Photocatalytic activity of inorganic sunscreens

Some inorganic pigments are used as ingredients for sunscreens as they can absorb, reflect or scatter UV radiation. Titanium dioxide and zinc oxide, w hich are used for this purpose, are semiconductor oxides and show photocata lytic activity. As a consequence, they can promote transformation of organi c molecules upon absorption of radiation. This work studies the activity of some of these pigments, provided by cosmetic producers, towards phenol, ch osen as a model aromatic molecule. An attempt is made to explain the differ ent activity of the various pigments, coated or uncoated, towards phenol.