Abstract: Spin trapping-ESR method was used to study the photo induced electron transfer process of benzyl alcohol on the surface of super fine particles of TiO₂.The results show that at different pH value, there are distinguishing differences about photochemical behaviors of benzyl alcohol on the colloid surface.At very low pH, signals of singlet oxygen were detected clearly.When pH value was about 3.0, super oxide anion dominated.When pH values were raised to 4-6,large amount of benzeloxyl radical was generated, especially when pH=6.When pH was about 7, besides benzeloxyl radical, some hydroxylethyl radical and benzyl radical occured.The photochemical mechanisms of photo-induced electron transfer process under different acidic conditions were discussed.

Key words: benzyl alcohol, colloid, photoinduced electron transfer, ESR