Revealing the Ultrafast Energy Transfer Pathways in Energetic Materials: Time-Dependent and Quantum State-Resolved.

Intramolecular vibrational energy transfer is gaining tremendous attention as a regulator of condensed-phase behavior and reactions. In polyatomic molecules, this transfer is an ultrafast process involving multiple modes with numerous quantum states. The inherent complexity and rapid evolution of these processes pose significant challenges to experimental observation, and the high computational costs make full quantum mechanical calculations impractical with current technology.

High-Energy and Thermally Stable Energetic Materials Based on an Azo-Fused Dinitramino Compound.

Here, azo-fused dinitramino energetic compound 5,5'-dinitramino-8,8'-azo-1,2,5-oxadiazolo[3,4-][1,2,4]triazolo[4,3-]pyrazine () and its energetic salts - have been prepared. Azo-fused dinitramino compound exhibits excellent detonation performance ( = 36.13 GPa, and = 9126 m s), which is obviously better than that of RDX ( = 8796 m s, and = 33.

An advanced furoxan-bridged heat-resistant explosive.

Nowadays, thousands of energetic materials have been synthesized, but only a few compounds meet all the high standards of detonation performance comparable to that of the widely used military explosive RDX, thermal stability comparable to that of the most widely used heat-resistant explosive HNS, and impact sensitivity comparable to that of the traditional explosive TNT. Also, as a goal, a novel and unexpected one-step method for constructing the furoxan-bridged energetic compound 3,4-bis(3,8-dinitropyrazolo[5,1-][1,2,4]triazin-4-amino-7-yl)-1,2,5-oxadiazole 2-oxide (OTF) has been achieved under the conventional TFA/100% HNO nitration reaction system from the acetic acid intermediate. In this work, OTF with a high density of 1.

Ultrafast vibrational energy redistribution in cyclotrimethylene trinitramine (RDX).

The microscopic mechanism of the energy transfer in cyclotrimethylene trinitramine (RDX) is of particular importance for the study of the energy release process in high-energy materials. In this work, an effective vibrational Hamiltonian based on normal modes (NMs) has been introduced to study the energy transfer process of RDX. The results suggest that the energy redistribution in RDX can be characterized as an ultrafast process with a time scale of 25 fs, during which the energy can be rapidly localized to the -NNO2 twisting mode (vNNO2), the N-N stretching mode (vN-N), and the C-H stretching mode (vC-H).

Discriminative Mechanical and Thermal Response of the H-N Bonds for the Energetic LLM-105 Molecular Assembly.

Molecular interactions in energetic materials form the key not only to the "structure stability, energy storage, ignition, and detonation" dynamics but also to the sensitivity to the loading of perturbation and the power intensity of radiation for the energetic substance, with the nature of the interactions remaining elusive. With the aid of perturbative Raman spectroscopy and the pressure-resolved density functional theory, we uncovered that the H-N bond of the intermolecular O:H-N bonds for LLM-105 shares the same negative compressibility and thermal expansivity of the H-O bond for the coupling O:H-O bond of water [ , 998, 1-68]. In contrast, the dangling H-N bond vibrating at a 3440 cm high frequency does otherwise due to the absence of coupling interaction and the undercoordination-driven bond contraction.

Femtosecond coherent anti-Stokes Raman spectroscopy study of vibrational dynamics of liquid chloroform.

Femtosecond time-resolved coherent anti-Stokes Raman spectroscopy (CARS) was used to study the dynamics of the vibrational modes of liquid chloroform. The vibrational modes were selectively excited and their coherent vibrational dynamics were obtained. Some subtle features that are difficult to distinguish in the ordinary spontaneous Raman spectrum, such as overtones and combinations of some fundamental vibrational modes, were recognized from the CARS transients.

Solution structures and ultrafast vibrational energy dissipation dynamics in cyclotetramethylene tetranitramine.

Steady-state and time-resolved infrared (IR) studies of cyclotetramethylene tetranitramine (HMX) were carried out, using the asymmetric nitro-stretch as probe, to investigate its solution structures and vibrational energy transfer processes in pure dimethyl sulfoxide (DMSO) and in a DMSO/water mixture. A linear IR spectrum in the nitro-stretching mode region shows two major bands and one minor band in DMSO but changes to the two major bands mainly picture when adding water as an antisolvent of HMX, suggesting a transition from well-solvated and less perfect β-conformation to a less-solvated and close-to-perfect β-conformation. The latter bears a similar asymmetric nitro-stretch vibration profile to the β-polymorph in the crystal form.

Vibrational energy redistribution in crystalline nitromethane simulated by molecular dynamics.

molecular dynamics simulations (AIMD) are systematically performed to study the Vibrational Energy Redistribution (VER) in solid nitromethane (NM) by combining normal mode decomposition and short-time Fourier transform technique. After the selective excitations of all fourteen intramolecular vibrational modes above 400 cm, four three-dimensional (3D) excitation and detected vibrational spectra are obtained. The evolution of the kinetic energy proportion of all vibrations are also given and discussed quantitatively.

The geometrical analysis of localization error characteristic in stereo vision systems.

The parameters of a stereo camera directly determine the accuracy of a stereo vision positioning system. In this paper, the relationship between camera parameter error and positioning error is established by using the geometric analysis method with a clear physical meaning. The error models of the relative position error and camera resolution error of the stereo camera are established.

Elucidating the Coupling Mechanisms of Rapid Intramolecular Vibrational Energy Redistribution in Nitromethane: Ab Initio Molecular Dynamics Simulation.

Ab initio molecular dynamics simulations are presented to investigate the intramolecular vibrational energy redistribution (IVR) of an isolated nitromethane molecule. A number of IVR processes are simulated by monitoring the kinetic energy of vibrational modes under selective low-lying vibrational excitations from their ground states (Δν = 1 or 2). Evolution of the normal-mode kinetic energy gives the ultrafast energy transfer processes from parent modes to daughter modes intuitively.

Thermochemistry and Initial Decomposition Pathways of Triazole Energetic Materials.

A thorough investigation of the initial decomposition pathways of triazoles and their nitro-substituted derivatives has been conducted using the MP2 method for optimization and DLPNO-CCSD(T) method for energy. Different initial thermolysis mechanisms are proposed for 1,2,4-triazole and 1,2,3-triazole, the two kinds of triazoles. The higher energy barrier of the primary decomposition path of 1,2,4-triazole (H-transfer path, ∼52 kcal/mol) compared with that of 1,2,3-triazole (ring-open path, ∼45 kcal/mol) shows that 1,2,4-triazole is more stable, consistent with experimental observations.

Ab initio molecular dynamics simulation of vibrational energy redistribution of selective excitation of C-H stretching vibrations for solid nitromethane.

Vibrational energy redistribution (VER) of energetic materials plays an important role in transferring the injected energy to the hot spots, but it is extremely challenging to understand the mechanism of VER from experimental or theoretical studies. Here, we combined nonequilibrium molecular dynamics with density functional theory to study the processes of VER for solid nitromethane after the selective excitation of the C-H stretching vibration. The VER processes are traced by monitoring the normal-mode kinetic energies of both excited and unexcited vibrations.

Role of electron in intramolecular vibrational energy redistribution: a simulation of time- and frequency-resolved CARS spectrum.

A coupled oscillator model with special attention to the electron is employed to simulate the time- and frequency-resolved coherent anti-Stokes Raman scattering (TFR-CARS) spectrum of benzene, where the electronic contribution is introduced as an oscillator as well as molecular vibration, and both the coupling between molecular vibrations and the coupling between electron and molecular vibration are involved. Through the simulation, the intramolecular vibrational energy redistribution (IVR) process is confirmed to occur more readily between the molecular vibrations with the same vibrational symmetry. Moreover, it is found that the electron plays a mediator role in the IVR process, and the coupling between electron and molecular vibration significantly increases the intramolecular vibrational energy transfer efficiency.

Development of a deep eutectic solvent-based matrix solid phase dispersion methodology for the determination of aflatoxins in crops.

A novel and sensitive deep eutectic solvent-based matrix solid phase dispersion (DES-MSPD) method for the determination of aflatoxins (AFB1, AFB2, AFG1, AFG2) in various crops was established using high-performance liquid chromatography with fluorescence detection (HPLC-FLD). The DES-MSPD sample preparation procedure was optimized. Based on the optimal conditions, the intra-day and inter-day variability for AFs in all crop samples was less than 7.

New perspective on the fluorescence and sensing mechanism of TNP chemosensor 2-(4,5-bis(4-chlorophenyl)-1H-imidazol-2-yl)-4-chlorolphenol.

For TNP chemosensor 2-(4,5-Bis(4-Chlorophenyl)-1H-Imidazol-2-yl)-4-Chlorolphenol (HPICI), previous thought with no theoretical basis was that excited-state intramolecular proton transfer (ESIPT) process and the ground-state HPICI-TNP complex are mainly responsible for its fluorescence emission and the detection of TNP. However, this interpretation has been proved to be wrong by the present theoretical DFT/TDDFT explorations. Actually, the strong fluorescence of HPICI is mainly induced by the local excitation of the enol form HPICI(E) without ESIPT, and the fluorescence quenching by TNP is due to the photo-induced electron transfer (PET) process together with the cooperative effect of hydrogen-bonding interaction and π-π stacking interaction coexisting in the HPICI-TNP complex.

Predicting the Initial Thermal Decomposition Path of Nitrobenzene Caused by Mode Vibration at Moderate-Low Temperatures: Temperature-Dependent Anti-Stokes Raman Spectra Experiments and First-Principals Calculations.

The lack of understanding of the initial decomposition micromechanism of energetic materials subjected to external stimulation has hindered its safe storage, usage, and development. The initial thermal decomposition path of nitrobenzene triggered by molecular thermal motion is investigated using temperature-dependent anti-Stokes Raman spectra experiments and first-principles calculations to clarify the initial thermal decomposition micromechanism. The experiment shows that the symmetric nitro stretching, antisymmetric nitro stretching, and phenyl ring stretching vibration modes are active as increasing temperature below 500 K.

Resonance Rayleigh scattering assay for EGFR using antibody immobilized gold nanoparticles.

A highly selectivity determination of epidermal growth factor receptor (EGFR) has been described in the article. Antibody immobilized cysteamine (Cys) functionalized gold nanoparticles (AuNP) were proposed as immunosensors, and resonance Rayleigh scattering (RRS) was used for detection. First, Cys stabilized AuNPs (Cys-AuNP) were prepared by the reduction of chloroauric acid with sodium borohydride in the presence of Cys.

Correction: Tracking intramolecular energy redistribution dynamics in aryl halides: the effect of halide mass.

[This corrects the article DOI: 10.1039/C8RA04979C.].

Tracking intramolecular energy redistribution dynamics in aryl halides: the effect of halide mass.

Selective excitation of C-H, C-C, CX and CX stretching vibrational modes in an orderly manner, detection of intramolecular energy redistribution and vibrational coupling in the electronic ground state of aryl halides are performed by time- and frequency-resolved Coherent Anti-Stokes Raman Scattering (CARS) spectroscopy. Intramolecular energy flow from parent modes to daughter modes is observed in the experiment. According to the experimental results, it is found that the up-hill vibrational energy flow from lower frequency modes to higher frequency ones is counterintuitive and energy redistribution efficiencies are controlled by the mass of the halide.

New insights into the sensing mechanism of a phosphonate pyrene chemosensor for TNT.

As security needs have increased, mechanism investigation has become of high importance in the development of new sensitive and selective chemosensors for chemical explosives. This study details a theoretical investigation of the sensing mechanism of a new phosphonate pyrene chemosensor for trinitrotoluene (TNT), suggesting a different interaction mode between the probe and TNT from the one previously reported. The invalidity of the mechanism of binding TNT through intermolecular hydrogen bonds was proved using the Gibbs free energy profile and 1H NMR analysis.

Stability, Elastic Properties, and Deformation of LiBN: A Potential High-Energy Material.

Searching for high-energy-density materials is of great interest in scientific research and for industrial applications. Using an unbiased structure prediction method and first-principles calculations, we investigated the phase stability of LiBN from 0 to100 GPa. Two new structures with space groups P4̅2 m and Pnma were discovered.

Reconsideration of the Detection and Fluorescence Mechanism of a Pyrene-Based Chemosensor for TNT.

The rapid detection of chemical explosives is crucial for national security and public safety, and the investigation of sensing mechanisms is important for designing highly efficient chemosensors. This study theoretically investigates the detection and fluorescence mechanism of a newly synthesized pyrene-based chemosensor for the detection of trinitrotoluene (TNT) through density-functional-theory (DFT) and time-dependent density-functional-theory (TDDFT) methods and suggests a different interaction product of the probe and TNT from previously reported ones [ Mosca et al. J.