Au Chak-Tong

Polymers anchored with carboxyl-functionalized di-cation ionic liquids as efficient catalysts for the fixation of CO2 into cyclic carbonates

A series of polymers grafted with functionalized di-cation imidazolium-based ionic liquids (P–FDIILs) were fabricated and evaluated as efficient catalysts for the synthesis of cyclic carbonates from epoxides and CO2 in the absence of a co-catalyst and a solvent. The P–FDIILs, especially the carboxyl-functionalized ones, perform well in the cycloaddition reaction at a low catalyst loading of 0.3 mol%. It is suggested that a combined effect of the carboxyl group, the imidazolium cation, and the halide anion facilitates the cycloaddition reaction. Furthermore, the methylene chain length between the imidazolium cation and the functional group, and the halide anion species, affect the activity of the catalysts. It is noted that the catalyst shows no significant loss of activity in a reusability test of five cycles. From the view point of industrial application, the catalyst is attractive due to its good stability and excellent catalytic efficiency.

Synthesis and Properties of Magnetic Composites of Carbon Nanotubes/Fe Nanoparticle

Magnetic composites of carbon nanotubes (CNTs) are synthesized by the in situ catalytic decomposition of benzene at temperatures as low as 400°C over Fe nanoparticles (mean grain size = 26 nm) produced by sol-gel fabrication and hydrogen reduction. The yield of CNT composite is up to about 3025% in a run of 6 h. FESEM and HRTEM investigations reveal that one-dimensional carbon species are produced in a large quantity. A relatively high value of magnetization is observed for the composite due to the encapsulation of ferromagnetic Fe3C and/or α-Fe. The method is suitable for the mass-production of CNT composites that contain magnetic nanoparticles.

Controllable synthesis, characterization, and growth mechanism of hollow ZnxCd1?xS spheres generated by a one-step thermal evaporation method

Novel hollow ZnxCd1−xS spheres that are uniform in size are synthesized through the one-step thermal evaporation of a mixture of Zn and CdS powder. From an X-ray diffraction (XRD) study, the hexagonal wurtzite phase of ZnxCd1−xS is verified, and the Zn mole fraction (x) is determined to be 0.09. According to the experimental results, we propose a mechanism for the growth of Zn0.09Cd0.91S hollow spheres. The results of the cathodoluminescence investigation indicate uniform Zn, Cd, and S distribution of alloyed Zn0.09Cd0.91S, instead of separate CdS, ZnS, or nanocrystals of a core-shell structure. To the best of our knowledge, the fabrication of ZnxCd1−xS hollow spheres of this kind by one-step thermal evaporation has never been reported. This work would present a new method of growing and applying hollow spheres on Si substrates, and the discovery of the Zn0.09 Cd0.91S hollow spheres would make the investigation of ZnxCd1−xS micro/nanostructures more interesting and intriguing.