Development and uniqueness test of highly selective atomic topological indices based on the number of attached hydrogen atoms.

On the basis of the atomic graph-theoretical index - aEAID (atomic Extended Adjacency matrix IDentification) and molecular adjacent topological index - ATID (Adjacent Topological IDentification) suggested by one of the authors (Zhang Q), a highly selective atomic topological index - aATID (atomic Adjacent Topological IDentification) index was suggested to identify the equivalent atoms in this study. The aATID index of an atom was derived from the number of the attached hydrogen atoms of the atom but omitting bond types. In this case, the suggested index can be used to identify equivalent atoms in chemistry but perhaps not equivalent in the molecular graph. To test the uniqueness of aATID indices, the virtual atomic data sets were derived from alkanes containing 15-20 carbon atoms and the isomers of Octogen, as well as a real data set was derived from the NCI database. Only four pairs of atoms from alkanes containing 20 carbons can't be discriminated by aATID, that is, four pairs of degenerates were found for this data set. To solve this problem, the aATID index was modified by introducing distance factors between atoms, and the 2-aATID index was suggested. Its uniqueness was examined by 5,939,902 atoms derived from alkanes containing 20 carbons and further 16,166,984 atoms from alkanes of 21 carbons, and no degenerates were found. In addition, another large real data set of 16,650,688 atoms derived from the PubChem database was also used to test the uniqueness of both aATID and 2-aATID. As a result, each atom was successfully discriminated by any of the two indices. Finally, the suggested aATID index was applied to the identification of duplicate atoms as data pretreatment for QSPR (Quantitative Structure-Property Relationships) studies.

Study on Mechanical Properties of Polyurethane Cross-Linked P(E-co-T)/PEG Blended Polyether Elastomer.

To improve the mechanical properties of polyurethane cross-linked poly (ethylene oxide-co-tetrahydrofuran) (P(E-co-T)) elastomers at room temperature, using poly (ethylene oxide-co-tetrahydrofuran) and high-molecular-weight polyethylene glycol (PEG) as raw materials and polyisocyanate N100 as curing agent, a series of polyurethane cross-linked blended polyether elastomers were prepared by changing the elastomer-curing parameter R value (n(-NCO)/n(-OH)) and P(E-co-T)/PEG ratio. Equilibrium swelling measurements showed that the chemical cross-linkage of the elastomers tended to decrease with the decreasing R value, the average molecular weight (Mc) of the network chain increased, and the density of the network chain (N0) decreased. Wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC) tests showed that PEG chain segments within the elastomers crystallized at room temperature, while the crystallinity increased with decreasing R value and increasing PEG content. The mechanical property tests showed that the elongation at break tended to decrease with increasing R value; the tensile strength first increased and then decreased. At R value 0.9, the elastomer presented good comprehensive mechanical properties. In addition, the mechanical properties of polyurethane cross-linked P(E-co-T)/PEG blended polyether elastomer showed an increasing trend with the increase in PEG content when the curing parameter of 0.9 remained unchanged.

Bioinspired Supramolecular Nanotoroids with Aggregation-Induced Emission Characteristics.

Supramolecular toroids have attracted continuous attention because of their fascinating topological structure and important role in biological systems. However, it still remains a great challenge to construct supramolecular functional toroids and clarify the formation mechanism. Herein, we develop a strategy to prepare supramolecular helical fluorescent nanotoroids by cooperative self-assembly of an amino acid and a dendritic amphiphile (AIE-den-1) with aggregation-induced emission characteristics. Mechanistic investigation on the basis of fluorescence and circular dichroism analyses suggests that the toroid formation can be driven by the interactions of AIE-den-1 with amino acid and goes through a topological morphology transformation from nanofibers to left-handed nanotoroids by means of a twist-fused-loop process.

Synthesis of two novel neutral polymeric bonding agents to enhance the mechanical properties of composite solid propellants.

Currently, only a few bonding agents can be utilized efficiently in nitramine filler material-based solid rocket energetic binder systems. Herein, we demonstrate the synthesis and specific characterization of two kinds of neutral polymeric bonding agents (NPBA-1 and NPBA-2) and their application in composite propellants consisting of the nitramine octogen (HMX) and glycidyl azide polymer (GAP). The as-obtained NPBAs were well-coated on the surface of HMX and RDX due to their functionalized groups, and they significantly affected the viscosity of the uncured propellant mixtures and possessed obviously enhanced mechanical properties in the cured AP/HMX/GAP propellant mixtures, even at low concentrations (down to 0.001 wt% of the whole propellant). In addition, because of the existence of an epoxy group and no hydroxyl functionalities, NPBA-2 exhibited improved mechanical strength and glass transition temperature as compared to NPBA-1, which has plenty of reactive hydroxyl groups. The as-synthesized epoxy-modified NPBAs are essential for obtaining NEPE propellants with high bonding and mechanical properties.

Facile Solution Process of VO2 Film with Mesh Morphology for Enhanced Thermochromic Performance.

The fabrication and applications of VO2 film continue to be of considerable interest due to their good thermochromic performance for smart windows. However, low visible transmittance (Tlum) and solar modulation efficiency (∆Tsol) impede the application of VO2 film, and they are difficult to improve simultaneously. Here, a facile zinc solution process was employed to control the surface structure of dense VO2 film and the processed VO2 film showed enhanced visible transmittance and solar modulation efficiency, which were increased by 7.5% and 9.5%, respectively, compared with unprocessed VO2 film. This process facilitated the growth of layered basic zinc acetate (LBZA) nanosheets to form mesh morphology on the surface of VO2 film, where LBZA nanosheets enhance the visible transmittance as an anti-reflection film. The mesh morphology also strengthened the solar modulation efficiency with small caves between nanosheets by multiplying the times of reflection. By increasing the zinc concentration from 0.05 mol/L to 0.20 mol/L, there were more LBZA nanosheets on the surface of the VO2 film, leading to an increase in the solar/near-infrared modulation efficiency. Therefore, this work revealed the relationship between the solution process, surface structure, and optical properties, and thus can provide a new method to prepare VO2 composite film with desirable performance for applications in smart windows.

Acid Solution Processed VO2-Based Composite Films with Enhanced Thermochromic Properties for Smart Windows.

As a typical thermochromic material, VO2 coatings can be applied to smart windows by modulating the transmission of near infrared (NIR) light via phase transition. However, the inherent undesirable luminous transmittance (Tlum) and solar modulation efficiency (ΔTsol) of pure VO2 impede its practical application. In order to solve this problem, the porous VO2 based composite film was prepared by magnetron sputtering and subsequent acid solution process with Zn2V2O7 particles used as a sacrificial template to create pores, which showed excellent Tlum (72.1%) and enhanced ΔTsol (10.7%) compared with pure VO2 film. It was demonstrated that the porous structure of the film caused by acid solution process could improve the Tlum obviously and the isolated VO2 nanoparticles presented strong localized surface plasmon resonance (LSPR) effects to enhance the ΔTsol. Therefore, this method will provide a facile way to prepare VO2 based films with excellent thermochromic performance and thus promote the application of the VO2 based films in smart windows.

Novel saprobic Hermatomyces species (Hermatomycetaceae, Pleosporales) from China (Yunnan Province) and Thailand.

During our survey of the diversity of woody litter fungi in China and Thailand, three Hermatomyces species were collected from dead woody twigs of Dipterocarpus sp. (Dipterocarpaceae) and Ehretiaacuminata (Boraginaceae). Both morphology and multigene analyses revealed two taxa as new species (Hermatomycesturbinatus and H.jinghaensis) and the remaining collections as new records of H.sphaericus. Hermatomycesturbinatus is characterized by 1) dimorphic conidia, having circular to oval lenticular conidia and 2) turbinate conidia consisting of two columns with two septa composed of 2-3 cells in each column. Hermatomycesjinghaensis is characterized by dimorphic conidia, having circular to oval lenticular conidia and clavate or subcylindrical to cylindrical conidia and consisting of one or two columns with 6-8 cells in each column. Phylogenetic analyses of combined LSU, ITS, tub2, tef1-α and rpb2 sequence data supports the placement of these new taxa within Hermatomycetaceae with high statistical support.

Synthesis and Stability of Hydrogen Storage Material Aluminum Hydride.

Aluminum hydride (AlH3) is a binary metal hydride with a mass hydrogen density of more than 10% and bulk hydrogen density of 148 kg H2/m3. Pure aluminum hydride can easily release hydrogen when heated. Due to the high hydrogen density and low decomposition temperature, aluminum hydride has become one of the most promising hydrogen storage media for wide applications, including fuel cell, reducing agents, and rocket fuel additive. Compared with aluminum powder, AlH3 has a higher energy density, which can significantly reduce the ignition temperature and produce H2 fuel in the combustion process, thus reducing the relative mass of combustion products. In this paper, the research progress about the structure, synthesis, and stability of aluminum hydride in recent decades is reviewed. We also put forward the challenges for application of AlH3 and outlook the possible opportunity for AlH3 in the future.

Green preparation of high-quality and low-cost graphene from discarded polyethylene plastic bags.

A facile method was used to prepare graphene from discarded polyethylene plastic bags in our work. In order to make high-quality graphene, PE plastic bags were ultrasonically cleaned, ball milled and microwave sintered successively. The height of the 2D band was 1.3 times that of the G band, which reveals that the layer number of as-prepared graphene was 1-2. The atomic ratio of C and O for graphene was more than 54, which indicates that it mainly consists of carbon. The size of graphene was within 4-10 µm. Bi-layer sheets were inevitably observed through high resolution imaging of graphene edges. The BET SSA and the electrical conductivity of graphene were 1521.3 m2 g-1 and 4618 S m-1, respectively. This work provides a new approach to large-scale and high-quality synthesis of graphene from waste polluting materials.

Deletion of P110δ promotes the development of myocarditis in ApoE­deficient mice by increasing mononuclear cell peritoneal infiltration.

Phosphoinositide 3-kinase catalytic subunit δ isoform (P110δ) is mainly expressed in white blood cells. It is involved in T and B lymphocyte differentiation, maturation and the neutrophil chemotaxis process. Apolipoprotein E (ApoE) is an arginine­rich alkaline protein, which is present in plasma chylomicron, low­density lipoprotein and very low­density lipoprotein. The present study aimed to determine the effects of P110δ deletion on myocarditis in ApoE­/­ mice. A mouse model of ApoE and P110δ double deletion was initially constructed; hematoxylin and eosin (H&E) staining was performed to detect the histological alterations in the mouse myocardium. Systolic and diastolic alterations, and alterations in the left ventricular fractional shortening (LVFS) and left ventricular ejection fraction (LVEF) were examined by electrocardiogram. Blood cell of ApoE and P110δ double mice was used to detect changes in white blood cells and monocytes. Western blotting was used to detect the expression levels of apoptosis­associated proteins, whereas flow cytometry was used to detect the percentage of apoptosis. Morphological alterations in myocardial cells were observed under a microscope. The results of polymerase chain reaction demonstrated that double deletion mice were successfully constructed. H&E staining revealed that cells in the ApoE­/­ mice were spindle­shaped; however, the nuclei were smaller in the double deletion mice. There was no change in cardiac contraction in normal mice; however, in double deletion mice, the systolic and diastolic contractions were markedly reduced. LVFS and LVEF were decreased compared with in the control group. Blood cell analysis indicated that the content of white blood cells and monocytes in the experimental group was significantly higher than that in the control group. Western blotting demonstrated that the expression levels of apoptotic proteins in double deletion mice were significantly higher compared with in the control group. Flow cytometry revealed that the apoptotic ratio was increased in double deletion mice compared with in the control group (42 vs. 21%). These findings suggested that deletion of P110δ may induce monocyte peritoneal infiltration and increase apoptosis, thus promoting the development of myocarditis.

Revealing the Charge Storage Mechanism of Nickel Oxide Electrochromic Supercapacitors.

Nickel oxide (NiO) is considered one of the most promising positive anode materials for electrochromic supercapacitors. Nevertheless, a detailed mechanism of the electrochromic and energy storage process has yet to be unraveled. In this research, the charge storage mechanism of a NiO electrochromic electrode was investigated by combining the in-depth experimental and theoretical analyses. Experimentally, a kinetic analysis of the Li-ion behavior based on the cyclic voltammetry curves reveals the major contribution of surface capacitance versus total capacity, providing fast reaction kinetics and a highly reversible electrochromic performance. Theoretically, our model uncovers that Li ions prefer to adsorb at fcc sites on the NiO(1 1 1) surface, then diffuse horizontally over the plane, and finally migrate in the bulk. More significantly, the calculated theoretical surface capacity (106 mA h g-1) accounts for about 77.4% of the total experimental capacity (137 mA h g-1), indicating that the surface storage process dominates the whole charge storage, which is in accordance with the experimental results. This work provides a fundamental understanding of transition-metal oxides for application in electrochromic supercapacitors and can also promote the exploration of novel electrode materials for high-performance electrochromic supercapacitors.

A One-Step Approach to N-(Hetero)aryl-3,5-dinitropyrazoles from (Hetero)aryl Amines.

Potassium 1,1,3,3-tetranitropropane-1,3-diide (K2TNP) was found to react readily with various (hetero)aryl amines (12 examples) to give corresponding N-(hetero)aryl-3,5-dinitropyrazoles in moderate to excellent yields. The reactions were performed at mild temperature, and most of the reactions completed in less than 4 h. Four potential energetic compounds show high enthalpy of formation, excellent thermal stability, and good sensitivity, with 3-(3,5-dinitropyrazol-1-yl)-1H-1,2,4-triazole (3j) being a potential 2,2',4,4',6,6'-hexanitrostibene (HNS) replacement.

Theoretical study on the gas-phase reaction mechanism of ammonia with nitrous oxide.

Applications of nitrous oxide (N2O) as an oxidant in green propellants and propulsion systems have attracted a lot of attention. In this study, the reaction pathways for the oxidation of ammonia (NH3) with N2O were studied using the B3LYP/6-31++G** method of density functional theory (DFT). The results reveal that the reaction between N2O and NH3 proceeds through a chain reaction mechanism. N2O reacts with NH3 to form N2 and NH3O first and then NH3O decomposes into NH3 and O. This process corresponds to the apparent reaction N2O+M=N2+O+M (M=NH3), but the energy barrier of the process (183.49 kJ/mol) is much lower than the direct decomposition reaction of N2O=N2+O (279.05 kJ/mol). The O radical produced in this process reacts subsequently with NH3 and N2O to produce more radicals such as NH2, OH, and NO, which will take part in further reactions like NH3+OH=NH2+H2O and NH2+NO=N2+H2O until the reactants are consumed.

A facile fabrication of porous fluoro-polymer with excellent mechanical properties based on high internal phase emulsion templating using PLA as co-stabilizer.

The stability of fluoro-high internal phase emulsion (fluoro-HIPE) systems and fluoro-polyHIPEs' mechanical strength require further improvement to meet the requirements of future applications. In this study, we used polylactic acid (PLA) as a co-stabilizer to improve the stability of the fluoro-polyHIPE. The effects of concentration and molecular weight of PLA on the pores of the fluoro-polyHIPEs were investigated. The addition of PLA produced a porous material with narrower void size distributions, higher specific surface areas and enhanced mechanical properties compared to the fluoro-polyHIPE material without the additive. The resulting fluoro-polyHIPE showed smaller pore sizes (void diameters ranged from 1-3 µm) and an improved hydrophobic nature (contact angle can reach to 148.6°). The crush strength and Young's modulus values can reach 4.42 and 74.07 MPa, respectively, at a PLA addition of 25 wt% (oil phase composition), representing increases of 246% and 650% over fluoro-polyHIPE without PLA addition. The fluoro-poly-HIPE demonstrated excellent mechanical properties compared to many engineering foams, such as melamine, polystyrene, and even graphite foams. Improvements in the performance of porous fluoropolymer materials will be beneficial for many applications, such as chemical adsorption and separation, etc.

Facile synthesis of diverse graphene nanomeshes based on simultaneous regulation of pore size and surface structure.

Recently, graphene nanomesh (GNM) has attracted great attentions due to its unique porous structure, abundant active sites, finite band gap and possesses potential applications in the fields of electronics, gas sensor/storage, catalysis, etc. Therefore, diverse GNMs with different physical and chemical properties are required urgently to meet different applications. Herein we demonstrate a facile synthetic method based on the famous Fenton reaction to prepare GNM, by using economically fabricated graphene oxide (GO) as a starting material. By precisely controlling the reaction time, simultaneous regulation of pore size from 2.9 to 11.1 nm and surface structure can be realized. Ultimately, diverse GNMs with tunable band gap and work function can be obtained. Specially, the band gap decreases from 4.5-2.3 eV for GO, which is an insulator, to 3.9-1.24 eV for GNM-5 h, which approaches to a semiconductor. The dual nature of electrophilic addition and oxidizability of HO(•) is responsible for this controllable synthesis. This efficient, low-cost, inherently scalable synthetic method is suitable for provide diverse and optional GNMs, and may be generalized to a universal technique.

Study on the anisotropic response of condensed-phase RDX under repeated stress wave loading via ReaxFF molecular dynamics simulation.

Anisotropic mechanical response and chemical reaction process of cyclotrimethylene trinitramine (RDX) along crystal orientations were studied with molecular dynamics simulations using ReaxFF potential under repeated stress wave loading. In the simulations, shocks were propagated along the [010], [001], [210], [100], [111], and [102] orientations of crystal RDX at initial particle velocity Up in the range of 1∼4 km/s. For shocks at Up ≤ 2 km/s, local stacking fault and molecular conformational change can only cause marginal temperature and pressure increase without molecular decomposition. As shocks increase to Up ≥ 2.5 km/s, rupture of N-NO2 bond accompanied by partial HONO elimination dominates the main chemical reactions at the initial stage. The ordering of the follow-up consumption of NO2 and ring-breaking rate is directly consistent with that of increasing rate in temperature and pressure. The (210) and (100) planes are more sensitive to shocks in temperature and pressure profiles than the (111) plane, which agrees well with experimental observations and theoretical results in the literature. Therefore, the repeated dynamic loading model in conjunction with MD simulation using ReaxFF potential for crystal RDX indicates that these methods can be applied to study the mechanical response and chemical reaction process of polymer bonded explosives that are commonly subjected to compressive and tensile stress waves observed in practice.

Facile synthesis and photoluminescence characteristics of blue-emitting nitrogen-doped graphene quantum dots.

A one-step hydrothermal method for synthesizing nitrogen-doped graphene quantum dots (N-GQDs) from organic carbon sources is presented in this paper. The high-quality N-GQDs can be obtained via tuning the degree of dehydration/carbonization of citric acid and doping of nitrogen atoms into the graphene lattice. The micromorphology, chemical structure, composition and photoluminescence (PL) characteristics of the N-GQDs were characterized systematically. The size of the obtained N-GQDs is about 5-10 nm with typical topographic heights of 0.8-2.5 nm. There is intense blue emission and excitation-independent PL behavior when the N-GQDs are in aqueous solution. The most remarkable innovation is that the fluorescence quantum yield (FL QY) of our N-GQDs is up to 75.2%, which is much higher than that of most reported GQDs (less than 25%). Thus, it is initially believed that synthesis parameters, hydrothermal process and nitrogen doping may greatly influence the surface state and bandgap of the GQDs, which are important in determining the PL characteristics of the N-GQDs.

A Sheet-like Carbon Matrix Hosted Sulfur as Cathode for High-performance Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries are a promising candidate of next generation energy storage systems owing to its high theoretical capacity and energy density. However, to date, its commercial application was hindered by the inherent problems of sulfur cathode. Additionally, with the rapid decline of non-renewable resources and active appeal of green chemistry, the intensive research of new electrode materials was conducted worldwide. We have obtained a sheet-like carbon material (shaddock peel carbon sheets SPCS) from organic waste shaddock peel, which can be used as the conductive carbon matrix for sulfur-based cathodes. Furthermore, the raw materials are low-cost, truly green and recyclable. As a result, the sulfur cathode made with SPCS (SPCS-S), can deliver a high reversible capacity of 722.5 mAh g(-1) at 0.2 C after 100 cycles with capacity recuperability of ~90%, demonstrating that the SPCS-S hybrid is of great potential as the cathode for rechargeable Li-S batteries. The high electrochemical performance of SPCS-S hybrid could be attributed to the sheet-like carbon network with large surface area and high conductivity of the SPCS, in which the carbon sheets enable the uniform distribution of sulfur, better ability to trap the soluble polysulfides and accommodate volume expansion/shrinkage of sulfur during repeated charge/discharge cycles.

A DFT study of the unimolecular decomposition of 1,2,4-butanetriol trinitrate.

To improve understanding of the unimolecular decomposition mechanism of 1,2,4-butanetriol trinitrate (BTTN) in the gas phase, density functional theory calculations were performed to determine various decomposition pathways at the B3LYP/6-311G** level. Two main mechanisms for the unimolecular decomposition of BTTN were found. In the first, homolysis of one of the O-NO2 bonds occurs to form •NO2 and CH2ONO2CHONO2CH2CH2O•, which subsequently decomposes to form CH3CHO + •CHO + 3NO2 + HCHO. In the second, successive HONO elimination reactions yield three HONO and OHCCH2CHONO2CH2ONO2 fragments, which subsequently decompose to form CH3CHO + 2CO + 3HONO. We also found that the first pathway has a slightly lower activation energy than the second. The results show that the pathway involving O-NO2 cleavage is slightly more energetically favorable than that involving HONO elimination.

Molecular dynamics of neutral polymer bonding agent (NPBA) as revealed by solid-state NMR spectroscopy.

Neutral polymer bonding agent (NPBA) is one of the most promising polymeric materials, widely used in nitrate ester plasticized polyether (NEPE) propellant as bonding agent. The structure and dynamics of NPBA under different conditions of temperatures and sample processing are comprehensively investigated by solid state NMR (SSNMR). The results indicate that both the main chain and side chain of NPBA are quite rigid below its glass transition temperature (Tg). In contrast, above the Tg, the main chain remains relatively immobilized, while the side chains become highly flexible, which presumably weakens the interaction between bonding agent and the binder or oxidant fillers and in turn destabilizes the high modulus layer formed around the oxidant fillers. In addition, no obvious variation is found for the microstructure of NPBA upon aging treatment or soaking with acetone. These experimental results provide useful insights for understanding the structural properties of NPBA and its interaction with other constituents of solid composite propellants under different processing and working conditions.