Flowerlike ZnO-Based Hetero Structural Photocatalytic Antibacterial Agents:Their Controllable Sythesis And Antibacterial Activities

In the field of photocatalytic materials, ZnO semiconductor possesses similar energy band structure and photocatalytic mechanism to TiO2. In its synthesis process and application of ZnO photocatalyst, the problems of wide band gap, high recombination efficiency of photo-generated carriers and photocorrosion still restrict its application and spread. Herein, we summarized the influence factors of photocatalytic activity and methods to enhance photocatalytic abilities of semiconductor in part of Introduction. Our researches focused on the improvement of photocatalytic activity of ZnO semiconductor by morphological control, transition-metal-ions doping, noble metal deposition and semiconductor coupling, and its application as a photocatalytic antibacterial agent. The specific contents of this paper were illustrated as below:1. Microwave-assisted synthesis of Ag-decorated flowerlike Zn0.995Ni0.005O Architectures with enhanced photocatalytic antibacterial and photoelectrochemical properties.Ni2+ions-doped ZnO (Zn1-xNixO) flowerlike microstructures assembled by Zn1-xNixO nanorods were prepared via a microwave-assisted process. The photocatalytic activities of Zn1-xNixO samples were evaluated by photodegradation of RhB dye under visible light irradiation. The results showed that the 0.5 mol% Ni-doped ZnO (Zn0.995Ni0.005O) sample exhibited the best photocatalytic activity for the decolorization of RhB. By choosing the Zn0.995Ni0.005O sample as substrate material, Ag nanoparticles (NPs) were deposited on the surface of Zn0.995Ni0.005O nanorods to form a novel Zno.995Ni0.005O@Ag (ZNO@Ag) heterojunction via a followed microwave-assisted process. Evidence of Ag NPs decorated onto Zn0.995Ni0.005O microspheres was obtained from SEM, HRTEM, XRD and EDS mapping, which revealed that monodispersed Ag NPs were deposited on the surface of the doped semiconductors. The ZNO@Ag heterojunction exhibited more excellent photocatalytic antibacterial activity than pure ZnO, Ni-doped ZnO and Ag NPs under visible light irradiation. It was mainly attributed to the synergistic effect of enhanced photocatalytic activity, which was ascribed to enhanced charge separation and charge transfer studied by photoelectrochemical measurements.2. Ag2S sensitized ZnO microflower architectures with enhanced visible light photocatalytic antibacterial activityAg2S was decorated on the surface of ZnO nanorods-assembled microflower architectures by a facile ion-exchange method at room temperature. A series of ZnO@Ag2S heterostructures with different deposition quantities of Ag2S was synthesized, and their photocatalytic activities were explored by using the model of photocatalytic degradation of RhB and antibacterial against Bacillus subtilis under visible light irradiation. Based on the experimental results, it can be shown that the photocatalysis of ZnO@Ag2S with 6 mol% deposition quantity of Ag2S possessed the highest visible light photocatalytic ability. The enhanced photocatalytic activity can be explained by its improved visible light response and the high efficiency of photogenerated charge separation. In addition, by using different radical scavengers, such as KBrO3 and tertiary butanol, we also did the detection test of reactive oxygen species and made a detailed discussion about photocatalytic antibacterial mechanism.