Wanjin Zhang

Constructing Carbon-Coated Fe3O4 Microspheres as Antiacid and Magnetic Support for Palladium Nanoparticles for Catalytic Applications

Fe₃O₄ microsphere is a good candidate as support for catalyst because of its unique magnetic property and large surface area. Coating Fe₃O₄ microspheres with other materials can protect them from being dissolved in acid solution or add functional groups on their surface to adsorb catalyst. In this paper, a carbon layer was coated onto Fe₃O₄ microspheres by hydrothermal treatment using polyethylene glycol as the connecting agents between glucose and Fe₃O₄ spheres. Through tuning the added amounts of reactants, the thickness of the carbon layer could be well-controlled. Because of the abundant reductive groups on the surface of carbon layer, noble metal ions could be easily adsorbed and in situ reduced to nanoparticles (6-12 nm). The prepared catalyst not only had unique antiacid and magnetic properties, but also exhibited a higher catalytic activity toward the reduction of methyl orange than commercially used Pd/C catalyst.

Preparation and characterization of Ag2S nanoparticles embedded in polymer fibre matrices by electrospinning

Polyvinylpyrrolidone (PVP)/Ag(2)S composite fibres were successfully prepared by a facile method called the electrospinning technique. Scanning electron microscopy analysis revealed the fibre morphology of the composite. Transmission electron microscopy showed spherical nanoparticles of the Ag(2)S component with an average particle size of about 15 nm and a good dispersion. X-ray diffraction results showed that a pure beta-Ag(2)S phase was obtained in the PVP fibres. X-ray photoelectron spectra (XPS) proved that the Ag and S elements exist in PVP/Ag(2)S composite fibres and quantitative analysis of the XPS showed that the atomic ratio of silver and sulfur was about 2. Fourier transform infrared and ultraviolet-visible spectroscopy were used to characterize the structure of the PVP/Ag(2)S composite fibres.

Fabrication of Pt/polypyrrole hybrid hollow microspheres and their application in electrochemical biosensing towards hydrogen peroxide

Pt/polypyrrole (PPy) hybrid hollow microspheres were successfully prepared by wet chemical method via Fe(3)O(4) template and evaluated as electrocatalysts for the reduction of hydrogen peroxide. The as-synthesized products were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS), X-ray diffraction (XRD), inductive coupled plasma emission spectrum (ICP) and Fourier-transform infrared spectra (FTIR) measurements. The results exhibited that ultra-high-density Pt nanoparticles (NPs) were well deposited on the PPy shell with the mean diameters of around 4.1nm. Cyclic voltammetry (CV) results demonstrated that Pt/PPy hybrid hollow microspheres, as enzyme-less catalysts, exhibited good electrocatalytic activity towards the reduction of hydrogen peroxide in 0.1M phosphate buffer solution (pH=7.0). The composite had a fast response of less than 2s with linear range of 1.0-8.0mM and a relatively low detection limit of 1.2microM (S/N=3). The sensitivity of the sensor for H(2)O(2) was 80.4mAM(-1)cm(-2).

Accurately Tuning the Dispersity and Size of Palladium Particles on Carbon Spheres and Using Carbon Spheres/Palladium Composite as Support for Polyaniline in H2O2 Electrochemical Sensing

With an accurate control of the dispersity and size of the palladium nanoparticles (Pd NPs), carbon spheres/Pd NPs composite was prepared without any extra reducing agents. In order to fully understand the formation mechanism and find out the best condition for the fabrication of carbon/Pd composite spheres, the effects of temperature, reaction time, pH value, and the weight ratio of PdCl(2) to carbon spheres on the morphology of the final products were investigated. A superior product with small (d = 7.66 nm, sigma = 1.94 nm), homogeneously distributed Pd crystals was obtained at pH 7 and a reaction temperature of 70 degrees C in ethanol. The Pd NPs decorated carbon sphere was used as support for electroactive polyaniline (PANI) in our work because it could enhance their sensing properties which were afforded by catalytic Pd NPs and hydrophilic carbon spheres. The sensor based on carbon/Pd/PANI exhibited a high sensitivity of 656.0693 mA M(-1) cm(-2) and a detection limit of 5.48 microM toward the reduction of H(2)O(2). In addition, the carbon/Pd/PANI sensor also showed good selectivity between H(2)O(2) and ascorbic acid.

Aniline dimer-COOH assisted preparation of well-dispersed polyaniline-Fe3O4 nanoparticles

Polyaniline (PANI)–Fe3O4 nanoparticles were obtained using a novel method: aniline dimer–COOH assisted polymerization. The synthetic strategy involved two steps: first, the composite of magnetic nanoparticles modified with aniline dimer–COOH was synthesized by a chemical precipitation method. Then aniline monomer and oxidant were added to create PANI–Fe3O4 nanoparticles. The structure of Fe3O4 nanoparticles capped with aniline dimer–COOH was characterized by Fourier transform infrared, ultraviolet–visible, x-ray photoelectron spectroscopy and x-ray diffraction analyses. Transmission electron microscope images of the PANI–Fe3O4 nanocomposite showed that the Fe3O4 nanoparticles were well dispersed in PANI matrices. The PANI–Fe3O4 composite was characterized by means of FTIR, XPS and XRD analyses. The PANI–Fe3O4 nanoparticles were found to be superparamagnetic. The hysteresis loop at room temperature showed high saturated magnetization (Ms = 21 emu g−1) and a low coercive force (μc = 0).

Surfactant directed synthesis of polypyrrole/TiO2 coaxial nanocables with a controllable sheath size

It was demonstrated that polypyrrole (PPy)/TiO2 coaxial nanocables with a controllable sheath size were prepared, assisted by sodium dodecyl sulphate (SDS) surfactant through in situ chemical oxidation polymerization in aqueous solution. The synthetic strategy involved three steps. (1) TiO2 nanofibres were prepared by an electrospinning method. (2) Surfactant molecules were absorbed on the surface of the TiO2 nanofibres. Then a columnar microregion containing a hard core (TiO2) and a soft interface (surfactant) was formed. (3) Pyrrole monomers and the oxidant to polymerize the pyrrole between the surfactant layer and the TiO2 nanofibres in aqueous solution were added, and then PPy/TiO2 coaxial nanocables could form. Transmission electron microscopy (TEM) images revealed the cable-like morphology of the composite nanostructures. The thickness of the sheath of PPy/TiO2 coaxial nanocables could be controlled by the quantity of the monomer. Fourier-transform infrared (FTIR) spectra, x-ray photoelectron spectra (XPS) and x-ray diffraction (XRD) patterns were used to characterize the chemical structure of the PPy/TiO2 coaxial nanocables.

Poly(acrylic acid)-guided synthesis of helical polyaniline/CdS composite microwires

Polyaniline (PANI) composite microwires containing CdS nanoparticles were synthesized guided by poly(acrylic acid) (PAA). It was found that the morphology of the composite microwires was affected by the concentration of PAA. When the concentration of PAA was lower than 0.1 mg ml−1, the PANI/CdS composite was wires. However, no wire-like structures of PANI/CdS composites were formed when the concentration of PAA was higher than 1.0 mg ml−1. The complex of CdS nanoparticles with PANI matrix was affected by the molar ratio of CdS to aniline. When the molar ratio was 1:75, CdS nanoparticles were well combined with PANI matrix. However, when the molar ratio was 1:150, no CdS nanoparticles were combined with PANI wires. SEM, TEM, FTIR and XRD characterized the PANI/CdS composite microwires and proved that the CdS nanoparticles are combined with the PANI matrix in some conditions, and TEM proved that some of the microwires are in fact of helical shape. The photoluminescence of CdS is slightly affected by its combination with the PANI matrix.

Preparation of unique PEDOT nanorods with a couple of cuspate tips by reverse interfacial polymerization and their electrocatalytic application to detect nitrite

By using Ce(SO4)2·4H2O as an oxidant and sodium bis(2-ethylhexyl) sulfosuccinate (AOT) as a surfactant, unique poly(3,4-ethylenedioxythiophene) (PEDOT) nanorods with a couple of cuspate tips were successfully prepared by reverse interfacial polymerization. The morphology of these PEDOT nanorods was very regular and well-dispersed with widths and lengths from one tip to another tip mostly in the range 40–60 nm and 370–460 nm, respectively. The chemical structure and formation mechanism of PEDOT nanorods are discussed in detail by several analysis methods. AOT played an important role during the formation of PEDOT nanorods. It could be combined with Ce4+ to form a unique template for the polymerization of 3,4-ethylenedioxythiophene (EDOT) in the cylindrical micelles formed by n-hexane, H2O and AOT. Furthermore, the application of PEDOT nanorod-modified glassy carbon electrode (GCE) as an electrochemical sensor for detecting nitrite was also investigated. Due to their good dispersibility and large surface area, PEDOT nanorods exhibited good linearity and sensitivity of cyclic voltammetry (CV) responses as well as amperometric responses for electrocatalytic oxidation of nitrite. It resulted in PEDOT nanorods acting as a good steady and sensitive electrode material for detecting nitrite.

Unique tetragonal starlike polyaniline microstructure and its application in electrochemical biosensing

Tetragonal starlike microstructures of polyaniline (PANI) doped with aspartic acid (AA) have been synthesized under hydrothermal conditions for the first time. It was found that the morphologies of the obtained samples were much sensitive to the concentration of the doping amino acid. Hydrothermal synthesis by monitoring the reaction time provided a platform for understanding the process of the polymerization. The products were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-visible spectroscopy (UV-vis), Fourier transmission infrared spectroscopy (FT-IR), and X-ray diffraction (XRD). Furthermore, the tetragonal starlike PANI modified glassy carbon electrode (GCE) exhibited high electrocatalytic activity for sensing dopamine.

Facile synthesis of phenyl-capped oligoanilines using pseudo-high dilution technique

Monodispersed phenyl-capped trianiline and tetraaniline were successfully synthesized by the reactions of diphenylamine with acetaldehyde-based Sckiffs bases of N-phenyl-1,4-phenylenediamine and 1,4-phenylenediamine, respectively, in the presence of ammonium persulfate and hydrochloric acid, subsequent deprotonation and reduction with phenylhydrazine. The reaction mechanism probably involves the slow hydrolysis of the Sckiffs bases and subsequent oxidative coupling reactions of the formed ammonium salts with diphenylamine at pseudo-high dilution condition of the salts.