Interplay between structure and magnetism in Mo12S9I9Mo_{12} S_9 I_9 nanowires

We investigate the equilibrium geometry and electronic structure of Mo$_{12}$S$_{9}$I$_{9}$ nanowires using ab initio Density Functional calculations. The skeleton of these unusually stable nanowires consists of rigid, functionalized Mo octahedra, connected by flexible, bi-stable sulphur bridges. This structural flexibility translates into a capability to stretch up to approximate 20% at almost no energy cost. The nanowires change from conductors to narrow-gap magnetic semiconductors in one of their structural isomers.Comment: 4 pages with PRL standards and 3 figure

New inorganic nanotube polymer nanocomposites: Improved thermal, mechanical and tribological properties in isotactic polypropylene incorporating INT-MoS2.

Environmentally friendly molybdenum disulfide (INT-MoS2) inorganic nanotubes were introduced into an isotactic polypropylene (iPP) polymer matrix to generate novel nanocomposite materials through an advantageous melt-processing route. The effects of INT-MoS2 content on the thermal, mechanical and tribological properties were investigated. The incorporation of INT-MoS2 generates notable performance enhancements through reinforcement effects, highly efficient nucleation activity and excellent lubricating ability in comparison with other nanoparticle fillers such as nanoclays, carbon nanotubes, silicon nitrides and halloysite nanotubes. It was shown that these INT-MoS2 nanocomposites can provide an effective balance between performance, cost effectiveness and processability, and should be of some interest in the area of multifunctional polymer nanocomposite materials

Excitonic emission in van-der-Waals nanotubes of transition metal dichalcogenides

Nanotubes (NTs) of transition metal dichalcogenides (TMDs), such as MoS2 and WS2, were first synthesized more than a quarter of a century ago; nevertheless, many of their properties have so far remained basically unknown. This review presents the state of the art in the knowledge of the optical properties of TMD NTs. We first evaluate general properties of multilayered TMD crystals, and analyze available data on electronic band structure and optical properties of related NTs. Then, the technology for the formation and the structural characteristics of TMD NTs are represented, focusing on the structures synthesized by chemical transport reaction. The core of this work is the presentation of the ability of TMD NTs to emit bright photoluminescence (PL), which has been discovered recently. By means of micro-PL spectroscopy of individual tubes we show that excitonic transitions relevant to both direct and indirect band gaps contribute to the emission spectra of the NTs despite the presence of dozens of monolayers in their walls. We highlight the performance of the tubes as efficient optical resonators, whose confined optical modes strongly affect the emission bands. Finally, a brief conclusion is presented, along with an outlook of the future studies of this novel member of the family of radiative NTs, which have unique potential for different nanophotonics applications.Comment: 38 pages, 11 fugures, 106 reference

Nuclear factor-κB inhibition provides additional protection against ischaemia/reperfusion injury in delayed sevoflurane preconditioning

Background and objectiveSevoflurane anaesthetic preconditioning (SPC) has been shown to limit nuclear factor-[kappa]B (NF-[kappa]B) activation and the production of inflammatory cytokines during myocardial ischaemia/reperfusion (I/R). Similarly, pharmacological inhibition of NF-[kappa]B using parthenolide is effective in limiting I/R injury. We, therefore, postulated that the protective effect of delayed SPC would be enhanced by pharmacological NF-[kappa]B inhibition during I/R.MethodsHearts from 2-month-old male Fisher 344 rats were exposed to 25 min global ischaemia followed by 60 min reperfusion. Rats were divided into four groups prior to I/R: control group; parthenolide group, treated with the I[kappa]B kinase inhibitor parthenolide intraperitoneally 10 min prior to heart isolation; SPC group, treated for 60 min with sevoflurane 48 h prior to heart isolation; and SPC + parthenolide group, treated with SPC for 1 h followed by parthenolide 48 h later. Infarct area, left ventricular function and Ca2+(i) were measured after I/R.ResultsDelayed SPC + parthenolide resulted in greater protection than either intervention alone, resulting in a significant reduction in infarct area and left ventricular developed pressure (mmHg; 84 +/- 19 compared with 15 +/- 14 in control hearts; P = 0.007). Left ventricular end-diastolic pressure also remained close to baseline values (9 +/- 2 mmHg, P = 0.02) during I/R, and the increase in Ca2+(i) seen with I/R was significantly blunted (P = 0.005).ConclusionSPC followed by parthenolide provides a significant protection from I/R injury in this model. As each intervention alone limits NF-[kappa]B activation with I/R, these data are consistent with additive effects of these dual modalities in limiting I/R injury due to NF-[kappa]B activation

The MoS2 Nanotubes with Defect-Controlled Electric Properties

We describe a two-step synthesis of pure multiwall MoS2 nanotubes with a high degree of homogeneity in size. The Mo6S4I6 nanowires grown directly from elements under temperature gradient conditions in hedgehog-like assemblies were used as precursor material. Transformation in argon-H2S/H2 mixture leads to the MoS2 nanotubes still grouped in hedgehog-like morphology. The described method enables a large-scale production of MoS2 nanotubes and their size control. X-ray diffraction, optical absorption and Raman spectroscopy, scanning electron microscopy with wave dispersive analysis, and transmission electron microscopy were used to characterize the starting Mo6S4I6 nanowires and the MoS2 nanotubes. The unit cell parameters of the Mo6S4I6 phase are proposed. Blue shift in optical absorbance and metallic behavior of MoS2 nanotubes in two-probe measurement are explained by a high defect concentration

Friction on a single MoS2 nanotube

Friction was measured on a single molybdenum disulfide (MoS2) nanotube and on a single MoS2 nano-onion for the first time. We used atomic force microscopy (AFM) operating in ultra-high vacuum at room temperature. The average coefficient of friction between the AFM tip and MoS2 nanotubes was found considerably below the corresponding values obtained from an air-cleaved MoS2 single crystal or graphite. We revealed a nontrivial dependency of friction on interaction strength between the nanotube and the underlying substrate. Friction on detached or weakly supported nanotubes by the substrate was several times smaller (0.023 ± 0.005) than that on well-supported nanotubes (0.08 ± 0.02). We propose an explanation of a quarter of a century old phenomena of higher friction found for intracrystalline (0.06) than for intercrystalline slip (0.025) in MoS2. Friction test on a single MoS2 nano-onion revealed a combined gliding-rolling process