Ultrafast Electron Injection from the S2 State of Carotenoids into TiO2 Nanoparticles

Dye molecules attached to TiO2 nanoparticles have been of a great interest in the applications including dye-sensitized solar cells. In this paper, TiO2 nanoparticle sensitized with a natural photosynthetic dye, 8'-apo-beta-caroten-8'-oic acid (ACOA) was investigated by femtosecond transient absorption spectroscopy. Ultrafast excited state dynamics of ACOA and electron injection and recombination dynamics between dye molecules and TiO2 nanoparticles were compared by changing the excitation wavelength between 403 and 480 nm. Ultrafast electron injection into TiO2 nanoparticles with quantum yields of 0.33 was observed for both excitation wavelengths.