Photoinduced electron transfer in heterosupramolecular assemblies of TiO₂ nanoparticles and terthiophene carboxylic acid in apolar solvents

Monodisperse stearic acid coated titanium dioxide nanoparticles (< 3 nm) have been prepared and characterized. The nanoparticles are soluble in common apolar organic solvents and bind to carboxylic acid functionalized π-conjugated oligomers to form heterosupramolecular assemblies. When [2,2′;5′,2″]terthiophene-5-carboxylic acid was coupled to the nanoparticles, the fluorescence of the terthiophene moiety of the heterosupramolecular system was completely quenched due to a photoinduced electron transfer from terthiophene to titanium dioxide. Time-resolved fluorescence and Stern-Volmer analysis revealed that the quenching is predominantly static rather than dynamic and occurs in apolar solvents.