PH and Procaine Sensing Characteristics of Extended-Gate Field-Effect Transistor Based on Indium Tin Oxide Glass

Abstract

The pH sensing properties of an extended-gate field-effect transistor (EGFET) based on indium tin oxide (ITO) glass are investigated in this study. The separating structures in the EGFET are examined using a current–voltage measurement system to measure I–V curves. A readout circuit is applied to measure the pH sensing EGFET output voltage, and nonideal factors (drift and hysteresis effects) are monitored in different buffer solutions (pH=1–11). It was found that separating structures for ITO glass sensors have a high pH sensitivity (∼55 mV/pH), a low drift rate and a small hysteresis width in the concentration range between pH=1 and 11 in buffer solutions. The EGFET was used in fabricating a drug-sensitive field-effect transistor (DrugFET) sensor for procaine hydrochloride. The DrugFET was prepared using a combination of the EGFET and a drug-sensitive membrane that measured the procaine concentration in the 1×10-2–1×10-6 mol/L range. The separating structure was used with a procaine DrugFET with a good response (∼200 s) at room temperature.