*4.4. Disinfection*

In 1985, Matsunaga et al. first reported the photocatalytic inactivation of bacteria on the surface of TiO2 [145]. Since then, a lot of research has been devoted to the photocatalytic inactivation of microorganisms such as bacteria, viruses, protozoa and so on [18,146–150]. Furthermore, due to the nonexistence of secondary pollution, photocatalytic disinfection is a promising alternative approach for water purification. Table 4 lists some of the most representative M/S nanocomposite photocatalysts for disinfection [151–159].

**Table 4.** M/S nanocomposite photocatalysts for disinfection.


Taking into account the practical application of photocatalytic disinfection for water purification, most of the light sources involved in the research are visible light as revealed in Table 4. Therefore, the enhanced properties of M/S nanocomposite photocatalysts for disinfection are mainly attributed to the SPR of the metal component. In the work of Shi et al., due to the SPR of Ag, the Ag/AgX (X = Cl, Br, I) photocatalysts exhibited remarkable properties for the inactivation of *Escherichia coli* under visible light illumination [157]. Shi el al. also evaluated the contribution of different photo-generated reactive species to the disinfection process by adding scavengers into the reaction system. The results indicated holes are the dominant reactive species over other reactive species such as electrons, •OH, H2O2 and so on.

#### **5. Conclusions and Perspectives**

In this review, we demonstrate the properties of M/S nanocomposite photocatalysts in relation to their structures for application in environmental remediation, selective organic

transformation, hydrogen evolution and disinfection. Due to the enhanced charge separation at the metal-semiconductor interface and increased absorption of visible light induced by the SPR of metals, M/S nanocomposite photocatalysts usually exhibit much better properties than pristine semiconductor photocatalysts.

For future development of M/S nanocomposite photocatalysts, our perspectives can be summarized as the following four points:


**Author Contributions:** Y.-s.F., J.L. and J.G.L. conceptualized this review; Y.-s.F. collected and analyzed the data; Y.-s.F. and J.L. wrote the paper.

**Funding:** This research was funded by National Key Research & Development Program of China through the gran<sup>t</sup> number 2017YFB0305300 and Joint Funds of the National Natural Science Foundation of China through the gran<sup>t</sup> number U1660203.

**Acknowledgments:** The authors would like to thank Tao Deng and Jianbo Wu for their valuable suggestions to this review.

**Conflicts of Interest:** The authors declare no conflict of interest.
