Development of high-κ HoTiO3 sensing membrane for pH detection and glucose biosensing

In this paper, we proposed an electrolyte–insulator–semiconductor (EIS) device incorporating a high-κ HoTiO3 sensing membrane deposited on Si substrates through co-sputtering for pH detection and glucose biosensing. X-ray diffraction, Auger electron spectroscopy, and atomic force microscopy were used to investigate the structural and morphological features of these films annealed at various annealing temperatures. We found that the EIS device fabricating a high-κ HoTiO3 sensing membrane annealed at 900 °C exhibited a higher sensitivity of 59.5 mV/pH (in the solutions from pH 2 to pH 12), a lower hysteresis voltage of 2.2 mV (in the pH = 7 → 4 → 7 → 10 → 7), and a smaller drift rate of 0.47 mV/h (in the pH 7 buffer solution) than those of the other annealing temperatures. These results are attributed to the small number of crystal defects and the large surface roughness. In addition, the enzymatic EIS-based glucose biosensor incorporating a high-κ HoTiO3 sensing membrane annealed at 900 °C allowed the potentiometric analysis of glucose, at concentrations ranging from 2 to 8 mM, with a sensitivity of 7.94 mV/mM.