Titanium Dioxide (UV-PCO) Photo catalyst coatings have been applied successfully to many cars, boats, trains, buses etc. to act as a antibacterial and air cleaning solution.

In Japan, there are more than 20,000 cars treated by photo catalyst.  In hospital, photo catalyst can kill bacteria on sickbed and appliance and no drug-fast bacteria left. Many families also use photo catalyst to kill bacteria to prevent illness. The relevant products are gargle, toothpaste, chewing gum, contact lens cleaning liquid, keeping fresh bag , flower living keeper and so on , which has a large market. With increase of people's environmental protection consciousness and society's advancement, Photo catalyst material will be applied gradually in various fields.

What is photocatalyst?

Photocatalyst is compounded by photocatalyst. It is general name of semiconductor material represented by nanometer titanium dioxide (TIO₂) with light catalyzing function. After TiO₂ absorbs ultraviolet light, inter electron is stirred up and formed into powerful oxide and hydroxide radicals. It has powerful oxidation ability, so it can destroy bacterial cell membrane, solidify virus protein and restrain virus's activity. Its killing bacteria ability can reach 99.9%. TiO₂ activates absorbed oxygen and moisture and occur free radicals (-OH) and (-O₂­) which can turn organic substance and harmful air into water and carbon dioxide so as to purify air. At the moment, chain degradation reaction occurs between the free radicals and kinds of contaminant each other.

According to lab test, photocatalyst can remove efficiently coliform, yellow staphylococcus, purulence bacteria and so on. Meantime has more powerful oxidation ability than ozone and negative oxygen ion. It also can decompose odor source. More ever, photocatalyst has powerful hydrophilic ability and keep off contamination to attach , can keep new building clean for a long time . Also it is innocuously and safe.  

Photocatalyst technology originates from Japan. In 1972, professors Fujishima and Dr.tengdaozhao in Tokyo University discover that radiating TiO₂ electrode with light can electrolyses water, it is called famous Honda-Fujishima Effect. After researched for 30 year basing on this principle, photocatalyst research made a great breakthrough. This technology has reached industrial demand and be applied widely. Now TiO₂  has been transformed into powder, solution, gel and paint material in present industrial condition and is widely applied in fields like sterilization, deodorization, preventing contamination and cleaning air .  

Reaction Mechanism

When the micro-particle of  nanostructured Titanium Dioxide(TiO₂) are exposed to 388nm UV light, its inner will stir up hole-electron pair ,and the hole-electron pair will quickly remove to its surface and activate absorbed oxygen and moisture and occur free radicals (-OH ) and active oxygen (-O_2­). At the moment, chain degradation reaction occurs between the free radicals and kinds of contaminant or bacteria each other.  For strong oxidation, the photo catalyst can implement the function of anti-bacteria by destroying the cell membrane. Specific detail reaction is like this, after titanium dioxide (TiO₂) absorbs sun light, it is formed to be electronegative high active electron e- , and positive hole h+. With effect of electric field, electron e- and hole h+ are separated and moved to surface of particle. According to energetic theory, h+ can oxygenates OH- and H₂O conglutinated on surface of TiO₂ into free radicle. More ever, free radicle has strong oxidation ability and can oxygenate and decompose various organic substance(e.g. Formaldehyde ,Benzene ,TVOC), bacteria and part inorganic contamination (Ammonia, NO_x) into non harmful substance: CO_{2 ,}H₂O . OH Free radicle has no selectivity to reactant, so it makes crucial effect in photo catalyzing . Meanwhile, high active electron e- has strong deoxidize ability and can deoxidize oxygen in air .