RESUMO
In this paper, we present a combined experimental and theoretical study to disclose, the structure, electronic and optical properties of CaMoO 4 :xTb 3+ ( x = 1%, 2%, and 4%) microspheres. The microspheres were prepared by ultrasonic spray pyrolysis method and characterized by experimental and theoretical techniques. Theoretical calculations and XRD patterns indicate that these crystals have a scheelite-type tetragonal structure. The morphology of the CaMoO 4 :xTb 3+ ( x = 1%, 2% and 4% mol) samples were investigated from the FEG-SEM results and the formation of microspheres with a spherical shape were observed. The optical properties were investigated by UV-Vis and PL spectroscopy, as well as the chromaticity coordinates of these compounds. This also allowed us to understand the charge transfer process that happens in the singlet state and the excited states, generating the photoluminescence emissions of the Tb doping process in CaMoO 4 microspheres.
RESUMO
In this paper, we present a combined experimental and theoretical study to disclose, for the first time, the structural, electronic, and optical properties of Ca10V6O25 crystals. The microwave-assisted hydrothermal (MAH) method has been employed to synthesize these crystals with different morphologies, within a short reaction time at 120 °C. First-principle quantum mechanical calculations have been performed at the density functional theory level to obtain the geometry and electronic properties of Ca10V6O25 crystal in the fundamental and excited electronic states (singlet and triplet). These results, combined with the measurements of X-ray diffraction (XRD) and Rietveld refinements, confirm that the building blocks lattice of the Ca10V6O25 crystals consist of three types of distorted 6-fold coordination [CaO6] clusters: octahedral, prism and pentagonal pyramidal, and distorted tetrahedral [VO4] clusters. Theoretical and experimental results on the structure and vibrational frequencies are in agreement. Thus, it was possible to assign the Raman modes for the Ca10V6O25 superstructure, which will allow us to show the structure of the unit cell of the material, as well as the coordination of the Ca and V atoms. This also allowed us to understand the charge transfer process that happens in the singlet state (s) and the excited states, singlet (s*) and triplet (t*), generating the photoluminescence emissions of the Ca10V6O25 crystals.
RESUMO
The COVID-19 pandemic has emerged as an unprecedented global healthcare emergency, demanding the urgent development of effective materials to inactivate the SARS-CoV-2 virus. This research was planned to disclose the remarkable biocidal activity of SiO2-Ag composites incorporated into low-density polyethylene. For this purpose, a joint experimental and theoretical [based on first-principles calculations at the density functional theory (DFT) level] study is performed. Biological assays showed that this material eliminatesStaphylococcus aureusand SARS-CoV-2 virus in just 2 min. Here, we investigate a previously unexplored process that we postulate may occur along the O2 and H2O adsorption and activation processes of pure and defective SiO2-Ag surfaces for the generation of reactive oxygen species (ROS). The obtained results help us to predict the nature of ROS: superoxide anion radicals, â¢O2-, hydroxyl radicals, â¢OH, and hydroperoxyl radicals, â¢HO2, that destroy and degrade the structure of the SARS-COV-2 virus. This is consistent with the DFT studies, where the energetic, electronic, and magnetic properties of the intermediates show a feasible formation of ROS. Present findings are expected to provide new insights into the relationship among the structure, property, and biocidal activity of semiconductor/metal SiO2-Ag composites.