Unraveling the Intrinsic Biocidal Activity of the SiO2-Ag Composite against SARS-CoV-2: A Joint Experimental and Theoretical Study.

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, •O2-, hydroxyl radicals, •OH, and hydroperoxyl radicals, •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.

Unconventional Disorder by Femtosecond Laser Irradiation in Fe2O3.

This paper demonstrates that femtosecond laser-irradiated Fe2O3 materials containing a mixture of α-Fe2O3 and ε-Fe2O3 phases showed significant improvement in their photoelectrochemical performance and magnetic and optical properties. The absence of Raman-active vibrational modes in the irradiated samples and the changes in charge carrier emission observed in the photocurrent density results indicate an increase in the density of defects and distortions in the crystalline lattice when compared to the nonirradiated ones. The magnetization measurements at room temperature for the nonirradiated samples revealed a weak ferromagnetic behavior, whereas the irradiated samples exhibited a strong one. The optical properties showed a reduction in the band gap energy and a higher conductivity for the irradiated materials, causing a higher current density. Due to the high performance observed, it can be applied in dye-sensitized solar cells and water splitting processes. Quantum mechanical calculations based on density functional theory are in accordance with the experimental results, contributing to the elucidation of the changes caused by femtosecond laser irradiation at the molecular level, evaluating structural, energetic, and vibrational frequency parameters. The surface simulations enable the construction of a diagram that elucidates the changes in nanoparticle morphologies.

Integration of experiment and computational modeling on the Tb doping process in CaMoO4 obtained by USP method: An efficient way to obtain photoluminescent materials.

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.

Characterization of CMY-2-type beta-lactamase-producing Escherichia coli isolated from chicken carcasses and human infection in a city of South Brazil.

BACKGROUND: Food-producing animals, mainly poultry, have been associated with the maintenance and dissemination of antibiotic-resistant bacteria, such as plasmid-mediated AmpC (pAmpC)-producing Enterobacteriaceae, to humans, thus impacting food safety. Many studies have shown that Escherichia coli strains isolated from poultry and humans infections share identical cephalosporin resistance, suggesting that transmission of resistance from poultry meat to humans may occur. The aim of this study was to characterize pAmpC-producing E. coli strains isolated from chicken carcasses and human infection in a restrict area and to determine their antimicrobial resistance profiles, and molecular type by multilocus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE). RESULTS: A total of 14 pAmpC-producing E. coli strains were isolated, including eight strains from chicken carcasses and six strains from human infections (from urine, tissue and secretion). The blaCMY-2 gene was identified in all pAmpC-producing E. coli strains by polymerase chain reaction (PCR) and DNA sequencing. High percentages of strains resistant to tetracycline, nalidixic acid and sulfamethoxazole-trimethoprim (78-92%) were detected, all of which were considered multidrug-resistant. Among the non-beta-lactam resistance genes, the majority of the strains showed tetA, tetB, sulI and sulII. No strain was considered an extended-spectrum beta-lactamases (ESBL) producer, and the blaTEM-1 gene was found in 2 strains isolated from human infection. Six strains from chicken carcasses and four strains from humans infections were linked to an ISEcp1-like element. Through MLST, 11 sequence types were found. Three strains isolated from human infection and one strain isolated from chicken carcasses belonged to the same sequence type (ST354). However, considerable heterogeneity between the strains from chicken carcasses and humans was confirmed by PFGE analysis. CONCLUSION: This study showed the prevalence of E. coli strains producing blaCMY-2 linked to ISEcp1 that were present in both chickens and humans in a restricted area. Our results also suggest the presence of a highly diverse strains that harbor pAmpC, indicating no clonal dissemination. Therefore, continuous monitoring and comparative analyses of resistant bacteria from humans and food-producing animals are needed.