Jieling Qin

Bifunctional TiO2/Ag3PO4/graphene composites with superior visible light photocatalytic performance and synergistic inactivation of bacteria

In this work, bifunctional TiO2/Ag3PO4/graphene (GR) composites have been prepared via the combination of ion-exchange method and hydrothermal approach, and the fabrication of “pizza-like” three-phase TiO2/Ag3PO4/GR composites has been achieved through the electrostatic-driven assembly of positively-charged Ag+ on negatively-charged graphene oxide (GO) sheets, followed by the nucleation & controlled growth of Ag3PO4 and the deposition of Degussa P25 on the GO surface. Consequently, the hydrothermal treatment leads to the generation of TiO2/Ag3PO4/GR composites with well-defined structures. The as-prepared composites exhibited highly efficient visible light photocatalytic activity toward organic dye molecule degradation and showed excellent bactericidal performance. This is the first report on the production of bifunctional three-phase metal oxide–Ag3PO4–GR composite materials with improved photocatalytic and antibacterial properties. The improved photocatalytic activity is attributed to the effective separation of photoexcited electron–hole pairs and fast charge transfer between components in the composite, while its excellent bactericidal performance is believed to come from intrinsic bacterial inactivation of Ag3PO4 and photo-induced antibacterial activity of active oxygen-containing radicals generated in the irradiated system. The proper molar ratio of Ag3PO4/TiO2 and the added amount of GO in the precursor have been considered to play crucial roles in the formation of bifunctional composites with promising properties. The TiO2/Ag3PO4/GR composite significantly decreases the percentage of expensive Ag-containing material while it reveals better photocatalytic and antibacterial performance than Ag3PO4, providing new insights into the low-cost, large-scale production of Ag3PO4-based function materials for practical applications.

Graphene-spindle shaped TiO2 mesocrystal composites: Facile synthesis and enhanced visible light photocatalytic performance

Graphene (GR)-TiO2 mesocrystal composites were prepared by a facile template-free process based on the combination of sol-gel and solvothermal methods, and were characterized using field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), Raman spectroscopy, UV-vis diffuse reflectance spectroscopy (UV-vis DRS), nitrogen absorption and electron spin resonance (ESR). Visible light photocatalytic performance of GR-TiO2 composites was evaluated for photocatalytic degradation of organic dye Rhodamine B. It was found that the amount of graphene oxide (GO) added obviously affects morphologies of TiO2 mesocrystals and photocatalytic activities of as-prepared nanocomposites. Composites prepared in the presence of different amounts of GO all exhibit higher photocatalytic activity than pure TiO2 mesocrystals and P25, the composite obtained by using 20mg GO presents the most uniform TiO2 mesocrystals in the composite and shows the highest photocatalytic efficiency. The mechanism for the generation of TiO2 mesocrystals in the GR-TiO2 composite is proposed and possible reasons for the enhancement in visible light photocatalytic efficiency are also discussed.