Nitrogen and sulfur co-doped Nb2C-MXene nanosheets for the ultrasensitive electrochemical detection dopamine under acidic conditions in gastric juice

This work reports the synthesis and application of nitrogen and sulfur co-doped Nb2C MXene (NS-Nb2C) for the sensing of dopamine (DA) in gastric juice. NS-Nb2C MXene was successfully synthesized in a one-step treatment of Nb2C using thiourea as N,S resource. The heteroatom doping strategy enables introduction of N,S into MXene nanosheets and simultaneously induces the increased interlayer spacing, high surface area, and enhanced electrical conductivity. It was found that NS-Nb2C is more electrochemically active than multilayered Nb2C nanosheets (ML-Nb2C) and delaminated Nb2C nanosheets (DL-Nb2C). Based on this, the as-prepared NS-Nb2C/Nafion/GCE was used to study the electrochemical behavior of dopamine in pH = 3.0. The sensing interface not only utilizes the unique two-dimensional (2D) nanosheet morphology of Nb2C that has a larger surface area and conductive network, but also takes advantage of the more active sites provided by doping. This enables the sensor to achieve ultra-sensitive detection of dopamine (S/N = 3) with a low limit of detection (LOD) of 0.12 µM. In addition, the prepared sensor has good stability and selectivity, and the results of detecting DA in simulated gastric juice is satisfactory. The results indicated that the Nb-based MXenes provided a promising tool for acidic electrochemical sensing applications.