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CuNi-ZrO2 nanocomposites were prepared by a simple coprecipitation technique of copper, nickel and zirconium ions with potassium carbonate. The structures of the nanocomposites were characterized by N2 physical adsorption, XRD, H2-TPR and STEM-EDS. The Cu0.05Ni0.45-ZrO2 nanocomposite showed outstanding catalytic performance in hydrogenation of levulinic acid (LA) to γ-valerolactone (GVL), especially NaOH solution (0.5 mol L-1) as a solvent. 100% LA conversion and > 99.9% GVL selectivity are achieved over Cu0.05Ni0.45-ZrO2 catalyst at 200 °C, 3 MPa for 1.5 h. Characterization results suggest that the excellent reactivity of the Cu0.05Ni0.45-ZrO2 may be due to a better reducibility of nickel oxide in the CuONiO-ZrO2, dispersion of Ni in the Cu0.05Ni0.45-ZrO2 compared to nickel oxide in the NiO-ZrO2 and Ni in the Ni0.5-ZrO2 and promotion of OH-. The results demonstrate that the Cu0.05Ni0.45-ZrO2 nanocomposite has potential to realize high efficiency and low-cost synthesis of liquid fuels from biomass.

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Layered double hydroxides have been widely used for electrochemical glucose detection due to their layered structure with more active sites, but they suffer from lower electrical conductivity and long-time hydrothermal preparation. In this paper, NiFe-layered double hydroxide nanosheets supported on nickel foam (NiFe-LDH NSs/NF) was prepared using an ultrafast and facile method via in-situ corroding foam nickel in FeCl3 solution under room temperature, and the whole synthetic process can be accomplished within several minutes. The as-fabricated NiFe-LDH NSs/NF shows significant catalytic activity in the glucose oxidation, showing its great promise in glucose detection. As a self-supported electrode, NiFe-LDH NSs/NF is favorable for glucose detection, with a sensitivity of 9.79 and 3.29 mA mM-1 cm-2 within the linear range of 0.001 to 1.16 mM and 1.16 to 4.67 mM, respectively. Moreover, NiFe-LDH NSs/NF is also selective and reliable towards glucose detection in drink sample.

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Defects engineering as an effective strategy was widely utilized to modulate catalytic performance for heterogeneous catalysts through tuning surface electronic surface and creating more active sites. In this work, porous Co-Mn oxide nanosheets with abundant oxygen vacancies (OVs-CMO NSs) were prepared via a simple "one-stone-two-birds" method. OVs were verified by various characterizations and found more favorable for O2 absorption and activation to produce more reactive O2•- radical, resulting in an improved oxidase-like activity in initiating 3,3',5,5'-tetramethylbenzidine (TMB) oxidation, with a lower Km value of 0.00717 mM and a higher Vmax of 2.086 × 10-7 M/s. Since heparin (Hep) shows an inhibition effect on OVs-CMO NSs-TMB chromogenic system due to strong absorption, a colorimetric sensing platform for Hep detection was established. The present colorimetric detection shows high sensitivity, good selectivity and reliability for normal goat serum. This work not only provides a high-performance non-precious metal oxidase mimic prepared by simple surface defect engineering, but also builds a sensitive colorimetric method for Hep detection.

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Here, we report the controllable synthesis of porous MnxCo1-xO microspheres and tunable catalytic activity in the oxidase mimicking reaction. Mn0.6Co0.4O possesses the best oxidase mimicking activity and can be used successfully in sulfide ion colorimetric detection with a low detection limit of 0.1 µM.

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Here, we report highly dispersed small ruthenium nanoparticles (NPs) anchored onto a porous carbon (Ru/PC) with a clean catalytic surface and explore their excellent peroxidase-like activity for 3,3',5,5'-tetramethylbenzidine oxidation mediated by H2O2, which allows sensitive colorimetric detection of H2O2 with a low detection limit of 3.8 µM. Moreover, it is also found that the Ru/PC has a high nitroreductase-like activity for 4-nitroaniline reduction triggered by NaBH4.

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Ever-growing efforts have been devoted to developing cost-effective and earth-abundant electrocatalysts with high-performance in biosensing and energy energy conversion. In this work, amorphous nickel-phosphorus (Ni-P) nanoparticles anchoring on Ni foam (Ni-P/NF) were prepared through a facile electroless deposition approach. The morphology and composition were characterized by scanning electron microscopy, x-ray diffraction and x-ray photoelectron spectroscopy. As an integrated anode, Ni-P/NF exhibits high performance towards glucose electrochemical sensing, with a high sensitivity of 13.89 mA mM-1 cm-2, a low detection limit of 1 µM, a wide detection ranges from 2 µM to 0.54 mM, and a quick response (<10 s), as well as good selectivity and reliability for real sample analysis in human serum. In addition to electrocatalytic glucose oxidation, Ni-P/NF shows remarkable catalytic activity towards oxygen evolution reaction (OER) in alkaline solution and it only needs an overpotential of 360 mV to afford 50 mA cm-2. Moreover, Ni-P/NF shows excellent durability under alkaline OER condition. All these results demonstrate Ni-P/NF as highly efficient integrated anode in both biosensing and energy conversion.

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Ultrafine and monodispersed iridium nanoparticles supported on nitrogen-functionalized carbon materials (Ir/NC) were prepared and served as an efficient oxidase mimic for 3',5,5'-tetramethylbenzidine (TMB) oxidation. Due to the inhibition effect of glutathione (GSH) on TMB oxidation, a sensitive colorimetric GSH detection approach was proposed.

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High electrical conductivity and more active sites exposure are crucial for improving the performance of electrocatalyst. Binary metal oxide nanoarray grown on conductive substrate offers a 3D self-supported electrode with a great promise in boosting its performance in enzyme-free glucose sensing. Here, NiMoO4 nanosheet arrays anchored on carbon cloth (NiMoO4 NSA/CC) was prepared via a simple hydrothermal synthesis and used as 3D self-supported electrode for enzyme-free glucose sensing. The morphology and composition of NiMoO4 nanosheet have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The electrochemical results show that NiMoO4 NSA/CC exhibits remarkable high catalytic activity towards glucose oxidation, with a wide linear response ranging from 1 µM to 0.9 mM, a high sensitivity of 4.13 mA/mM·cm2, and a low detection limit of 1 µM (S/N = 3). The enhanced performance might be attributed to the merits of nanosheet arrays with large surface area, self-supported electrode with 3D open network, as well as bimetallic component with high conductivity. Furthermore, NiMoO4 NSA/CC also shows good selectivity and reliability for glucose detection in human serum. This work offers a new pathway for the construction of enzyme-free glucose sensor with high performance. Graphical abstract ᅟ.

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