Superlight and Superflexible Three-Dimensional Semiconductor Frameworks A(X≡Y)4(A=Si, Ge; X/Y=C, B, N) with Tunable Optoelectronic and Mechanical Properties from First-Principles

Chemical Bonding and Activity of Atomically Dispersed Silicon in Two- and Three-Dimensional Materials

On the basis of the especially tunable electronic property of Si, several kinds of nanomaterials with atomically dispersed Si were constructed and characterized by extensive first-principles calculations and ab initio molecular dynamics (AIMD) simulations. The new-type Si(X≡Y)n wide-bandgap semiconductors featuring through-space d-π* hyperconjugation exhibit unique properties in photoelectric conversion, photoconductivity, structural mechanics, etc. The SiC8 siligraphene with the planar tetracoordinate Si (ptSi) has a high lithium-storage capacity and comparably facile surface migration behaviors of both Li and Li+, making it a promising anode material for high-performance Li-ion batteries. The atomically dispersed Si sites of 2D monolayer materials, such as ptSi and three- and four-coordinated Si atoms, generally exhibit remarkable catalytic activity toward CO2 activation with different electron mechanisms, resulting in different scaling relations between the activity and the p-band center. The computational findings enrich the understanding of structural and chemical properties of silicon and open up avenues for developing Si-based functional materials.

Electronic, Mechanical and Elastic Anisotropy Properties of X-Diamondyne (X = Si, Ge)

The three-dimensional (3D) diamond-like semiconductor materials Si-diamondyne and Ge-diamondyne (also called SiC4 and GeC4) are studied utilizing density functional theory in this work, where the structural, elastic, electronic and mechanical anisotropy properties along with the minimum thermal conductivity are considered. SiC4 and GeC4 are semiconductor materials with direct band gaps and wide band gaps of 5.02 and 5.60 eV, respectively. The Debye temperatures of diamondyne, Si- and Ge-diamondyne are 422, 385 and 242 K, respectively, utilizing the empirical formula of the elastic modulus. Among these, Si-diamondyne has the largest mechanical anisotropy in the shear modulus and Young's modulus, and Diamond has the smallest mechanical anisotropy in the Young's modulus and shear modulus. The mechanical anisotropy in the Young's modulus and shear modulus of Si-diamondyne is more than three times that of diamond as determined by the characterization of the ratio of the maximum value to the minimum value. The minimum thermal conductivity values of Si- and Ge-diamondyne are 0.727 and 0.524 W cm-1 K-1, respectively, and thus, Si- and Ge-diamondyne may be used in the thermoelectric industry.

Dimethylformamide-stabilised palladium nanoclusters catalysed coupling reactions of aryl halides with hydrosilanes/disilanes

N,N-Dimethylformamide-stabilised Pd nanocluster (NC) catalysed cross-coupling reactions of hydrosilane/disilane have been investigated. In this reaction, the coupling reaction proceeds without ligands with low catalyst loading. N,N-Dimethylacetamide is a crucial solvent in these reactions. The solvent effect was considered by various techniques, such as transmission electron microscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis. The Pd NCs can be recycled five times under both hydrosilane and disilane reaction conditions.

A highly efficient and reusable Pd NCs catalyst system for silylation of aryl halides was developed.