Photochemical behaviors during the photosensitization of colloidal TiO2 particles by a newly synthesized multidentate squaraine

A new squaraine dye Bis(4-N,N-dicarboxymethyl- 2-hydroxyphenyl)squaraine (SQ) which could be used as organic photovoltaic materials, was synthesized, and its molecular structure was fully characterized by elemental analysis, IR, 1H NMR and MS. SQ exhibits strong absorption band over 600–700 nm. Addition of TiO2 colloids to the ethanol solution of SQ resulted in the increase of optical density, quenching of fluorescence and shortened fluorescence lifetime. The apparent association constant between the sensitizer and semiconductor as measured from the fluorescence quenching data, was 2427 M–1. Fluorescence lifetime measurements gave the rate constant for the electron injection process from the excited singlet of SQ to the conduction band of TiO2 nanoparticles as 2.55 · 10 8 s–1. In addition, SQ doped SiO2 gel glass slices were prepared and characterized by absorption and emission spectra.