Ultra-low charge transfer resistance carbons by one-pot hydrothermal method for glucose sensing

Hydrothermal carbon (HTC) is typically well-dispersed, but it remains a great challenge for HTC to become conductive. Co-doping with heteroatoms has been confirmed to be an effective strategy to significantly promote the electrical conductivity of carbon. Moreover, there is no simple and green method to construct sensitive HTC based electrochemical biosensors until now. In this paper, N and S dual-doped carbon (NS-C) with ultra-low charge transfer resistance is easily synthesized from L-cysteine and glucose in a hydrothermal reaction system. The morphology, structural properties and electrochemical properties of the as-prepared NS-C are analyzed. In comparison with the undoped hydrothermal (UC) modified glassy carbon electrode (GCE), the charge transfer resistance of UC (476 Ω) is ten times the value of NS-C (46 Ω. The developed biosensor shows a better performance to detect glucose in a wide concentration range (50-2500 μmol L-1) with the detection limit of 1.77 ^mol L-1 (S/N=3) and a high sensitivity (0.0554 μA cm-2 μmol-1 L). The apparent Michaelis-Menten constant value of GCE/NS-C/GOx/nafion modified electrode is 0.769 mmol L-1, indicating a high affinity of glucose oxidase to glucose. These results demonstrate that the hydrothermal method is an effective way for preparing high electrical conductivity carbon with excellent performances in biosensor application.