Research of fluorescent properties of photo-induced electron transfer of 5(6)-carboxyfluorescein dye-sensitized TiO ₂ nanoparticles

Anatased TiO ₂ nanoparticles were prepared by controlling hydrolysis of the TiCl ₄. Time-resolved fluorescence experiments were carried out to study the photo-induced electron transfer dynamics in the system of the 5(6)CFL dye-sensitized TiO ₂ nanoparticles. For the aboved system, the formation of the charge transfer complex is attributed to the coupling interaction between the wave functions of the excited electronic state of the dye (Ψ(D ^*)) and the charge separated state (Ψ(D ⁺ + e ^-)). On excitation of 5(6)CFL dyesensitized TiO ₂ nanoparticle system. The injection of electrons into the conduction band of TiO ₂ nanoparticles takes place in two different ways: through the excited state of the 5(6)CFL dye and through direct injection from the charge transfer complex. The timeresolved fluorescence experimental results indicate that the free 5(6)CFL dye in water has double-exponential decay with lifetimes τ1 = 41 ps (74.4%) and τ2 = 3.22 ns (25.6%). However, 5(6)CFL dye-sensitized TiO ₂ nanoparticles have triple-exponential decay with lifetimes of τ1 = 44 ps (90.4%), τ2 = 478 ps (8.6%) and τ3 = 2.41 ns (1.0%). Our research will provide a valuable reference for the mechanism of dye-sensitized solar cell.