The Sensing Characteristics Investigation of a Potentiometric Ascorbic Acid Biosensor Integrated With Analog-to-Digital Converter

In this study, an enzymatic ascorbate oxidase/(AO) ruthenium dioxide (RuO
₂
) ascorbic acid (AA) biosensor was realized by a radio frequency (RF) sputtering system. The characteristics of the RuO
₂
sensing membrane were analyzed by field-emission scanning electron microscope (FE-SEM) and energy-dispersive X-ray spectroscopy (EDS). Moreover, electrochemical impedance spectroscopy (EIS) was performed to show that a higher concentration of AA caused a larger capacitance of the RuO
₂
membrane. Therefore, more charges can be accumulated on the sensing membrane. To read out the AA sensing signals, an instrumentation amplifier (IA) integrated with an analog-to-digital converter (ADC) was utilized to substitute the traditional data acquisition (DAQ) device. Then, the analog signals were converted into binary codes and transmitted to the computer, and the binary codes were multiplied by the weighting and converted to decimal codes. Hence, the average sensitivity and the linearity were obtained which were 58.22 mV/decade and 0.991, respectively. The hysteresis effects of the AO/RuO
₂
AA biosensor were also discussed. The hysteresis voltages in forward and reverse cycles were 3.77 mV and 4.59 mV, respectively.