Quantum yield of heterogeneous photocatalytic systems: Further applicationof an experimental method for determining the absorbed photon flow

The present paper reports additional results obtained with a method already proposed and used to measure absorbed and reflected photons during the occ urrence of heterogeneous process carried out in the presence of a polycryst alline semiconductor solid suspended in aqueous solution. The limit of vali dity of the method is discussed and the influence of various parameters is reported. Moreover, the quantum yield for a probe photoreaction, i.e. 4-nit rophenol photo-oxidation carried out in aqueous suspensions containing vari ous amounts of polycrystalline TiO2 (anatase) of different particle sizes, was determined by using monochromatic (lambda = 366 nm) or polychromatic li ght (lambda = 300-400 nm). The results indicated that the quantum yield was higher when light in the range 300-400 nm was used.