A simple two-step method was employed for preparing nano-sized gold nanoparticles-graphene composite to construct a GNPs-GR-SDS modified electrode. Hemoglobin (Hb) was successfully immobilized on the surface of a basal plane graphite (BPG) electrode through a simple dropping technique. Direct electrochemistry and electrocatalysis of the hemoglobin-modified electrode was investigated. The as-prepared composites showed an obvious promotion of the direct electro-transfer between hemoglobin and the electrode. A couple of well-defined and quasi-reversible Hb CV peaks can be observed in a phosphate buffer solution (pH 7.0). The separation of anodic and cathodic peak potentials is 81 mV, indicating a fast electron transfer reaction. The experimental results also clarified that the immobilized Hb retained its biological activity for the catalysis toward NO. The biosensor showed high sensitivity and fast response upon the addition of NO, under the conditions of pH 7.0, potential -0.82 V. The time to reach the stable-state current was less than 3 s, and the linear response range of NO was 0.72-7.92 μM, with a correlation coefficient of 0.9991.

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A glassy carbon electrode (GCE) modified with multiwall carbon nanotubes (MWCNTs) for electrochemical square-wave stripping voltammetric (SWV) determination of antimony (III) was introduced. Various experimental parameters, such as the amounts of carbon nanotubes, the deposition potential and time, the electrolyte solution, etc, were thoroughly optimized and discussed. Under the optimum experimental conditions, the MWCNTs-modified GCE exhibited well linear behaviour in the antimony(III) concentration range from 0.04 to 0.26 mg/L (R=0.9983) with a detection limit of 3.20×10-4mg/L (S/N=3) under a 360 s accumulation. The proposed electrode also exhibited encouraging properties for measurements of simulated water samples.