Surface modification of B-TiO2 by deposition of Au nanoparticles to increase its photocatalytic activity under simulated sunlight irradiation.

Abstract: Photocatalytic activity of TiO₂ under visible light irradiation can be improved by doping with nonmetal atoms. However, inter-band energy states formed upon substitutional or interstitial doping can act as recombination centers, hindering the separation of the charge carriers. In this work, sol-gel synthesized TiO₂ was doped with different loadings of boron, namely 0.25, 0.5, 1, 2, and 4 wt. %, and superficially modified by the deposition of Au nanoparticles (0.5, 1.0, and 1.5 wt. %). Particle size of doped TiO₂ decreased with the increase of boron loading, while surface area increased accordingly. B₂O₃ was segregated from TiO₂ when boron loading surpassed 1 wt. %. Light absorption of the doped materials was slightly blue shifted as the boron loading increased, more likely because of the quantization effect. Tiny and well dispersed Au nanoparticles were efficiently deposited on the B-TiO₂ materials. Au nanoparticle size (3-5 nm) showed no modification as Au loading increased, although deposition rate slightly decreased with the boron loading. The complete mineralization of sulfamethoxazole under UV-A/visible light irradiation was obtained using the (0.5 wt. %) Au/(0.25 wt. %) B-TiO₂ material. Electrochemical characterization showed how inter band energetic states increased the separation of the photo-produced charge carriers, while Au nanoparticles hampered the recombination rate via the electron trap effect. Photocatalytic materials displayed high stability. Photoactivity dropped when tap water was tested, because of the dissolved components in the liquid matrix. Some intermediates were identified via LC-MS/MS analysis, which displayed lower antibiotic activity than the parent compound.Sol-gel synthesized TiO₂ was doped with boron, and superficially modified by deposition of Au nanoparticles. The complete mineralization of sulfamethoxazole under UV-A/visible light irradiation was obtained using the (0.5 wt. %) Au/(0.25 wt. %) B-TiO₂ material. Inter band energetic states speed up the separation of the photo-produced charge carriers, while Au nanoparticles hamper the recombination rate via the electron trap effect Boron doped TiO₂ is efficiently synthesized by the sol-gel reaction in a wide range of B loadings.Boron doping impacted on the physical, chemical and optical properties of TiO₂.Doping increased separation of charge carriers while Au NPs acted as electron traps.Outstanding visible light driven photocatalytic performance of the Au/B-TiO₂ materials.High stability of the Au/B-TiO₂ materials and low activity in tap water. [ABSTRACT FROM AUTHOR]