Jieming Cao

Synthesis of single crystalline CdS nanowires with polyethylene glycol 400 as inducing template

Abstract Solvothermal technique, an one-step soft solution-processing route was successfully employed to synthesize single crystalline CdS nanowires in ethylenediamine medium at lower temperature (170 □) for 1–8 d. In this route, polyethylene glycol 400 (PEG400) was used as surfactant, which played a crucial role in preferentially oriented growth of semiconductor nanowires. Characterizations of as-prepared CdS nanowires by X-ray powder diffraction(XRD), transmission electron microscopy(TEM) indicate that the naonowires, with typical diameters of 20nm and lengths up to several micrometers, have preferential [001] orientation. Also, investigations into the physical properties of the CdS nanowires were conducted with UV-Vis absorption spectroscopy and photoluminescence emission spectroscopy. The excitonic photo-optical phenomena of the nanowires shows the potential in the practical applications.

Template synthesis of three-dimensional cubic ordered mesoporous carbon with tunable pore sizes.

Three-dimensional cubic ordered mesoporous carbons with tunable pore sizes have been synthesized by using cubic Ia3d mesoporous KIT-6 silica as the hard template and boric acid as the pore expanding agent. The prepared ordered mesoporous carbons were characterized by powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption–desorption analysis. The results show that the pore sizes of the prepared ordered mesoporous carbons with three-dimensional cubic structure can be regulated in the range of 3.9–9.4 nm. A simplified model was proposed to analyze the tailored pore sizes of the prepared ordered mesoporous carbons on the basis of the structural parameters of the silica template.

Synthesis of Novel Flower-Like Zn(OH)F via a Microwave-Assisted Ionic Liquid Route and Transformation into Nanoporous ZnO by Heat Treatment

Zinc hydroxide fluoride (Zn(OH)F) with novel flower-like morphology has been prepared via a microwave-assisted ionic liquid route. The flower-like Zn(OH)F particle has six petals and every petal is composed of lots of acicular nano-structure. Nanoporous ZnO is obtained by thermal decomposition of as-prepared Zn(OH)F in air, and the flower-like morphology is well retained. In the process of synthesis, ionic liquid 1-Butyl-3-methylimidazolium tetrafluoroborate is used as both the reactant and the template.

Template Synthesis of Carbon Nanofibers Containing Linear Mesocage Arrays

Carbon nanofibers containing linear mesocage arrays were prepared via evaporation induced self-assembly method within AAO template with an average channel diameter of about 25 nm. The TEM results show that the mesocages have an elongated shape in the transversal direction. The results of N2 adsorption–desorption analysis indicate that the sample possesses a cage-like mesoporous structure and the average mesopore size of the sample is about 18 nm.

Improving lithium–sulfur battery performance via a carbon-coating layer derived from the hydrothermal carbonization of glucose

Sulfur possesses a high specific capacity as a rechargeable lithium battery cathode. However, the commercial applications of sulfur cathodes are limited by the poor electronic/ionic conductivity of elemental sulfur and polysulfides, volume expansion of sulfur during the discharge process, and the high solubility of long-chain lithium polysulfides (Li2Sn, 4 ≤ n ≤ 8). Herein, we design a core–shell structure composed of active carbon (AC) and an amorphous carbon-coating layer to encapsulate the sulfur in the carbon matrix. The carbon-coating layer obtained from the hydrothermal carbonization of glucose can effectively entrap the polysulfides. Furthermore, the composite matrix provides a conducting framework serving as an electrochemical reaction chamber for the sulfur cathode. After wrapping AC–S with an amorphous carbon layer, the obtained composite cathode can effectively confine the polysulfides and buffer the volume change. Consequently, the resulting composite cathode possesses a high specific capacity, good rate capability, and stable cycling performance. At 0.2 A g−1 current density, the as-prepared carbon-coated AC–S composite cathode shows a high specific discharge capacity of 1103 mA h g−1. At a current density of 0.8 A g−1 and 1.6 A g−1, the composite cathode exhibits 75% capacity retention over 150 cycles. The Coulombic efficiency of the cell remains at approximately 95%.

Towards outstanding dielectric consumption derived from designing one-dimensional mesoporous MoO2/C hybrid heteronanowires

One-dimensional (1D) microwave absorbers have been verified to have a predominant morphology due to their significant anisotropy, large surface area, and great dielectric attenuation compared to other microstructures. Consequently, in this research, novel 1D mesoporous MoO2/C heteronanowires have been designed through an in situ facile synthesis process. As well as their attractive morphology, building multiple interfaces for polarization between MoO2 and carbon, inducing dipole polarization of MoO2 and constructing conductive networks among nanowires endow the composites with outstanding dielectric dissipated properties, allowing excellent microwave absorption (MA) performance. Therefore, at the appropriate filling condition of 25 wt%, the MoO2/C nanowire-paraffin achieved a minimum reflection loss of −47.6 dB at 11.1 GHz and a bandwidth of 3.8 GHz in the range of 9.9–13.7 GHz with a thickness of 2 mm, thus it has the potential to be a lightweight candidate of microwave absorbing material.

Synthesis of Microfiber with Secondary Nanostructure by Cotton Template

Hierarchical microfibers were prepared by using cotton as the template and as the precursor via an ultrasonic assistance route. The results of scanning electron microscope characterization showed that the concentration of had a significant effect on the morphology of microfiber. At low concentration of , the microfiber was composed of nanorods with single crystal structure. With increasing the concentration of , the secondary nanostructure of microfibers had a transformation from nanorod to nanoparticle. The results of adsorption-desorption analysis indicated that microfibers had BET surface area of about 25 /g. This synthesis provides a new way to control the secondary nanostructure of microfiber by adjusting the concentration of precursor. Furthermore, the mechanism for the replication was proposed and discussed.

An Easy and Green Route for the Fabrication of NiO Nanoparticles by Starch Template

NiO nanoparticles have been prepared by thermal decomposition of the nickel acetate/starch precursor in air. N2 adsorption-desorption analysis show that the resultant NiO samples possess nanoporous structures and large BET surface areas. The Brunauer-Emmet-Teller (BET) surface area of NiO increases from 17 to 38 m2·g−1 because of the use of the starch template. The surface area decreases and the average pore diameter increases for the NiO products with increasing heat treatment temperature. The formation mechanism of the NiO nanoparticles was proposed. Furthermore, the electrochemical measurements indicate that the NiO nanoparticles have favorable faradaic pseudocapacitive behavior. The method has also been demonstrated for nickel nitrate.

22-P-08-Formation of carbon nanotubes on various molecular sieves supported metal oxides

Publisher Summary This chapter discusses the formation of carbon nanotubes on various molecular sieves supported metal oxides. The carbon nanotubes are formed on metal oxide-supported zeolite by the decomposition of acetylene hydrocarbon at 700°C. The optimum reaction conditions of growth of nanotubes on various molecular sieve catalysts, including Y, A, MOR, ZSM-5, and MCM-41, are studied. Iron/cobalt (Fe/Co)-supported Y zeolite catalyst can be considered the best catalyst for the growth of nanotubes in them. Masses of carbon nanotubes with uniform diameter of about 30 nm are obtained over pretreated Y zeolite. The states of iron in Fe-supported Y catalyst measured by Mossbauer spectrum during three stages of original, hydrogen reduced, and catalytic synthetic nanotubes indicate that the hydrogen generated during the reaction is enough to reduce the Fe(III) to subvalence active state.