Features of the near-infrared phosphorescence of singlet oxygen 1 O 2 photosensitized by TiO 2 in solutions have been investigated. The short-lived phosphorescence of 1 O 2 with spectral maximum at approximately 1300 nm is observed to follow excitation by pulsed laser radiation at 355 nm of TiO 2 suspended in CCl 4 and water H 2 O. The shorter lifetime and spectral shift of this phosphorescence, as compared with phosphorescence of 1 O 2 sensitized by phenalenone in these solvents, are attributed to the adsorbed state of emitting singlet oxygen. The observed laser pulse energy dependence indicates the two-photon and three-photon nature of this phosphorescence initiation in CCl 4 and H 2 O, respectively. The formation of 1 O 2 in CCl 4 is assumed to be provided by the sequence of one-photon excitation of TiO 2 , giving rise to superoxide anion O 2 − and one-photon photodetachment of electron from O 2 − . The photodetachment of electron from O 2 − in water H 2 O is a two-photon process because of higher solvation energy of superoxide anion in water. The processes that govern the rise and decay of singlet oxygen phosphorescence sensitized by TiO 2 are discussed. The factors affecting the yield of singlet oxygen provided by electron photodetachment are also considered.

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