Qinghai Shu

Molecular dynamics simulations for 5,5′-bistetrazole-1,1′-diolate (TKX-50) and its PBXs

Molecular dynamics has been carried out to simulate the well-known new explosive compound 5,5′-bistetrazole-1,1′-diolate (TKX-50) and TKX-50 based polymer bonded explosives (PBXs) with four kinds of polymer binders, such as, fluorine (F2311), fluorine resin (F2641), polyethylene glycol (PEG) and ethylene-vinyl acetate copolymer (EVA). The isotropic mechanical properties (tensile modulus, bulk modulus, shear modulus and Poisson’s ratio), moldability, and bonding energy are reported for first time for TKX-50 crystal and TKX-50 based PBXs. The mechanical properties of the explosive can be effectively raised by adding polymer binders in small amounts and the ability of different polymer binders improving the plasticity of TKX-50 in the increasing order PEG > EVA > F2641 = F2311. The moldability of TKX-50 based PBXs is better than that of pure TKX-50, and the increasing order is PEG > EVA > F2311 > F2641. The interaction between each of the crystalline surfaces and each of the polymers is different, the order of the abilities of different binders to combine TKX-50 crystal decreases as follows: F2311 > PEG ≈ F2641 > EVA. The calculated detonation performances for pure TKX-50 and TKX-50 based PBXs show that both of them are comparable with those of HMX. Ultimately, as for the four polymer binders, PEG is considered the best one for explosive TKX-50.

A new multifunctional Schiff-based chemosensor for mask-free fluorimetric and colorimetric sensing of F− and CN−

A Schiff-based chemosensor DSS was designed for selective and simultaneous detection and/or determination of F(-) and CN(-) by distinguishable changes in both solution color and spectroscopic responses within same sample due to the strong emission enhancement at distinct emission bands without any mask. In addition, the sensing mechanism was evaluated by NMR titration and DFT calculations.

A single molecular fluorescent probe for selective and sensitive detection of nitroaromatic explosives: A new strategy for the mask-free discrimination of TNT and TNP within same sample

A simple naphthalene based fluorescent probe was first time reported as dual sensing of 2,4,6-trinitrotolune (TNT) and 2,4,6-trinitrophenol (TNP) by distinguishable changes in both solution color change and fluorescence within same sample without any mask agent. Upon addition of TNT and TNP, the strong emission quenching at 412nm and a new emission band at 530nm was observed, respectively. In addition, the sensing mechanism was evaluated by DFT calculations by Gaussian 09 software.

Squaramide-based lab-on-a-molecule for the detection of silver ion and nitroaromatic explosives

A squaramide based chemosensor SA was developed as a quantitatively operating lab-on-a-molecule, for the detection of silver ions and nitroaromatic explosives in aqueous solution, showing significant emission quenching and absorption enhancement in dual channel along with a distinct solution color change.

A simple ratiometric and colorimetric chemosensor for the selective detection of fluoride in DMSO buffered solution.

A derivative of squaramide (cyclobuta[b]quinoxaline-1, 2(3H, 8H)-dione) has been synthesized for the ratiometric and colorimetric sensing of F(-) in aqueous solution in competitive fashion. With F(-), probe 1 showed a highly selective naked-eye detectable color change along with a characteristic UV-Vis absorbance over other tested ions, which probably originates from the deprotonation occurred between 1 and F(-), as proved by the (1)H NMR titration experiments and DFT calculations.

Thermal hazard assessment of 4,10-dinitro-2,6,8,12-tetraoxa-4,10-diazaisowutrzitane (TEX) by accelerating rate calorimeter (ARC)

The thermal decomposition behaviors of 4,10-dinitro-2,6,8,12-tetraoxa-4,10-diazaisowutrzitane (TEX) were studied by using accelerating rate calorimetry to achieve the hazard assessment of TEX explosive, and the kinetic parameters were studied from the measured self-heating rate data by assuming a zero-order reaction. Moreover, the specific heat capacity date of TEX was obtained from differential scanning calorimetry. These results could be contributed to improve the safety in the reaction, transportation, and storage processes of TEX.

Dissolution Properties of Dihydroxylammonium 5,5ʹ-Bistetrazole-1,1ʹ-diolate and Disodium 5,5ʹ-Bistetrazole-1,1ʹ-diolate in Water

The dissolution and thermochemical properties of dihydroxylammonium 5,5ʹ-bistetrazole-1,1ʹ-diolate (TKX-50) and its intermedium disodium 5,5ʹ-bistetrazole-1,1ʹ-diolate ([Na2(H2O)4]BTO) in water at 298.15 K were studied using a C-80 Calvet microcalorimeter. Empirical formulae for the calculation of the molar enthalpies of dissolution (ΔdissH), relative partial molar enthalpies (ΔdissHpartial), and relative apparent molar enthalpies (ΔdissHapparent) were deduced by the experimental results of the dissolution processes of TKX-50 and [Na2(H2O)4]BTO in water. Finally, the corresponding kinetic equations describing the dissolution processes were dα/dt = 10−2.95(1 − α)0.64 for the dissolution of TKX-50 in water and dα/dt = 10−2.76(1 − α)1.07 for the dissolution of [Na2(H2O)4]BTO in water.

Diketopyrrolopyrrole-based polymer with a semi-fluorinated side chain for high-performance organic thin-film transistors

A diketopyrrolopyrrole (DPP) unit with a semi-fluorinated side chain was copolymerized with bithiophenyl (BT) to afford a novel donor–acceptor (D–A) conjugated polymer PFDPP–BT (FDPP refers to the semi-fluorinated DPP unit). The non-fluorinated polymer PDPP–BT was synthesized as the reference polymer to investigate the effect of fluorination of side chains on the morphology of thin films and charge-carrier mobility. Organic thin-film transistors based on these two polymers showed decent device performance. Interestingly, the semiconductor polymer PFDPP–BT exhibited hole mobility about 3 times higher than that of the related PDPP–BT. Atomic force microscopy (AFM) and X-ray diffraction (XRD) measurements demonstrated that the semi-fluorinated side chains had a great effect on the thin film morphology and crystallinity, which led to enhancement in device performance.

Investigation into the Coating and Desensitization Effect on HNIW of Paraffin Wax/Stearic Acid Composite System

2,4,6,8,10,12-Hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (HNIW) was bonded by fluorine rubber and then desensitized by paraffin wax (PW), stearic acid (SA), and a PW/SA composite system using an aqueous suspension method. The coating and desensitization effects of the composite systems on HNIW and the influence of the addition of SA on the mechanical properties of the coated HNIW samples were studied. In addition, the PW/SA composite solution was simulated using a molecular dynamics method, and the relationship between the desensitization effect on HNIW and the properties of the composite solution was investigated. The results showed that the PW/SA composite system, of which the desensitization effect on HNIW was between those of the two desensitizers, could effectively coat HNIW and that the composite solution had the most stable and well-distributed state when using benzene as solvent with the mass ratio of PW/SA equal to 7/3 or 3/7, thus resulting in the best desensitization effect on HNIW. Moreover, the addition of stearic acid was successful in enhancing the mechanical properties of the coated HNIW samples.

Thermal hazard assessment of TNT and DNAN under adiabatic condition by using accelerating rate calorimeter (ARC)

The thermal decomposition behaviors of 2,4,6-Trinitrotoluene (TNT) and 1-methoxy-2,4-dinitro-benzene (DNAN) were studied by using a NETSCH company accelerating rate calorimetry. Hazard indicators such as onset temperature, adiabatic temperature rise, initial self-heat temperature, maximum self-heating rate, and time-to-maximum temperature rise rate have been determined directly. The kinetic parameters, such as the activation energy (Ea) and the pre-exponential factor (A) were studied from the measured self-heating rate data by assuming order reaction.