Wensheng Yang

Well-dispersed Co3O4/Co2MnO4 nanocomposites as a synergistic bifunctional catalyst for oxygen reduction and oxygen evolution reactions.

Co3O4/Co2MnO4 nanocomposites, derived from a single-source CoMn-layered double hydroxide precursor, exhibit excellent bifunctional oxygen electrode activities for both oxygen reduction and evolution reactions, which can be attributed to the large specific surface area and well-dispersed heterogeneous structure of the nanocomposites.

Gold Nanoparticle-Embedded Porous Graphene Thin Films Fabricated via Layer-by-Layer Self-Assembly and Subsequent Thermal Annealing for Electrochemical Sensing

A uniform three-dimensional (3D) gold nanoparticle (AuNP)-embedded porous graphene (AuEPG) thin film has been fabricated by electrostatic layer-by-layer assembly of AuNPs and graphene nanosheets functionalized with bovine serum albumin and subsequent thermal annealing in air at 340 °C for 2 h. Scanning electron microscopy (SEM) investigations for the AuEPG film indicate that an AuNP was embedded in every pore of the porous graphene film, something that was difficult to achieve with previously reported methods. The mechanism of formation of the AuEPG film was initially explored. Application of the AuEPG film in electrochemical sensing was further demonstrated by use of H(2)O(2) as a model analyte. The AuEPG film-modified electrode showed improved electrochemical performance in H(2)O(2) detection compared with nonporous graphene-AuNP composite film-modified electrodes, which is mainly attributed to the porous structure of the AuEPG film. This work opens up a new and facile way for direct preparation of metal or metal oxide nanoparticle-embedded porous graphene composite films, which will enable exciting opportunities in highly sensitive electrochemical sensors and other advanced applications based on graphene-metal composites.

Carbon Nanorings and Their Enhanced Lithium Storage Properties

depend on parameters such as their layer number, diameter and length. Strict control along the radial direction of CNTs has already been achieved, and CNTs with the minimum number of walls (single-walled [ 5 ] ) and a minimum internal diameter of 0.4 nm [ 6 ] have been successfully synthesized. However, along the axial direction, the length of CNTs has proved to be much more diffi cult to control during synthesis process. If these diffi culties can be overcome, enabling super-short CNTs to be synthesized, the resulting materials should have fascinating properties with applications in biomedicine, [ 3 , 4 ] catalysis, [ 7 ] hydrogen storage [ 8 ]

Direct electrochemistry and electrocatalysis based on a film of horseradish peroxidase intercalated into Ni–Al layered double hydroxide nanosheets

Positively charged Ni-Al layered double hydroxide nanosheets (Ni-Al LDHNS) have been used for the first time as matrices for immobilization of horseradish peroxidase (HRP) in order to fabricate enzyme electrodes for the purpose of studying direct electron transfer between the redox centers of proteins and underlying electrodes. X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) revealed that the HRP-Ni-Al LDHNS film had an ordered structure and that HRP was intercalated into Ni-Al LDHNS with a monolayer arrangement. Field emission scanning electron microscopy (FESEM) showed that the HRP-Ni-Al LDHNS film had a uniform, porous morphology. UV-vis spectroscopy indicated that the intercalated HRP retained its native structure after incorporation in the Ni-Al LDHNS film. The immobilized HRP in Ni-Al LDHNS on the surface of a glassy carbon electrode (GCE) exhibited good direct electrochemical and electrocatalytic responses to the reduction of hydrogen peroxide (H(2)O(2)) and trichloroacetic acid (TCA). The resulting H(2)O(2) biosensor showed a wide linear range from 6.00 x 10(-7)M to 1.92 x 10(-4)M, low detection limit (4.00 x 10(-7)M) and good stability. The results show that Ni-Al LDHNS provide a novel and efficient platform for the immobilization of enzymes and realizing direct electrochemistry and that the materials have potential applications in the fabrication of third-generation biosensors.

Nanosheet-based titania microspheres with hollow core-shell structure encapsulating horseradish peroxidase for a mediator-free biosensor.

Nanosheet-based titania (TiO(2)) microspheres with a hollow core-shell structure have been synthesized and employed to immobilize horseradish peroxidase (HRP) in order to fabricate a mediator-free biosensor. The morphology and structure of the TiO(2) microspheres were characterized by X-ray diffraction, scanning electron microscopy and transmission electronic microscopy. A possible growth mechanism has been proposed. Spectroscopic and electrochemical measurements revealed that the TiO(2) microspheres are an immobilization support with biocompatibility for enzymes, affording good enzyme stability and bioactivity. Due to the nanosheet-based hollow core-shell structure of the TiO(2) microspheres, the direct electron transfer of HRP is facilitated and the resulting biosensor displayed good performance for the detection of H(2)O(2), with both a low detection limit of 0.05 μM and a wide linear range of 0.4-140 μM, as well as a fast response and excellent long-term stability. The nanosheet-based TiO(2) microspheres with hollow core-shell structure, can be used for the efficient entrapment of other redox-active proteins and have wide potential applications in biosensors, biocatalysis, biomedical devices and bioelectronics.

Synthesis and Electrochemical Characterization of Co–Al Layered Double Hydroxides

Co-Al layered double hydroxides (LDHs) have been synthesized by a method involving separate nucleation and aging steps. The effects of varying thermal treatment and Co/Al mole ratio on their microscopic form, surface area, crystallinity, and electrochemical behavior have been investigated. Co-Al LDHs with Co/Al ratio of 2:1 retain a layered structure up to 160°C, and the electrochemically active Co sites become increasingly exposed. The material obtained after heating at 160°C exhibited supercapacitor behavior with a high specific capacitance of 684 F/g and a good working capacity at large specific current. This material may be a potential electrode material for supercapacitors.

Facile fabrication of yolk–shell structured porous Si–C microspheres as effective anode materials for Li-ion batteries

Yolk–shell structured porous Si–C microspheres have been fabricated by magnesiothermic reduction of silica spheres inside carbon shells and exhibit excellent electrochemical performance due to the porous yolk–shell structure.

Synthesis of Polypyrrole-Intercalated Layered Manganese Oxide Nanocomposite by a Delamination∕Reassembling Method and Its Electrochemical Capacitance Performance

A polypyrrole-intercalated layered manganese oxide nanocomposite (PPy-MnO 2 ) has been synthesized by a delamination/ reassembling process. X-ray diffraction analysis shows that the basal spacing of the PPy-MnO 2 nanocomposite is 1.38 nm. The room-temperature conductivity of the PPy-MnO 2 nanocomposite is found to be 1.3 × 10 -1 S/cm, which is 4-5 orders of magnitude higher than that of the pristine manganese oxide (6.1 × 10 -6 S/cm). The improved specific capacitance of the PPy-MnO 2 nanocomposite (290 F/g) compared with that of the pristine manganese oxide (221 F/g) is attributed to a combination of the conductivity effect and the high specific capacitance of PPy.

Self-assembled dipeptide-gold nanoparticle hybrid spheres for highly sensitive amperometric hydrogen peroxide biosensors.

Novel self-assembled dipeptide-gold nanoparticle (DP-AuNP) hybrid microspheres with a hollow structure have been prepared in aqueous solution by a simple one-step method. Diphenylalanine (FF) dipeptide was used as a precursor to form simultaneously peptide spheres and a reducing agent to reduce gold ions to gold nanoparticles in water at 60°C. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed that formed AuNPs were localized both inside and on the surface of the dipeptide spheres. Horseradish peroxidase (HRP) as a model enzyme was further immobilized on the dipeptide-AuNP hybrid spheres to construct a mediate H2O2 amperometric biosensor. UV-vis spectroscopy showed that the immobilized HRP retained its original structure. Cyclic voltammetry characterization demonstrated that the HRP/dipeptide-AuNP hybrid spheres modified glassy carbon electrode showed high electrocatalytic activity to H2O2. The proposed biosensor exhibited a wide linear response in the range from 5.0×10(-7) to 9.7×10(-4)M with a high sensitivity of 28.3µAmM(-1). A low detection limit of 1.0×10(-7)M was estimated at S/N=3. In addition, the biosensor possessed satisfactory reproducibility and long-term stability. These results indicated that the dipeptide-AuNP hybrid sphere is a promising matrix for application in the fabrication of electrochemical biosensors due to its excellent biocompatibility and good charge-transfer ability.

A Co–Al Layered Double Hydroxides Nanosheets Thin-Film Electrode Fabrication and Electrochemical Study

A highly oriented and densely packed Co-Al layered double hydroxides (LDHs) nanosheets thin-film electrode has been successfully fabricated by drying a transparent colloidal suspension of Co-Al LDHs nanosheets on a pretreated indium tin oxide-coated glass plate substrate. The electrochemical investigations show that this thin-film electrode has good supercapacitor behavior with a high specific capacitance of up to 2000 F/cm 3 (667 F/g), a good electrochemical stability, and a high-rate capability. These excellent electrochemical properties obtained can be attributed to the special microstructure of the thin-film electrode. This thin-film electrode may be a potential electrode for thin-film supercapacitors.