FABRICATION OF pH SENSOR BASED ON EG-FET WITH SENSING ELECTRODE USING POLYPYRROLE

Abstract

pH is a very common parameter that needs to be measured in many different fields such as agriculture, food and biomedicine. In this work, we present the research results following a simple approach to fabricating a pH sensor based on an extended gate field-effect transistor (EG-FET) with sensing electrode utilized by conducting polymer. Conducting polypyrrole (PPy) film was directly deposited on a Si substrate by a vapour phase polymerization using catalytic oxidation FeCl₃. Scanning electron microscope (SEM) was used to investigate  surface morphology of the PPy synthesized film and it showed a high porosity. Fourier transform infrared (FTIR) and Raman spectroscopy were used to examine the specific bonding structures of the PPy film. pH sensor was configured with the PPy electrode connected to the extended gate of FET (2N5457). The sensor exhibited an output characteristic of linear dependence on the pH value and a high sensitivity (105.9 µA/pH) in correspondence with the investigated pH range from 5 to 9.