Surfactant-assisted hydrothermally synthesized MoS_2 samples with controllable morphologies and structures for anthracene hydrogenation

MoS_2 samples with controllable morphologies and structures were synthesized using surfactantassisted hydrothermal processes.The effects of surfactants（PEG,PVP,P123,SDS,AOT,and CTAB）on the morphologies and structures of MoS_2 samples were investigated.The results revealed that spherical,bulk-like,and flower-like MoS_2 particles assembled by NH4~＋-intercalated MoS_2 nano-sheets were synthesized.The morphologies of the MoS_2 samples and their structures（including the slab length and the number of stacked layers） of MoS_2 nano-sheets in these samples could be controlled by adjusting the surfactants.Mono-dispersed spherical MoS_2 particles could be synthesized with PEG via the creation of MoS_2 nano-sheets with slab lengths shorter than 15 nm and fewer than six stacked layers.Possible formation mechanisms of these MoS_2 samples created via surfactant-assisted hydrothermal processes are proposed.Further,the catalytic activities of MoS_2 samples for anthracene hydrogenation were evaluated in a slurry-bed reactor.The catalyst synthesized with the surfactant PEG exhibited the highest catalytic hydrogenation activity.Compared with the other catalysts,it had a smaller particle size,mono-dispersed spherical morphology,shorter slab length,and fewer stacked layers;these were all beneficial to exposing its active edges.This work provides an efficient approach to synthesize transition metal sulfides with controllable morphologies and structures.

A SURFACTANT-ASSISTED APPROACH FOR PREPARING COLLOIDAL AZO POLYMER SPHERES WITH NARROW SIZE DISTRIBUTION

A surfactant-assisted method for preparing colloidal spheres with narrow size distribution from a polydispersed azo polymer has been developed in this work. The colloidal spheres were formed through gradual hydrophobic aggregation of the polymeric chains in THF-H2O dispersion media, which was induced by a steady increase in the water content. Results showed that the addition of a small amount of surfactant （SDBS） could significantly narrow the size distribution of the colloidal spheres. The size distribution of the colloidal spheres was determined by the concentrations of azo polymer and the amount of surfactant in the systems. When the concentrations of polymer and surfactant amount were in a proper range, colloidal spheres with narrow size distribution could be obtained. The colloidal spheres formed by this method could be elongated along the polarization direction of the laser beams to be a new type of the colloid-based functional materials. upon Ar^＋ laser irradiation. The colloidal spheres are considered

Enhanced coercivity and remanence of PrCo_5 nanoflakes prepared by surfactant-assisted ball milling with heat-treated starting powder

PrCo5 nanoflakes with strong texture and high coercivity of 8.15 kOe were prepared by surfactant-assisted ball milling with heat-treated starting powder. The thickness and length of the as-milled nanoflakes are mainly in the ranges of 50–100 nm and 0.5–3 μm, respectively. The x-ray diffraction patterns demonstrate that the heat treatment can increase the single phase and crystallinity of the PrCo5 compound, and combined with the demagnetization curves, indicate that the single phase and crystallinity are important for preparing high-coercivity and strong-textured rare earth permanent magnetic nanoflakes. In addition, the coercivity mechanism of the as-milled PrCo5 nanoflakes is studied by the angle dependence of coercivity for an aligned sample and the field dependence of coercivity, isothermal（IRM） and dc demagnetizing（DCD）remanence curves for an unaligned sample. The results indicate that the coercivity is dominated by co-existing mechanisms of pinning and nucleation. Furthermore, exchange coupling and dipolar coupling also co-exist in the sample.

Enhanced CO oxidation activity of CuO/CeO_2 catalyst prepared by surfactant-assisted impregnation method

A modified CuO/CeO2 catalyst was prepared by surfactant-assisted impregnation method and showed better catalytic activity for low temperature CO oxidation than that from conventional impregnation method. The physicochemical properties of different CuO/CeO2 catalysts were characterized by thermogravimetrie and differential scanning calorimetric measurements （TG-DSC）, X-ray diffraction （XRD）, N2 adsorpti0n-desorption, Raman spectroscopy, H2 temperature-programmed reduction （H2-TPR）, tern- perature-programmed desorption of 02 （O2-TPD）, and diffuse reflectance infrared Fourier transform spectroscopy （DRIFTS）. The re- sults suggested that the addition of hexadecyl trimethyl ammonium bromide （CTAB） into the impregnation solution could improve the dispersion of CuO species, which could facilitate Cu2＋ incorporating into CeO2 lattice and strengthened the synergistic effects between CuO and CeO2, making the lattice oxygen more active, and eventually resulting in enhanced activity for CO oxidation.

Preparation of hollow alumina nanospheres via surfactant-assisted flame spray pyrolysis

Hollow A1203 nanospheres with well-defined structure and shape were successfully prepared via flame spray pyrolysis （FSP） in the presence of a surfactant as droplet stabilizer. The morphology and structure of the nanospheres were systematically characterized by transmission electron microscopy, scanning electron microscopy, and N2 sorption. A solution of hydrated aluminum nitrate, polyethylene glycol （PEG） and absolute ethanol was sprayed into a flame to transform droplets into particles after evaporation and surface nucleation, forming hollow AI203 nanospheres from aluminum nitrate decomposition. The surfactant was found effective in producing smaller droplets because of decreased surface tension and viscosity, while the combination of oxygen atoms on PEG chains and aluminum ions in solution reduced interfacial turbulence, leading to increased stability of the droplets.

Surfactant-assisted hydrothermal synthesis of MoS_(2) micro-pompon structure with enhanced photocatalytic performance under visible light

MoS_(2) nanomaterial with the micro-pompon structure was synthesized by a surfactant-assisted hydrothermal method.The morphologies and structures of as-prepared MoS_(2) micro-pompon were investigated by adding different types of surfactants such as cetyltrimethyl ammonium bromide(CTAB),sodium dodecylbenzene sulphonate(SDBS),and polyvinyl pyrrolidone(PVP).The results indicated that the morphology of MoS_(2) could be controlled and changed effectively by the cationic sur-factant of CTAB.A reasonable growth mechanism for hollow structured MoS_(2) micro-pompon by hydrothermal processes was proposed.Further,photocatalytic degradation properties of MoS_(2) micro-pompon under visible light were evaluated by degradation of common organic dyes,which include rhodamine B(RhB),congo red,methyl orange,and methylene blue.The results indicated that MoS_(2) micro-pompon owned the highly selective catalytic ability to RhB with degradation efficiency of 95%in 60 min and 68%in 30 min.With the additive of the surfactant,the MoS_(2)-CTAB sample exhibited an enhanced ability of photocatalytic activity where degradation efficiency was improved to 92%in 30 min.The method employed in this work could be expanded to fabricate other sulfides with the controllable morphology and structure to further regulate the photocatalytic performance.

Efficient quantum dot sensitized solar cells via improved loading amount management

High light-harvesting efficiency and low interfacial charge transfer loss are essential for the fabrication of high-efficiency quantum dot-based solar cells(QDSCs). Increasing the thickness of mesoporous TiO2films can improve the loading of pre-synthesized QDs on the film and enhance the absorbance of photoanode, but commonly accompanied by the increase in the unfavorable charge recombination due to prolonged electron transmission paths. Herein, we systematically studied the influence of the balance between QD loading and TiO2film thickness on the performance of QDSCs. It is found that the relative thin photoanode prepared by the cationic surfactant-assisted multiple deposition procedure has achieved a high QD loading which is comparable to that of the thick photoanode commonly used. Under AM 1.5G illumination, Zn–Cu–In–Se and Zn–Cu–In–S based QDSCs with optimized 11.8 μm photoanodes show the PCE of 10.03% and 8.53%, respectively, which are comparable to the corresponding highest PCE of Zn–Cu–In–Se and Zn–Cu–In–S QDSCs(9.74% and 8.75%) with over 25.0 μm photoanodes. Similarly, an impressive PCE of 6.14% was obtained for the CdSe based QDSCs with a 4.1 μm photoanode, which is slightly lower than the best PCE(7.05%)of reference CdSe QDSCs with 18.1 μm photoanode.

Anisotropic Sm_2Co_(17) nano-flakes produced by surfactant and magnetic field assisted high energy ball milling

Anisotropic Sm2C017 flakes with high aspect ratio were prepared by magnetic field assisted high energy ball milling in the presence of heptane and oleic acid （OA）. The thickness of flakes was only tens of nanometers. Coercivity of 3 kOe was achieved in the nano-flakes. Most interestingly, the magnetic crystalline anisotropy of Sm2C017 flakes was improved compared to that of particles made by traditional ball milling. These anisotropic Sm2CoL7 nano-flakes could be the building blocks for the future high-performance nano-composite permanent magnets with an enhanced energy product.