•A novel and uniform Au-PtNPs/PyTS-NG nanocomposite was fabricated by direct electrodeposition method.•The prepared nanocomposite exhibited excellent catalytic activity to the oxidation of nitrite.•An amperometric sensor with a linear range of 0.5–1621 μM and a detection limit of 0.19 μM was set up.•Detection of nitrite in real samples was studied.In this work, we report a novel Au-Pt bimetallic nanoparticles (Au-PtNPs) decorated on the surface of nitrogen-doped graphene (NG) functionalized with 1, 3, 6, 8-pyrene tetra sulfonic acid sodium salt (PyTS) by direct electrodeposition method. The results of scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and electrochemical impendence spectrum (EIS) reveal that the Au-PtNPs were successfully anchored on the surface of NG sheets with a diameter of 20–40 nm. Further, the prepared Au-PtNPs/PyTS-NG nanocomposite exhibits superior catalytic activity for the oxidation of nitrite. Under optimal experimental conditions, an amperometric sensor with a linear range of 0.5–1621 μM and a detection limit of 0.19 μM (S/N=3) for the detection of nitrite was set up and applied to real samples.

•A novel PyTS–NG nanocomposite was successfully prepared.•The material has better dispersivity and conductivity.•A sensitive electrochemical sensor based on PyTS–NG was fabricated for simultaneous determination of UA, XA and HX.A highly sensitive and selective method was developed for simultaneous detection of uric acid (UA), xanthine (XA) and hypoxanthine (HX) based on a 1,3,6,8-pyrene tetra sulfonic acid sodium salt functionalized nitrogen-doped graphene (PyTS–NG) composite. The material was synthesized by utilizing a facile ultrasonic method via π–π conjugate action between 1,3,6,8-pyrene tetra sulfonic acid sodium salt (PyTS) and nitrogen-doped graphene (NG) molecule. Compared with pristine NG, the material had better dispersivity and conductivity, which might be attributed to a large number of edge-plane-like defective sites on the surface of PyTS–NG that would accelerate electron transfer between electrode and species in solution. The surface morphology was characterized by scanning electron microscopy and transmission electron microscopy. The electrochemical behaviors of UA, XA and HX on the surface of PyTS–NG were investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Under the optimized condition, the linear ranges for the determination of UA, XA and HX were 9–1000, 8–800 and 8–200 μM, with the detection limits (S/N = 3) of 0.331, 0.0838 and 0.231 μM, respectively. Furthermore, the practical application of the present method was evidenced by determining UA, XA and HX in human blood serum and urine samples.

•Trp-GR was synthesized by utilizing a facile ultrasonic method.•The material as prepared had well dispersivity in water and better conductivity than pure GR.•Trp-GR/GCE showed excellent potential for the determination of AA, DA and UA.•The proposed method was applied for the analysis of AA, DA and UA in real samples.A new type of tryptophan-functionalized graphene nanocomposite (Trp-GR) was synthesized by utilizing a facile ultrasonic method via π–π conjugate action between graphene (GR) and tryptophan (Trp) molecule. The material as prepared had well dispersivity in water and better conductivity than pure GR. The surface morphology of Trp-GR was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. The electrochemical behaviors of ascorbic acid (AA), dopamine (DA), and uric acid (UA) were investigated by cyclic voltammetry (CV) on the surface of Trp-GR. The separation of the oxidation peak potentials for AA–DA, DA–UA and UA–AA was about 182 mV, 125 mV and 307 mV, which allowed simultaneously determining AA, DA, and UA. Differential pulse voltammetery (DPV) was used for the determination of AA, DA, and UA in their mixture. Under optimum conditions, the linear response ranges for the determination of AA, DA, and UA were 0.2–12.9 mM, 0.5–110 μM, and 10–1000 μM, with the detection limits (S/N = 3) of 10.09 μM, 0.29 μM and 1.24 μM, respectively. Furthermore, the modified electrode was investigated for real sample analysis.