Everyone desires to have a safe and healthy living environment free from any harmful substitute and bacteria. Photocatalysis is lately attracting people's attention for the purpose. Photocatalysis is a substrate, which can stimulate a chemical reaction with light energy. One of such photocatalys substrates is titanium dioxide (TiO2), which is known as a material used in cosmetics and food additives. Once titanium dioxide gets UV light, it will decompose the organics by oxidation-reduction reaction and that gives the effects of sterilization and purification. These effects are commercialized in air/water purifiers and coating for exterior walls. By getting UV light on titanium dioxide coating, the reaction will decompose the dirt on the surface of walls and will prevent it from the dirt. UV light at less than 380nm wavelength is indispensable that titanium dioxide can absorb. UV lamps are conventionally used but more efficient, longer life and safe UV LEDs are prospective replacement for the photocatalysis.