Huanhuan Wang

Core–sheath structured bacterial cellulose/polypyrrole nanocomposites with excellent conductivity as supercapacitors

Core–sheath structured conductive nanocomposites were prepared by wrapping a homogenous layer of polypyrrole (PPy) around bacterial cellulose (BC) nanofibers via in situ polymerization of self-assembled pyrrole. By manipulating the ordered core–sheath nanostructure, BC/PPy nanocomposites were achieved and outstanding electrical conductivity as high as 77 S cm−1 was obtained with the optimized reaction protocols, i.e., feeding mass ratio of BC/Py 1 : 10, molar ratio of FeCl3/Py 0.5 : 1, molar ratio of HCl/Py 1.2 : 1, volume ratio of DMF–H2O 1 : 2, reaction temperature 0 °C, and reaction time 6 h. The BC/PPy nanocomposites demonstrated promising potential for supercapacitors, with a highest mass specific capacitance hitting 316 F g−1 at 0.2 A g−1 current density. The whole-optimized protocol in preparing highly conductive PPy/BC composites may be readily extended to the preparation of new conductive materials based on core–sheath structured BC nanocomposites for various technological applications.

Sandwich-structured MnO2/polypyrrole/reduced graphene oxide hybrid composites for high-performance supercapacitors

The rational preparation of hierarchical MnO2/polypyrrole (PPy)/reduced graphene oxide (rGO) nanosheets in a sandwich structure is presented. By co-assembly of MnO2/GO and PPy/GO into layer-by-layer architecture and reduction of GO, ternary (MnO2, PPy)/rGO composites were first fabricated. The materials were fully characterized in terms of structure, morphology and electrochemical properties. The unique architecture offers the composites good capacitance by taking advantage of the strong synergistic effect of each component. A maximum specific capacitance as high as 404 F g−1 was obtained for this composite electrode. And over 91% of the initial capacitance was retained after 5000 continuous cycles. The good electrochemical performance and long-term cycling stability make this approach attractive in developing multifunctional hierarchical composites for high-performance supercapacitors.

Exploration of a β-cyclodextrin clicked chiral stationary phase in high-performance liquid chromatography

The baseline enantioseparation of 19 racemic drugs including ondansetron, citalopram, galanthamine base, pregabalin, timolol, atenolol, tropicamide, ephedrine hydrochloride, flavanoids and aryl alcohols has been successfully achieved with a cyclodextrin clicked chiral stationary phase in high performance liquid chromatography. The best separation results were presented under optimized conditions. The effect of organic modifiers including methanol and acetonitrile on the enantioseparation of racemates was also studied. Chiral resolutions of 4.19 and 4.42 were achieved for citalopram and tropicamide, respectively.

Structural, electrical and optical properties of Mg-doped CuAlO2 films by pulsed laser deposition

CuAl1−xMgxO2 (x = 0, 0.01, 0.02, 0.05) films were deposited on sapphire and fused silica substrates by pulsed laser deposition and underwent annealing in an Ar atmosphere at the temperature of 1000 °C. The effects of Mg concentration on the structural, morphological, electrical and optical properties were investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), UV-visible-NIR spectrophotometry and a Hall effect measurement system. The results indicate that Mg is successfully doped into the CuAlO2 film with p-type conduction after annealing. Single and pure-phase CuAl1−xMgxO2 (x = 0, 0.01, 0.02, 0.05) films with c-axis orientation are obtained on sapphire substrates in the studied doping range, and a secondary phase is not detected by XRD measurements. The substitution of Mg2+ ions in Al3+ sites induces lattice distortion and results in the decline of the crystalline quality. The Hall effect measurement reveals that the carrier concentration increases and Hall mobility decreases with the increase of Mg doping concentration. The resistivity of the CuAl1−xMgxO2 films decreases and then increases with increasing Mg doping concentration from 0 to 5%. The minimum resistivity of 11.45 Ω cm is obtained at room temperature for the CuAl1−xMgxO2 films with x = 2%. The optical transmittance gradually reduces with the increase of Mg concentration due to the enhancement of absorption of incident photons. The optical band gaps of CuAl1−xMgxO2 films are found to decrease from 3.54 to 3.43 eV as the Mg doping concentration increased from 0 to 5% due to the formation of impurity energy levels.