A novel enzyme-free and In-vivo glucose detection method utilizing ferric oxide modified zinc oxide nanorods and immobilized with a nafion membrane

An enzyme-free, reproducible, and sensitive glucose sensor was fabricated using ZnO NRs modified with ferric oxide Fe₂O₃ and immobilized with a nafion membrane. A controllable and a cost effective hydrothermal growth method was utilized to grow well-allied and high dense ZnO NRs on a FTO/glass substrate. Due to the higher isoelectric point of ZnO NRs IEP ~ 9.4 comparing with ferric oxide, the entire electroactive area of the working electrode of the sensor was successfully and effectively modified resulting in a wide linear response of the sensor to changes in D-glucose concentrations. The fabricated sensor exhibited a linear amperometric response to changes in glucose concentrations from 1-22 mmol/L, which is within the physiological interest of glucose level for diabetic patients. Because of the high surface to volume ratio provided by the ZnO NRs, the high electrocatalyst ability of Fe₂O₃, and the high affinity between ZnO NRs and Fe₂O₃, the sensor showed a high sensitivity in the order of 0.052 µA cm^-2 (mg/dL)^-1, a lower detection limit as 0.027 mM, and a fast and a sharp repose time ~1 s. The sensor was proved to be reproducible with a degradation rate around 10% after one month. The enzyme-free glucose sensor can be used clinically for In-vivo glucose detection.