Jinchun Tu

Synthesis of Fe3O4@SiO2–Ag magnetic nanocomposite based on small-sized and highly dispersed silver nanoparticles for catalytic reduction of 4-nitrophenol

In this work, we report a facile method to generate core-shell structured Fe(3)O(4)@SiO(2)-Ag magnetic nanocomposite by an in situ wet chemistry route with the aid of polyvinylpyrrolidone as both reductant and stabilizer. This method can effectively prevent Ag nanoparticles from aggregating on the silica surface, thus resulting highly dispersed and small-sized Ag nanoparticles. The as-prepared nanocomposite is composed of a central magnetite core with a strong response to external fields, an interlayer of SiO(2), and numerous highly dispersed Ag nanoparticles with a narrow size distribution. Furthermore, the Fe(3)O(4)@SiO(2)-Ag nanocomposite showed high performance in the catalytic reduction of 4-nitrophenol and could be easily recycled by applying an external magnetic field while maintaining the catalytic activity without significant decrease even after running 15 times.

One-pot synthesis of ordered mesoporous silver nanoparticle/carbon composites for catalytic reduction of 4-nitrophenol

Ordered mesoporous silver nanoparticle/carbon composites have been produced by a one-pot synthesis method. They have open mesopores (4.2-5.0 nm), large specific surface areas (465-584 m(2) g(-1)) and high pore volumes (0.29-0.50 cm(3) g(-1)) and contain stable, confined but accessible Ag nanoparticles. As a result, they show high performance in catalytic reduction of 4-nitrophenol (4-NP). The mesostructure and particle size as a function of Ag content were studied and correlated with the catalytic activity. The ordered mesoporous carbon framework and highly dispersed Ag nanoparticles make the material a novel system for effective contacting with the reactants and catalysis of the reaction.

3D NiO hollow sphere/reduced graphene oxide composite for high-performance glucose biosensor

The 3D NiO hollow sphere/reduced graphene oxide (rGO) composite was synthesized according to the coordinating etching and precipitating process by using Cu2O nanosphere/graphene oxide (GO) composite as template. The morphology, structure, and composition of the materials were characterized by SEM, TEM, HRTEM, XPS, and Raman spectra, and the electrochemical properties were studied by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and amperometry. Moreover, the electrochemical activity of the composite materials with different morphologies were also investigated, which indicating a better combination of the NiO hollow sphere and the rGO. Used as glucose sensing material, the 3D NiO hollow sphere/rGO composite modified electrode exhibits high sensitivity of ~2.04u2009mAu2009mM−1 cm−2, quick response time of less than 5u2009s, good stability, selectivity, and reproducibility. Its application for the detection of glucose in human blood serum sample shows acceptable recovery and R.S.D. values. The outstanding glucose sensing performance should be attributed to the unique 3D hierarchical porous superstructure of the composite, especially for its enhanced electron-transfer kinetic properties.

Rapid synthesis of rGO conjugated hierarchical NiCo2O4 hollow mesoporous nanospheres with enhanced glucose sensitivity

NiCo2O4 nanospheres, a type of conjugated reduced graphene oxide (rGO), are compounded by a simple and easy synthesis of Cu2O/GO and fabricated NiCo2O4/rGO nanocomposites based on a Cu2O/GO template. The structure and morphology of the hierarchical NiCo2O4/rGO are characterized by x-ray diffraction, x-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy. The electrochemistry properties of NiCo2O4/rGO composites toward glucose are determined based on a glassy carbon electrode, and the results indicate that the hollow nanospheres of NiCo2O4/rGO could achieve high-sensitivity detections of glucose. The NiCo2O4/rGO composite has a detection range of 0.04 mM to 1.28 mM, a sensitivity of 2082.57 μA mM-1 cm-2, and a detection limit of 0.7 μM. The composite further exhibits obvious stability, superior reproducibility, and excellent selectivity. This study demonstrates that NiCo2O4/rGO is a unique and material with high potential in glucose sensing.

Hierarchical NiCo2O4 Hollow Sphere as a Peroxidase Mimetic for Colorimetric Detection of H2O2 and Glucose

In this work, the hierarchical NiCo2O4 hollow sphere synthesized via a “coordinating etching and precipitating” process was demonstrated to exhibit intrinsic peroxidase-like activity. The peroxidase-like activity of NiCo2O4, NiO, and Co3O4 hollow spheres were comparatively studied by the catalytic oxidation reaction of 3,3,5,5-tetramethylbenzidine (TMB) in presence of H2O2, and a superior peroxidase-like activity of NiCo2O4 was confirmed by stronger absorbance at 652 nm. Furthermore, the proposed sensing platform showed commendable response to H2O2 with a linear range from 10 μM to 400 μM, and a detection limit of 0.21 μM. Cooperated with GOx, the developed novel colorimetric and visual glucose-sensing platform exhibited high selectivity, favorable reproducibility, satisfactory applicability, wide linear range (from 0.1 mM to 4.5 mM), and a low detection limit of 5.31 μM. In addition, the concentration-dependent color change would offer a better and handier way for detection of H2O2 and glucose by naked eye.

Rapid synthesis of hollow Ni(OH)2 with low-crystallinity for the electrochemical detection of ascorbic acid with high sensitivity

In this work, hollow Ni(OH)2 with low crystallinity was rapidly synthesized based on Cu2O template, which had a small particle size and high reaction activity. The resultant products were characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and Raman spectroscopy. Results showed that Cu2O had a small particle size, and could shorten the reaction time for preparing hollow Ni(OH)2. Then, Ni(OH)2 was used to modify a glassy carbon electrode and found to perform well in ascorbic acid detection, with a linear range of 10 μM to 0.20 mM and the detection limit of 3 μM (S/N = 3). The sensitivity was 1747.71 μA mM−1 cm−2, which was due to the hollow Ni(OH)2 with low crystallinity.

3D Copper Foam-Supported CuCo2O4 Nanosheet Arrays as Electrode for Enhanced Non-Enzymatic Glucose Sensing

CuCo2O4 anchored on Cu foam (CuCo2O4/CF) with polycrystalline features was fabricated by a mild process based on solvothermal reaction and subsequent calcination in this work. The structure and morphology of the obtained materials were thoroughly characterized by X-ray diffraction, X-ray photoelectron spectroscopy, field-emission scanning electron microscopy, and transmission electron microscopy. According to the above analysis, the morphology of the CuCo2O4 was nanosheet arrays. Meanwhile, the CuCo2O4 was grown on Cu foam successfully. The CuCo2O4/CF displayed good electrochemical properties for glucose detection at a linear range from 0 mM to 1.0 mM. Meanwhile, the detection limit was as low as 1 μM (S/N = 3), and the sensitivity was 20,981 μA·mM−1·cm−2. Moreover, the selectivity and the stability were tested with excellent results. This nanomaterial could show great potential application in electrochemical sensors.

Microwave-assisted fast synthesis of hierarchical NiCo2O4 nanoflower-like supported Ni(OH)2 nanoparticles with an enhanced electrocatalytic activity towards methanol oxidation

NiCo2O4 nanoflowers were synthesized through a microwave-assisted hydrothermal method and used as a type support for Ni(OH)2 nanoparticles. In the three-dimensional NiCo2O4 nanoflowers, two-dimensional ultrathin nanosheets supported the Ni(OH)2 nanoparticles by homogeneous precipitation. The materials were characterized by field-emission scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. The electrochemical oxidation of methanol was probed through the NiCo2O4/Ni(OH)2 modification on a glassy carbon electrode in an alkaline medium by employing cyclic voltammetry (CV) and chronoamperometry (CA). The current density of the NiCo2O4/Ni(OH)2 electrode in 1 M KOH with 0.5 M methanol ascends to 92.3 A g−1 and restores to 94.6% of the primitive value through the replacement with a new solution after a long-term CV cycling (500 cycles). Therefore, the compounds further corroborate their excellent electrocatalytic activity and superb perennial stability for methanol oxidation. This study demonstrates that NiCo2O4/Ni(OH)2 is a peculiar material with an outstanding performance in direct methanol fuel cells.