No abstract

Silver nanoparticles (AgNPs) at different amounts have successfully been deposited, by simple impregnation on the titanium dioxide (TiO 2) developed by the hydrothermal method. A textural and structural study of prepared materials was conducted using different analysis techniques, namely X-Ray Diffraction (XRD), Diffuse Reflectance UV-Vis (DR/UV-Vis) spectroscopy, Fourier Transform Infrared (FTIR) spectroscopy, in addition to the Brunauer-Emmett-Teller (BET) method. The nanostructured prepared materials were tested for their antibacterial activity on four strains, i. e. two Gram-negative (GÀ) bacteria, namely Escherichia coli ATCC 8739 and A. baumanni ATCC 19606, and two Gram positive (G +) bacteria, i. e. S.aureus ATCC 6538 and E.cloacae ATCC 13047. The antioxidant effect was also tested on the reference radical DPPH°(2,2-diphenyl-1-picrylhydrazyle). AgNPs supported on TiO2 showed good antibacterial activity against the four selected strains. In addition, the minimum inhibitory concentration (MIC) was observed in the case of the low-grade silverdoped catalyst (0.1 % Ag/TiO2). Differently from the antibacterial activity, the antioxidant effect of the prepared materials was found to be pronounced in the cases of materials with high silver contents for which there was degradation of the radical in comparison with the one of the reference acid.

This work demonstrates a two-step gram-scale synthesis of presynthesized silver (Ag) nanoparticles impregnated with mesoporous TiO 2 and evaluates their feasibility for wastewater treatment and hydrogen gas generation under natural sunlight. Paracetamol was chosen as the model pharmaceutical pollutant for evaluating photocatalytic performance. A systematic material analysis (morphology, chemical environment, optical bandgap energy) of the Ag/TiO 2 photocatalyst powder was carried out, and the influence of material properties on the performance is discussed in detail. The experimental results showed that the decoration of anatase TiO 2 nanoparticles (size between 80 and 100 nm) with 5 nm Ag nanoparticles (1 wt %) induced visible-light absorption and enhanced charge carrier separation. As a result, 0.01 g/L Ag/TiO 2 effectively removed 99% of 0.01 g/L paracetamol in 120 min and exhibited 60% higher photocatalytic removal than pristine TiO 2 . Alongside paracetamol degradation, Ag/TiO 2 led to the generation of 1729 μmol H 2 g −1 h −1 . This proof-of-concept approach for tandem pollutant degradation and hydrogen generation was further evaluated with rare earth metal (lanthanum)-and nonmetal (nitrogen)-doped TiO 2 , which also showed a positive response. Using a combination of ab initio calculations and our new theory model, we revealed that the enhanced photocatalytic performance of Ag/TiO 2 was due to the surface Fermi-level change of TiO 2 and lowered surface reaction energy barrier for water pollutant oxidation. This work opens new opportunities for exploiting tandem photocatalytic routes beyond water splitting and understanding the simultaneous reactions in metal-doped metal oxide photocatalyst systems under natural sunlight.