ZnO/AAO photocatalytic membranes for efficient water disinfection: Synthesis, characterization and antibacterial assay

• Published in: Applied surface science Vol. 448; pp. 104 - 114
• Main Authors: Najma, Bibi, Kasi, Ajab Khan, Khan Kasi, Jafar, Akbar, Ali, Bokhari, Syed Muzamil Ali, Stroe, Izabela RC
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.08.2018
• Subjects: AAO membranes; Anodic aluminum oxide (AAO); Photocatalysis; Reactive oxygen species (ROS); ZnO; ZnO; Anodic aluminum oxide (AAO); Photocatalysis; AAO membranes; Reactive oxygen species (ROS)
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2018.04.063

[Display omitted] •Porous ZnO/AAO membranes were prepared by growing ZnO nanosheets on AAO substrates.•The ZnO nanosheets networks were found polycrystalline with a band gap of 3.09 eV.•SEM images revealed high hierarchical porosity and surface area for the networks.•The membranes were tested against water-borne bacterial pathogen, E. coli.•The membranes showed strong antibacterial activity in dark and UV light conditions. Novel type of ZnO/AAO photocatalytic membranes were fabricated by growing highly dense and porous network of ZnO nanosheets on nanoporous anodic aluminum oxide (AAO) using the facile hydrothermal approach. The structural properties of the membranes were investigated by field emission gun scanning electron microscopy (FEG-SEM) and X-ray diffraction spectroscopy (XRD). The ZnO nanosheet networks were found polycrystalline, showing mainly (100) and (002) ZnO reflections. The XRD results suggested that the ZnO-AAO interface promotes lattice disorder mainly along the polar-axis while the nonpolar plane remains less defective. The energy dispersive X-ray spectrometry (EDX) confirmed the formation of pure ZnO. In addition, Fourier transform infrared spectroscopy (FTIR) indicated an intense absorption band in the range of 661–780 cm−1 for stretching vibrations of Zn–O bond and also specified the presence of intrinsic crystal defects. The diffuse reflectance spectroscopy (DRS) revealed an optical absorption edge of 401 nm and a band gap of 3.09 eV for grown ZnO nanosheet mesh. Moreover, the DRS studies also substantiated the existence of crystal defects by recognizing a red shift in the band gap, and a trail of low energy absorptions in the reflectance spectrum in the range of 400–800 nm. Due to the corrugated surface morphology and hierarchical porosity of ZnO scaffolds on porous AAO substrates, the membranes possess a great deal of catalytic surface and demonstrated a strong antibacterial activity against water-borne bacteria Escherichia coli (E. coli) under dark and UV light conditions. Our results showed that fabricated ZnO/AAO membranes have great potency for photocatalytic disinfection of contaminated water on account of their large catalytic surface and inherent porosity which can facilitate the mass transfer and diffusion of oxygen species and Zn+2 ions during the disinfection process. This morphology-function relationship is highly effective for designing cost effective, efficient, environment-friendly, and self-antifouling photocatalytic disinfectants.