Two-photon luminescence enhancement of silver nanoclusters photodeposited onto mesoporous TiO2 film

We report on two-photon luminescence of silver nanoparticles grown on non-crystalline mesoporous TiO2 issued of the sol–gel process. The growth is achieved by surface photocatalytic reduction from silver nitrate solution. A structural hierarchy of this particular TiO2 system results in a characteristic distance between nanoparticles ∼10–100 nm that is optimal for the electromagnetic field enhancement. The microscope images evidence multiple bright luminescence spots at two-photon near-IR femtosecond laser excitation due to the field enhancement effect. The spectra suggest homogeneous size distribution of emitting silver clusters over the sample area on the scale below 100 nm.