Permanent clean house with titanium dioxide
Not so long ago, chemical engineers discovered how to use titanium dioxide to keep buildings free of discoloring pollution. Titanium dioxide breaks down organic molecules including those in grime and pollution when exposed to light and water and then releases them into the air. Two chemical qualities make TiO2 an all-purpose cleaner. First, the chemical is light-sensitive. When it is struck by photons, it reacts with air and water vapor to accelerate the breakdown of organic materials. It's a bit like an artificial photosynthesis, but whereas plants use sunlight to break down carbon dioxide and turn it into oxygen, TiO2 uses light to turn scourges like grease and bacteria into carbon dioxide, hydrogen and other by-products that escape into the air. Second, TiO2 is hydro-philic, or water-loving. Instead of repelling water as tiles and glass do when they encourage water to bead materials coated with TiO2 attract water, causing it to sheet across the surface, taking by-products and oversize particles with it. The result: Guck rarely gets a chance to build up, and it washes away easily when it does. Cortie says TiO2's atomic structure must be changed so that it's compatible with the energy spectrum of visible light'no easy task. Plus, that alteration must be made without disrupting its chemical inertness; otherwise, it might not stay put on whatever it's meant to coat.
Source: popsci.comAdded: 20 March 2007