The formation of ReS(2) inorganic fullerene-like structures containing Re(4) parallelogram units and metal-metal bonds

The encapsulation of ReO(x) within ReS(2) inorganic fullerene-like cages is described for the first time. The encapsulate was prepared by the sulfidization of both hand-milled and ball-milled samples of ReO(2); partial conversion of the oxide to the sulfide was achieved with the degree of sulfidization depending on the exposure to the sulfidizing agent, H(2)S.     

Fabrication of Transparent,Tough, and Conductive Shape‐Memory Polyurethane Films by Incorporating a Small Amount of High‐Quality Graphene

We report a mechanically strong, electrically and thermally conductive, and optically transparent shape‐memory polyurethane composite which was fabricated by introducing a small amount (0.1 wt%) of high‐quality graphene as a filler. Geometrically large (≈4.6 μm²), but highly crystallized few‐layer graphenes, verified by Raman spectroscopy and transmission electron microscopy, were prepared by the sonication of expandable graphite in an organic solvent. Oxygen‐ containing functional groups at the edge plane of graphene were crucial for an effective stress transfer from the graphene to polyurethane. Homogeneously dispersed few‐layered graphene enabled polyurethane to have a high shape recovery force of 1.8 MPa cm⁻³. Graphene, which is intrinsically stretchable up to 10%, will enable high‐performance composites to be fabricated at relatively low cost and we thus envisage that such composites may replace carbon nanotubes for various applications in the near future.     

Comparison of three different phosphorescent methodologies in solution for the analysis of naphazoline in pharmaceutical preparations

We present results from a comparative study of three proposed phosphorimetric methods for determination of naphazoline (NPZ) in solution. The first method is based on use of micelles to stabilize phosphorescence signals in solutions at room temperature (MS-RTP). The second is based on the use of a heavy atom salt and sodium sulfite as an oxygen scavenger to obtain room-temperature phosphorescence (HAI-RTP) in solution. The last method employs an optical sensor for NPZ based on the phosphorescent properties of the analyte on a solid sensor phase. The aim of this work was to compare time consumption, simplicity, sensitivity, selectivity, detection, and quantification limits for use of these three phosphorimetric methods to determine naphazoline in pharmaceutical preparations. The most simple, sensitive, and reproducible of the three methods for naphazoline analysis is the HAI-RTP method. Detection limits are 4.9, 1.7, and 9.4 ng mL^–1, respectively, for the MS-RTP, HAI-RTP, and optosensor methods.     

Low‐Temperature Solution Synthesis of Few‐Layer 1T ′‐MoTe2 Nanostructures Exhibiting Lattice Compression

Molybdenum ditelluride, MoTe₂, is emerging as an important transition‐metal dichalcogenide (TMD) material because of its favorable properties relative to other TMDs. The 1T ′ polymorph of MoTe₂ is particularly interesting because it is semimetallic with bands that overlap near the Fermi level, but semiconducting 2H‐MoTe₂ is more stable and therefore more accessible synthetically. Metastable 1T ′‐MoTe₂ forms directly in solution at 300 °C as uniform colloidal nanostructures that consist of few‐layer nanosheets, which appear to exhibit an approx. 1 % lateral lattice compression relative to the bulk analogue. Density functional theory calculations suggest that small grain sizes and polycrystallinity stabilize the 1T ′ phase in the MoTe₂ nanostructures and suppress its transformation back to the more stable 2H polymorph through grain boundary pinning. Raman spectra of the 1T ′‐MoTe₂ nanostructures exhibit a laser energy dependence, which could be caused by electronic transitions.     

From C60 to negatively curved graphite

With the discovery of C₆₀ or Buckminsterfullerene a new kind of materials with important applications has emerged. Orginary graphite is composed of flat hexagonal layers. If pentagons are introduced, the graphite sheets start to curve in such a way that 12 pentagons are needed to close the structure and form fullerenes. Starting from the properties of 2D manifolds or surfaces, we have found that by introducing rings with more than six carbon atoms, periodic structures with the same topology as triply periodic minimal surfaces, we have found that by introducing rings with more than six carbon atoms, periodic structures with the same topology as triply periodic minimal surfacds can be constructed. The D, G, P, H and I-WP type surfaces have been obtained from graphite-like sheets. In terms of the Gaussian curvature K, ordinary and cylindrical graphite have K=O, Fullerenes have K>O and triply periodic surfaces decorated with graphite have K60. Geometric and physical properties of hypothetical periodic graphite foams will be discussed.     

Ultra‐light carbon nanotube sponge as an efficient electromagnetic shielding material in the GHz range

CVD synthesised CNT flexible sponge with density lower than 0.02 g cm^–3 has been found to serve as high performance EMI shielding material without the aid of any polymer infiltration or impregnation. Due to its extreme lightweight, the specific SE of the CNT‐sponge was found to be as high as 1100 dB cm³ g^–1, having a total SE above 20 dB in the whole 1–18 GHz range, and being able to shield by absorption. The material is the best of our knowledge this specific SE value appears to be the highest reported hitherto. Improved EM absorbers should fulfil the synergic requirements of being low reflective and highly absorptive. In our CNT‐sponges this condition is not satisfied because, although their net absorption ability is strongly remarkable, their high electrical conductivity favours the wave to be reflected at the input interface. Therefore, this sponge material would have a great potential for microwave‐frequency applications that need negligible reflection and great absorption when combined in a multilayered structure that could prevent the wave to be reflected at the input interface. (© 2014 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Sodium chloride-catalyzed oxidation of multiwalled carbon nanotubes for environmental benefit

A sodium chloride (NaCl) catalyst (0.1 w/w %) lowers the oxidation temperature of graphitized multiwalled carbon nanotubes: MWCNT-20 (diameter: 20-70 nm) and MWCNT-80 (diameter: 80-150 nm). The analysis of the reaction kinetics indicates that the oxidation of MWCNT-20 and MWCNT-80 mixed with no NaCl exhibits single reaction processes with activation energies of E(a) = 159 and 152 kJ mol(-1), respectively. The oxidation reaction in the presence of NaCl is shown to consist of two different reaction processes, that is, a first reaction and a second reaction process. The first reaction process is dominant at a low temperature of around 600 degrees C, while the second reaction process becomes more dominant than the first one in a higher temperature region. The activation energies of the first reaction processes (MWCNT-20: E(a1) = 35.7 kJ mol(-1); MWCNT-80: E(a1) = 43.5 kJ mol(-1)) are much smaller than those of the second reaction processes (MWCNT-20: E(a2) = 170 kJ mol(-1); MWCNT-80: E(a2) = 171 kJ mol(-1)). The comparison of the kinetic parameters and the results of the spectroscopic and microscopic analyses imply that the lowering of the oxidation temperature in the presence of NaCl results from the introduction of disorder into the graphitized MWCNTs (during the first reaction process), thus increasing the facility of the oxidation reaction of the disorder-induced nanotubes (in the second reaction process). It is found that the larger nanopits and cracks on the outer graphitic layers are caused by the catalytic effect of NaCl. Therefore, the NaCl-mixed samples showed more rapid and stronger oxidation compared with that of the nonmixed samples at the same residual quantity.