Bright and Robust Phosphorescence Achieved by Non-Covalent Clipping.

Phosphorescent materials with bright emission in versatile media are important for their practical applications, which require to lower the susceptibility of triplet excitons to surroundings. Herein a non-covalent clipping strategy has been developed to attain this objective, by designing a tweezer receptor to encapsulate PtII -based triplet emitters through two-fold π-stacking interactions. The PtII emitters display robust phosphorescence by virtue of synergistic rigidifying and shielding effects, which are hardly influenced by emitter concentration, oxygen content, and solvent polarity changes. The phosphorescent colors are elaborately modulated by varying ligand substitutes on PtII emitters. Circularly polarized phosphorescence is further amplified for chiral PtII emitters, by taking advantage of dual phosphorescence and chirality enhancement upon non-covalent tweezer complexation. Overall, the clipping approach paves the way for the development of high-performance phosphorescent materials with bright emission, environmental robustness, and facile color tunability.

Stabilization of the Pentazolate Anion in a Zeolitic Architecture with Na20 N60 and Na24 N60 Nanocages.

The experimental detection and synthesis of pentazole (HN5 ) and its anion (cyclo-N5- ) have been actively pursued for the past hundred years. The synthesis of an aesthetic three-dimensional metal-pentazolate framework (denoted as MPF-1) is presented. It consists of sodium ions and cyclo-N5- anions in which the isolated cyclo-N5- anions are preternaturally stabilized in this inorganic open framework featuring two types of nanocages (Na20 N60 and Na24 N60 ) through strong metal coordination bonds. The compound MPF-1 is indefinitely stable at room temperature and exhibits high thermal stability relative to the reported cyclo-N5- salts. This finding offers a new approach to create metal-pentazolate frameworks (MPFs) and enables the future exploration of interesting pentazole chemistry and also related functional materials.

Does increasing pressure always accelerate the condensed material decay initiated through bimolecular reactions? A case of the thermal decomposition of TKX-50 at high pressures.

Performances and behaviors under high temperature-high pressure conditions are fundamentals for many materials. We study in the present work the pressure effect on the thermal decomposition of a new energetic ionic salt (EIS), TKX-50, by confining samples in a diamond anvil cell, using Raman spectroscopy measurements and ab initio simulations. As a result, we find a quadratic increase in decomposition temperature (Td) of TKX-50 with increasing pressure (P) (Td = 6.28P2 + 12.94P + 493.33, Td and P in K and GPa, respectively, and R2 = 0.995) and the decomposition under various pressures initiated by an intermolecular H-transfer reaction (a bimolecular reaction). Surprisingly, this finding is contrary to a general observation about the pressure effect on the decomposition of common energetic materials (EMs) composed of neutral molecules: increasing pressure will impede the decomposition if it starts from a bimolecular reaction. Our results also demonstrate that increasing pressure impedes the H-transfer via the enhanced long-range electrostatic repulsion of H+δH+δ of neighboring NH3OH+, with blue shifts of the intermolecular H-bonds. And the subsequent decomposition of the H-transferred intermediates is also suppressed, because the decomposition proceeds from a bimolecular reaction to a unimolecular one, which is generally prevented by compression. These two factors are the basic root for which the decomposition retarded with increasing pressure of TKX-50. Therefore, our finding breaks through the previously proposed concept that, for the condensed materials, increasing pressure will accelerate the thermal decomposition initiated by bimolecular reactions, and reveals a distinct mechanism of the pressure effect on thermal decomposition. That is to say, increasing pressure does not always promote the condensed material decay initiated through bimolecular reactions. Moreover, such a mechanism may be feasible to other EISs due to the similar intermolecular interactions.

Facile fabrication of porous CL-20 for low sensitivity high explosives.

A facile solvent/non-solvent co-crystallization technology is applied to fabricate porous CL-20, which exhibits interesting morphologies and low sensitivity with ß-cyclodextrin as a crystal modifier.

CNT@Fe3O4@C coaxial nanocables: one-pot, additive-free synthesis and remarkable lithium storage behavior.

By using carbon nanotubes (CNTs) as a shape template and glucose as a carbon precursor and structure-directing agent, CNT@Fe3O4@C porous core/sheath coaxial nanocables have been synthesized by a simple one-pot hydrothermal process. Neither a surfactant/ligand nor a CNT pretreatment is needed in the synthetic process. A possible growth mechanism governing the formation of this nanostructure is discussed. When used as an anode material of lithium-ion batteries, the CNT@Fe3O4@C nanocables show significantly enhanced cycling performance, high rate capability, and high Coulombic efficiency compared with pure Fe2O3 particles and Fe3O4/CNT composites. The CNT@Fe3O4@C nanocables deliver a reversible capacity of 1290 mA h g(-1) after 80 cycles at a current density of 200 mA g(-1), and maintain a reversible capacity of 690 mA h g(-1) after 200 cycles at a current density of 2000 mA g(-1). The improved lithium storage behavior can be attributed to the synergistic effect of the high electronic conductivity support and the inner CNT/outer carbon buffering matrix.

Interfacial engineered RDX/TATB energetic co-particles for enhanced safety performance and thermal stability.

1,3,5-Trinitro-1,3,5-triazinane (RDX) has attracted considerable attention in energy-related fields. However, the safety performance of RDX needs to be improved in terms of various external stimuli. Herein, such issues of RDX could be well balanced through hydrothermal assembly with the assistance of insensitive 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) in a low content of 10 wt% (named RT co-particles). The TATB spread outside and were embedded inside of the resultant RT co-particles, which were examined via X-ray computed tomography and a three-dimensional laser scanning confocal microscope. As a result, the impact safety performance of RT co-particles could be drastically enhanced to 17.5 J by the TATB lubricant effect, demonstrating over twice the value of that of raw RDX (6 J) and mixtures (7 J). Moreover, an interfacial reconstruction between RDX and TATB was witnessed due to the strong interfacial interaction, as examined by theoretical simulation. Inspired by this, a delayed exothermic decomposition temperature of RT co-particles (244.4 °C) has been achieved when compared with that of RDX (241.4 °C). As demonstrated, an energetic co-particle strategy may provide an effective pathway toward remarkably improved mechanical and thermal safety performance, shedding light on other energetic materials.

Host-guest energetic nanocomposites based on self-assembly of multi-nitro organic molecules in nanochannels of mesoporous materials.

Host-guest energetic nanocomposites have been synthesized by self-assembly of the high energy density compound HNIW in nanometer-scale channels of an ordered mesoporous material SBA-15. The complete impregnation of HNIW can be achieved in acetone solvent at ambient temperature, and the maximum amount was around 70 wt%. Structural characterizations were systematically provided by XRD, TEM, N(2) adsorption, TG, (13)C solid-state NMR and FT-IR. The tendency of multi-nitro organic molecules to self-assemble when the solvent evaporated has been described. Hydrogen bond interactions were considered as the main driving force, so the choices of matched host matrix and guest organic compounds were pivotal for implementing this process. The thermal properties of nanocomposites were measured by DSC analysis. Compared with pure HNIW and a physical mixture, the decomposition peak temperature of the confined crystals decreased about 11 °C, while the total amount of heat released slightly increased. This strategy can also be expanded to other similar host-guest systems.

Preparation and characterization of nano amitriptyline hydrochloride particles by spray freeze drying.

Aim: To investigate the enhancement of bioavailability by the usage of drug nanoparticles for increasing the efficacy of antidepressant therapeutic value. Materials & methods: Nano-amitriptyline HCI (AMT·HCl) particles were successfully prepared via a simple spray freeze drying (SFD) method. Results: The as-prepared nanoparticles are amorphous instead of crystalline. The mean size of AMT·HCl nanoparticles is 90 nm. In in vitro evaluation, AMT·HCl nanoparticles have greatly improved the dissolution compared with pure bulk materials, which have potential for enhancing human bioavailability and diminishing toxic effect. A nanoparticle formation mechanism was also proposed. Conclusion: These findings promote the development of antidepressant therapeutic evaluation based on the usage of AMT·HCl nanoparticles by SFD method and indicate that SFD is an alternative for a range of nanoparticle preparation in industrial pharmacy.

The Safety Properties of a Potential Kind of Novel Green Primary Explosive: Al/Fe2O3/RDX Nanocomposite.

Green primary explosives have gained wide attention for environmental protection. A potential novel lead-free primary explosive, Al/Fe2O3/RDX hybrid nanocomposite was prepared by ultrasonic mixing, and its safety properties are discussed in detail. Results showed that their sensitivity and safety properties were a function of the specific surface area and proportions of their ingredients. Their impact sensitivity fell and their static discharge, flame, and hot bridge wire sensitivities rose as the specific surface area of nano-Fe2O3 increased. As the amount of Al/Fe2O3 nanothermite was increased, its impact sensitivity fell and its flame sensitivity rose; their static discharge and hot bridge wire sensitivities, however, followed an inverted "U" type change trend and were determined by both the particle size of the ingredients and the resistance of the nanocomposite. Their firing properties in an electric detonator depended on the proportion of the constituents. Thus, green nanoscale primary explosives are appropriate for a range of initiatory applications and can be created by adjusting their specific surface area and the amount of their constituents.

A simple and versatile strategy for taming FOX-7.

A novel derivatization strategy was developed for the exciting reactive chemistry of FOX-7. The as-synthesized FOX-7-derived polynitro compounds exhibited high crystal densities, excellent detonation performances, and good impact and friction sensitivities. This study opens a new path for the ever-expanding chemistry of FOX-7.

A promising high-energy-density material.

High-energy density materials represent a significant class of advanced materials and have been the focus of energetic materials community. The main challenge in this field is to design and synthesize energetic compounds with a highest possible density and a maximum possible chemical stability. Here we show an energetic compound, [2,2'-bi(1,3,4-oxadiazole)]-5,5'-dinitramide, is synthesized through a two-step reaction from commercially available reagents. It exhibits a surprisingly high density (1.99 g cm-3 at 298 K), poor solubility in water and most organic solvents, decent thermal stability, a positive heat of formation and excellent detonation properties. The solid-state structural features of the synthesized compound are also investigated via X-ray diffraction and several theoretical techniques. The energetic and sensitivity properties of the explosive compound are similar to those of 2, 4, 6, 8, 10, 12-(hexanitrohexaaza)cyclododecane (CL-20), and the developed compound shows a great promise for potential applications as a high-energy density material.High energy density materials are of interest, but density is the limiting factor for many organic compounds. Here the authors show the formation of a high density energetic compound from a two-step reaction between commercially available compounds that exhibit good heat thermal stability and detonation properties.

Cyanotetrazolylborohydride (CTB) anion-based ionic liquids with low viscosity and high energy capacity as ultrafast-igniting hypergolic fuels.

A series of hypergolic cyanotetrazolylborohydride (CTB) anion-based ionic liquids have been synthesized by a straightforward N-hydroboration of tetrazole followed by a salt metathesis reaction, which exhibited remarkably low viscosity (<20 mPa s), high density (often >1.1 g cm-3), and ultra-short ignition delay time (as short as 1.4 ms) upon contact with white fuming nitric acid (WFNA).

Pentazadiene: a high-nitrogen linkage in energetic materials.

A novel N5-linear energetic moiety of pentazadiene has been constructed for the first time from a triazene precursor. Thus, a series of 1,3,5-tri(tetrazol-5-yl)pentaza-1,4-dienes have been synthesized in moderate to high yields by treatment of 1,3-bis(tetr-azol-5-yl)triazenes with 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDCI) under mild conditions. All compounds were fully characterized using IR spectroscopy, 1H and 13C NMR spectroscopy, HRMS, and differential scanning calorimetry (DSC), and, in the case of 1,3,5-tri(2-methyltetrazol-5-yl)pentaza-1,4-diene (2a) together with single crystal X-ray structuring and 15N NMR spectroscopy. Calculations predict that 2a has a heat of formation of 1699.2 kJ mol-1.

Study of Six Green Insensitive High Energetic Coordination Polymers Based on Alkali/Alkali-Earth Metals and 4,5-Bis(tetrazol-5-yl)-2 H-1,2,3-triazole.

Constructing insensitive high-performance energetic coordination polymers (ECPs) with alkali/alkali-earth metal ions and a nitrogen-rich organic backbone has been proved to be a feasible strategy in this work. Six diverse dimensional novel ECPs (compounds 1-6) were successfully synthesized from NaI , CsI , CaII , SrII , BaII ions and a nitrogen-rich triheterocyclic 4,5-bis(tetrazol-5-yl)-2 H-1,2,3-triazole (H3 BTT). All compounds show outstanding stability and low sensitivity, the thermal stability of these ECPs are significantly improved as the structural reinforcement increases from 1D to 3D, in which the decomposition temperature of 3D BaII based compound 6 is as high as 397 °C. Long-term storage experiments show that compounds 5 and 6 are stable enough at high temperature. Moreover, the six compounds hold considerable detonation performances, in which CaII based compound 5 possesses the detonation velocity of 9.12 km s-1 , along with the detonation pressure of 34.51 GPa, exceeding those of most energetic coordination polymers. Burn tests further certify that the six compounds can be versatile pyrotechnics.

[Synthesis and spectral study of molybdovanadophosphoric heteropoly compound containing glycine with tri-vanadium-substituted Dawson structure].

A new molybdovanadophosphoric heteropoly compound containing glycine with tri-vanadium-substituted Dawson structure, namely C2 H14O64P2Mo1515V3 x 5H2O was synthesized and structurally characterized by elemental analysis, including IR spectra, X-ray and TGA powder diffraction. The median lethal dose (LD50) was 3 798. 83 mg x kg(-1), and the range of 95% confidence limit was 2 976. 81-4 847. 85 mg x kg(-1). According to the study, this new compound may be regarded as a low toxic compound.

Low Temperature Vacuum Synthesis of Triangular CoO Nanocrystal/Graphene Nanosheets Composites with Enhanced Lithium Storage Capacity.

CoO nanocrystal/graphene nanosheets (GNS) composites, consisting of a triangular CoO nanocrystal of 2~20 nm on the surface of GNS, are synthesized by a mild synthetic method. First, cobalt acetate tetrahydrate is recrystallized in the alcohol solution at a low temperature. Then, graphene oxide mixed with cobalt-precursor followed by high vacuum annealing to form the CoO nanocrystal/GNS composites. The CoO nanocrystal/GNS composites exhibit a high reversible capacity of 1481.9 m Ah g(-1) after 30 cycles with a high Coulombic efficiency of over 96% when used as anode materials for lithium ion battery. The excellent electrochemical performances may be attributed to the special structure of the composites. The well-dispersed triangular CoO nanocrystal on the substrate of conductive graphene can not only have a shorter diffusion length for lithium ions, better stress accommodation capability during the charge-discharge processes and more accessible active sites for lithium-ion storage and electrolyte wetting, but also possess a good conductive network, which can significantly improve the whole electrochemical performance.

Ultrasonic approach to the synthesis of HMX@TATB core-shell microparticles with improved mechanical sensitivity.

To improve the safety of sensitive explosive HMX while maintaining explosion performance, a moderately powerful but insensitive explosive TATB was used to coat HMX microparticles via a facile ultrasonic method. By using Estane as surface modifier and nano-sized TATB as the shell layer, the HMX@TATB core-shell microparticles with a monodisperse size and compact shell structure were successfully constructed. Both scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) results confirmed the formation of perfect core-shell structured composites. Based on a systematic and comparative study of the effect of experimental conditions, a possible formation mechanism of core-shell structure was proposed in detail. Moreover, the perfect core-shell HMX@TATB microparticles exhibited a unique thermal behavior and significantly improved mechanical sensitivity compared with that of the physical mixture.

Mesoporous CNT@TiO2-C nanocable with extremely durable high rate capability for lithium-ion battery anodes.

A well-designed nanostructure CNT@TiO2-C with fine anatase TiO2 particle (< 8 nm), good electronic conducting network (inner CNT core and outer carbon layer), and mesoporous structure was prepared by a simple and green one-pot hydrothermal reaction. The utilization of glucose in the hydrothermal process not only solves the interfacial incompatibility between CNTs and titanate sol and controls the nucleation and growth of TiO2 particles, but also introduces a uniform, glucose-derived, carbon-layer on the TiO2 particles. The nanosized TiO2 particle, high conducting network, and interconnected nanopores of the CNT@TiO2-C nanocable greatly improve its electrochemical performances, especially rate capability. The CNT@TiO2-C nanocables show remarkable rate capability with reversible charge capacity of 297, 240, 210,178 and 127 mAh g(-1) at 1C, 5C, 10C, 20C and 50C, respectively, as well as excellent high rate cycling stability with capacity retention of 87% after 2000 cycles at 50C.

Needle-like Co3O4 anchored on the graphene with enhanced electrochemical performance for aqueous supercapacitors.

We synthesized the needle-like cobalt oxide/graphene composites with different mass ratios, which are composed of cobalt oxide (Co3O4 or CoO) needle homogeneously anchored on graphene nanosheets as the template, by a facile hydrothermal method. Without the graphene as the template, the cobalt precursor tends to group into urchin-like spheres formed by many fine needles. When used as electrode materials of aqueous supercapacitor, the composites of the needle-like Co3O4/graphene (the mass ratio of graphene oxide(GO) and Co(NO3)2·6H2O is 1:5) exhibit a high specific capacitance of 157.7 F g(-1) at a current density of 0.1 A g(-1) in 2 mol L(-1) KOH aqueous solution as well as good rate capability. Meanwhile, the capacitance retention keeps about 70% of the initial value after 4000 cycles at a current density of 0.2 A g(-1). The enhancement of excellent electrochemical performances may be attributed to the synergistic effect of graphene and cobalt oxide components in the unique multiscale structure of the composites.

A novel preparation method for drug nanocrystals and characterization by ultrasonic spray-assisted electrostatic adsorption.

PURPOSE: The purpose of this study was to develop a novel and continuous method for preparing a nanosized particle of drug crystals and to characterize its properties. MATERIALS AND METHODS: A new apparatus was introduced to crystallize nanosized drug crystals of amitriptyline hydrochloride as a model drug. The samples were prepared in the pure state by ultrasonic spray, and elaborated deposition was completed via electrostatic adsorption. Scanning electron microscopy, X-ray powder diffraction, and atomic force microscopy were used to characterize the size of the particles; this was subsequently followed by differential scanning calorimetry. RESULTS AND DISCUSSION: Nanoparticles of drug crystals were successfully prepared. The size of the drug crystals ranged from 20 nm to 400 nm; the particle size of amitriptyline hydrochloride was approximately 71 nm. The particles were spherical and rectangular in shape. Moreover, the melting point of the nanoparticles decreased from 198.2°C to 196.3°C when compared to raw particle crystals. Furthermore, the agglomeration effect was also attenuated as a result of electrostatic repulsion among each particle when absorbed, and depositing on the inner wall of the gathering unit occurred under the electrostatic effect. CONCLUSION: Ultrasonic spray-assisted electrostatic adsorption is a very effective and continuous method to produce drug nanocrystals. This method can be applied to poorly water-soluble drugs, and it can also be a very effective alternative for industrial production. Once the working parameters are given, drug nanocrystals will be produced continuously.