Ultrasensitive detection of trace Hg(â ¡) in acidic conditions using DMABR loaded on sepiolite: Function, application and mechanism studies.

Fast and real-time detection of trace Hg(Ⅱ) by fluorescent probes under acidic conditions is urgently required due to the high toxicity and accessibility to creatures and human being. However, fluorescent probes for Hg(Ⅱ) detection in environmental samples are rarely reported due to the protonation potential of acidic mercury sources. In this study, the SD probe was developed by 5-(p-dimethylaminobenzylidene) rhodanine (DMABR) loaded on sepiolite by hydrothermal treatment, and showed excellent Hg(Ⅱ) detection performances for mercury sources at pH 4-10 due to buffering ability of the hyperconjugated lactam rings. Sepiolite functioned as the support skeleton to decrease intermolecular transition, and thus increased the sensitivity. At pH 4, the SD probe showed high selectivity and sensitivity for Hg(Ⅱ) among various species, with low LOD and binding constant of 4.78 × 10-9 M and 1.34 × 106 M-1, respectively. Through DFT calculations, MAS 1H NMR and 2D-COS analysis, the detection mechanism was demonstrated as SN1 substitution of the spontaneous leaving H on amino groups in the transient state during tautomeric equilibrium, rather than the expected high-affinity sulphydryl. Additionally, the SD probe exhibited promising potential in quantifying water-soluble and bioavailable Hg(Ⅱ) in acidic polluted soil and water samples. Moreover, real-time detection was realized by paper-based strips.

Computational method on highly efficient D-π-A-π-D-based different molecular acceptors for organic solar cells applications and non-linear optical behaviour.

Eight molecular structures (BT-A1 to BT-A8) with high-performance non-fullerene acceptor (NFA) were selected for organic solar cells (OSCs) and non-linear optical (NLO) applications. Their electronic, photovoltaic (PV) and optoelectronic properties were tuned by adding powerful electron-withdrawing groups to the acceptor (A) of the D-π-A-π-D structure. Using time-dependent density functional theory (TD-DFT) techniques, based on the laws of quantum chemical calculations, the absorption spectra, stability of the highest and lowest-energy molecular orbitals (HOMO/LUMOs), electron density, intramolecular charge transfer (ICT), transition density matrix (TDM), were examined. The binding energy (Eb) and density of states (DOS) were probed to realize the optoelectronic analysis of the structures BT-A1 to BT-A8. Noncovalent interactions (NCIs) based on a reduced density gradient (RDG) were used to describe the nature and strength of D-A interactions in the molecules BT-A1 to BT-A8. The new refined molecules BT-A1 to BT-A8 exhibited strong absorbance bands between 408-721 nm and high electron transfer contribution (ETC) ranges between 87-96 %, along with the smallest excitation energies (Ex) between 1.71-3.55 eV in the solvent dichloromethane. Dipolar moment strengths ranging from 0.38 to 4.72 Debye in both the excited and ground states have determined with good solubility properties of BT-A1 to BT-A8 in polar solvent. Highly effective charge mobilities and prevention of charge recombination have been demonstrated by the electron (0.18-0.41 eV) and hole RE values (0.13-0.89 eV) for the new compounds. Power conversion efficiencies (PCE) of BT-A1 to BT-A8 were nearly the same because of better outcomes compared to the molecules in the BT. Compared to poly[4.8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b: 4,5-b']dithiophene-2,6- diyl-alt-(4-2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2-6-diyl)] (PTB7-Th), the open circuit voltages (Voc) of compounds BT-A1 to BT-A8 were ranged from 1.52 to 2.13 eV. The polarizability (α) and hyperpolarizability (ß) of the molecules BT-A1 to BT-A8 were used to determine the non-linear optical (NLO) properties. The results showed that BT-A2, BT-A6 and BT-A7 have good NLO activity. This computational analysis demonstrates the superiority of the molecules with NFA. Hence the compounds are advised for the use in production of high-performance OSCs and NLO activity.

Theoretical investigation on regulating photophysical properties and proton transfer behavior by electronegativity for near-infrared emitting styryl dyes.

Our main focus is to explore the atomic electronegativity-dependent photoinduced behavior of styryl derivatives (HBO, HBS, and HBSe). The results of structural parameter calculation by the DFT method show that the intramolecular hydrogen bonds of normal and tautomer form are strengthened and weakened, respectively, in an excited state (S1), which is conducive to the excited intramolecular proton transfer (ESIPT) process. The enhancement of excited hydrogen bond is beneficial to the ESIPT process from the aspects of infrared vibration frequency (IR), Mulliken's charge analysis, and density gradient reduction (RDG). Additionally, by determining the bond energy with the band critical point (BCP) parameter, we found that the lower the electronegativity of the atom, the larger the hydrogen bond strength at the excited state and the more likely ESIPT reaction occurs. Meanwhile, the intramolecular H-bonds O-H…N in HBO, HBS, and HBSe are enhanced with the weakened electron-withdrawing capacity of the atom (from O to S and Se). Subsequently, frontier molecular orbital (FMOs) and charge density difference (CDD) analyses essentially revealed that electron redistribution induces the ESIPT process. Low atomic electronegativity exhibits the high chemical activity of the excited state. Furthermore, to demonstrate the electronegativity-dependent ESIPT behavior of the system, we built potential energy curves (PECs) and located the transition states (TS) of proton transfer processes.

Theoretical design and evaluation of efficient small donor molecules for organic solar cells.

CONTEXT: The development of high-efficiency photovoltaic devices is the need of time with increasing demand for energy. Herein, we designed seven small molecule donors (SMDs) with A-π-D-π-A backbones containing various acceptor groups for high-efficiency organic solar cells (OSCs). Molecular engineering was performed by substituting the acceptor group in the synthesized compound (BPR) with another highly efficient acceptor group to improve the photoelectric performance of the molecule. METHOD: The photovoltaic, optoelectronic, and photophysical properties of the proposed compounds (BP1-BP7) were investigated in comparison to BPR using DFT and TD-DFT at MPW1PW91/6-311G(d,p) level of theory. All molecules we designed have red-shifted absorption spectra. The modification of the acceptor fragment of the BPR resulted in a reduced HOMO-LUMO energy gap; thus, the designed compounds (BP1-BP7) had improved optoelectronic responses as compared with the BPR molecule. Various key factors that are crucial for efficient SMDs such as exciton binding energy, frontier molecular orbitals (FMOs), absorption maximum (λmax), open circuit voltage (VOC), dipole moment (µ), excitation charge mobilities, and the transition density matrix of (BPR, BP1-BP7) have also been studied. Low reorganizational energy (holes and electrons) values provide high charge mobility, and all the designed compounds are efficient in this regard. Here, BP6 exhibits low excitation energy (1.66 eV), highest open circuit voltage (2.00 V), normalized VOC (77.23), and fill factor (0.931). Consequently, the superiority of the designed molecules advises experimenters to envision future developments in extremely effective OSC devices.

An Efficient One-Step Reaction for the Preparation of Advanced Fused Bistetrazole-Based Primary Explosives.

The first example of [5,6,5]-tricyclic bistetrazole-fused energetic materials has been obtained through a one-step reaction from commercial and inexpensive 4,6-dichloro-5-nitropyrimidine. This one-step reaction including nucleophilic substitution, nucleophilic addition, cyclization, and electron transfer is rarely reported, and the reaction mechanism and scope is well investigated. Among target compounds, organic salts exhibit higher detonation velocities (D: 8898-9077 m s-1) and lower sensitivities (IS: 16-20 J) than traditional high energy explosive RDX (D = 8795 m s-1; IS = 7.5 J). In addition, the potassium salt of 5-azido-10-nitro-bis(tetrazolo)[1,5-c:5',1'-f]pyrimidin (DTAT-K) possesses excellent priming ability, comparable to traditional primary explosive Pb(N3)2, and ultralow minimum primary charge (MPC = 10 mg), which is the lowest MPC among the reported potassium-based primary explosives. The simple synthesis route, free of heavy metal and expensive raw materials, makes it promising to quickly realize this material in large-scale industrial production as a green primary explosive. This work accelerates the upgrade of green primary explosives and enriches future prospects for the design of energetic materials.

Crystal morphology prediction of CL-20 and 1,4-DNI co-crystal at different temperatures.

CONTEXT: The morphologies of hexanitrohexaazaisowurtzitane (CL-20) and 1,4-dinitroimidazole (1,4-DNI) co-crystal under vacuum or solvent at different temperatures were predicted. The CL-20/1,4-DNI co-crystal has six important growth crystal planes: (002), (011), (101), (11‒1), (110), (111). The areas of (002), (101), and (011) planes account for a relatively large proportion, which are important crystal planes that affect the crystal morphology. The crystal habits at different temperatures were simulated. The simulation results showed that the crystal plane attachment energy of CL-20 and 1,4-DNI co-crystal increases with the increase of temperature, indicating that the increase of temperature is conducive to the growth of crystal planes. The aspect ratio decreases with the increase of temperature and the morphology of co-crystal becomes more spherical at a higher temperature. The theoretical predictions are in good agreement with the experiment. The simulation results can provide guidance for the crystallization of CL-20/1,4-DNI to obtain a nearly spherical crystal morphology. METHODS: The CL-20/1,4-DNI unit cell structure was geometrically optimized by the COMPASS force field. The AE model was used to predict the morphology of CL-20/1,4-DNI under vacuum, resulting in the most morphologically important growth planes. Ethyl acetate was selected as the solvent. The interaction energy between the solvent and the crystal plane, and the attachment energies in solvent at 298 K, 320 K, 340 K, 360 K, and 380 K were predicted. The NVT ensemble is used in the molecular dynamics calculation process. The simulation step is 1 fs and the total simulation time is 500 ps. The Andersen thermostat is selected as the temperature control method. In the potential energy calculation, the atom-based and Ewald methods were selected to calculate the van der Waals force and the electrostatic interaction force, respectively.

Organic conversion tea farms can have comparable economic benefits and less environmental impacts than conventional ones-A case study in China.

Lack of experience concerning the organic conversion period and its associated challenges have made it difficult for conventional farmers to convert to organic farming. In this study, using a combined life cycle assessment (LCA) with data envelopment analysis (DEA) approach, we investigated farming management strategies, and environmental, economic, and efficiency impacts of organic conversion tea farms (OCTF, N = 15) compared to conventional (CTF, N = 13) and organic (OTF, N = 14) tea farms in Wuyi County, China for a year-round (2019). We found that the OCTF reduced agricultural inputs (environmental impacts) and applied more manual harvesting (increased added value) to pull through the conversion period. According to the LCA results, OCTF showed a similar integrated environmental impact index compared with OTF but significantly (P < 0.05) lower than CTF at both midpoint and endpoint levels. In terms of economic assessment, OTF showed the significantly highest total revenue (18.7 thousand $ ha-1 yr-1) and profit (13.7 thousand $ ha-1 yr-1) (P < 0.05) among the farm types. In contrast, OCTF and CTF did not show significant differences in relation to these economic indicators (P > 0.05). The total cost and cost-profit ratio did not show significant differences among the three farm types. Considering the DEA analysis, there were no significant differences in the technical efficiency of all farm types. However, the eco-efficiency of OCTF and OTF was significantly higher than that of CTF. Therefore, conventional tea farms can survive the conversion period with competitive economic and environmental benefits. In this regard, policies should promote organic tea cultivation and agroecological practices to enhance the sustainable transformation of tea production systems.

Facile synthesis of triazine-based microporous organic network for high-efficient adsorption of flumequine and nadifloxacin: A comprehensive study on adsorption mechanisms and practical application potentials.

Flumequine (FLU) and nadifloxacin (NAD), as emerging contaminants, have received extensive attention recently. In this study, a triazine-based microporous organic network (TMON) was synthetized and developed as an excellent adsorbent for FLU and NAD. The adsorption behavior and influence factors were investigated in both single and binary systems. Insight into the adsorption mechanisms were conducted through experiments, models, and computational studies, from macro and micro perspectives including functional groups, adsorption sites, adsorption energy and frontier molecular orbital. The results showed that the maximum adsorption capacities of TMON for FLU and NAD are 325.27 and 302.28 mg/g under 30 °C higher than records reported before. TMON exhibits the better adaptability and anti-interference ability for influence factors, leading to the preferable application effect in kinds of real water samples. TMON also shows the application potentials for the adsorption of other quinolone antibiotics and CO2 capture. Hydrogen-bonding interaction played the most critical role compared to π-π stacking effect, π-π electron-donor-acceptor interaction, CH-π interaction, and hydrophobic interaction during the adsorption. TMON could be regarded as a promising environmental adsorbent for its large surface area, stable physical and chemical properties, excellent recyclability, and wide range of applications.

Decomposition mechanism of 1,3,5-trinitro-2,4,6-trinitroaminobenzene under thermal and shock stimuli using ReaxFF molecular dynamics simulations.

To obtain atomic-level insights into the decomposition behavior of 1,3,5-trinitro-2,4,6-trinitroaminobenzene (TNTNB) under different stimulations, this study applied reactive molecular dynamics simulations to illustrate the effects of thermal and shock stimuli on the TNTNB crystal. The results show that the initial decomposition of the TNTNB crystal under both thermal and shock stimuli starts with the breakage of the N-NO2 bond. However, the C6 ring in TNTNB undergoes structural rearrangement to form a C3-C5 bicyclic structure at a constant high temperature. Then, the C3 and C5 rings break in turn. The main final products of TNTNB under shock are N2, CO2, and H2O, while NO,  N2, H2O and CO are formed instead at 1 atm under a constant high temperature. Pressure is the main reason for this difference. High pressure promotes the complete oxidation of the reactants.

Nitrogen-rich polycyclic pentazolate salts as promising energetic materials: theoretical investigating.

Pentazolate (cyclo-N5-) salts are nitrogen-rich compounds with great development potential as energetic materials due to their full nitrogen anion. However, the densities of available N5- salts are generally low, which seriously lowers their performances. It is necessary to screen out cyclo-N5- salts with high density. To this end, eight new non-metallic cyclo-N5- salts based on fused heterocycle were designed. -NH2, -NO2, and -O- groups were introduced into the compounds to adjust and improve the detonation performance and impact sensitivity of cyclo-N5- salts. By theoretical calculations and Hirshfeld surface analyses, the densities, heats of formation, detonation performance, sensitivities, and crystal structures of the title compounds were predicted, and the contribution of hydrogen bond as well as π-π stacking to the stability of cyclo-N5- salt was revealed. The results indicate that the densities of title compounds are higher than 1.85 g cm‒3, and the sensitivities of these compounds are predicted to be lower than that of HMX. The detonation properties of a (D = 9.47 km s-1, P = 41.21 GPa) and d (D = 9.44 km s-1, P = 40.26 GPa) are better than those of HMX. These mean that using fused ring as a cation and introducing proper substituents are an effective method to improve cyclo-N5- salt's density and balance the detonation performance and sensitivity.

Overlapping Root Architecture and Gene Expression of Nitrogen Transporters for Nitrogen Acquisition of Tomato Plants Colonized with Isolates of Funneliformis mosseae in Hydroponic Production.

Understanding the impact of arbuscular mycorrhizal fungi (AMF) upon the nitrogen (N) uptake of tomato (Lycopersicum esculentum L.) plants is crucial for effectively utilizing these beneficial microorganisms in industrial hydroponic tomato production. Yet it remains unknown whether, besides fungal delivery, the AMF also affects N uptake via altered plant root growth or whether, together with changed N transporters expression of hosts, this impact is isolate-specific. We investigated tomato root architecture and the expression of LeAMT1.1, LeAMT1.2, and LeNRT2.3 genes in roots inoculated with five isolates of Funneliformis mosseae, these collected from different geographical locations, under greenhouse conditions with nutritional solution in coconut coir production. Our results revealed that isolate-specific AMF inoculation strongly increased the root biomass, total root length, surface area, and volume. Linear relationships were found between the total root length and N accumulation in plants. Furthermore, expression levels of LeAMT1.1, LeAMT1.2, and LeNRT2.3 were significantly up-regulated by inoculation with F. mosseae with isolate-specific. These results implied N uptake greater than predicted by root growth, and N transporters up-regulated by AMF symbiosis in an isolate-specific manner. Thus, an overlap in root biomass, architecture and expression of N transporters increase N acquisition in tomato plants in the symbiosis.

Three-dimension hierarchical composite via in-situ growth of Zn/Al layered double hydroxide plates onto polyaniline-wrapped carbon sphere for efficient naproxen removal.

In this work, a novel adsorbent, 3D hierarchical CS@PANI@ZnAl-LDH composite, has been successfully fabricated through the hydrothermal synthesis of the carbon sphere, oxidative polymerization of polyaniline, and in-site growth of ZnAl-layered double hydroxides, simultaneously applied for the naproxen removal from aqueous solutions. The dynamics and isotherms fit better with the pseudo-second-order and Langmuir model, demonstrating the chemisorption, monolayer, and endothermic process. In addition, the high uptake capacities of CS@PANI@ZnAl-LDH for naproxen was 545.5 mg/g at 298 K when the pH was 5.0, outperforming most previously reported materials. Moreover, after five adsorption-desorption cycles, the spent CS@PANI@ZnAl-LDH maintains high removal efficiency and structural composition, revealing excellent recyclability and stability. Furthermore, Fourier transformed infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS) analyses indicate electrostatic interactions, π-π interactions, and hydrogen bonding between CS@APNI@ZnAl-LDH and naproxen. Quantitative analyses, Localized orbit locator (LOL)-π isosurface, and Independent Gradient Model further verify the adsorption mechanisms mentioned above, indicating the synergistic effects between PANI and ZnAl-LDH improve the elimination ability for naproxen. Significantly, Hirshfeld surface analyses reveal that naproxen behaves as the H-bond acceptor, and the ZnAl-LDH acts as the H-bond donor. This work provided a feasible way to design purification materials for wastewater treatment.

Peroxymonosulfate activation through 2D/2D Z-scheme CoAl-LDH/BiOBr photocatalyst under visible light for ciprofloxacin degradation.

The synergistic effect between photocatalytic and peroxymonosulfate (PMS) activation has been widely applied in the field of sewage treatment. In this work, we synthesized a two-dimensional/two-dimensional (2D/2D) CoAl-LDH/BiOBr Z-scheme photocatalyst via a simple method. Then, multiple detection results demonstrated that CoAl-LDH was successfully anchored onto BiOBr, as well as formed an intimate interaction. Moreover, the photocatalytic degradation performance of the catalysts/PMS/vis system had been explored under several conditions (e.g., different catalyst doses, PMS doses, anions and pollutants). The 8 wt% CoAl-LDH/BiOBr composite exhibited the highest degradation efficiency (96%) of ciprofloxacin (CIP). In addition, radicals quenching experiments and electron paramagnetic resonance (EPR) indicated that •O2- and 1O2 were the primary radicals for CIP degradation. The photoelectrochemical measurement and photoluminescence (PL) confirmed that 8 wt% CoAl-LDH/BiOBr exhibited the highest separation and transfer rate of charge carriers. The liquid chromatography-mass spectrometer (LC-MS) analysis revealed that oxidation of the piperazine ring and defluorination were the main CIP degradation pathways. Density functional theory (DFT) calculation, including the laplacian bond order (LBO) and Fukui index, which was consistent with the results of LC-MS. This study explained the superiority of the synergistic effect between photocatalysis and PMS activation on the degradation of pollutants.

Atomic perspective revealing for combustion evolution of nitromethane/nano-aluminum hydride composite.

Adding aluminum hydride (AlH3) into energetic materials (EMs) can improve their combustion and energy performance effectively. However, the potential mechanism of AlH3 on EMs is still unclear. Based on the ReaxFF-lg method, the thermal decomposition of nitromethane/nano-aluminum hydride (NM/nano-AlH3) composites were studied. The addition of AlH3 reduces the energy barrier and increases the energy release during the decomposition of NM, accelerates the decomposition of NM. The main way of AlH3 oxidation involves the capture of O atoms from NM. The results show that AlH3 content and passivated layer affect the oxidation and hydrogen release of AlH3. The explosion of small particle size AlH3 leads to rapid oxidation and hydrogen release. The oxidation of large particle size AlH3 is dominated by the inward and outward diffusion of O and Al atoms. The products of NM/nano-AlH3 composites are H2O, CO2, N2 gases, and Al clusters. This work is expected to guide the application of AlH3 in EMs.

Encapsulating aluminum nanoparticles into carbon nanotubes for combustion: a molecular dynamics study.

Metal nanoparticles are easily deactivated by migration-aggregation in combustion. Encapsulated nanoparticles are one of the tools for coping with the stability challenges of metal nanoparticles. The self-assembly details of aluminum nanoparticles (ANPs) encapsulated into carbon nanotubes (CNTs) were demonstrated by molecular dynamics simulations. The simulation results show that ANPs can completely self-roll into CNTs to form a stable core-shell structure by inertial force and van der Waals force. Inside the tubes, ANPs move toward the cap at a velocity of 2.27 Å ps-1. However, it increases to 3.17 Å ps-1 when near the cap of CNTs. The initiation of the ANPs' oxidation and degradation can be effectively checked by coating CNTs. The diffusion of the Al atoms in the encapsulated ANPs occurred earlier than their oxidation in combustion, verified by using ReaxFF molecular dynamics simulations. The morphological evolutions of the nanostructures in the initial combustion of the encapsulated ANPs are predicted. The interplay between the encapsulated ANPs' responses and external stimuli is classified into core-shell separation, shell damage, and core-shell burst, which provides insights into the oxidation mechanism of encapsulated nanoparticles.

Coarse-grained force-field for large scale molecular dynamics simulations of polyacrylamide and polyacrylamide-gels based on quantum mechanics.

We developed a new coarse-grained (CG) molecular dynamics force field for polyacrylamide (PAM) polymer based on fitting to the quantum mechanics (QM) equation of state (EOS). In this method, all nonbond interactions between representative beads are parameterized using a series of QM-EOS, which significantly improves the accuracy in comparison to common CG methods derived from atomistic molecular dynamics. This CG force-field has both higher accuracy and improved computational efficiency with respect to the OPLS atomistic force field. The nonbond components of the EOS were obtained from cold-compression curves on PAM crystals with rigid chains, while the covalent terms that contribute to the EOS were obtained using relaxed chains. For describing PAM gels we developed water-PAM interaction parameters using the same method. We demonstrate that the new CG-PAM force field reproduces the EOS of PAM crystals, isolated PAM chains, and water-PAM systems, while successfully predicting such experimental quantities as density, specific heat capacity, thermal conductivity and melting point.

Theoretical research about nonmetallic energetic salts with pentazolate anion.

Significant progress has been made in the synthesis of nitrogen-rich high-energy salts by pairing pentazolate anion (cyclo-N5-) with different cations since cyclo-N5- was synthesized. It is difficult to screen out cyclo-N5- salts with high energy quickly and effectively in experiment, while theoretical research can realize this goal. Herein, nineteen high-energy salts, which were composed of tetrazole cation and cyclo-N5- anion, were designed. And their properties were studied via density functional theory and volume-based thermodynamic methods. The results indicate that most salts have high densities, low sensitivities, and good detonation properties. In particular, salt 14 (ρCalib = 1.802 g/cm3, ΔHf = 1058.4 kJ/mol, D = 9.38 km/s, P = 39.10 GPa, h50 = 44.92 cm) exhibits excellent detonation performance (approximating that of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20)) superior to 1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), and lower impact sensitivity than CL-20 or HMX. Hence salt 14 is regarded as promising candidates for high-performance energetic materials.

Phytochelatins formation kinetics and Cd-induced growth inhibition in Lolium perenne L. at elevated CO2 level under Cd stress.

Elevated CO2 levels may alleviate toxicities induced by environmental stresses in plants, such as heavy metals. To assess this possibility, seedlings of Lolium perenne L. were exposed to different Cd stress and CO2 levels during hydroponic culture. The kinetics of growth, Cd accumulation, and thiol formation were investigated. Elevated CO2 levels increased the growth rate from 30 to 75%, and decreased the Cd accumulation rate from 36 to 42%, leading to a decrease of Cd content in root and shoot. However, an increase in Cd transport from root to shoot was observed at elevated CO2 under Cd stress. The production of phytochelatins (PCs) occurred earlier at elevated CO2 level than at ambient CO2 level after exposure to Cd stress. The mean SH/Cd ratio was relatively higher at elevated CO2 level, but elevated CO2 level significantly decreased thiol contents. The reduction of Cd contents, earlier production of PCs, and relatively higher SH/Cd ratio at the elevated CO2 level alleviated Cd toxicity in root and shoot to some extent, causing significant yield increase of L. perenne after exposure to Cd stress. This study could provide an important data support and theoretical basis in understanding the effects of elevated CO2 on plant growth, heavy metal accumulation, and thiol formation.

Reactive molecular dynamics simulation of thermal decomposition for nitromethane/nano-aluminum composites.

The thermal decomposition of pure nitromethane (NM) and NM/nano-aluminum (Al) composites was simulated by reactive molecular dynamics with ReaxFF-lg corrected force field parameters. The initial decomposition pathway of NM molecules in pure NM is C-N bond rupture. However, NM is decomposed early by the initial pathway of N-O bond rupture when it mixes with nano-Al because of the strong attraction of Al to O. The decomposition process of NM/nano-Al can be divided into three stages: adsorption, slow decomposition, and rapid decomposition. The addition of nano-Al particles decreases the energy barrier in decomposition, increases the released energy, and reduces the decomposition temperature of NM. Adding 3% Al to the explosive can make the detonation pressure 3.083% higher than that of pure system. Compared with pure NM, the energy barrier of 16% Al composite is 25.63 kcal/mol lower and the energy released is 22.99 kcal/mol more. There is an optimal amount of Al contents being added to the NM composite by which the largest total numbers of gaseous products (N2, H2O, and CO2) are released. The effect of Al additives on CO2 production is the most obvious. The maximum detonation pressure can be achieved by adding an appropriate amount of nano-Al, which is similar to the experimental results. Graphical abstract.

Thermal Decomposition Mechanism of 1,3,5,7-Tetranitro-1,3,5,7-tetrazocane Accelerated by Nano-Aluminum Hydride (AlH3): ReaxFF-Lg Molecular Dynamics Simulation.

ReaxFF-low-gradient reactive force field with CHONAl parameters is used to simulate thermal decomposition of 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX) and AlH3 composite. Perfect AlH3 and surface-passivated AlH3 particles were constructed to mix with HMX. The simulation results indicate HMX is adsorbed on the surface of particles to form O-Al and N-Al bonds. The decomposition of HMX and AlH3 composite is an exothermic reaction without energy barrier, but the decomposition of pure HMX needs to overcome the energy barrier of 133.57 kcal/mol. Active nano-AlH3 causes HMX to decompose rapidly at low temperature, and the primary decomposition pathway is the rupture of N-O and C-N bonds. Adiabatic simulation shows that the energy release and temperature increase of HMX/AlH3 is much larger than those of the HMX system. Surface-passivated AlH3 particles only affect the initial decomposition rate of HMX. In HMX and AlH3 composites, the strong attraction of Al in AlH3 to O and the activation of the intermediate reaction by H2 cause HMX to decompose rapidly. The final decomposition products of pure HMX are H2O, N2, and CO2, and those of HMX/AlH3 are H2O, N2, and Al-containing clusters dominated by C-Al. The final gas production shows that the specific impulse of HMX/AlH3 is larger than that of HMX.