Penicillin detection with nanocrystalline‐diamond field‐effect sensor

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 µM and a high sensitivity of 60–70 mV/decade in a wide linear range of 0.005–2.5 mM penicillin G concentration. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)