Toward an Understanding of the Growth of Ag Filaments on α‑Ag₂WO₄ and Their Photoluminescent Properties: A Combined Experimental and Theoretical Study

A combined experimental and theoretical study was conducted on the structure and electronic properties of α-Ag₂WO₄ to clarify the nucleation and growth processes of Ag filaments on α-Ag₂WO₄ crystals induced by electron beam irradiation under electron microscopy. X-ray diffraction with Rietveld analysis, micro-Raman and Fourier-transform infrared spectroscopy were used to analyze the structural order/disorder of α-Ag₂WO₄ crystals. These complementary techniques indicated that the microwave-assisted hydrothermal method employed in the synthesis of α-Ag₂WO₄ crystals leads to the freezing of distorted [WO₆] and [AgO_<i>y</i>] (<i>y</i> = 2, 4, 6 and 7) clusters as the constituent polyhedra of α-Ag₂WO₄. On the basis of the theoretical and experimental results, we provide a complete assignment of the structure of α-Ag₂WO₄ and describe the relationship among the disorder, nucleation growth, rate of Ag formation, and photoluminescence behavior before and after the irradiation of the accelerated electron beam. Density functional theory (DFT) studies indicated significant changes in the order–disorder of the initial α-Ag₂WO₄electronic structure, with a decrease in the band gap value from 3.55 to 2.72 eV. The first stages of the electron irradiation on α-Ag₂WO₄ crystal were investigated by DFT calculations, and we have derived a mechanism to describe the formation and growth of Ag filaments during the electronic excitation of the [AgO₂] cluster

Potentiated Electron Transference in α‑Ag₂WO₄ Microcrystals with Ag Nanofilaments as Microbial Agent

This study is a framework proposal for understanding the antimicrobacterial effect of both α-Ag₂WO₄ microcrystals (AWO) synthesized using a microwave hydrothermal (MH) method and α-Ag₂WO₄ microcrystals with Ag metallic nanofilaments (AWO:Ag) obtained by irradiation employing an electron beam to combat against planktonic cells of methicillin-resistant Staphylococcus aureus (MRSA). These samples were characterized by X-ray diffraction (XRD), FT-Raman spectroscopy, ultraviolet visible (UV–vis) measurements, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and high resolution transmission electron microscopy (HRTEM). The results reveal that both AWO and AWO:Ag solutions have bacteriostatic and bactericidal effects, but the irradiated sample is more efficient; i.e., a 4-fold of the MRSA planktonic cells as compared to the nonirradiated sample was observed. In addition, first principles calculations were performed to obtain structural and electronic properties of AWO and metallic Ag, which provides strong quantitative support for an antimicrobacterial mechanism based on the enhancement of electron transfer processes between α-Ag₂WO₄ and Ag nanoparticles