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In the present paper, we demonstrated a facile one-step and effective electrochemical strategy to synthesize graphene/NiO nanocomposites, which represents a new type of graphene/transition metal complex heterostructure. For the electrochemical deposition at the potential range of −1.2 to 0 V, graphite oxide (GO) was electrochemically reduced to graphene, accompanied by the simultaneous formation of NiO with a nanoparticle morphology. The obtained nanocomposites were characterized by scanning electron microscopy and electrochemical techniques. It was found that a large amount of NiO nanoparticles with diameter of 100–200 nm were uniformly grown on both sides of graphene nanosheets. Electrochemical experiments indicated that the composite film had a large surface area and enhanced electron-transfer rate compared with only NiO nanoparticles, due to an efficient electrical network through NiO nanoparticles direct anchoring on the surface of graphene. Moreover, as a model, glucose and methanol were selected as small molecules to investigate the electrocatalytic properties of the nanocomposites. The results showed that an enhanced electrocatalytic performance of the nanocomposites was obtained. The nanocomposites based sensor exhibited a rapid and highly sensitive response to glucose and methanol, which might find promising applications in medical applications, biological fuel cells and food industries.

In the present study, a biosensor was prepared using the water-soluble sulfonated graphene with the aim of achieving the selective and sensitive determination of dopamine (DA) in the presence of ascorbic acid (AA) and uric acid (UA). The aromatic π–π stacking and electrostatic attraction between positively charged DA and negatively charged sulfonated graphene can accelerate the electron transfer whereas weakening AA and UA oxidation on the sulfonated graphene-modified electrode. Fourier transform infrared spectra (FTIR), energy dispersive X-ray spectroscopy (EDX), atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used to characterize the successful synthesis of sulfonated graphene sheets. Differential pulse voltammetry was used for electrochemical detection, the separation of the oxidation peak potentials for AA-DA, DA-UA and UA-AA was about 227 mV, 125 mV and 352 mV, which allowed selectively determining DA. A broad linear range, low detection limit, along with good ability to suppress the background current from large excess ascorbic acid (AA) and uric acid (UA) were obtained. The as-prepared sulfonated graphene sheets exhibited superior performance over conventional negatively charged Nafion films, such as flexible film thickness, unique nanostructure, excellent anti-interference ability, high sensitivity and selectivity. The proposed method was used to detect DA in real hydrochloride injection sample, human urine and serum samples with satisfactory recovery results.