Photocatalysis using semiconductors under irradiation has
been extensively studied for about three decades. In 1972, Fujishimna
and Honda discovered the photocatalytic splitting of water on TiO2
electrodes. This event marked the beginning of a new era in
heterogeneous photocatalysis. The main focus of previous studies have
been to investigate the principal applicability of photocatalysis systems
for efficient treatment of water polluted with toxic
substances. Quantum size effects on photoreactions for semiconductor
nanoparticles have only been recently studied.