Fabrication and electrical characterization of carbon nanotube based enzyme field effect transistor for cholesterol detection

In this work, carbon nanotube based ENFET for cholesterol detection has been developed. The fabricated device replaces silicon substrate with PEI doped carbon nanotube which offers high carrier mobility, excellent stability and enhanced sensitivity. The device is fabricated on indium tin oxide glass substrate. Zirconia (ZrO2) having high dielectric constant is used as top and bottom gate insulator. PPy/K/CNT nanocomposite serves as the sensing layer for the cholesterol ENFET. Cholesterol oxidase (ChOx) is immobilized covalently on the sensing layer for detection of cholesterol. Carbon nanotube composites with conductive polymers offer fast electron transfer kinetics between reaction sites and the active binding sites. Moreover, polypyrrole also works as a support matrix for enzyme immobilization. The fabricated device has been characterized for detection of cholesterol (0.5-24 mM). Electrical response has been recorded using (Scientific SM 7023) multimeter in the presence of phosphate buffer solution. The device showed good linearity for cholesterol concentration from 0.5-19.5 mM. and Michaelis-Menten constant (Km) was found to be 3.4 mM. The life time of the sensor is up to 5 months with response time less than 1 second.