High- Dy₂TiO₅ electrolyte-insulator-semiconductor urea biosensors

In this study, we report on an electrolyte-insulator-semiconductor (EIS) device with a novel high-k Dy₂TiO₅ sensing membranes deposited on Si substrates through reactive cosputtering method. The effect of thermal annealing (700, 800, and 900C) on the structural and surface properties of Dy₂TiO₅ sensing membrane was investigated by x-ray diffraction, x-ray photoelectron spectroscopy, and atomic force microscopy. The EIS device incorporating a Dy₂TiO₅ sensing film that had been annealed at 800C exhibited good sensing characteristics, including a high sensitivity (57.59 mV/pH in solutions from pH 2-12), a small hysteresis voltage (0.2 mV in the pH loop 7 → 4 → 7 → 10 → 7), and a low drift rate (0.362 mV/h in the buffer solution at pH 7). This improvement can be attributed to the small number of crystal defects and the large surface roughness. Furthermore, a hybrid configuration of the Dy₂TiO ₅ membrane-EIS with urease-immobilized film was prepared by the entrapment of enzyme molecules in alginate hydrogel and was demonstrated for urea biosensing. Results demonstrated that the Dy₂TiO₅ EIS biosensor was able to detect urea with good linearity (R² 0.99) and reasonable sensitivity of 118.38 mV/pC_urea in the urea concentration range of 1-32 mM.