Chiral sensing using a complementary metal-oxide semiconductor-integrated three-transducer microsensor system

Different chiral cyclodextrin derivatives were dissolved in a polysiloxane matrix and have been used as sensitive coatings on a three-transducer microsystem including a calorimetric, a mass-sensitive, and a capacitive chemical sensor. Upon exposure to chiral analytes, such as methyl lactate and methyl-2-chloropropionate, all three transducers showed distinct chiral discrimination of these analytes. The signals were found to constitute a convolution of sorption thermodynamics and transducer-specific contributions, which included, in the case of the capacitive sensor, molecular orientation effects so that even opposite-sign signals for the two enantiomers resulted. The sensor response curves of all three transducers could be explained and fitted by applying a model that essentially implies the superposition of a Langmuir isotherm representing specific interactions, predominant at low concentrations, and a Henry isotherm for nonspecific physisorption. The results disclosed here show that, on the one hand, sensor techniques can be used to reveal details of enantioselective analyte-receptor or analyte-matrix interactions and that, on the other hand, sensors may provide an even more pronounced chiral discrimination ("discrimination enhancement") with respect to sorption-thermodynamics-determined gas chromatography as a consequence of the transducer-specific signal contributions.