Quantum Yields of Photoluminescence of TiO2 Photocatalysts

Here, we determined the quantum yields of photoluminescence (ΦLumi) of five commercially available TiO2 photocatalysts (two rutile and three anatase; particle diameter: 7–400 nm) by comparison with ΦLumi values obtained for three luminescent inorganic standard materials. The shapes of the luminescence spectra of the photocatalysts were similar to those reported previously. Very small ΦLumi values were obtained for all five photocatalysts [e.g., 5.2 × 10–6 for nano-sized anatase TiO2 (particle diameter: 7 nm)], indicating that photoluminescence is a minor channel in the photophysical processes of these materials. In addition, ΦLumi was much larger for the photocatalysts with a larger particle size than for those with a smaller particle size for both anatase and rutile TiO2, which implies that luminescence arises predominantly from the bulk of the particles and that the surface plays a role as a quenching center in both polymorphs. The origin of the luminescence is discussed in relation to the previous studies.