Ultra small sub-1 nm platinum nanoparticles were synthesized, characterized and deposited on TiO2 support. The presence of sub-1 nm clusters was confirmed by STEM. They exhibited a striking photocatalytic activity for both liquid and gas phase oxidation reactions, which have a significant potential for environmental applications. We believe that this experimental result is the first ever experimental demonstration of very promising properties of such small clusters for environmental photocatalysis. The NO2 conversion on these catalysts was 5 times higher as compared to that of unmodified catalysts, whereas 4 times increase in activity was observed for liquid phase oxidation of phenol. Another distinct component of this work included a novel use of modified DRIFT spectroscopy for photocatalytic testing, which allowed us to observe both surface and gas phase processes in situ. (C) 2012 Elsevier B.V. All rights reserved.