Intermolecular Interactions and Thermodynamic Properties of 3,6-Diamino-1,2,4,5-tetrazine-1,4-dioxide Dimers: A Density Functional Theoretical Study

Three fully optimized structures of 3,6-diamino-1,2,4,5-tetrazine-1,4-dioxide (LAX-112) dimers have been obtained with the density functional theory (DFT) method at the B3LYP/6-311++G level. Vibrational frequency calculations were carried out to ascertain that each structure is a minimum (no imaginary frequencies). The intermolecular interaction energy is calculated with the basis set superposition error (BSSE) correction and zero point energy (ZPE) correction. The greatest corrected binding energy among the three dimers is –42.38 kJ mol–1. The charge redistribution mainly occurs on the adjacent O(N)……H atoms between submolecules and the charge transfer between two subsystems is very small. Natural bond orbital (NBO) analysis was performed to reveal the origin of the interaction. Based on the vibrational analysis, the standard thermodynamic functions (heat capacities (cop), entropies (Som ) and enthalpies (Hom)) and the changes of thermodynamic properties from the monomer to dimer with the temperature ranging from 200.00 K to 800.00 K have been obtained using statistical thermodynamics. The results show that the strong hydrogen bonds dominantly contribute to the dimers, while the bonding energies are not only determined by the hydrogen bonding. The dimerization process of dimer II can occur spontaneously at room temperature.KEYWORDS 3,6-Diamino-1,2,4,5-tetrazine-1,4-dioxide (LAX-112), intermolecular interaction, density functional theory (DFT), natural bond orbital (NBO) analysis, thermodynamic properties

Thermal Behaviour and Detonation Characterization of N-Benzoyl-3,3-dinitroazetidine

N-benzoyl-3,3-dinitroazetidine(BDNAZ) is a derivative of 3,3-dinitroazetidine (DNAZ). Its thermal behaviour was studied by DSC methods. The results show that there are one melting process and two exothermic decomposition processes. The kinetic parameters of the intense exothermic decomposition process were obtained from the analysis of the DSC curves. The apparent activation energy, pre-exponential factor and the mechanism function are 170.77 kJ mol–1, 1014.12 s–1 and f(α) = (1–a)–1/2, respectively. The specific heat capacity of BDNAZ was determined with a continuous Cp mode of a micro-calorimeter. The standard mole specific heat capacity ofBDNAZwas 286.31 J mol1 K–1 at 298.15 K. Using the relationship between Cp and T with the thermal decomposition parameters, the time of the thermal decomposition from initialization to thermal explosion (adiabatic time-to-explosion, tTIAD), the self-accelerating decomposition temperature (TSADT), thermal ignition temperature (TTIT), critical temperatures of thermal explosion (Tb) and period of validity (t0.9) were obtained to evaluate its thermal safety. The detonation velocity (D) and pressure (P) of BDNAZ were estimated by using the nitrogen equivalent equation according to the experimental density.KEYWORDS N-benzoyl-3,3-dinitroazetidine(BDNAZ), thermalbehaviour, non-isothermalkinetics, thermalsafety, detonation characterization

Thermal Effects and Small Signal Modulation of 1.3-μm InAs/GaAs Self-Assembled Quantum-Dot Lasers

We investigate the influence of thermal effects on the high-speed performance of 1.3-μm InAs/GaAs quantum-dot lasers in a wide temperature range (5–50°C). Ridge waveguide devices with 1.1 mm cavity length exhibit small signal modulation bandwidths of 7.51 GHz at 5°C and 3.98 GHz at 50°C. Temperature-dependent K-factor, differential gain, and gain compression factor are studied. While the intrinsic damping-limited modulation bandwidth is as high as 23 GHz, the actual modulation bandwidth is limited by carrier thermalization under continuous wave operation. Saturation of the resonance frequency was found to be the result of thermal reduction in the differential gain, which may originate from carrier thermalization

Molecular Mechanisms of Membrane Deformation by I-BAR Domain Proteins

Conclusions: These data define I-BAR domain as a functional member of the BAR domain superfamily and unravel the mechanisms by which I-BAR domains deform membranes to induce filopodia in cells. Furthermore, our work reveals unexpected divergence in the mechanisms by which evolutionarily distinct groups of I-BAR domains interact with PI(4,5)P(2)-rich membranes

Improved ground-state modulation characteristics in 1.3 μm InAs/GaAs quantum dot lasers by rapid thermal annealing

We investigated the ground-state (GS) modulation characteristics of 1.3 μm InAs/GaAs quantum dot (QD) lasers that consist of either as-grown or annealed QDs. The choice of annealing conditions was determined from our recently reported results. With reference to the as-grown QD lasers, one obtains approximately 18% improvement in the modulation bandwidth from the annealed QD lasers. In addition, the modulation efficiency of the annealed QD lasers improves by approximately 45% as compared to the as-grown ones. The observed improvements are due to (1) the removal of defects which act as nonradiative recombination centers in the QD structure and (2) the reduction in the Auger-related recombination processes upon annealing

Filming a live cell by scanning electrochemical microscopy: label-free imaging of the dynamic morphology in real time

The morphology of a live cell reflects the organization of the cytoskeleton and the healthy status of the cell. We established a label-free platform for monitoring the changing morphology of live cells in real time based on scanning electrochemical microscopy (SECM). The dynamic morphology of a live human bladder cancer cell (T24) was revealed by time-lapse SECM with dissolved oxygen in the medium solution as the redox mediator. Detailed local movements of cell membrane were presented by time-lapse cross section lines extracted from time-lapse SECM. Vivid dynamic morphology is presented by a movie made of time-lapse SECM images. The morphological change of the T24 cell by non-physiological temperature is in consistence with the morphological feature of early apoptosis. To obtain dynamic cellular morphology with other methods is difficult. The non-invasive nature of SECM combined with high resolution realized filming the movements of live cells

Enhancing Nanoparticle-Based Visible Detection by Controlling the Extent of Aggregation

Visible indication based on the aggregation of colloidal nanoparticles (NPs) is highly advantageous for rapid on-site detection of biological entities, which even untrained persons can perform without specialized instrumentation. However, since the extent of aggregation should exceed a certain minimum threshold to produce visible change, further applications of this conventional method have been hampered by insufficient sensitivity or certain limiting characteristics of the target. Here we report a signal amplification strategy to enhance visible detection by introducing switchable linkers (SLs), which are designed to lose their function to bridge NPs in the presence of target and control the extent of aggregation. By precisely designing the system, considering the quantitative relationship between the functionalized NPs and SLs, highly sensitive and quantitative visible detection is possible. We confirmed the ultrahigh sensitivity of this method by detecting the presence of 20 fM of streptavidin and fewer than 100 CFU/mL of Escherichia coli

Modular and predictable assembly of porous organic molecular crystals

Nanoporous molecular frameworks are important in applications such as separation, storage and catalysis. Empirical rules exist for their assembly but it is still challenging to place and segregate functionality in three-dimensional porous solids in a predictable way. Indeed, recent studies of mixed crystalline frameworks suggest a preference for the statistical distribution of functionalities throughout the pores rather than, for example, the functional group localization found in the reactive sites of enzymes. This is a potential limitation for 'one-pot' chemical syntheses of porous frameworks from simple starting materials. An alternative strategy is to prepare porous solids from synthetically preorganized molecular pores. In principle, functional organic pore modules could be covalently prefabricated and then assembled to produce materials with specific properties. However, this vision of mix-and-match assembly is far from being realized, not least because of the challenge in reliably predicting three-dimensional structures for molecular crystals, which lack the strong directional bonding found in networks. Here we show that highly porous crystalline solids can be produced by mixing different organic cage modules that self-assemble by means of chiral recognition. The structures of the resulting materials can be predicted computationally, allowing in silico materials design strategies. The constituent pore modules are synthesized in high yields on gram scales in a one-step reaction. Assembly of the porous co-crystals is as simple as combining the modules in solution and removing the solvent. In some cases, the chiral recognition between modules can be exploited to produce porous organic nanoparticles. We show that the method is valid for four different cage modules and can in principle be generalized in a computationally predictable manner based on a lock-and-key assembly between modules

Observation of a ppb mass threshoud enhancement in \psi^\prime\to\pi^+\pi^-J/\psi(J/\psi\to\gamma p\bar{p}) decay

The decay channel $\psi^\prime\to\pi^+\pi^-J/\psi(J/\psi\to\gamma p\bar{p})$ is studied using a sample of $1.06\times 10^8$ $\psi^\prime$ events collected by the BESIII experiment at BEPCII. A strong enhancement at threshold is observed in the $p\bar{p}$ invariant mass spectrum. The enhancement can be fit with an $S$-wave Breit-Wigner resonance function with a resulting peak mass of $M=1861^{+6}_{-13} {\rm (stat)}^{+7}_{-26} {\rm (syst)} {\rm MeV/}c^2$ and a narrow width that is $\Gamma<38 {\rm MeV/}c^2$ at the 90% confidence level. These results are consistent with published BESII results. These mass and width values do not match with those of any known meson resonance.Comment: 5 pages, 3 figures, submitted to Chinese Physics