Papers by Keyword: Ag

Abstract: In this research, a comparison was made between the optical and chemical properties of ZnO-Ag composites with different ZnO and Ag ratios synthesized using extracts obtained from mimosa and Andrographis paniculata plants. The optical properties of the synthesized ZnO-Ag composites were analyzed, focusing on parameters such as absorption and bandgap energy. Moreover, the bandgap, which indicates the energy difference between the valence and conduction bands, was calculated to assess the compounds' electronic behavior. Furthermore, the chemical properties of the ZnO-Ag composites were investigated. This involved analyzing the chemical bond, crystal structure, and crystalline size using X-ray diffraction (XRD) and Fourier Transform Infrared Spectrometer (FT-IR). The experimental findings demonstrated that the crystal sizes of ZnO and Ag in ZnO-Ag composites synthesized using Mimosa pudica extract were considerably smaller compared to those synthesized using Andrographis paniculata extract. Consequently, the energy gap of the ZnO-Ag compounds synthesized with mimosa extract was higher in comparison to those synthesized with Andrographis paniculata extract. By comparing the optical and chemical properties of the ZnO-Ag composites synthesized from mimosa and Andrographis paniculata extracts, valuable insights can be gained regarding the influence of these plant extracts on the resulting composites.

Abstract: The present work reviews the results of the photoluminescence (PL) study of silver-doped ZnO nanostructures synthesized by both physical and chemical methods. ZnO is a semiconductor with a binding energy of 60 meV, which ensures efficient near-band-edge band emission at a temperature of 300K and ultraviolet emission of bulk ZnO, and ZnO has a bandgap energy of 3.37 eV at room temperature. By tuning the growth process parameters of silver-doped ZnO nanostructures, the optical properties of ZnO can be controlled for use in various optoelectronic components, biosensors, blue-emitting diodes, and even white light sensors.

Abstract: Waterborne disease has changed a basic challenge in human population. recently, the use of nanotechnology and application of nanomaterials for the control of pathogens in water is widely increased in research. Common indicator for microbial quality of water are determine presence of total and fecal coliforms. The purpose of this study was to evaluate the effect of Silver (Ag) and zinc oxide (ZnO) nanoparticles (NPs) and combination of them in removing total and fecal coliform bacteria from contaminated water. In this experimental study a synthetic solution was made by adding effluent to distilled water. In each run, the nano silver (20-100 μg /L) and ZnO NPs (0.25-2 mg/L) were added to contaminated water. The samples were tested by 15-tube series method based on the instruction 9221-B of 21th edition of standard method book on water and wastewater experiments. Bacteria removal efficiency were examined in contact times (15, 30,60, 90 and 120) minutes. Our data indicate a decrease in the number of bacteria (MPN) in the presence of the nanoparticles. Results revealed that the removal percentage of coliform bacteria removal increased with increasing the contact time and concentrations of nanoparticles. Ag NPs at a concentration of 100 μg /L and ZnO NPs at a concentration of 2 mg/L showed the highest percentage of removal bacteria and the combination of ZnO and Ag NPs have been high synergistic behavior against coliform bacteria in contaminated water. therefore, using a combination of ZnO and Ag NPs can become a new and efficient method for the removal of indicator bacteria from contaminated water.

Abstract: Ag nanoparticles and GO co-modified Co-g-C₃N₄ composites were prepared successfully. The visible-light adsorption of the optimized GO-Ag@Co-g-C₃N₄ was improved significantly by the SPR effect of Ag nanoparticles, and the separation efficiency of photo-induced electron-hole pairs of g-C₃N₄ was accelerated to a large extent by the heterojunction structure of the composite and the superior conductivity of GO. The optimized GO-Ag@CoCN showed promising degradation efficiency for RhB (10 mg/L) under visible light illumination (λ>420 nm) for 160 min, which was 130% and 16.5% higher than the performance using bare g-C₃N₄ and optimized Ag@Co-g-C₃N₄, respectively. This work provided a novel way for improving the optical property and photocatalytic activity of g-C₃N₄.

Abstract: The article presents the results of an investigation of microstructural features and mechanical characteristics of Al-5.0Cu-0.5Mg alloy containing up to 0.4 wt. % Ag and up to 0.1 wt. % Ce. The experiment was conducted using optical microscopy, Scanning Electron Microscopy as well as an electron probe micro-analyzer and Differential Scanning Calorimetry. Samples in cast condition and after heat treatment were examined. The melting temperatures of non-equilibrium eutectics (non-equilibrium solidus), equilibrium solidus and liquidus were determined. The optimal temperature of the homogenizing heat treatment was determined, which was 500°C. Using this heat treatment mode resulted in the elimination of dendritic segregation and complete dissolution of silver in aluminum. Injection of cerium into the Al-Cu-Mg-Ag system during crystallization of the melt is accompanied by the formation of a coarse four-component phase, which has the morphology of polyhedrons, is on the grain boundaries. The estimation of the relation between microstructure characteristics and mechanical properties of the alloy has been made.

Abstract: Octahedral layered birnessite (OL) was synthesized by redox method, and OL supported Ag catalysts (xAg/OL, x = 0.1wt%, 0.2wt%, 0.3wt%, 0.5wt%) were prepared by ion exchange method. Then catalysts were characterized by XRD, SEM, BET, H₂-TPR, TG, O₂-TPD and in-situ DRIFTS, while the catalytic activity of CO was evaluated. Among xAg/OL samples, the 0.3Ag/OL exhibited the best catalytic activity for CO oxidation (T₅₀ = 105 ^oC and T₉₀ = 135 ^oC). The results show that the chemical adsorption of oxygen, the low-temperature reducibility and the strong interaction between the Ag species and OL are related to the excellent catalytic activity of xAg/OL. The reaction mechanism was studied by in-situ DRIFTS. First, O₂ was adsorbed and activated on the oxygen vacancies of xAg/OL, then formed oxygen free radical attacked the adsorbed CO and produced CO₂, subsequently CO₂ desorbed from the catalyst surface. Oxygen vacancies was supplemented by gas O₂, thus circulating.

Abstract: In this manuscript, the structural properties such as the distance inter-reticular of samples is studied, In the fact, four samples were used symbolized as follows: E tAg(Å), the only difference is the thickness of the Silver buffer layer (tAg= 0, 50, 100 and 150 Å) to find out how the thickness of this layer depends on the structural characteristics of the Iron thin layer, all samples are deposited using molecular beam epitaxy (MBE) at room temperature onto Si (100) substrate. The structural properties of all samples examined using X-ray diffraction method at small and high angles. The small angles X-Ray diffraction curves confirmed to us that there is a clear difference between the surface structure of the samples by varying the number of Kiessig Fringes, Also high angles X-Ray diffraction curves assured us this difference through the clear variation in the angular positions of the peaks of Bragg and the distances inter-reticular values from a sample to the other.

Abstract: The platinum (Pt) degradation, poisoning and carbon corrosion in acidic fuel cell has led to explore the research in alkaline fuel cell. However, the high cost of Pt has brought a lot of studies to find replacement for Pt catalyst. Due to that, silver metal is selected as non-Pt catalyst and supported by the nitrogen and phosphorus-doped on graphene for oxygen reduction reaction in alkaline medium. The adsorption energy and mechanism of the oxygen reduction reaction is studied by using density functional theory (DFT) calculation. The support catalyst of graphene is doped with three atom nitrogen and phosphorus namely as N3 and P3, respectively. The Ag supported on N3 and P3 are tested on O₂, OOH, O and OH species. There are two types adsorption of O2 on N3 and P3 which is side and end-on adsorption configuration. The N3-Ag has similar adsorption energy for both configurations, but P3-Ag has low adsorption energy by end-on adsorption configuration. The effect of doped atoms on graphene also have been tested on O₂, OOH, O and OH species. The result shows that increasing nitrogen doping atom has decreased the adsorption energy of O2 and vice versa on phosphorus atoms. A single phosphorus doping atom on graphene has shown the lowest adsorption energy, but the end-on configuration of P3-Ag has shown most stable adsorption. The schematic free energy profile shows that both N3-Ag and P3-Ag have high possibilities to be followed in oxygen reduction reaction mechanism but P3-Ag has advantage due to stable adsorption as non-Pt catalyst. The Ag metal supported on nitrogen and phosphorus-doped graphene show promising result to be a catalyst in alkaline fuel cell.

Abstract: We prepared ytterbium and silver co-doped tantalum-oxide (Ta₂O₅:Yb,Ag) thin films using a simple co-sputtering method and evaluated photoluminescence (PL) properties of the films after annealing. We found that a PL peak at a wavelength of 980 nm due to Yb³⁺ can be strongly enhanced by Ag doping. From X-ray diffraction measurements, we found that Ag₂Ta₈O₂₁ and orthorhombic Ta₂O₅ crystalline phases are very important in order to enhance the 980-nm peak observed from our Ta₂O₅:Yb,Ag thin films. Because of the human-body transmittability of the 980-nm wavelength, such films are applicable to a novel real-time X-ray dosimeter system.

Abstract: MgO and silver-containing MgO (AgMgO, 3.3, 9.1 at% Ag) films were sol-gel coated on titanium to improve its antibacterial property. Thermal analyses of MgAc₂·4H₂O powder revealed that MgO was crystallized at 400 °C. X-ray diffraction analysis showed that MgO was converted to Mg(OH)₂ or Mg₅(CO₃)₄(OH)₂·4H₂O during the ageing in air. Silver nanoparticles at the surface of AgMgO films were identified by scanning electron microscopy and x-ray photoelectron spectroscopy. The MgO film was about 1.5 um thick. The potentiodynamic polarization test in the Ca-free Hank’s balanced salt solution showed that the coated titanium samples had better corrosion resistance than the polished one. The dissolution of silver nanoparticles resulted in a current peak in the polarization plots. In the antibacterial test against E. Coli, the inhibition zone width was 0.3, 1.6, 2.0 mm for the films with 0, 3.3, 9.1 at% Ag, respectively. The bactericidal mechanisms of the MgO and AgMgO films were discussed. The present work would provide a facile method for antibacterial surface modification of titanium based osteo-implants.