Ultra small sub-1 nm gold nanoparticles were synthesized, characterized and deposited on TiO2 Support. They exhibited a remarkable photocatalytic activity for both liquid and gas phase oxidation reactions, which have a significant potential for environmental applications. The NO2 conversion on such catalysts was 6 times higher as compared to that of unmodified catalysts. This is the first ever application of such small clusters for environmental photocatalysis. The presence of sub-1 nm clusters was confirmed by TEM. MALDI-TOF MS and UV-vis spectroscopy. This work also included the novel use of modified DRIFT spectroscopy for photocatalytic testing as well improvement of known Au clusters synthesis procedures. (C) 2011 Elsevier B.V. All rights reserved.