Penicillin detection with nanocrystalline-diamond field-effect sensor

Abstract

Nanocrystalline-diamond (NCD) films have been utilised for the detection of penicillin G for the first time. The developed penicillin-sensitive biosensor consists of a field-effect capacitive electrolyte-diamond-insulator-semiconductor (EDIS) structure with an immobilised enzyme layer that covers the gate region of the sensor. Undoped NCD thin films of about 100 nm thickness were grown on a p-Si-SiO2 (50 nm thermally grown SiO2) structure by microwave plasma-enhanced chemical vapour deposition. The enzyme penicillinase has been adsorptively immobilised directly onto the O-terminated NCD surface. The EDIS biosensors have been characterised in buffer solutions with different content of penicillin G by means of capacitance-voltage and constant-capacitance method. The developed penicillin biosensor possesses a low detection limit of 5 mu M and a high sensitivity of 6070 mV/decade in a wide linear range of 0.005-2.5 mM penicillin G concentration. (C) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.