Glucose Detection With a Commercial MOSFET Using a ZnO Nanowires Extended Gate

ZnO nanowires were grown on Ag wire with a diameter of ${\sim}\hbox{250}\ \mu$ m and used in an electrochemical sensor. The enzyme glucose oxidase (GOD) was immobilized on the ZnO nanowires, and the Ag wire was connected directly to the gate of a MOSFET. Upon exposure to glucose (1– $\hbox{100}\ \mu$M), the electrochemical response from the GOD induced a stable measurable voltage change on the gate leading to a strong modulation of the current through the MOSFET. For a sensor with uniform ZnO nanowires functionalized with GOD, a fast response time of less than 100 ms was demonstrated. The effect of the uniformity of the ZnO nanowires on the sensing property was also investigated. The extended-gate arrangement facilitated glucose detection in small sample volumes, and made it possible to demonstrate the present sensor concept using a standard low-threshold MOSFET. The extended-gate MOSFET sensor approach demonstrates the possibility and potential of the use of nanostructures coupled to standard electronic components for biosensing applications.