Visible Photoluminescent Zinc Oxide Nanorods for Label-Free Nonenzymatic Glucose Detection

Diabetes mellitus affects a significant percentage of the world's population, and the incidence of this disease is expected to increase exponentially in the coming years. The development of practical and low-cost glucose sensors is of utmost importance to monitor and manage diabetes and diabetes associated complications. In this scope, a nonenzymatic glucose sensor was produced by growing zinc oxide (ZnO) nanorods on a cellulose-based substrate by microwave-assisted hydrothermal synthesis. The developed sensor relies on ZnO nanorods' photocatalytic ability to photo-oxidize glucose, eliminating the need to use an oxidase enzyme. The quantification of glucose is based on the quenching of the ZnO's photoluminescence signal by the hydrogen peroxide produced during the nonenzymatic oxidation of this monosaccharide. The developed sensor possesses a sensitivity of 1.46%/mM, a linear range between 0.5 and 30 mM, and a limit of detection of 0.103 mM. The sensor showed good selectivity for glucose, and it was also demonstrated that there was a high correlation between the glucose concentration values obtained using the sensor's calibration curve and the clinical data of human plasma samples, therefore validating the use of ZnO nanorods to monitor the glucose concentration in human plasma samples. This work reports for the first time a ZnO-based eco-friendly, stable, and highly selective alternative for glucose monitoring, pointing to a promising future for metal oxide nanostructures for biomedical sensors.