Hydrogen‐rich titanium oxides have recently attracted attention as active photocatalysts with excellent photoabsorption. Herein, the optical properties of hydrogen titanate (H2Ti3O7) are calculated both for the perfect crystal and in the presence of a high concentration of oxygen, hydroxyl, and hydrogen vacancies (VO, VOH, and VH, respectively). Spin‐polarized density functional theory calculations with the Hubbard correction (DFT+U) predict VH as the dominant defect, as a consequence of the low formation energy and the insignificant accompanied structural rearrangement. By the GW approximation, it is found that VO and VOH create localized deep defect states below the conduction band (by 2.11 and 3.30 eV, respectively), whereas VH leads to a shift of the Fermi level moved inside the valence band. All the vacancies result in excitonic transitions in the infrared and visible regions in the absorption spectra, as calculated by solving the Bethe–Salpeter equation (BSE). Overall, comparison between single‐particle theories and BSE results shows that excitonic effects are very important in this material. Delocalized excitons are observed in the case of VO and VH, which can be important to suppress electron–hole recombination, thus contributing to the enhancement of the photocatalytic activity of the material.

Abstract:The prepared silver/chitosan nanocomposite and chitosan nanoparticles in this study may demonstrate the potential in optimizing the minimum amount required to achieve complete inactivation of various Coliform bacteria in Nile water. Chitosan nanoparticles were prepared based on the ionic gelation of the prepared chitosan and silver nanoparticles were reduced by Solenostemma Argel extract. Finally, chitosan silver-loaded nanoparticles were prepared by dispersing silver nanoparticles onto the chitosan nanoparticles. The SEM images exhibited a diameter range of 10 nm–30 nm for both of the fabricated silver nanoparticles and chitosan nanoparticles. The UV-Vis analysis confirmed the formation of Ag nanoparticles by the appearance of the characteristic peak at 410 nm. The antibacterial activity of chitosan nanoparticles and silver-loaded nanoparticles was evaluated against the Coliform bacteria. Results show an improvement in the inhibition of the growth of various bacteria tested when silver nanoparticles were introduced which was (0.03g/100ml). Consequently, chitosan silver-loaded nanoparticles could be recommended as an efficient antibacterial material for water disinfection.