different processes of interaction between metal and semiconductor nanoparticles. PbSe molecular clusters and quantum dots more efficiently grow in deep layers with a low silver concentration. The near-surface glass layers with a high silver concentration exhibit formation of Ag metal nanoparticles, on the surface of which interaction with PbSe molecular clusters leads to the formation of Ag–Se–Pb bonds, which transform into Ag2Se layers in the process of heat treatment. The appearance of the new phase is confirmed by X-ray diffraction.

The influence of silver ion exchange on the luminescence properties of Er-Yb silicate glasses

A set of zinc-silicate glasses with different ratios of Er-Yb as well amount of Zn was fabricated. The preparation of silver doped glasses was carried out using the Ag-Na ion-exchange method to enhance Er-Yb luminescence properties of the material. The samples were also annealed for 1–5 h to further support the creation of silver nanoparticles. Intensive absorption at 980 nm was observed in absorption spectra after ion exchange and annealing as well. Also luminescence spectra in the near-infrared range were measured and results showed positive effect of ion exchange process on luminescence properties. Luminescence intensity at 1530 nm was increased almost three times. Possible mechanisms responsible for the increase of the luminescence intensity are also discussed in this paper. We suggest that the enhancement of erbium luminescence intensity is caused by the energy transfer from isolated Ag+ ions to Er.

A New Fabrication Method for Single‐Layer Nanosheets by Silver‐Assisted Exfoliation

AbstractThe discovery of 2D forms of matter, pioneered by graphene, has not only triggered new insights into fundamental physics but also pushed the limits of miniaturization. To process nanosheets into ultrathin functional devices, the development of scalable exfoliation routes is of key interest. Here, we demonstrate for the first time a mild, yet highly effective silver‐ion‐based exfoliation route for layered transition metal oxides. Single layer transition metal oxide nanosheets were obtained by applying silver ion exchange and subsequent treatment of the silver‐intercalated phases with an aqueous suspension containing organic iodides. This generic exfoliation route can be widely applied also to acid‐sensitive materials and allows the modification of the nanosheets with non‐conventional organic ligands, which owing to their chemical functionality may be used to tailor the optoelectronic and surface properties of the nanosheet–ligand hybrid.

The influence of silver ion exchange on the formation and luminescent properties of lead sulfide molecular clusters and quantum dots

PbS molecular clusters and quantum dots are formed by heat treatment in fluorophosphate glasses of the Na2O3–Р2O5–Ga2O3–AlF3–ZnO(S)–PbF2 system with different lead concentrations. PbS molecular clusters are characterized by optical absorption in the range of 300–800 nm and low quantum yields, which decrease from 8.9 to 2.7% with a semiconductor component concentration. It is shown that the parameters of formation of quantum dots luminescing in the wavelength range of 1000–1500 nm are considerably different at different semiconductor component concentrations. The influence of silver ion exchange on the formation of PbS nanoparticles is studied. Introduction of silver stimulates the growth of molecular clusters, which is seen in the absorption spectra. A possible mechanism of interaction of silver nanoparticles with PbS quantum dots is presented.

Silver-exchanged zeolite LTA molecular sieving membranes with enhanced hydrogen selectivity

In the present work, we report a new road to enhance the gas separation performances of the zeolite Na-LTA membrane by tuning the pore size of zeolite LTA through silver cation exchange. Through the functionalization of the alumina support by using 3-aminopropyltriethoxysilane (APTES), a thin, phase-pure and well intergrown zeolite Na-LTA membrane with a thickness of about 5.0µm can be facilely prepared on the APTES-modified macroporous α-Al2O3 tube. After a following silver exchange treatment of the as-synthesized zeolite Na-LTA membranes, the sodium ions in zeolite Na-LTA framework are replaced by silver ions, thus forming zeolite Ag-LTA membranes with a narrower pore diameter. The zeolite Ag-LTA membranes were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). It is found that both the morphology and structure of the zeolite Na-LTA membrane keep unchanged after silver-exchange, and no cracks, pinholes or other defects are observed in the membrane layer. The zeolite Ag-LTA membrane shows high hydrogen selectivity due to the reduction of pore size of the zeolite Ag-LTA. For the separation of the binary mixture at 50°C and 2.0bar, the separation factor of H2/C3H8 is α≈120.8, which by far exceeds α≈19.4 of the starting Na-LTA membrane, and are also much higher than the separation factors previously reported for the H2/C3H8 mixture on zeolite membranes.

Influence of silver and potassium ion exchange on physical and mechanical properties of soda lime glass

This study aims to investigate the ion exchanged soda lime glasses in terms of their physical and mechanical properties. By the motivation of preparing mechanically strengthened glass also representing antimicrobial property, commercial soda lime glass was subjected to ion exchange treatment using AgNO3KNO3 mixed salt bath. Ion exchange treatment was performed using different salt bath concentrations at varying temperatures and time. After the ion exchange treatment, glass samples were examined by considering the amount of incorporated silver and potassium into the glass, density changes and the variation of the transmittance in the visible region. Treated glasses were further investigated by means of their surface and mechanical properties such as wettability, indentation behaviors including hardness and resistance to indentation cracking, scratch resistance and bending strength. The transmission of the treated glasses showed a decrease due to the coloring effect of silver. Wettability of the glass surface was reduced, while hydrophilicity was decreased after the ion exchange treatment. Almost 20% increase in the Vickers hardness values, substantial enhancement in the indentation crack resistance and scratch resistance as well as averagely 3.5–4 times higher bending strength were achieved for all of the treated glass samples compared to the untreated glass. This study addressed that the simultaneous incorporation of silver and potassium provided significant improvements on the mechanical properties of the soda lime glass.

Antimicrobial Activity of Silver Ions Released from Zeolites Immobilized on Cellulose Nanofiber Mats.

In this study, we exploit the high silver ion exchange capability of Linde Type A (LTA) zeolites and present, for the first time, electrospun nanofiber mats decorated with in-house synthesized silver (Ag(+)) ion exchanged zeolites that function as molecular delivery vehicles. LTA-Large zeolites with a particle size of 6.0 μm were grown on the surface of the cellulose nanofiber mats, whereas LTA-Small zeolites (0.2 μm) and three-dimensionally ordered mesoporous-imprinted (LTA-Meso) zeolites (0.5 μm) were attached to the surface of the cellulose nanofiber mats postsynthesis. After the three zeolite/nanofiber mat assemblies were ion-exchanged with Ag(+) ions, their ion release profiles and ability to inactivate Escherichia coli (E. coli) K12 were evaluated as a function of time. LTA-Large zeolites immobilized on the nanofiber mats displayed more than an 11 times greater E. coli K12 inactivation than the Ag-LTA-Large zeolites that were not immobilized on the nanofiber mats. This study demonstrates that by decorating nanometer to micrometer scale Ag(+) ion-exchanged zeolites on the surface of high porosity, hydrophilic cellulose nanofiber mats, we can achieve a tunable release of Ag(+) ions that inactivate bacteria faster and are more practical to use in applications over powder zeolites.

Effect of silver ions and clusters on the luminescence properties of Eu-doped borate glasses

Silver ions and clusters were applied to Eu3+-doped borate glasses via the Ag+–Na+ ion exchange method. Eu3+/Eu2+ ion luminescence enhancement was achieved after silver ion exchange. Absorption spectra showed no band at 420nm, which indicates that silver nanoparticles can be excluded as a silver state in the glass. Silver ion aggregation into clusters during the ion exchange process may be inferred. The effect of silver ions and clusters on rare earth emissions was investigated using spectral information and lifetime measurements. Significant luminescence enhancements were observed from the energy transfer of Ag+ ions and clusters to Eu3+/Eu2+ ions, companied with the silver ions aggregated into the clusters state. The results of this research may extend the current understanding of interactions between rare-earth ions and Ag species.

Formation of Core–Shell Bimetallic Nanostructures in Alkali Silicate Glasses in the Course of Silver and Copper Ion Exchange and Thermal Treatment

Experimental data on the formation of the core–shell bimetallic spherical nanostructures in alkali silicate glasses is presented. The Ag–Cu and Cu–Ag core–shell bimetallic spherical nanostructures were formed in the near-surface glass layers by the successive Na+ → Ag+ and Na+ → Cu+ or Na+ → Cu+ and Na+ → Ag+ ion exchange and subsequent thermal treatment above the glass transition temperature. The optical density measurements have shown that the Ag–Cu core–shell nanostructures provide three plasmon resonances and the Cu–Ag core–shell nanostructures provide at least four plasmon resonances. Experimental results obtained are confirmed by computer simulation in the dipole quasistatic approximation.

Saturable absorption of silver nanoparticles in glass for femtosecond laser pulses at 400 nm

The commercially available glass BK7 was chosen to prepare silver-rich layer within the glass by the silver (Ag) ion exchange method in order to enhance its nonlinear optical properties. The glass substrates were doped with Ag at 320°C by a 50-minute Ag+↔Na+ ion exchange in a melt of NaNO3 and KNO3 containing 14mol% of AgNO3. Then, one piece of glass BK7 containing Ag ions (as-exchanged sample) was annealed in air for 1h at 600°C to prepare the as-annealed sample. The thickness of the layer containing Ag in the as-exchanged glass BK7 was measured to less than 1μm. It was found that during the post-exchanged annealing most silver diffused deeply into the glass substrate leading to increase the thickness of the layer to 110μm. However, some amount of Ag nucleated during the annealing, thus creating small nanoparticles (NPs) with an average size of 2nm. The linear and nonlinear optical properties of the as-exchanged and as-annealed glass BK7 were studied. The as-exchanged sample showed no absorption in the visible spectral region whereas, as-annealed glass BK7 showed a peak absorption at 420nm which can be attributed to the presence of Ag NPs formed in this glass. The nonlinear optical behavior of the samples was investigated using 800nm and 400nm femtosecond pulses. Strong saturable absorption was observed in the as-annealed sample at 400nm. This feature promises an efficient way for designing all optical switching devices appropriate for the second harmonic of the Ti-sapphire laser. Using nonlinear transmission (NLT) method the saturation intensity for the as-annealed sample was determined 8.5×1011W·cm−2. An intensity dependent switching from saturable absorption (SA) to reverse saturable absorption (RSA) was also observed when the as-annealed sample was irradiated simultaneously by 800nm and 400nm femtosecond pulses.

Development of Silver Ion Doped Antibacterial Clays and Investigation of Their Antibacterial Activity

Kaolinite, sepiolite, and clinoptilolite were used as carriers to develop antibacterial materials. The materials were enriched in sodium by ion exchange. Silver ion exchange by silver nitrate followed by phosphoric acid treatment enabled the controlled release of silver. The antibacterial function of the materials was investigated by halo test and the amount of silver released was investigated by energy dispersive X-ray spectroscopy. The enhanced antibacterial efficiency was obtained by minimizing the silver release which further provided longevity to the material and prevented the health risks posed by excess silver release.

Kinetics and Equilibrium Studies for the Removal of Cobalt, Manganese, and Silver in Ethanol using Dowex 50W-x8 Cation Exchange Resin

Organic solvents such as ethanol, find a wide range of applications in fuel, pharmaceutical industries, food industries, and paint formulations, among others. The removal of Ag(I), Co(II), and Mn(II) ions in ethanol by cation exchange resin, Dowex 50W-x8, was investigated. The adsorption characteristics of metal ions onto Dowex 50W-x8 resin were described by Langmuir isotherms. The maximum sorption exchange capacities at 298 K were obtained as 47.4 mg g−1, 52.6 mg g−1, and 58.5 mg g−1 for Ag(I), Co(II), and Mn(II), respectively. The data was also fitted to Temkin and Dubinin-Radushkevich adsorption isotherm models to evaluate other adsorption properties. The ion exchange of silver, cobalt, and manganese on cation exchange resin followed pseudo-second-order kinetics, and the intraparticle diffusion was rate-determining step. The thermodynamic parameters indicated that the sorption of metal ions onto Dowex 50W-x8 resin was spontaneous (negative ΔG°) and endothermic in nature (positive ΔH°) implying that the adsorption capacity increased with increasing temperature. The resin can be regenerated by eluting metal ions with 3.0 mol L−1 HNO3 followed by washing it with 10 mL of Millipore water and 10 mL of 2.0 M NaOH, respectively. The proposed method was applied for metal ion removal in real ethanol samples.

Effect of the photoinduced charge exchange of Ag+ ions on the sensitized luminescence of Eu3+ in oxide films

It has been found that the excitation of silver ions by ultraviolet radiation in GeO2-Eu2O3-Ag and SiO2-Eu2O3-Ag films is accompanied by the weakening of silver-ion-sensitized luminescence of Eu3+ ions. The degree and rate of such weakening vary in wide ranges depending on the nature of the matrix, thermal treatment temperature, and energy of an exciting photon. The revealed effect has been explained by the photoinduced charge exchange of silver ions in complex Ag-Eu centers.

Silver confined within zeolite EMT nanoparticles: preparation and antibacterial properties.

The preparation of pure zeolite nanocrystals (EMT-type framework) and their silver ion-exchanged (Ag(+)-EMT) and reduced silver (Ag(0)-EMT) forms is reported. The template-free zeolite nanocrystals are stabilized in water suspensions and used directly for silver ion-exchange and subsequent chemical reduction under microwave irradiation. The high porosity, low Si/Al ratio, high concentration of sodium and ultrasmall crystal size of the EMT-type zeolite permitted the introduction of a high amount of silver using short ion-exchange times in the range of 2-6 h. The killing efficacy of pure EMT, Ag(+)-EMT and Ag(0)-EMT against Escherichia coli was studied semi-quantitatively. The antibacterial activity increased with increasing Ag content for both types of samples (Ag(+)-EMT and Ag(0)-EMT). The Ag(0)-EMT samples show slightly enhanced antimicrobial efficacy compared to that of Ag(+)-EMT, however, the differences are not substantial and the preparation of Ag nanoparticles is not viable considering the complexity of preparation steps.

Silver Exchange of Layered Metal Oxides and Their Photocatalytic Activities

Layered Dion–Jacobson phases RbLaNb2O7 and RbA2Nb3O10 (A = Ca, Sr) and the Ruddlesden–Popper phase Rb2La2Ti3O10 were prepared by solid-state methods at a reaction time of 50 h and a temperature of 1100 °C. The products were silver-exchanged within a AgNO3 flux at a reaction time of 24 h and a temperature of 250 °C. Substitution of silver cations into the interlayer spacing of the layered structures is found to decrease the optical bandgap sizes on average by ∼0.5 to ∼1.0 eV. The products were found by scanning electron microscopy (SEM) to exhibit irregularly shaped platelet morphologies with an average size of ∼1–5 μm across their lateral dimensions and stepped edges ranging from ∼20 to ∼300 nm in height. Significant increases in photocatalytic hydrogen production rates for all silver-exchanged products were observed. The silver-exchanged RbA2Nb3O10 layered structures exhibited the highest photocatalytic hydrogen formation rates under ultraviolet and visible irradiation (∼13,616 μmol H2·g–1·h–1). These ra...

Effects of silver ion exchange and subsequent treatments on the UV–VIS spectra of silicate glasses. I. Undoped, CeO2-doped, and (CeO2 + Sb2O3)-codoped photo-thermo-refractive matrix glasses

The effects of the silver ion exchange and of subsequent UV irradiation and/or heat treatment on the optical density spectra of photo-thermo-refractive matrix glass samples both virgin and doped with cerium and/or antimony oxides were investigated. The incorporation of silver by ion exchange for ~15min at 310°C was found to cause, for all glasses except those with CeO2 content around 0.1mol% or more, a shift of the UV limit of strong absorption to the greater wavelengths by ~70–100nm due to the occurrence of Ag+-related absorption. Complicated changes caused by the UV irradiation and/or heat treatment of ion-exchanged samples in the location of their UV limit of strong absorption and in the absorption throughout the 330–550nm region were analyzed and shown to be greatly influenced by (i) the kind of dopant(s), (ii) chances for shifting the redox and other equilibria involving the dopants at temperatures of particular treatment processes, and (iii) NaBr presence in the glass batch composition. The effect of NaBr addition was explained tentatively in terms of formation, after the heat treatment, of AgBr clusters or nanocrystals.

Lead Chalcogenide Quantum Dot‐Doped Glasses for Photonic Devices

Tunable absorption and photoluminescence (PL) of lead chalcogenide quantum dots (QDs) doped in glasses due to the quantum confinements effect have been actively investigated for application as saturable absorbers, laser sources, and fiber‐optic amplifiers. Optical properties of QDs have been carefully monitored by controlling their sizes through heat treatment and rare‐earth ion doping. Two‐ and three‐dimensional precipitation of lead chalcogenide QDs were also realized using silver ion exchange and femtosecond laser irradiation in combination with thermal treatment. Prototypes of microstructured single‐mode fibers and tapered fiber amplifiers containing QDs proved potentials of these materials for fiber‐optic amplifiers application. Further research works on QD‐doped solid core fibers, surface passivation of quantum dots and their application for the mid‐infrared optical devices are necessary.

Antibacterial Properties of Titanate Nanofiber Thin Films Formed on a Titanium Plate

A sodium titanate nanofiber thin film and a silver nanoparticle/silver titanate nanofiber thin film formed on the surface of a titanium plate exhibited strong antibacterial activities against methicillin‐resistant Staphylococcus aureus, which is one of the major bacteria causing in‐hospital infections. Exposure of the sodium titanate nanofiber thin film to ultraviolet rays generated a high antibacterial activity due to photocatalysis and the sodium titanate nanofiber thin film immediately after its synthesis possessed a high antibacterial activity even without exposure to ultraviolet rays. Elution of silver from the silver nanoparticle/silver titanate nanofiber thin film caused by the silver ion exchange reaction was considered to contribute substantially to the strong antibacterial activity. The titanate nanofiber thin films adhered firmly to titanium. Therefore, these titanate nanofiber thin film/titanium composites will be extremely useful as implant materials that have excellent antibacterial activities.