Improving Linear Range Limitation of Non-Enzymatic Glucose Sensor by OH− Concentration

Abstract

To combat diabetes mellitus(DM), a chronicle metabolic disease, from which more than 400 million people suffered in the world, the patients must check the blood glucose level 4-5 times daily with an enzyme-based blood glucose meter and adjust blood glucose levels accordingly. The problem is that enzymatic glucose meters become unstable in the tropics. Therefore, the non-enzymatic method has been urged for blood glucose monitoring, among which the transition metal oxide electrode was found to be promising. However, despite the prolonged effort, its linear detection range is usually much smaller than the glucose level of diabetic patients, calling for an effective solution. Despite many previous attempts, none have solved the problem. Such a challenge has now been conquered by raising the NaOH concentration in the electrolyte, where amperometry, X-ray diffraction, Fourier-transform infrared spectroscopy, and Nuclear magnetic resonance measurements have been conducted. The linear range has been successfully enhanced to 40 mM in 1000 mM NaOH solution, and it was also found that NaOH affected the degree of glucose oxidation, which influenced the current response during sensing. It was expected that the alkaline concentration must be 25 times higher than the glucose concentration to enhance the linear range, much contrary to prior understanding.