Recently, solvothermal technique was used to explore and construct 3D(micro/nano)V2O5 growth on (M-PSi) as a sensing gate for the pH EG-FET device. The sensor has high sensitivity and a linear response in the pH range of 2-12, as well as relatively high hysteresis. However, around pH 12, the membrane gradually degrades and redox species in solution cause significant pH measurement errors. To overcome the limitations of a manufactured sensor, a thick layer of selective proton permeable Nafion was coated as a protective layer over the sensing gate 3D(micro/nano)V2O5 using the drop-casting method. Utilizing an x-ray diffractometer and field emission scanning electron microscopy, the structural and morphological features of the sensing layer were analyzed. The Nafion coating on the sensing gate pH EG-FET device decreased its sensitivity, modified linearity in the linear and saturation regions, and reduced hysteresis with significantly less drift. The sensor's great stability is due to Nafion's chemical resistance and capability to transport protons, which lowers the interference produced by anionic oxidizing or redwing (redox) species on the response of an uncoated electrode. Nafion can be considered a potential candidate as a protective layer for different MOx based pH sensors in a complicated environment for various biomedical applications.
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