Two-dimensional Layer-like Structure Research Articles

Te doped 1T/2H-MoSe2 nanosheets with rich defects as advanced anode materials for high-rate sodium ion half/full batteries

MoSe2 with a two-dimensional layer-like structure has been considered a promising anode material for sodium-ion batteries (SIBs) on account of its high capacity and rich reserves on Earth.

A novel terbium–mercury compound: Preparation, structure, and properties

Using a hydrothermal reaction, a novel 4f–5d isonicotinic acid complex {[Tb2(IA)6(H2O)4](Hg3Cl7)} n( nHgCl4)· nCl·4 nH3O (1, HIA = isonicotinic acid) was synthesized and it was characterized by single crystal X-ray diffraction technique. Compound 1 is characterized by a two-dimensional layer-like structure. The photoluminescence measurement using solid-state samples uncovered that it shows four emission peaks at 489, 546, 587, and 622 nm, of which the peak at 546 nm is the strongest. These peaks could be assigned to the 5 D4 → 7 F6, 5 D4 → 7 F5, 5 D4 → 7 F4, and 5 D4 → 7 F3 transitions of the Tb3+ ions, respectively. The energy transfer mechanism of the photoluminescence emission was described by means of the energy level scheme of the Tb3+ ions and the isonicotinic acid ligand. Compound 1 shows remarkable CIE (Commission Internationale de I’Éclairage) chromaticity coordinates of (0.3633, 0.5038) in the yellowish green region. Compound 1 possesses a wide semiconductor band gap of 2.97 eV, as unveiled by the solid-state UV-Vis diffuse reflectance experiment.

Structure and properties of a novel bimetallic praseodymium(III)-manganese(II) compound with a two-dimensional layer-like structure

A novel compound [Pr2(IA)6(H2O)4MnCl2(H2O)4]n (1; HIA is isonicotinic acid) was prepared. The praseodymium(III) cation is surrounded by eight oxygen atoms and exhibits a square antiprismatic PrO8 geometry. The manganese(II) ion shows a hexagonal bipyramid. Adjacent Pr3+ cations are interconnected by IA groups to give a one-dimensional (1-D) chain. The chains are further connected by the MnCl2(H2O)4 moieties to give a two-dimensional (2-D) layer. Complex 1 shows red photoluminescence, which comes from the 1D2 → 3H4, 3P0 → 3H6, 3P0 → 3F2 and 3P1 → 3F3 transitions of praseodymium(III) ions. It possesses a band gap of 1.98 eV.

Grafting of polystyrene onto reduced graphene oxide by emulsion polymerization for dielectric polymer composites: High dielectric constant and low dielectric loss tuned by varied grafting amount of polystyrene

In this work, polystyrene-grafted reduced graphene oxides (rGO-PS) were prepared via the emulsion polymerization with reserving the two-dimensional layer-like structure of graphene. TGA, FTIR, Raman results show that the amounts of polystyrene (PS) grafted on rGO from low to medium, high values can be tuned via incorporating different content of styrene in the PS polymerization recipe. Subsequently a series of PS-based composites containing different loading of rGO with variant amount of PS grafted on rGO were prepared. The effects of grafting amount on the resulting dielectric properties were carefully investigated. Compared with the composites containing rGO without any treatment, significantly increased dielectric constant and lower dielectric loss are observed for the composites with rGO-PS. Moreover, with increasing the amounts of grafted PS on rGO, the dielectric constants exhibit an increasing trend whereas the dielectric loss keeps at a stable level. For instance, when the loading of filler is fixed at 5wt%, the composites containing rGOs with highest amount of grafted PS exhibit a maximum of dielectric constant 394.6@100Hz, which is over 20 times larger than that of composites containing rGO. However, a relatively low dielectric loss tangent 0.45@100Hz and conductivity 4.04×10−9S/cm@100Hz are observed in the composites containing rGOs with highest amount of grafted PS, which is even lower than that of composites containing rGO. The improved interfacial polarization induced by the constructed PS layer between rGO and PS matrix is invoked to be responsible for the improved dielectric constant; on the other hand, the PS layer can restrict the conduction loss and suppress the dielectric loss. This work indicates that the dielectric performance of composites could be effectively ameliorated through the strategy of reasonably designing the interface structure of conductive fillers.

Poly[[diaqua-bis-[μ(4)-5-nitro-isophthalato-κ(4)O(1):O(1):O(3):O(3')]bis-[μ(3)-pyridine-4-carboxyl-ato-κ(3)O:O':N]tricobalt(II)] tetra-hydrate

The title compound, {[Co3(C6H4NO2)2(C8H3NO6)2(H2O)2]·4H2O}n, exhibits a two-dimensional layer-like structure in which the CoII ions exhibit two kinds of coordination geometries. One nearly octa­hedral CoII ion with crystallographic inversion symmetry is coordinated to six carboxyl­ate O atoms from four bridging 5-nitro­isophthalate (NIPH) ligands and two isonicotinate (IN) anions, while the other type of CoII ion binds with one N atom and one carboxyl­ate O atom from two IN anions, two carboxyl­ate O atoms from two different NIPH anions and one ligated water mol­ecule, displaying a distorted square-pyramidal coordination geometry. Three adjacent CoII ions are bridged by six carboxyl­ate groups from four NIPH ligands and two IN anions to form a linear trinuclear secondary building unit (SBU). Every trinuclear SBU is linked to its nearest neighbours in the ab plane, resulting in a two-dimensional layer-like structure perpendicular to the c axis. Along the a-axis direction neighbouring mol­ecules are connected through carboxyl­ate and pyridyl units of the IN anions, along the b axis through carboxyl­ate groups of the NIPH ligands. The H atoms of one free water mol­ecule are disordered in the crystal in a 1:1 ratio. Typical O—H⋯O hydrogen bonds are observed in the lattice, which include the following contacts: (a) between coordinated water mol­ecules and carboxyl­ate O atoms of the NIPH anions, (b) between lattice water mol­ecules and carboxyl­ate O atoms of the NIPH anions, and (c) between coordinated and lattice water mol­ecules. These inter­molecular hydrogen bonds connect the two-dimensional layers to form a three-dimensional supra­molecular structure.

Poly[[bis(acetonitrile-κN)bis[μ2-2,2′-(methylenedithio)bis(1,3,4-thiadiazole)-κ2N4:N4′]copper(II)] bis(perchlorate) acetonitrile solvate

In the title compound, {[Cu(C5H4N4S4)2(C2H3N)2](ClO4)2·C2H3N}n, the CuII atom occupies a crystallographic inversion centre and is six-coordinated by six N atoms of four symmetry-related 2,2′-(methyl­enedithio)bis­(1,3,4-thia­diazole) (L) ligands and two acetonitrile mol­ecules in a slightly distorted octa­hedral geometry. The ligand L adopts an N:N′-bidentate bridging mode in a trans configuration, bridging the Cu atoms via translation symmetry, forming a two-dimensional layer-like structure. The perchlorate ions serve as acceptors for inter­molecular C—H⋯O hydrogen bonds, which link the layers into a three-dimensional network. The ClO4 − anion is disordered with an occupation ratio of 0.658:0.342.

High-temperature superconductivity-ten years on

It is now some 10 years since the first high-temperature superconductors were discovered. This article describes the background leading to their discovery and the heady events of the first few years. The two-dimensional layer-like structure of these materials is emphasized. Their basic properties are described as well as our present theoretical understanding of the physical nature of their superconducting behaviour. A discussion is given of their applications and likely future developments.