Luminescence Techniques in Reinvestigation Into Photocatalytic Reactivity of Tio2

13th International Symposium on Bioluminescence & Chemiluminescence Symposium Abstract

Luminescence techniques in reinvestigation into photocatalytic reactivity of TiO2

Kimura J-I CL Advisor, Tohoku Electronic Industrial Co., Ltd. 6-6-6 Shirakashidai, Rifu, Miyagi, 981-0134, Japan [email protected]

Titanium oxide (TiO2) has been used as a photocatalyst for more than 30 years. It is interesting fact that the source of the active species from TiO2 is still debated. In this study, we tried to reinvestigate a reagent-grade titanium oxide (TiO2) by luminescence techniques. In thermally excited luminescence of TiO2, emission spectrum measurements and temperature dependence of luminous intensity are essential to interpret observed luminescence. Titanium oxide exhibited luminescence when it was heated in temperatures ranging from 100ºC to 160ºC under nitrogen atmosphere. Temperature dependence of the luminous intensity provided activation energy to be 92 -1 kJ mol . Thermally excited luminescence spectrum of TiO2 measured at 160ºC in nitrogen exhibited two spectral groups: an emission peak with a maximal at 440 nm and a set of line spectrum comprising of 480, 580, and 680nm due to singlet oxygen. In this study photocatalytic luminescence is defined as the light emission from a photocatalyst after stop of UV-visible light irradiation. Photocatalytic luminescence of TiO2 irradiated with blacklight (365 nm) and fluorescent light in nitrogen showed almost the same spectrum as the thermally excited spectrum stated above. They are different from those obtained for metal oxides such as stainless steel and quartz, which provide only green emission with a peak at near 500 nm but no emission due to singlet oxygen. Active species of TiO2 have been believed to be due to hydroxyl radical (·OH) and superoxide anion (O2·-). From the experimental evidence obtained in this study, singlet oxygen will be a good candidate of active species because of their strong oxidizing power. We can propose regeneration process of oxygen for TiO2, that is, it can generate active oxygen by daylight and absorb oxygen at night.