Titanium dioxide ion-sensitive extended gate field effect transistor (ISEGFET): selective detection of potassium ions in artificial blood serum

Potassium ions (K+\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${K}<^>{+}$$\end{document}) are crucial for many physiological processes. Here we report on the use of a titanium dioxide (TiO2) extended gate field effect transistor as an ion sensor (ISEGFET). We tested within its critical concentration range in artificial blood serum for this. The TiO2 thin films were prepared via a solvothermal process over the conductive glass (coated with indium-tin oxide (ITO)). The prepared samples were tested by X-ray diffraction, Raman spectroscopy, for their phase structures, electron scanning microscopy, and X-ray photoelectron spectroscopy for their morphology and surface element contents. The TiO2/ITO samples were prepared as electrodes, and the threshold voltage and the drain - source current measurements were recorded against a reference electrode. The potential sensitivity of the electrodes was in the range 42 mV/pK - 47 mV/pK, and its current sensitivity was in the range 0.50-0.71 mA1/2/pK with K+ concentration covers the range between 100 mu M and 100 mM. The lower limit of detection was approximately 100 mu M. The devices were tested in the concentration range of 3.5 mM-10 mM, where the potential sensitivity was recorded between 7.5 mV/mM and 10 mV/mM in artificial blood serum. The devices reveal a stable performance within two months.