We calculated the longitudinal acoustic phonon limited electron mobility of 14 two dimensional semiconductors with composition of MX 2 , where M (= Mo, W, Sn, Hf, Zr and Pt) is the transition metal, and X is S, Se and Te. We treated the scattering matrix by deformation potential approximation. We found that out of the 14 compounds, MoTe 2 , HfSe 2 and HfTe 2 , are promising regarding to the possible high mobility and finite band gap. The phonon limited mobility can be above 2500 cm 2 V −1 s −1 at room temperature.

in order to restrict the loss of material. Furthermore, due to their scalability and flexibility, 3D flexible electronics (see Supporting Information (SI), where Table S1 contains a list) were considered revolutionary materials and were used in many fields such as imperceptible electronic devices, wearable electronic devices, and bionic technology. [11][12][13] Recently studies have shown the encapsulation of sulfur in the pores of carbon materials, such as meso-/microporous carbons, [11] cable-shaped carbon, [12] and carbon nanotubes/fibers, [13] can reduce the capacity fading. However, such nonpolar flexible carbon materials have a destructive disadvantage; they only have physical van der Waals (vdW) adsorption for polar Li 2 S n , which leads to the facile detachment of Li 2 S n from the carbon surface. [14] This proves that carbon-based materials alone cannot serve as the perfect host. In light of this new insight, various types of polar functional groups on carbon-based materials have been demonstrated to increase the interaction between Li 2 S n species and the electrode; these materials can generally be categorized into three types: polymers (polyaniline, polypyrrole, poly(3,4ethylenedioxythiophene) (PEDOT)), [15] metal oxides

Owing to the high theoretical specific capacity (1166 mAh g), lithium sulfide (LiS) has been considered as a promising cathode material for Li-S batteries. However, the polysulfide dissolution and low electronic conductivity of LiS limit its further application in next-generation Li-S batteries. In this report, a nanoporous LiS@C-Co-N cathode is synthesized by liquid infiltration-evaporation of ultrafine LiS nanoparticles into graphitic carbon co-doped with cobalt and nitrogen (C-Co-N) derived from metal-organic frameworks. The obtained LiS@C-Co-N architecture remarkably immobilizes LiS within the cathode structure through physical and chemical molecular interactions. Owing to the synergistic interactions between C-Co-N and LiS nanoparticles, the LiS@C-Co-N composite delivers a reversible capacity of 1155.3 (99.1% of theoretical value) at the initial cycle and 929.6 mAh g after 300 cycles, with nearly 100% Coulombic efficiency and a capacity fading of 0.06% per cycle. It exhibits excellent rate capacities of 950.6, 898.8, and 604.1 mAh g at 1C, 2C, and 4C, respectively. Such a cathode structure is promising for practical applications in high-performance Li-S batteries.

Three-dimensional aerogel with ultrathin tellurium nanowires (TeNWs) wrapped homogeneously by reduced graphene oxide (rGO) is realized via a facile hydrothermal method. Featured with high conductivity and large flexibility, the rGO constructs a conductive three-dimensional (3D) backbone with rich porosity and leads to a free-standing, binder-free cathode for lithium-tellurium (Li-Te) batteries with excellent electrochemical performances. The cathode shows a high initial capacity of 2611 mAh cm(-3) at 0.2 C, a high retention of 88% after 200 cycles, and a high-rate capacity of 1083 mAh cm(-3) at 10 C. In particular, the 3D aerogel cathode delivers a capacity of 1685 mAh cm(-3) at 1 C after 500 cycles, showing pronounced long-cycle performance at high current density. The performances are attributed to the well-defined flexible 3D architecture with high porosity and conductivity network, which offers highly efficient channels for electron transfer and ionic diffusion while compromising volume expansion of Te in charge/discharge. Owing to such advantageous properties, the reported 3D rGO/tellurium nanowire (3DGT) aerogel presents promising application potentials as a high-performance cathode for Li-Te batteries.

Whether a metallic ground state exists in a two-dimensional system beyond Anderson localization remains an unresolved question. We studied how quantum phase coherence evolves across superconductor–metal–insulator transitions through magnetoconductance quantum oscillations in nanopatterned high-temperature superconducting films. We tuned the degree of phase coherence by varying the etching time of our films. Between the superconducting and insulating regimes, we detected a robust intervening anomalous metallic state characterized by saturating resistance and oscillation amplitude at low temperatures. Our measurements suggest that the anomalous metallic state is bosonic and that the saturation of phase coherence plays a prominent role in its formation.

Neither of the two typical two-dimensional materials, graphene and single layer MoS2, are good enough for developing semiconductor logical devices. We calculated the electron mobility of 14 two-dimensional semiconductors with composition of MX2, where M (=Mo, W, Sn, Hf, Zr and Pt) are transition metals, and Xs are S, Se and Te. We approximated the electron phonon scattering matrix by deformation potentials, within which long wave longitudinal acoustical and optical phonon scatterings were included. Piezoelectric scattering in the compounds without inversion symmetry is also taken into account. We found that out of the 14 compounds, WS2, PtS2 and PtSe2 are promising for logical devices regarding the possible high electron mobility and finite band gap. Especially, the phonon limited electron mobility in PtSe2 reaches about 4000 cm2·V-1·s-1 at room temperature, which is the highest among the compounds with an indirect bandgap of about 1.25 eV under the local density approximation. Our results can be the first guide for experiments to synthesize better two-dimensional materials for future semiconductor devices.

The Classroom Practices Survey was conducted by The National Research Center on the Gifted and Talented (NRC/GT) to determine the extent to which gifted and talented students receive differentiated education in regular classrooms. Six samples of third and fourth grade teachers in public schools, private schools and schools with high concentrations of four types of ethnic minorities were randomly selected to participate in this research. The major finding of this study is that third and fourth grade classroom teachers make only minor modifications in the regular curriculum to meet the needs of gifted students. This result holds for all types of schools sampled. It also holds for classrooms in different parts of the country and for different types of communities. Implications of these findings for researchers and gifted education specialists are discussed.

Three-dimensional (3D) CNT/graphene-Li2S (3DCG–Li2S) cathodes with 81.4 wt % record Li2S loading have been realized through solvothermal reaction and a subsequent liquid-infiltration-evaporation coating method. The highly flexible, conductive 3D mesoporous interconnected network based on two-dimensional (2D) graphene nanosheets and one-dimensional (1D) carbon nanotubes (CNTs) provides highly efficient channels for electron transfer and ionic diffusion, and leads to a low solubility of polysulfides in electrolytes in charges/discharges. Without polymeric binders or conductive additives, the freestanding 3DCG–Li2S cathode exhibits record electrochemical performances including reversible discharge capacities of 1123.6 mAh g–1 and 914.6 mAh g–1, 0.02% long-term capacity decay per cycle and a high-rate capacity of 514 mAh g–1 at 4 C. The reported 3DCG–Li2S aerogel with ultrahigh Li2S content presents promising application potentials in high-performance Li–S batteries.