Cu²⁺-doped Carbon Nitride/MWCNT as an Electrochemical Glucose Sensor

The rational design of electrocatalysts with abundant active sites and high conductivity is the key to the development of glucose sensors. Herein, we report the preparation of a Cu ²⁺-doped C ₃N ₄ supported on multi-walled carbon nanotube (MWCNT) network (Cu ²⁺-C ₃N ₄/MWCNT) as a highly efficient non-enzymatic glucose sensing system. The morphologic and structural investigations using TEM, AFM, XRD, XPS, EPR, and i-V response indicate the successful insertion of Cu ²⁺ into the C ₃N ₄ inter-layers via an out-of-plane on-top configuration and the consequent exfoliation of C ₃N ₄ layers without forming CuO or Cu(OH) ₂. Such material can act as an electrocatalyst for glucose electrooxidation, and MWCNT can greatly reduce the charge transfer resistance and enhances activity. An optimised Cu ²⁺ doping level (12 wt%) in Cu ²⁺-C ₃N ₄/MWCNT was established to realise high sensitivity towards glucose sensing (929 mA/M cm ²), large linear range (0.5 μM∼12 mM), low detection limit (0.35 μM), and short response time (<3 s). Excellent selectivity against the interferents, such as dopamine, ascorbic acid, sucrose, and lactose, is also observed. In the blood serum tests, as-prepared glucose sensor reports comparable and reproducible results, demonstrating its practical potentials.