Circular Dichroism of Porphyrin J-Aggregates Induced by Adsorbed d-Tartaric Acid on Mesoporous TiO2 Film

Abstract

Abstract Circular dichroism (CD) signals of J-aggregates of 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (TPPS4) fixed on mesoporous TiO2 film were induced by adsorption of d-tartaric acid. The intensity of the induced CD signal at 477 nm derived from TPPS4 J-aggregates adsorbed on TiO2 film increased depending strongly on the concentration of d-tartaric acid dissolved in the surrounding water and the immersion time of TPPS4-adsorbed TiO2 film in acidic water. Especially, in acidic water with high concentrations of d-tartaric acid, the CD intensity increased enormously with the elapse of immersion time, accompanying a decrease of J-aggregates adsorbed on TiO2 film. The amount of d-tartaric acid adsorbed on TiO2 film should determine the CD intensity of J-aggregates. When d-tartaric acid dimethyl ester, which has an effect similar to d-tartaric acid on the induction of CD of TPPS4 J-aggregates in an aqueous solution, was used instead of d-tartaric acid, a slight CD at 477 nm was observed, clearly showing that the chemisorption of chiral molecules on the TiO2 surface through an anchoring group was critical for inducing the CD signal of J-aggregates.