Capacitive sensing of amino acids using caliraxene-coated silicon transducers

The possibility of using capacitance and flat band voltage as measurable quantities for determining amino acids that are neither electroactive nor with strong UV-vis absorption has been explored. The sensors were fabricated by immobilizing calixarene derivatives on Si/SiO2/Si3N4 transducers. The measurements were made in sulfuric acid media of ca. pH 1 and in physiological buffer of pH 7.4. The different calixarene derivatives showed varying sensitivities to the amino acids ranging from 8 to 137 mV/decade.