Influence of adsorbed water and oxygen on the photoluminescence and EPR ofPor-TiO2 (anatase)

The influence of adsorbed water, oxygen, air and vacuum on the photolumines cence (PL) and electron paramagnetic resonance (EPR) has been investigated in situ and quasi in situ for por-TiO2 (anatase). The broad PL signal in th e visible spectral region decreases with increasing partial pressure of oxy gen and vanishes at pressures higher than 1 mbar. Adsorption of water leads (i) to a fast quenching and (ii) to a subsequent increase of the PL signal . The concentration of the O-2(-), O-, O-3(-) anion-radicals depends sensit ively on the surface conditioning and on the illumination of the por-TiO2. Ti3+ centers could be observed only in vacuum treated samples. The concentr ations of the Ti-3+ and oxygen anion radicals are in the range of 10(15) an d 10(17) cm(-3), respectively.