Giant nonlinear optical response application for nanoporous titanium dioxide photocatalytic activity monitoring

Giant nonlinear optical response has been observed for nanoparticle TiO2 (anatase modification) layers within sub-gap photon energy excitation in picosecond range. The obtained effective cubic optical nonlinearity value χ(3)eff ∼10–5 esu is six orders of magnitude higher than the bulk response in transparency range. The effect can be explained with resonant excitation of oxygen vacancies and related defect states , which also act as photocatalytic active centers at the nanoparticle surface. The magnitude of the nonlinear optical response correlates with the photocatalytic activity and depends on the samples preparation conditions. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)