Visible-Light-Induced Intermolecular Trifluoromethyl Heteroarylation of Vinyl Ethers for the Syntheses of ß-Trifluoromethyl Alkyl Thiochromones.

Herein, we reported a transition-metal-free three-component trifluoromethyl heteroarylation of vinyl ethers under visible light irradiation. This protocol proceeded through a radical addition/cyclization sequence which hinged on the intrinsic nucleo/electrophilic reactivity of both the radicals, alkene, and alkynones, allowing ß-trifluoromethyl alkyl thiochromones furnished with high efficiency and excellent functional group tolerance. By virtue of this procedure, three distinct chemical bonds including C(sp2)-C(sp3), C(sp3)-C(sp3), and C(sp2)-S have been successively forged in a single pot.

Ultra-low lattice thermal conductivity and anisotropic thermoelectric transport properties in Zintl compound ß-K2Te2.

A good thermoelectric (TE) performance is usually the result of the coexistence of an ultralow thermal conductivity and a high TE power factor in the same material. In this paper, we investigate the thermal transport and TE properties of the Zintl compound ß-K2Te2 based on a combination of first-principles calculations and the Boltzmann transport equation. Remarkably, the calculated lattice thermal conductivity κL in hexagonal ß-K2Te2 is ultralow with a value of 0.19 (0.30) W m-1 K-1 along the c (a and b) axis at 300 K due to the small phonon group velocity and phonon lifetime, which is comparable to the κL for wood and promises possible good TE performance. By taking the fully anisotropic acoustic deformation potential scattering, polar optical phonon scattering, and ionized impurity scattering into account, the rational electron scattering and transport properties are captured, which indicates a power factor exceeding 2.0 mW m-1 K-2. As a result, the anomalously high n-type ZT of 2.62 and p-type ZT of 3.82 at 650 K along the c axis are obtained in the hexagonal ß-K2Te2, breaking the long-term record of ZT < 3.5 in the majority of the reported TE materials until now. These findings support that hexagonal ß-K2Te2 is a potential candidate for high-efficiency TE applications.

Fabrication, structural characterization and photoluminescence of Q-1D semiconductor ZnS hierarchical nanostructures.

Quasi-one-dimensional semiconductor ZnS hierarchical nanostructures have been fabricated by thermal evaporation of a mixture of ZnS nanopowders and Sn powders. Sn nanoparticles are located at or close to the tips of the nanowires (or nanoneedles) and served as the catalyst for quasi-one-dimensional ZnS nanostructure growth by a vapour-liquid-solid mechanism. The morphology and microstructure of the ZnS hierarchical nanostructures were measured by scanning electron microscopy and high-resolution transmission electron microscopy. The results show that a large number of ZnS nanoneedles were formed on the outer shells of a long and straight ZnS axial nanowire. The ZnS axial nanowires grow along the [001] direction, and ZnS nanoneedles are aligned over the surface of the ZnS nanowire in the radial direction. The room temperature photoluminescence spectrum exhibits a UV weak emission centred at 337 nm and one blue emission centred at 436 nm from the as-synthesized single-crystalline semiconductor ZnS hierarchical nanostructures.