TiO2. Used for so many things. A report a couple of weeks ago in C&E news talked about how it is used in sunscreen. But I'd like to talk more about the compound in general here. What is it? How does it work?
Firstly-what is it?
A combination of titanium and 2 oxygen atoms. A solid crystal with a crystal structure.
How does that work? Shouldn't I have listed a structure? The way it works is that TiO2 has a variety of forms. The three most common ones are rultile and anatase and brookite. Anatase and Rutlie are tetrahedral. Brookite is orthorombic. Control over these forms can usually be accomplished in the design stage through temperature control at synthesis.
Which form do you want? That depends on your application.
Anatase is generally more reactive. The article I linked to above contains interesting experiments about sunscreens on metal. Anatase TiO2 was seen to increase radical production.
It is also used in solar cell designs.
Rutile is what seems to be better for sunscreens. Less reactive, it sticks to reflecting. Another common use is white paint. Reflecting all wavelengths of light ends up looking white. The UV reflectance gives TiO2 sunscreen capabilities.
Brookite, the last of our forms, is not white. It is a rare form, and doesn't seem to be commonly commercially used
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