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In this paper nitrogen-doped graphene (NG) nanosheets were used as the modifier on the surface of glassy carbon electrode (GCE). The modified electrode (NG/GCE) was further applied to the sensitive detection of dopamine (DA) by voltammetric method. Due to the unique properties of NG such as large surface area and excellent electrocatalytic activity, electrochemical response of DA was greatly enhanced on NG/GCE with a pair of well-defined redox peaks appeared on cyclic voltammogram. Electrochemical behaviors of DA on NG/GCE were carefully investigated with the electrochemical parameters calculated. Under the selected conditions the oxidation peak currents of DA had a good linear relationship with its concentration in the range from 8.0 × 10-7 mol L-1 to 8.0 × 10-4 mol L-1 with a detection limit of 2.55 × 10-7 mol L-1 (3σ). The proposed method was further applied to the DA injection samples determination with satisfactory results. [ABSTRACT FROM AUTHOR]

In this paper nickel oxide (NiO) nanoflower was synthesized and used for the realization of direct electrochemistry of horseradish peroxidase (HRP). By using carbon ionic liquid electrode (CILE) as the substrate electrode, NiO-HRP composite was casted on the surface of CILE with chitosan (CTS) as the film forming material and the modified electrode was denoted as CTS/NiO-HRP/CILE. UV-Vis absorption and FT-IR spectra confirmed that HRP retained its native structure after mixed with NiO nanoflower. Direct electron transfer of HRP on the modified electrode was investigated by cyclic voltammetry with a pair of quasi-reversible redox waves appeared, indicating that the presence of NiO nanoflower on the electrode surface could accelerate the electron transfer rate between the electroactive center of HRP and the substrate electrode. Electrochemical behaviors of HRP on the modified electrode were carefully investigated. The HRP modified electrode showed excellent electrocatalytic activity to the reduction of trichloroacetic acid with wider linear range and lower detection limit. Therefore the presence of NiO nanoflower could provide a friendly biocompatible interface for immobilizing biomolecules and keeping their native structure. The fabricated electrochemical biosensor displayed the advantages such as high sensitivity, good reproducibility and long-term stability. [ABSTRACT FROM AUTHOR]