# Recent Advances and Applications of Semiconductor Photocatalytic Technology
## 6 Application
### Photocatalytic Disinfection  
As well as non-biological contaminants such as organic pesticides, antibiotics, and heavy metals in water, the harm caused by biological pollution such as medical sewage and domestic wastewater cannot be underestimated. Most pathogenic microorganisms can cause harm to human health by ingestion, respiration, or skin contact. According to the report, millions of people are dying or dead as a result of infection with pathogens annually [356].  
Traditional sterilization methods for disinfection such as chlorination, ozonation, and ultraviolet light all have disadvantages. Chlorine can kill most bacteria and viruses, but the chlorine byproducts generated during the reaction can also endanger human health. Ozone oxidation technology is highly demanding on equipment and complicated to operate. Low-pressure ultraviolet disinfection can only inactivate bacteria on the surface of sewage; at the same time, the equipment is poor in reliability and expensive. For the first time, [PERSON] et al. [357] demonstrated that photocatalytic technology can eliminate pathogens including _Lactobacillus_, yeast, and _Escherichia coli_. Thereafter, photocatalytic antibacterial materials have been gradually known and developed.  
In the past few decades, the photocatalytic technology of nanomaterials has been rapidly developed in solar photocatalytic sterilization and other aspects [358; 359; 360; 361; 362; 363; 364; 365; 3667]. The reaction mechanism of photocatalytic sterilization is to destroy the cell wall and oxidize coenzyme A enzymes and genetic material. Under ultraviolet light irradiation, -OH radicals and O\({}^{2-}\) radicals generated on the surface of the photocatalyst easily adhere to the cell wall surface of the bacteria. These free radicals can cause the leakage of K\({}^{+}\) ions in the cell fluid, the oxidation of coenzyme A in the cell, or the destruction of the DNA double helix structure. There is also a class of photocatalysts that do not produce active -OH during photocatalytic and antimicrobial processes, and this type of photocatalyst sterilizes pathogens using photogenerated holes. As a new sterilization method, photocatalytic sterilization has the advantages of high safety, strong stability, and wide antibacterial properties, and it demonstrates broad application prospects.  
[PERSON] et al. [368] obtained TiO\({}_{2}\)/SiO\({}_{2}\) and Ag-TiO\({}_{2}\)/SiO\({}_{2}\) photocatalysts by hydrolysis and the calcination method. Figure 15 shows the survival rate of spore-forming _Bacillus subtilis_ to treatment time under UV irradiation and dark conditions and the relationship between the doping amount of Ag and the disinfection rate constant, respectively. Figure 15A shows that the viability of sporulated _Bacillus subtilis_ reduced only when using Ag-TiO\({}_{2}\)/SiO\({}_{2}\) under ultraviolet irradiation. As shown in Figure 15B, the optimum range of the Ag doping amount is 0.5-1.0 wt%.  
Figure 14: (**A**) Schematic illustration of procedures for the fabrication of 3 DOM TiO\({}_{2}\) films loaded with gold nanoparticles. (**B**) Photocatalytic degradation of benzoic acid (BA) over (a) i-Au-TiO\({}_{2}\)-o without UV irradiation, (b) nanocrystalline TiO\({}_{2}\), (c) i-TiO\({}_{2}\)-o, and (d) i-Au–TiO\({}_{2}\)-o under UV irradiation [354].