Weichun Ye

Simultaneous electrochemical determination of uric acid, xanthine and hypoxanthine based on poly(l-arginine)/graphene composite film modified electrode

Poly(l-arginine)/graphene composite film modified electrode was successfully prepared via a facile one-step electrochemical method and used for simultaneous determination of uric acid (UA), xanthine (XA) and hypoxanthine (HX). The electrochemical behaviors of UA, XA and HX at the modified electrode were studied by cyclic voltammetry and differential pulse voltammetry (DPV), and showed that the modified electrode exhibited excellent electrocatalytic activity toward the oxidation of the three compounds. The calibration curves for UA, XA and HX were obtained over the range of 0.10-10.0, 0.10-10.0 and 0.20-20.0 μM by DPV, respectively and the detection limits for UA, XA and HX were 0.05, 0.05 and 0.10 μM (S/N=3), respectively. With good selectivity and high sensitivity, the modified electrode has been applied to simultaneous determination of UA, XA and HX in human urine with satisfactory result.

Fluoride-assisted galvanic replacement synthesis of Ag and Au dendrites on aluminum foil with enhanced SERS and catalytic activities

Although Al has a lower redox potential [Al3+/Al, −1.67 V vs. SHE] than most metallic ions, metal galvanic replacement reactions on pure aluminum foil can be hardly observed because of the existence of the thin layer of aluminum oxide, In this work, we develop a facile, economical and general approach to achieve large-scale production of silver and gold dendrites as well as other metal hierarchical micro/nanostructures (Cu, Pt, Pd, Ni, Co and Zn) on commercial aluminum foil in the presence of NaF or NH4F. Studies of the galvanic replacement reaction by open circuit potential–time (OCP–t) measurements demonstrate that fluoride plays an important role in etching the alumina layer and thus induces the continuous proceeding of the galvanic replacement reaction. The synthesis process is carried out at room temperature and without any templates, surfactants, or special reagents. The obtained silver and gold dendrites show significantly enhanced SERS signals of a self-assembled monolayer of 2-naphthalenethiol and 4-mercaptobenzoic acid, and also could effectively catalyze the reduction reaction of 4-nitrophenol and 2-nitrophenol at room temperature.

Flower-like N-doped MoS2 for photocatalytic degradation of RhB by visible light irradiation.

In this paper, the photocatalytic performance and reusability of N-doped MoS2 nanoflowers with the specific surface area of 114.2 m(2) g(-1) was evaluated by discoloring of RhB under visible light irradiation. Results indicated that the 20 mg fabricated catalyst could completely degrade 50 ml of 30 mg l(-1) RhB in 70 min with excellent recycling and structural stability. The optimized N-doped MoS2 nanoflowers showed a reaction rate constant (k) as high as 0.06928 min(-1) which was 26.4 times that of bare MoS2 nanosheets (k = 0.00262). In addition, it was about seven times that of P25 (k = 0.01) (Hou et al 2015 Sci. Rep. 5 15228). The obtained outstanding photocatalytic performance of N-doped MoS2 nanoflowers provides potential applications in water pollution treatment, as well as other related fields.

Sensitive determination of thymol based on CeO2 nanoparticle–decorated graphene hybrid film

A novel thymol electrochemical sensor based on a CeO2 nanoparticle–decorated graphene hybrid was introduced. The hybrid was characterized by X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy. The electrochemical behavior of thymol on the CeO2/graphene modified glassy carbon electrode was investigated in pH 7.0 phosphate buffer solution by cyclic voltammetry and differential pulse voltammetry. Compared with the bare glassy carbon electrode, the proposed electrode showed improved analytical performance characteristics in catalytic oxidation of thymol. Under the selective conditions, the modified electrode showed a linear voltammetric response for the thymol within a concentration range of 1.0 × 10−7 to 1.8 × 10−5 mol L−1, and a value of 5.0 × 10−8 mol L−1 was calculated for the detection limit (S/N = 3). Furthermore, good selectivity with high sensitivity was obtained for the determination of thymol in real samples.

Fabrication of a CuS/graphene nanocomposite modified electrode and its application for electrochemical determination of esculetin

In this paper, a CuS/graphene nanocomposite modified glassy carbon electrode (GCE) was successfully constructed and used for determination of esculetin. The electrochemical behavior of esculetin was studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The results indicated that the synergistic effect between CuS nanoparticles (NPs) and graphene enhanced the electrochemical response of esculetin. Under optimal conditions, the DPV peak current increased linearly with the esculetin concentration in the range from 1.0 × 10−7 to 1.0 × 10−4 mol L−1, and the detection limit (S/N = 3) was 5.8 × 10−8 mol L−1. Furthermore, a good selectivity with high sensitivity was obtained for the determination of esculetin in real samples.

Competition and cooperativity of σ-hole and π-hole intermolecular interactions between carbon monoxide and bromopentafluorobenzene

Theoretical investigations of the interactions between carbon monoxide (CO) and bromopentafluorobenzene (C6F5Br) have been carried out at both M06-2X/6-311++G(2d,2p) and M06-2X/aug-cc-pVTZ levels of theory. Because both C and O atom-ends of CO show negative electrostatic potential, they can favorably interact with the positive electrostatic potential generated by the σ-hole of Br and the π-hole of the aromatic ring of C6F5Br, yielding four different dimers and trimers. Their structures, spectroscopy and nature were systematically studied. The competition between the interactions involving the σ-hole of the Br atom and the π-hole of C6F5Br with the C and O atom-ends of CO was illustrated for the dimers and trimers, and meanwhile, the cooperativity between the two components of the trimers was elaborated. In addition, the experimental FT-IR and fluorescence spectra were measured for C6F5Br and the mixed C6F5Br and CO system without and with the solvent of hexane to gain information on the formation of molecular complexes between C6F5Br and CO. The results presented in this work are beneficial for the understanding of the competition and cooperativity of σ- and π-hole intermolecular interactions.

Catalytic Oxidation of Hydroquinone in Aqueous Solution over Bimetallic PdCo Catalyst Supported on Carbon: Effect of Interferents and Electrochemical Measurement

Palladium-cobalt alloy nanoparticles were synthesized and dispersed on carbon black support, aiming to have a less expensive catalyst. Catalytic behaviors of PdCo/C catalyst for the oxidation of hydroquinone (HQ) with H2O2 in aqueous solution were evaluated using high-performance liquid chromatography (HPLC). The results revealed that PdCo/C catalyst had better catalytic activity than an equal amount of commercial Pd/C and Co/C catalysts because of the d-band hybridization between Pd and Co. The effects of pH value, solvent, and various interferents including inorganic and organic compounds on the efficiency of HQ oxidation were further investigated. Furthermore, on the basis of mixed potential theory, comprehensive electrochemical measurements such as the open-circuit potential-time (OCP-t) technique and Tafel plot were efficient to assess the catalytic activity of the catalyst, and the results obtained were consistent with those of HPLC measurements. The efficient HQ oxidation was closely associated with the catalytic activity of PdCo nanoparticles because they accelerated the electron-transfer process and facilitated the generation of OH radicals.

Efficient visible light-induced degradation of rhodamine B by W(NxS1-x)(2) nanoflowers

Here, W(NxS1−x)2 nanoflowers were fabricated by simple sintering process. Photocatalytic activity results indicated our fabricated N-doped WS2 nanoflowers shown outstanding photoactivity of degradating of rhodamine B with visible light. Which is attributed to the high separation efficiency of photoinduced electron–hole pairs, the broadening of the valence band (VB), and the narrowing of energy band gap. Meanwhile, our work provided a novel method to induce surface sulfur vacancies in crystals by introduing impurities atoms for enhancing their photodegradation.

Hexagram-like CoS-MoS2 composites with enhanced activity for hydrogen evolution reaction

Hexagram-like CoS-MoS2 composites were prepared on indium tin oxide (ITO) conductive glasses via cyclic voltammetry electrodeposition using Co(NO3)2 and (NH4)2MoS2 as precursors and tested for application in hydrogen evolution reaction (HER). The structure of CoS-MoS2 composites was characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), and X-ray photoelectron spectrum (XPS). Electrochemical characterizations indicate that CoS-MoS2 composites exhibit more excellent catalytic activity and stability than MoS2. Compared with pure MoS2, the hexagram-like CoS-MoS2 composites with increased specific surface area improved the density of exposed active sites, and the Co binding S edges in CoS-MoS2 composites promote the number of highly catalytic edge sites and decreased the binding energy △GH. Moreover, the effects of different substrates on the CoS-MoS2 composites were also investigated. Our further understanding of this highly active hydrogen evolution catalyst can facilitate the development of economical electrochemical hydrogen production systems.

Operando Synthesis of a Dendritic and Well‐Crystallized Molybdenum Oxide/Silver Catalyst for Enhanced Activity in the Hydrogen Evolution Reaction

Dendritic MoO3/Ag with good crystallinity has been prepared through an operando method. In the hydrogen evolution reaction (HER), this catalyst, which was designed to utilize the best properties of each component material, showed a high catalytic activity. After the precursor was drop‐cast onto a glassy carbon electrode, a reductive potential was applied to the coated electrode, and H2 evolution occurred within the range of potentials. The overpotential required to evolve H2 at the benchmark rate decreased progressively with subsequent voltammetric cycles, until a steady state was reached at which only 145 mV of overpotential was required to pass −10 mA cm−2 of current density. During the electrocatalysis, the precursor was converted to catalyst through an operando method. This operando‐synthesized MoO3/Ag catalyst has a low Tafel slope (43 mV dec−1), low overpotential (145 mV), and excellent durability for HER. It has the potential to be a promising material for HER.