Abstract: To construct a poly(methacrylic acid) molecularly imprinted electrochemical sensor based on two-dimensional Ti₃C₂T_x nanosheets/conductive carbon black (KB) composite for the detection of dopamine (DA). In this study, two-dimensional Ti₃C₂T_x nanosheets/conductive KB composites were prepared by wet etching and ultrasonic mechanical mixing techniques. DA was used as the template molecule and methacrylic acid as the functional monomer. A molecularly imprinted polymer film selective for DA was fabricated on the surface of the d-Ti₃C₂T_x/KB modified electrode by electrochemical deposition. The composition and morphology of the materials were analyzed by X-ray diffraction, field emission scanning electron microscopy and transmission electron microscopy. The electrochemical performance of the modified electrode was investigated by cyclic voltammetry using potassium ferricyanide as an electron probe. The electrochemical response of the electrode to DA was examined by pulse voltammetry. The detection conditions such as the mass ratio of the modified material, the ratio of the functional monomer to the cross-linker, the number of electrochemical deposition cycles, the enrichment time, and pH were optimized. The detection results showed that the constructed sensor had a high electrochemical response to DA, with a detection range of 1×10^-6 - 1×10^-2 M and a minimum detection limit of 4.228 μM (S/N = 3). The sensor exhibited good anti-interference and repeatability. DA in urine samples was detected by the standard addition method, with recovery rates ranging from 82.5% to 93.75% and RSDs all below 5%. The DA detection molecularly imprinted electrochemical sensor constructed in this experiment has high sensitivity and reliability, providing a method and idea for the detection of DA samples.

Key words: Dopamine, Electrochemical sensor, Molecular imprinting, MXenes, Ti₃C₂T_x; Ketjen black