Liquid gated ZnO nanorod FET sensor for ultrasensitive detection of Hepatitis B surface antigen with vertical electrode configuration.

Detection of the Hepatitis-B surface antigen at the attomolar level is demonstrated using antibody functionalized liquid gated ZnO nanorods field effect transistor (FET) biosensor with vertical electrode configuration. The sensor is operated in heterodyne mode at high frequency to overcome the problem of Debye screening effect in physiological analyte. Enhanced penetration of the electric field lines through the nanorods enables significant improvement in the limit of detection and sensitivity compared to that of the conventional lateral electrode configuration. The combined effect of the probable change in the threshold voltage and the carrier mobility for vertical electrode configuration lead to a sensitivity of around 75% at 1 fM (which is an enhancement by 200%) and a detection limit of 20 aM with a dynamic range from 20 aM to 1 pM. The detection limit which is achieved with the proposed label free sensor in physiological analyte using antibodies is lowered by more than three orders of magnitude compared to the existing reports.