A highly dispersible and stable nanocomposite of Cu(tpa)-GO (Cu(tpa) = copper terephthalate metal-organic framework, GO = graphene oxide) was prepared through a simple ultrasonication method. The morphology and structure of the obtained composite were characterized via scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-vis, Fourier-transform infrared (FT-IR), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). On the basis of the characterization results, the binding mechanism of the Cu(tpa) and GO was speculated to be the cooperative interaction of π-π stacking, hydrogen bonding, and Cu-O coordination. The electrochemical sensing property of Cu(tpa)-GO composite was investigated through casting the composite on a glassy carbon electrode (GCE), followed by an electro-reduction treatment to transfer the GO in the composite to the highly conductive reduced form (electrochemically reduced graphene, EGR). The results demonstrated that the electrochemical signals and peak profiles of the two drugs of acetaminophen (ACOP) and dopamine (DA) were significantly improved by the modified material, owing to the synergistic effect from high conductivity of EGR and unique electron mediating action of Cu(tpa). Under the optimum conditions, the oxidation peak currents of ACOP and DA were linearly correlated to their concentrations in the ranges of 1-100 and 1-50 μM, respectively. The detection limits for ACOP and DA were estimated to be as low as 0.36 and 0.21 μM, respectively.

A novel metal-organic framework (MOF)-based electroactive nanocomposite containing graphene fragments and HKUST-1 was synthesized via a facile one-step solvothermal method using graphene oxide (GO), benzene-1,3,5-tricarboxylic acid (BTC), and copper nitrate (Cu(NO)) as the raw materials. The morphology and structure characterization revealed that the GO could induce the transformation of HKUST-1 from octahedral structure to the hierarchical flower shape as an effective structure-directing agent. Also, it is interesting to find out that the GO was torn into small fragments to participate in the formation of HKUST-1 and then transformed into the reduction form during the solvothermal reaction process, which dramatically increased the surface area, electronic conductivity, and redox-activity of the material. Electrochemical assays showed that the synergy of graphene and HKUST-1 in the nanocomposite leaded to high electrocatalysis, fast response, and excellent selectivity toward the reduction of hydrogen peroxide (HO). Based on these remarkable advantages, satisfactory results were obtained when the nanocomposite was used as a sensing material for electrochemical determination of HO in the complex biological samples such as human serum and living Raw 264.7 cell fluids.

The metal–organic framework (MOF) of Cu3(btc)2 (btc = benzene-1,3,5-tricarboxylic acid) is covalently immobilized at chitosan (CS)–electrochemically reduced graphene oxide (ERGO) hybrid film modified electrode, which is characterized by scanning electron microscope (SEM), energy-dispersive X-ray spectra (EDS), and electrochemistry. The MOF-based electrode is applied as an electrochemical sensing platform for the simultaneous detection of dihydroxybenzene isomers (DBIs) of catechol (CT), resorcinol (RS), and hydroquinone (HQ). The results show that the DBIs present well-resolved and intense voltammetric signals at the modified electrode, due to the synergic effect contributing from Cu3(btc)2 with unique porous framework structure and ERGO with high electronic conductivity. The excellent distinguishing efficiency of the sensor toward DBIs is also confirmed by the quantum chemical computation. Quantitative analysis assays by differential pulse voltammetry shows that the sensor has wide linear ranges and low detection limits for the DBIs. The developed sensor is also applied for the determination of DBIs in the real water sample, and satisfactory results are obtained. This work strongly implies that the MOFs have great potential in the construction of novel electrochemical sensor for isomers.

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Developing facile methods to prepare nonprecious metal-based electrocatalysts for sensing analysis of biomolecules is an attractive issue in the electrochemical and life science fields. In this work, we highlighted a strategy to facilely synthesize one-dimensional Ni3C/Ni nanochains with excellent electrocatalytic oxidation for glucose through a simple solvothermal method with the assistance of 2-methylimidazole. The characterization assays showed that 2-methylimidazole could effectively regulate the formation of the one-dimensional chain-like shape of the product, and meanwhile, provide the active carbon for the growth of the Ni3C. The electrochemical and density functional theory (DFT) studies revealed that the Ni3C component in the Ni3C/Ni nanochains was the critical catalytic site for glucose oxidation, while the metallic Ni can effectively promote the electron-transfer kinetics. Beneficial from both the structural and compositional advantages, the Ni3C/Ni nanochain-based sensor exhibits a wide linear range from 1.0 to 6.5 μM, a low determination limit of 0.28 μM, and a high sensitivity of 299.4 μA mM–1 cm–2 for glucose sensing analysis. We believe that the Ni3C/Ni nanochains with impressive electrocatalytic performance will be good candidates for electrochemical sensing of glucose in clinical applications.