Enhanced pH Sensing Performance of ZnO-PANI Composite in Extended-Gate Field-Effect Transistor Sensors

Precise pH monitoring plays a critical role in a variety of environmental, biomedical, and industrial processes. This study presents the development of a pH sensor based on an extended-gate field-effect transistor (EGFET) incorporating a zinc oxide-polyaniline (ZnO-PANI) composite thin film as the sensing material. Compared to conventional single-component sensing films, the ZnO-PANI composite offers enhanced electrochemical activity and improved charge transport, contributing to superior sensing performance. The sensor exhibited a sensitivity of 57.0 mV/pH, closely approaching the ideal Nernstian response, and demonstrated excellent linearity with a correlation coefficient (R<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>) of 0.9892. Additionally, its current response yielded a sensitivity of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$-1.4589(\mu ~\mathrm{A})^{1 / 2} / \text{pH}$</tex> with outstanding linearity (R<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>=0.9994). The results indicate that the ZnO-PANI composite is a promising candidate for reliable, miniaturized, and real-time pH sensing applications.