Highly Sensitive and Selective Sol-Gel Spin-Coated Composite TiO2–PANI Thin Films for EGFET-pH Sensor

• Published in: Gels
• Main Author: Kamarozaman N.S.; Zainal N.; Rosli A.B.; Zulkefle M.A.; Nik Him N.R.; Abdullah W.F.H.; Herman S.H.; Zulkifli Z.
• Format: Article
• Language: English
• Published: MDPI 2022
• Online Access: https://www.scopus.com/inward/record.uri?eid=2-s2.0-85141700947&doi=10.3390%2fgels8110690&partnerID=40&md5=f33045bd9a7a33456b3d91e1ac294c5c

A highly selective and sensitive EGFET-pH sensor based on composite TiO2–PANI had been developed in this work. A sol-gel titanium dioxide (TiO2) and the composite of TiO2 with semiconducting polyaniline (PANI) were deposited using a simple spin-coating method on an indium tin oxide (ITO) substrate. The films have been explored as a sensing electrode (SE) of extended gate field-effect transistor (EGFET) for pH applications in the range of pH 2 to 12. The pH sensitivities between TiO2, TiO2–PANI bilayer composite, and TiO2–PANI composite thin films were discussed. Among these, the TiO2–PANI composite thin film showed a super-Nernstian behavior with high sensitivity of 66.1 mV/pH and linearity of 0.9931; good repeatability with a standard deviation of 0.49%; a low hysteresis value of 3 mV; and drift rates of 4.96, 5.54, and 3.32 mV/h in pH 4, 7, and 10, respectively, for 6 h. Upon applying the TiO2–PANI composite as the SE for nitrate measurement, low sensitivity of 12.9 mV/dec was obtained, indicating that this film is a highly selective sensing electrode as a pH sensor. The surface morphology and crystallinity of the thin films were also discussed. © 2022 by the authors.