Two photon absorption cross-sections and fluorescence dynamics of Riboflavin, Fluorescein 548, Coumarin 519 and
Quinizarin adsorbed onto reactive (TiO2) and non-reactive (ZrO2) semiconductor nanoparticles have been investigated.
These dye molecules are chosen because of their inherently different anchoring groups with which they can bind to
semiconductor nanoparticles giving a handle to probe the influence of anchoring group as well as molecule-nanoparticle
electronic coupling on the two-photon absorption and nonlinear optical properties. Two-photon excited fluorescence
technique has been utilized to monitor the two photon absorption cross-sections and the dynamics of singlet states are
followed with femto second fluorescence upconversion. Interesting cross-section trends have been observed where the
TPA cross-section of chromophore on ZrO2 surface is similar or lower to that of the free dye while the cross-sections
seem to be higher on the surface of reactive TiO2 nanoparticle surface. Fluorescence upconversion investigations were
able to probe the electronic interactions of the chromophore with semiconductor nanoparticle and also the adsorption of
the chromophores on the surface of the nanoparticle.