Remarkable enantioselectivity of molecularly imprinted TiO2 nano-thin films

TiO2 nano-thin films with imprinted (R)- and (S)-enantiomers of propranolol, 1,1′-bi-naphthol, and 2-(4-isobutylphenyl)-propionic acid were fabricated on quartz plates by spin-coating their solutions with Ti(O-nBu)4 in a toluene-ethanol mixture (1:1, v/v). After template removal, the imprinted films showed better binding for original templates than to the corresponding enantiomers. The assessment of template incorporation, template removal, and re-binding was conducted through UV–vis measurements. Significant enhancement of enantioselectivity was achieved by optimization of the film thickness and by heat-treatment of the imprinted films. After subtraction of non-specific binding, the optimized films provided chiral recognition with the enantioselectivity of almost 100% for (R)-propranolol and 95% for (S)-propranolol.