Aromatic-ring dependence of interfacial charge-transfer transitions between TiO2 nanoparticles and aromatic carboxylic acids

Interfacial charge-transfer transitions (ICTTs) between organic compounds and inorganic semiconductors enable the absorption of visible light with colourless organic molecules and direct charge separation for their potential applications in photoenergy conversions and chemical sensing. TiO2 nanocomplexes with aromatic carboxylic acids are one of the most important ICTT systems for photoenergy conversions. Here, we report the aromatic-ring dependence of ICTT in TiO2 nanocomplexes with benzoic acid, naphthalene-2-carboxylic acid, and anthrancene2-carboxylic acid. Our research reveals the significant red-shift of ICTT by expanding the pi-conjugated system from the benzene to anthracene ring and elucidates the mechanism.