Photoelectrochemical Enantioselective Recognition of Amino Acid Enantiomers on (001) Facet TiO2 Surface

TiO2 with high exposure of (001) facet and chiral recognition ability (L-(001) TiO2) was successfully fabricated employing L-phenylalanine (L-Phe) as template molecule. Compared with the common L-TiO2 photoanode with no special exposed facet, L-(001) TiO2 photoanode exhibited superior chiral recognition and enantioselective photoelectrochemical (PEC) oxidation ability toward the template molecule L-Phe attributed to its preferential adsorption on the imprinting sites with contrast to the other enantiomer D-Phe. The photocurrent response of L-Phe on L-(001) TiO2 was 8 times that on L-TiO2. Meanwhile, the PEC recognition factor on L-(001) TiO2 was obtained as 2.9, which was about 1.9 times that on L-TiO2. The results may be presumably attributed to the better imprinting expression on L-(001) TiO2 with more accessible surface imprinting sites and enhanced PEC catalytic activity, which was beneficial for the fast PEC oxidation of the adsorbed template molecules and further amplified the PEC enantioselectivity. Finally, the different PEC oxidation kinetics of the two enantiomers on L-(001) TiO2 was also investigated, and the PEC oxidation rate constant of L-Phe on L-(001) TiO2 was 1.6 times that of D-Phe. It was believed that the present work will provide meaningful experimental and theoretical foundation for fabricating PEC electrode with chiral recognition ability.