Electrochemical detection of dopamine and uric acid using a titanium nitride-graphene composite sensor

Dopamine (DA) and uric acid (UA) are small biological molecules involved in many important processes in the human body. Their concentrations are closely related to human health. Abnormal concentrations of these molecules lead to various diseases, such as Parkinson's and gout, so monitoring of DA and UA in blood and urine, respectively, is very meaningful in clinical analysis. Electrochemical sensor detection is a widely-used method in the field of biological analysis owing to its advantages of simple operation, high sensitivity, low cost, environmental friendliness, etc. In this paper, titanium nitride (TiN) nanomaterial with chrysanthemum morphology was synthesized by hydrothermal and reduction nitridation methods toward preparation of an effective electrochemical sensor for human testing. It was further combined with reduced graphene oxide (rGO) through the hydrothermal method to form a titanium nitride-reduced graphene oxide (TiN-rGO) composite material. The phase and morphology of the material were characterized and analyzed by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and other test methods. The results show that the TiN-rGO composite material maintaines the three-dimensional chrysanthemum-like morphology of TiN, and the transparent and wrinkled morphology of rGO. The chrysanthemum-like TiN is uniformly coated with the layered rGO. The TiN-rGO/GCE electrochemical sensor was then prepared by modifying the glassy carbon electrode (GCE) with TiN-rGO composite material for the determination DA and UA levels in the human body. Due to the synergistic effect of TiN and rGO in the composite, the constructed electrochemical sensor exhibits excellent electrochemical performance. The detection results show that the detection limits of DA and UA for the TiN-rGO/GCE electrochemical sensor are 0.11 and 0.12 μmol·L⁻¹, respectively, and the linear ranges are 0.5‒210 μmol·L⁻¹ and 5‒350 μmol·L⁻¹, respectively. TiN-rGO/GCE electrochemical sensor also has good anti-interference, reproducibility and stability, and has been successfully applied in the detection of DA and UA in real human samples.