Cu2O/nitrogen-doped grapheme（NG） nanocomposite material was prepared via a facile one step chemical reduction and characterized by means of X-ray diffraction（XRD） and scanning electron microscopy（SEM）. A new electrochemical sensor was then fabricated by coating Cu2O/nitrogen-doped graphene nanocomposite with Nation on glassy carbon electrode（Cu2O/NG/Nation/GCE）. The electrochemical response of this modified electrode toward of- loxacin was examined by cyclic voltammetry. The results indicate that Cu2O/NG/Nafion composite-modified elec- trode exhibits higher catalytic activity in the electrochemical oxidation of ofloxacin compared with glassy carbon electrode（GCE）, Cu2O/Nafion modified electrode（Cu2O/Nafion/GCE）, and N-doped graphene/Nation modified electrode（NG/Nafion/GCE）. Under optimal conditions, the peak current was found to be linearly proportional to the concentration of ofloxacin in the 0.5-27.5 μmol/L and 27.5-280 μmol/L ranges with a lower detection limit of 0.34 μmol/L, higher sensitivity of 39.32 μA-L-mmoV1 and a shorter reaction time of less than 2 s. In addition, Nation can enhance the stability of the modified electrode and prevent some negative species. Thus the modified electrode exhibits good selectivity and a long working life. The Cu2O/NG/Nafion composite modified electrode shows promising application in electrochemical sensors, biosensors, and other related fields because of its excellent properties.
A new ruthenium complex containing bidentate xanthate ligands was synthesized in a good yield. This complex was characterized by elemental analysis, proton nuclear magnetic resonance（tH NMR）, Fourier transform infrared（FTIR） and UV-Vis spectroscopies. The cyclic voltammetry of the complex revealed one quasi-redox wave centered at Ru（III）/Ru（II） couple, indicating its catalytic potential. So the preparation of a glass carbon electrode modified with ruthenium xanthate complex and its electrocatalytic activity toward the oxidation of tryptophan（Trp） were also studied. The experimental results show that the modified electrode had excellent electrocatalytic activity for the oxidation of tryptophan. Moreover, under the optimized conditions, the oxidation peak current was propor- tional to tryptophan concentration in a range of 2.5×10-7 to 5.0× 10-5 mol/L with a correlation coefficient of 0.9928 and a detection limit of 8.3 × 10-8 mol/L（S/N=3）. Using the proposed method, tryptophan was successfully determined in pharmaceutical samples with standard addition method.
