Acid-treated carbon nanotubes/polypyrrole/fluorine-doped tin oxide electrodes with high sensitivity for saliva glucose sensing

Abstract

To alleviate the discomfort caused by the blood sampling process, a noninvasive saliva glucose sensor is investigated in this study. Owing to the low glucose concentration in the body fluid, the fabricated sensor is requested to possess high sensitivity. Herein, a chemical polymerization method is used to deposit polypyrrole (PPy) on a fluorine-doped tin oxide (FTO) conductive glass substrate followed by modification with acid treated carbon nanotubes (acid-CNTs) via the drop-casting method in order to fabricate acid-CNTs/PPy/FTO electrodes. In addition, the sensing device uses glucose oxidase as an enzyme to catalyze the redox reaction and improve the electrode selectivity. The electron transfer resistance decreases with layer-by-layer CNTs modification, and the acid-treatment time of CNTs significantly affects the sensing performance. The acid-CNTs/PPy/FTO electrodes exhibit excellent sensing performance with a high sensitivity of 95.26 μA/mMcm2 and a broad linear range of 10–700 μM with a R2 of 0.9958. Moreover, the acid-CNTs/PPy/FTO electrodes show high selectivity to glucose along with excellent stability. Furthermore, the sensing capability of the acid-CNTs/PPy/FTO electrode is tested using artificial saliva, that further confirms high potential of acid-CNTs/PPy/FTO electrodes in the noninvasive diagnosis of diabetes.