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A novel graphene-NiO-polyaniline (Gr-NiO-PANI) was prepared by electrolysis, electrodeposition and electropolymerization methods, respectively. The X-ray diffraction (XRD) proved the successful preparation and composition of the Gr-NiO-PANI hybrid. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were used to further determine the structure and morphology of as-prepared composites. Cyclic voltammetry confirmed that Gr-NiO-PANI composite had excellent detection effect on urea. By comparing the electrochemical behavior of Gr-NiO-PANI with Gr-NiO and Gr-PANI modified electrodes toward urea, the role of NiO in composite and the detection mechanism of urea were explored. A common linear sweep voltammetry technique was used to detect urea. The test results showed that urea exhibited a good response on the Gr-NiO-PANI modified electrode. In the range of 60∼160 μM urea concentration, the response current of the Gr-NiO-PANI modified electrode is proportional to the urea concentration, and the concentration stand curve equation was I(μA) = −0.0886C(μM) + 58.39 (R 2 = 0.9917). The as-fabricated sensor exhibited high sensitivity (1.266 μA/μM), lower limit of detection (7.35 μM), excellent reproducibility, and so it can provide a simple and cheap method for detection of urea in environmental monitoring, agriculture, medical industry.

Schematic of the fabrication of CoNi2S4/PANI.

A novel titanium dioxide–graphene–polyaniline (TiO2–RGO–PANI) hybrid was prepared by the one-pot method and used as a nonenzymatic electrochemical sensor for glucose detection. The composition and structural morphology of the as-prepared composites were determined by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The characterization results showed that TiO2–RGO–PANI is mainly composed of Ti, O, C and N and their weight percentages are 67.68%, 21.57%, 10.70% and 0.05%, respectively, indicating that the TiO2–RGO–PANI composite catalyst has been successfully prepared and presents a poriferous coral structure. A series of electrochemical tests such as cyclic voltammetry tests declared that TiO2–RGO–PANI composite possessed a low limit of detection (LOD) (7.46[Formula: see text][Formula: see text]M), good repeatability, selectivity and stability. In the concentration range of 10–180[Formula: see text][Formula: see text]M, the hybrid presented linear diffusion, and the linear equation was [Formula: see text] (C/mM), the correlation coefficient [Formula: see text]. In addition, the comparison of the merits of this proposed electrode with some recent nonenzymatic glucose sensors indicates that this highly sensitive TiO2–RGO–PANI complex glucose sensor provides a simple, low-cost, nonenzymatic method for glucose detection, and has promising applications in clinical diagnostics and medical analysis.

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