Papers by Keyword: Silver

Abstract: In this study, silver-silica (Ag/SiO₂) was synthesized using the sol-gel method by silica from rice husks. Silica derived from rice husk waste was previously synthesized using the sol gel method. In addition, the Ag material used in this study was also performed into silver nanoparticles (AgNPs). This method was chosen to obtain an Ag/SiO₂ composite with nano size and high purity. AgNPs were synthesized using silver nitrate (AgNO₃) by reduction method at 90 °C. The reducing agent and stabilizer used is trisodium citrate. UV-Vis, FTIR, XRD, and SEM-EDX were used for the analysis Ag/SiO₂ composites. Uv-Vis analysis results Ag/SiO₂ has an absorption peak at a wavelength of 412 nm with a bandgap energy of 2.25 eV. These peaks indicate that AgNPs have formed in the SiO₂ membrane. The FTIR results revealed the Si-O-Si bonds which indicated the presence of silica and the Ag-O functional group, and the presence of AgNPs. The results of XRD analysis showed that the silica structure formed was cristobalite and silver crystals in the face center cubic (fcc) shape. The results of the SEM-EDX morphological analysis showed that the Ag/SiO₂ nanocomposite was shaped like sharp stone chips and the presence of small granules (granules) with different particle sizes and shapes, slightly porous and the composition of the compounds in the Ag/SiO₂ nanocomposite indicated the presence of various chemical elements in the sample, including carbon, oxygen, sodium, silica, and silver.

Abstract: The introduction of antimicrobial nanoparticles into nanofiber coatings is significant for enhancing microbial corrosion protection. Here, electrospun polysulfone nanofiber (PSU-Nf) and PSU-Nf functionalized with biogenic silver nanoparticles (AgNPs) coatings (PSU-Nf-AgNPs) used for Cobalt (Co) corrosion resistance in a marine environment containing Aeromonas eucrenophila (A. eucrenophila). We utilized the barrier function of the PSU-Nf and the bacterial inhibition property of the AgNPs that are synthesized using bacteria. The thickness of nanofiber coatings was 233.11 ± 33.64 µm analyzed by optical microscope and beadless morphology of nanofibers was observed using scanning electron microscope (SEM). The corrosion behavior of Co coated with PSU-Nf and PSU-Nf-AgNPs in abiotic and in the presence of the bacterium environment was investigated via polarization techniques and electrochemical impedance spectroscopy (EIS). Corrosion analysis reveals that the charge transfer resistance (R_ct) increased because of the addition of the nanostructure resulting in a reduction in corrosion rate. SEM micrographs show Co surface was severely damaged by a microbial corrosive attack with severe crevices. However, the PSU-Nf and especially PSU-Nf-AgNPs coated Co surface was still covered by nanofiber coatings as the bacteria colony was not noticed. In addition, the results of the performing bacterial disk diffusion method indicated that electrospun PSU-Nf-AgNPs have good antibacterial activity against Gram-positive, Gram-negative, and model biofilm bacterium. It was found that the uncoated Co surface had severe crevices and offered poor corrosion resistance under mineral salt medium with A. eucrenophila strain. Therefore, PSU-Nf-AgNPs coated Co exhibited better corrosion resistance in mineral salt medium containing bacteria.

Abstract: Several attempts have been conducted to improve the mechanical properties of mineral trioxide aggregate (MTA), including the addition of various nanoparticle materials such as silver and titania. The smaller the added material, the higher the material’s ability to fill the cavity of MTA, thus increasing the tensile strength of MTA after hydration. In this study, the effect of silver nanoparticles (AgNP) concentration and titania (TiO2) mass variation on the tensile strength of MTA was investigated. The ratio of MTA mass to AgNP volume used was 1 g to 330 μL, while TiO2 was added to MTA powder in a solid-solid state with a mass variation. The results show that the addition of AgNP and TiO2 to MTA powder can significantly increase the tensile strength of MTA from 0.404±0.125 to 1.044±0.021 and 1.378±0.391 MPa for 1.5% Ag and 0.5% TiO2, respectively.

Abstract: Short Multi-Walled Carbon Nanotubes functionalized with OH group (MWCNTs-OH) were used to synthesize flexible MWCNTs networks. The MWCNTs suspension was synthesized using Benzoquinone (BQ) and N, N Dimethylformamide alcohol (DMF) in specific values and then deposited on filter paper by filtration from suspension (FFS) method. Polypyrrole (PPy) conductive polymer doped with metallic nanoparticles (MNPs) prepared using in-situ chemical polymerization method. To improve the properties of the MWCNTs networks, a coating layer of (PPy) conductive polymer, PPy:Ag nanoparticles, and PPy: Cu nanoparticles were applied to the network. The fabricated networks were characterized using an X-ray diffractometer (XRD), UV-Vis. spectrometer, and Atomic Force Microscope (AFM). XRD results revealed that the broadening for the (002) peak decreased after being coated with PPy and increased for the doped samples with MNPs, indicating on decrease in the crystalline size (MWCNTs/PPy) sample and increasing for doped ones with Ag and Cu MNPs. AFM images revealed that the surface roughness of the MWCNTs-OH network decreased after being coated with PPy, PPy: Ag, and PPy: Cu. With the help of AFM and XRD results, the CNTs contain 14 layers, while the inner and outer diameters were 18.2 nm and 27 nm receptivity. The UV-Vis. spectrum of MWCNTs showed several peaks, the highest in the 350 nm range. The coated of MWCNTs greatly affected the absorption spectrum, with many bands appearing between 300 to 450 nm and increasing the absorbance along the overall spectrum. For samples doped with Ag NPs and Cu NPs, a weak absorption peak of the plasmonic resonance frequency of the metallic nanoparticles. Analysis of Raman spectra shows that (I_D/I_G) ratios for all networks are less than one, which prove that the fabricated networks have few impurities and have good homogeneity. This work aimed to synthesize and characterize a flexible MWCNTs network and develop it by coated with a layer of conductive polymer and metallic nanoparticles for gas sensing application using quick and straightforward preparation methods.

Abstract: In this study, pristine graphene/silver/molybdenum disulphide (G/Ag/MoS₂) and reduced graphene oxide/silver/molybdenum disulphide (rGO/Ag/MoS₂) composites materials were prepared via green solvothermal synthesis method and evaluated as supercapacitor electrodes. The morphology and structure of composites were examined by using Scanning Electron Microscopy (SEM), Energy dispersive spectroscopy (EDX), X-ray diffraction spectroscopy (XRD), and Raman spectroscopy. SEM and TEM indicate successful reduction of silver nitrate (AgNO₃) to spherical Ag nanoparticles (NPs) by sodium citrate. The Ag NPs were observed to be evenly deposited on sheets of rGO and MoS₂. From the XPS analysis, the spherical Ag NPs exist in zero-valent state, reflecting successful reduction. Based on cyclic voltammetry (CV) performed under 50 mV/s scan rate, G/Ag/MoS₂ ternary composite exhibits the highest specific capacitance of 56.38 F/g which is 31 % and 29 % enhancement in specific capacitance of rGO/Ag/MoS₂ ternary composite and Ag/MoS₂ binary composite, respectively. It is believed that the presence of graphene may provide conductive pathway and a larger surface area for the distribution of Ag NPs.

Abstract: A comparative analysis of the occupational hazard was done when working with widely known cyanide electrolytes and new thiocarbamide and citrate acid-based electrolytes. For this purpose, we made use of available reference data on maximum permissible substance concentrations, i.e. process solution components. Appropriate computations were done to define the environmental hazard of the electrolytes used for the application of silver, gold and copper coatings and also for the electrochemical silver polishing. Consideration was given to the reactions that proceed in cyanide and thiocarbamide-citrate bathes. The main drawbacks and advantages of given electrolytes have been established. Special attention was paid to the quality of galvanic products. It was proved that the suggested electrolytes are highly competitive with cyanide analogues as for their visual appearance, density and other characteristics of the condition of treated surface. These turned out to be labor saving and energy efficient and have substantially lower harmful effect on the human health and environment.

Abstract: The Fe₃O₄/ZnO/Ag nanocomposite has been successfully synthesized, and the material was applied as a photocatalyst to degrade titan yellow. The Fe₃O₄ was synthesized through sono-coprecipitation method using NH₄OH as a precipitating agent. The synthesized ZnO/Ag was performed via coprecipitation method using ethylene glycol, zinc acetate, and silver nitrate as a reagent. This study investigated several parameters, such as the effect of time reaction, equilibrium state, and material responsiveness under visible light irradiation. The XRD measurement indicated the presence of ZnO, Ag, and Fe₃O_4, whereas the TEM image displayed the photocatalyst had a nanosized particle with approximately 17 nm. The photocatalyst activity has shown the equilibrium process at 60 minutes. The highest degradation (up to 90%) of titan yellow was achieved by Fe₃O₄/ZnO/Ag nanocomposite. The reusability test showed that Fe₃O₄/ZnO/Ag nanocomposite had high stability and could be used up to three times.

Abstract: Adsorption of Ag(I) on dithizone-immobilized coal fly ash (Dtz-CFA) from PT Madukismo Factory, Yogyakarta, Indonesia has been investigated. Immobilization of dithizone on activated coal fly ash (Act-CFA) was done by stirring the mixture of two precursors in toluene medium at 50 °C for 16 h. Parameters influencing adsorption of Ag(I) such as pH of solution, contact time and initial concentration of Ag(I) ions were optimized. FT-IR and XRD characteriztions show that the surface of fly ash has successfully immobilized by dithizone. The optimum conditions for Ag(I) adsorption are reached at pH 6, contact time of 45 min and initial concentration of 100 mg g^-1. The ability of Dtz-CFA to adsorb Ag(I) metal ions significantly increases as compared to that of Act-CFA. Kinetic and isotherm adsorption studies suggest that adsoption of Ag(I) using both Act-CFA and Dtz-CFA follows a second-order pseudo reaction and Langmuir isotherm model, respectively. These results indicate that Dtz-CFA may be used as prospective adsorbent for removing Ag(I) ion.

Abstract: The chemical technology for recovery precious metals Au and Ag from mature flotation tailings of copper-pyrite ores by two-stage sintering with chlorine-ammonium reagents and leaching of bakes with water is developed. The chemical extraction of gold and silver is carried out, using NH₄Cl and NH₄NO₃ reagents in the ratios of 1:1 at a temperature of 250 °C, and 2:1 at 200 °C. In accordance with the obtained results, a chemical technology of enrichment rejects of copper-pyrite ores processing and a scheme of primary apparatus chain for implementing this technology are proposed. The economic effect of the technology realization is calculated. This effect is 96.3 million rubles with a payback period of 8 years when processing enrichment rejects of copper-pyrite ores in amount of 109.5 thousand tons per year under the conditions of JSC “Uchaly Mining and Metallurgical Combine”.

Abstract: This study depicts substantial characteristics of copper and silver pastes, dispensed and cured by oven processing. Different analyses, such as second electron microscopy (SEM), rheometry, thermogravimetric analysis (TGA), UV-VIS-NIR-spectroscopy and 4-point measurement were used. This work also will illustrate some results of computational design of experiment (DOE) and regression analyses for jet and mechanical printing processes.