Waste eggshell membrane-templated synthesis of functional Cu2+–Cu+/biochar for an ultrasensitive electrochemical enzyme-free glucose sensor

A fast and sensitive test of blood glucose levels is very important for monitoring and reducing diabetic complications. Herein, a simple and sensitive non-enzymatic glucose sensing platform was fabricated by employing Cu2+–Cu+/biochar as the catalyst. The Cu2+–Cu+/biochar was synthesized through a bio-inspired synthesis, in which waste eggshell membrane (ESM) was introduced as a template to absorb Cu2+, then converting it into Cu2+–Cu+ biochar via a rapid pyrolysis. The structure and properties of the as-prepared Cu2+–Cu+ biochar were determined by scanning electron microscopy (SEM), FT-IR spectroscopy, Raman spectroscopy and cyclic voltammetry (CV). Due to great advantages of Cu2+–Cu+/biochar, such as high electrical conductivity, unique three-dimensional porous network and large electrochemically active surface area, the as-prepared Cu2+–Cu+ biochar modified electrode showed high catalytic activity towards glucose oxidization. The fabricated enzyme-free glucose sensor showed excellent performance for glucose determination with a linear range of 12.5–670 μM, and a limit of detection (LOD) of 1.04 μM. Moreover, the as-fabricated sensor has good anti-interference ability and stability. Finally, the proposed senor has been successfully applied to detect glucose in clinical samples (human serum). Owing to the green synthesis method, using biowaste ESM as a template, and the superior catalytic performance and low cost of Cu2+–Cu+/biochar, the developed sensor shows great potential in clinical applications for direct sensing of glucose.