Pump-probe diffuse reflectance measurements were carried out on partic
ulate titanium(IV) oxide photocatalysts in the form of aqueous suspens
ion and dry powder. A linear relation between second-order rate consta
nts of electron-hole recombination for the suspension and powder syste
ms was seen by analyses of decay profile of charge carriers. Presence
of air gave negligible effect on the recombination kinetics, but loadi
ng of platinum (Pt) significantly reduced the rate constant.