Development of high-κ Eu₂Ti₂O₇ EIS devices using poly-N-isopropylacrylamide as an enzyme encapsulation material for pH detection and uric acid biosensing

In this study, we proposed an electrolyte-insulator-semiconductor (EIS) device fabricating a high-κ Eu₂Ti₂O₇ sensing membrane deposited on Si substrates through cosputtering for pH detection and uric acid biosensing applications. The EIS device incorporating a high-κ Eu₂Ti₂O₇ sensing membrane annealed at 900 C exhibited a higher sensitivity of 59.03 mV/pH, a smaller hysteresis voltage of 2.8 mV, and a lower drift rate of 0.586 mV/h compared to those of the other annealing temperatures. These results are attributed to the small number of crystal defects and the large surface roughness. Furthermore, for high-κ Eu₂Ti₂O₇ EIS-based bio-sensing application, a phase tunable poly-N-isopropylacrylamide (PNIPAAm) was used as an enzyme encapsulating material, making the loading and removal of a biological recognition element on a biosensor easily. In this study, a hybrid configuration of the high-κ Eu₂Ti₂O₇ EIS biosensor with an uricase-immobilizing PNIPAAm film attached was established and was demonstrated for uric acid biosensing. The sensitivity of a Eu ₂Ti₂O₇ EIS biosensor was 17.6 mV/mM for uric acid concentrations ranging from 2 to 8 mM.