Imprinting of chiral molecular recognition sites in thin TiO2 films associated with field-effect transistors: Novel functionalized devices for chiroselective and chirospecific analyses

(R)- or (S)-2-Methylferrocene carboxylic acids, (R)-1 or (S)-1, (R)- or (S) -2-phenylbutanoic acid, (R)-2 or (S)-2, and (R)- or (S)-2-propanoic acid, ( R)-3 or (S)-3, can be imprinted in thin TiO2 films on the gate surface of i on-sensitive field-effect transistor (ISFET) devices. The imprinting is per formed by hydrolyzing the respective carboxylate Ti-IV butoxide complex on the gate surface, followed by washing off the acid from the resulting TiO2 film The imprinted sites reveal chiroselectivity only towards the sensing o f the imprinted enantiomer. The chiral recognition sites reveal not only ch iroselectivity but also chirospecificity and, for example, the (R)-2-imprin ted film is active in the sensing of (R)-2, but insensitive towards the sen sing of (R)-2-phenylpropanoic acid, (R)-3, which exhibits a similar chirali ty. Similarly, the (R)-3-imprinted film is inactive in the analysis of (R)- 2. The chiroselectivity and chirospecificity of the resulting imprinted fil ms are attributed to the need to align and fit the respective substrates in precise molecular contours generated in the cross-linked TiO2 films upon t he imprinting process.