Melamine-Based Nanocomposites for Selective Dopamine and Uric Acid Sensing

The formation process of carbon dots (CDs) is mostly polymerization; recently, studies on the polymerization of carbon families (graphene oxide and C60) have been receiving exciting attention. Herein, a protocol of prepolymerization and electropolymerization of monomer (melamine) and nanomonomer (CDs fixed melamine residues) was proposed to prepare a nanocomposite for selective dopamine (DA) and uric acid (UA) sensing. The nanomonomer was prepared by hydrothermal prepolymerization of melamine, and then the nanocomposite was formed in situ by electropolymerization of the CDs/carboxylated multiwalled carbon nanotubes (MWCNTs-COOH)-modified glassy carbon electrode (GCE) in KCl solution. Scanning electron microscopy, transmission electron microscopy, energy-dispersive spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, cyclic voltammetry, electrochemical impedance spectroscopy, and differential pulse voltammetry were used to characterize the properties of the nanocomposite. Under optimal conditions, the electrochemical sensor shows selectivity and a wide linear range from 0.1 to 10 μM for DA and 0.1 to 200 μM for UA, with the detection limit of 0.023 and 0.064 μM (S/N = 3) in the presence of AA, respectively. In addition, the proposed sensor was also applied to selectively test DA and UA in the presence of 500 μmol/L AA in real samples with satisfactory recovery.