The Hysteresis Reduction Approach for Urea Biosensor Modified by Silver Nanoparticles

The goal of this research is to reduce the hysteresis effect of the urea biosensor modified by urease-silver nanoparticles (Ag NPs)/ruthenium dioxide (RuO2) thin film. A new analog back-end circuit with a voltage regulation approach was proposed for hysteresis reduction. A urea biosensor based on urease-Ag NPs/RuO2 sensing film was fabricated. The sensing characteristics of the urea biosensor such as average sensitivity, response time, and interference effect, were measured by the voltage-time (V-T) measurement system. The experiment results showed that the average sensitivity and linearity of the urea biosensor in a wide range of urea solution (0.833 mu M-8.33 mM) were 48.73 mV/decade and 0.996, respectively. The response time was 22 seconds and the limit of detection was 0.37 mu M. Moreover, the electrochemical impedance analysis (EIS) was used to analyze the charge transfer ability of urease-Ag NPs/RuO2 thin film. By applying the voltage regulation approach, the proposed analog back-end circuit can hold the response voltage of the biosensor at a stable level. Therefore, the hysteresis voltage was reduced. With the proposed backed-end circuit in urea solution cycle of 30mg/dL -> 10 mg/dL -> 30 mg/dL -> 50mg/dL -> 30 mg/dL, the hysteresis voltage was reduced from 4.57 mV to 3.35 mV (26% reduction) comparing with V-T measurement system. The hysteresis voltage in the opposite urea solution cycle of 30 mg/dL -> 50 mg/dL -> 30 mg/dL -> 10 mg/dL -> 30 mg/dL was reduced from 3.71 mV to 2.62 (29% reduction) mV comparing with V-T measurement system.