Fabrication of TiO₂–Bi₂WO₆ Binanosheet for Enhanced Solar Photocatalytic Disinfection of E. coli: Insights on the Mechanism

Abstract

TiO2-Bi2WO6 binanosheet (TBWO), synthesized by a facile two-step hydrothermal method, was used as an effective visible-light-driven photocatalyst for the inactivation of E. coli and was characterized by TEM, SEM, XRD, FTIR, XPS, and BET. A series of TBWOs with different doping ratios of TiO2 loading from 10 to 55 wt % were synthesized. Among all of the TBWOs, 40% TBWO exhibited the best bacteria disinfection efficiency, and the quantity of viable bacteria could reach 10° with 40% TBWO (100 μg/mL) after being illuminated for 4 h. Furthermore, the confocal fluorescent-based cell live/dead test and the SEM technology were applied to verify the photocatalytically lethal effect toward E. coli and the rupture of bacterial membranes. The leak of bacterial contents, including the bacterial genome represented by relevant 16srDNA, and total protein were detected by PCR and bicinchoninic acid assay. In this work, the antibacterial mechanism was studied by employing photoelectrochemical techniques, electron spin resonance (ESR), and scavengers of different reactive species, revealing the pivotal roles of electron hole (h(+)) and electron (e(-)) in the photocatalytic process. In addition, the •O2(-) and •OH radicals were also detected in the TBWOs system by ESR. It was found that the adsorption of visible light and separation of photogenerated carriers within TiO2 have been largely promoted after being coupled with Bi2WO6, which should be responsible for the improved bactericidal effect.

Recent Progress in Two‐Dimensional Antimicrobial Nanomaterials

“…Subsequently, an inner electric field will be excited on the biphase interface and holes in the VB of Bi 2 WO 6 will transfer to that of TiO 2 . Hence, the light‐sensitized oxygen reduction reaction will occur, giving rise to the formation of ROS to attack bacterial cells (Figure ) . Zeng et al.…”

“…The excellent conductor Fe 3 O 4 can trap photogenerated e − and inhibit the recombination of e − /h + pairs . Along with strong absorption in the visible‐light region, the obtained nanomaterials showed superior antibacterial efficiency (Figure A) . The Fe 3 O 4 –TNS can be easily recycled from water through magnetic separation, which facilitates reuse of the photocatalyst and avoids secondary environmental pollution.…”

“…[46] Charge-separated pairs will be generated in Bi 2 WO 6 upon visible-light irradiation.S ubsequently,a ni nner electric fieldw ill be excited on the biphase interface and holes in the VB of Bi 2 WO 6 will transfer to that of TiO 2 .H ence, the light-sensitized oxygen reduction reaction will occur,g iving rise to the formation of ROS to attack bacterial cells ( Figure 3). [47] Zeng et al demonstrated that carbond ot (C-dot) modified TiO 2 -rGO nanocomposite has high charge-transfer efficiency because of the promising electron-accepting ability of C-dots. [129] This facilitates the formationo fp hotogenerated separatede À /h + pairs ands ubsequentlyROS.…”

Two‐dimensional nanomaterials for photocatalytic water disinfection: recent progress and future challenges

“…(a) TEM images of TiO 2 (40%)‐Bi 2 WO 6 , insert is the HRTEM image; (b) schematic drawing of the photocatalytic antibacterial process of the TiO 2 (40%)‐Bi 2 WO 6 ; copyright (2016) American Chemical Society.…”

“…The pH of reaction media is crucial in photocatalysis processes, since the surface charges of photocatalysts and cell membrane change with pH value. For example, in the case of TiO 2 ‐Bi 2 WO 6 , a low pH value was favorable, as the negatively charged bacteria could be better adsorbed on the nanostructure in a low pH condition . Oppositely, for g‐C 3 N 4 ‐AgBr, high pH with more hydroxyl ions was favorable for cell disinfection, which sequentially geared up the formation of •OH via oxidization.…”