Energetic Parameters Research Articles

Fabrication of Energetic Metal-Organic Frameworks: Potassium 5-Carboxylato-3,4-Dinitropyrazole and Potassium 5-(Hydrazinecarbonyl)-3,4-Dinitropyrazole.

Energetic materials have been widely applied in civil and military fields, whose thermostability is a key indicator to evaluate their safety levels under severe conditions. Herein, two novel energetic metal-organic frameworks (EMOFs), namely, 4 and 6, were experimentally obtained and comprehensively characterized. The two EMOFs both possess unique three-dimensional (3D) coordination structures. With a high crystal density of 2.184 g·cm-3, EMOF 4 exhibits outstandingly superior thermostability (onset: 290 °C; peak: 303 °C), while EMOF 6 features onset and peak decomposition temperatures of 220 and 230 °C. The calculated energetic parameters of 4 and 6 are as follows: detonation velocity: 8731 m·s-1 and 8294 m·s-1; detonation pressure: 26.5 and 26.4 GPa. Compared to EMOF 6, EMOF 4 features high energy, excellent thermostability, and low mechanical sensitivities, which should be partly attributed to more plentiful coordination interactions. More coordination bonds are conducive to strengthening the EMOF framework, which needs much more energy to collapse, thereby maintaining higher thermal stability. The above favorable characteristics not only indicate EMOF 4 has a promising future in applications as a thermostable explosive but also provide an effective and feasible strategy for developing novel heat-resistant energetic materials via reinforced frame structures of EMOFs.

Facile synthesis of a recyclable multifunctional magnetic adsorbent prepared from H2O2-modified carbon clay/rice flour polymer/Fe3O4 nanoparticles interface for effective removal of ibuprofen

BackgroundThe combination between magnetite nanoparticles with natural carbohydrate polymers and aluminosilicates is recommended to be a positive strategy in the design of a new type of low-cost, high–efficiency, and eco-friendly magnetic adsorbents for decontamination of toxic pharmaceutical compounds from water. In particular, ibuprofen (IBP) is found to be one of the common drugs detected in water bodies, which is a suggestively alarming state. MethodsA fresh sample of gossan (iron-bearing weathered product) was used in the fabrication of magnetite nanoparticles (MNPs) to be used in the decoration of a bio-composite prepared from H2O2-activated black clay (BC) and biodegradable rice flour (RF) interface. The as-synthesized magnetic biosorbent (BC/RF/MNPs) was characterized by FTIR, FESEM, TEM, XRD, DSC, and TGA techniques and employed in the remediation of ibuprofen at pH 7.0 and temperatures of 25, 40, and 50°C. The adsorption results were fitted to kinetics, traditional isotherms, and statistical physical models to better understand the interaction between IBP and BC/RF/MNPs adsorbent. Significant findingThe pseudo-second-order (PSO) and Freundlich equations described the IBP adsorption system. Monolayer and double-layer advanced statistical physics models were employed to analyze the geometry and interactions mechanism at the molecular scale. The double-layer model showed the best-fitting results, and thus, its steric and energetic parameters and thermodynamic functions were explained. The number of the removed IBP molecules per site (steric n parameter) ranged from 0.55 to 0.84 suggesting the involvement of parallel and non-parallel orientations in the removal process. The adsorption capacity at saturation (Qsat) increased from 45.73 to 67.90mg/g at 25 - 50 ºC signifying endothermic interactions. The adsorption energy ranged from 0.42 to 3.42kJ/mol reflecting the physical interactions between IBP and BC/RF/MNPs. Thermodynamic functions suggested the endothermic and spontaneous nature of the IBP adsorption process. Adsorption/desorption results suggested the high stability and economic benefit of BC/RF/MNPs sorbent.

Frequency conversion of a chirped Ti:sapphire laser pulse to 11.4 μm wavelength with SrMoO4 Raman shifter and LiGaS2 DFG crystal

The simple mid-IR laser source based on femtosecond Ti:Sapphire laser and successive frequency conversion of its stretched up to 50 ps pulses in SrMoO4 Raman-active crystal and LiGaS2 second order nonlinear crystal is demonstrated. Energy of the mid-IR pulse at 11.4 μm wavelength was up to 250 nJ that was four times higher than the previous results for the similar setup. The influence of pump pulse intensity on spectral and energetic parameters of laser pulses after SrMoO4 and LiGaS2 crystals were studied in details.

Divalent transition metal complexes of nitrogen, oxygen and sulfur containing ligand: design, structural, spectral, pH-metric, theoretical molecular modeling, analytical and mechanism studies

In the present study, the 1-Nicotinoyl-4-phenyl thiosemicarbazide (H2NPT) multidentate nitrogen, oxygen and sulfur containing ligand is being synthesized in a simple single step reaction by condensing 1:1 molar ratio of ethanolic solutions of both phenyl isothiocyanate and nicotinoyl hydrazine. The prepared H2NPT and its complexes with Co2+, Ni2+ and Zn2+ and Cu2+ were characterized by pH-metric titrations, elemental analysis, FTIR, electronic spectra and thermogravimetric (TGA) analyses. The association constant of the ligand and the stability constants of its complexes were calculated by pH-metric measurements in 50% ethanol–water mixture. Also, DFT method was used to draw the geometry of all compounds and the parameters such as bond lengths, bond angles, dipole moment, Frontier orbitals (HOMO, LUMO), MEP and other energetic parameters (optical energy gap, softness, hardness, electronegativity) were evaluated. The prepared H2NPT reacted with Co2+, Ni2+ and Zn2+ and Cu2+ metal ions to form colored precipitates that were readily floated to the surface solution using oleic acid (HOL) surfactant with vigorous shaking of the flotation cell. The heavy metals' concentrations in the dissolved precipitates are determined by flame atomic absorption spectrometry (FAAS). The different parameters affecting the flotation process were thoroughly investigated, viz. pH of sample solution, concentration of ligand, metal ions and HOL, temperature and interfering ions. Nano-gram quantities of Cu2+, Co2+, Ni2+ and Zn2+in 1500-ml samples are quantitatively determined with 1-Nicotinoyl-4-phenyl thiosemicarbazide (H2NPT) at pH 3.0–6.5 for Cu2+ and at 7.0–7.5 for Co2+, Ni2+ and Zn2+. The concentrations of these heavy metals are increased 300-fold. Interferences, on the flotation process, from various foreign ions were avoided by adding excess H2NPT. The mode of chelation between H2NPT and the investigated metal ions is proposed to be through the S, N and/or O atoms of the ligand. The mechanism of flotation is proposed to be due to an electrostatic interaction between the HOL surfactant and the formed metal–ligand complexes through H-bond formation. The proposed multi-element flotation methodology has been utilized for the determination of the analytes in certified reference materials, alloys, synthetic mixtures and in water samples with a recovery % more than 90% and a relative standard deviation (RSD), as a precision < 2%.

Ligand-based drug design of Pinocembrin derivatives against Monkey-Pox disease

Severe pathogen infections, such as Monkeypox disease caused by the Monkeypox virus, easily spread in different animals and then into humans. There is an urge for novel therapeutic options, such as medicine/vaccine development to control it. Therefore, we designed Pinocembrin derivatives and performed in silico analysis such as molecular docking by PyRx software, molecular dynamics (MD) simulations at 100 ns, binding free energy estimation by AMBER20 software, ADMET profile, and Pass prediction. Optimal results were observed for two derivatives (07 and 11), exhibiting interactions with key residues of the selected protein. These interactions were substantiated by a range of structural and energetic parameters, including binding energies, solvation-free energy models, dynamic fluctuations, hydrogen bonding, and solvent accessibility. Notably, ligands 07 and 11 displayed exceptional binding affinities of −10.3 kcal/mol and −9.6 kcal/mol, respectively. RMSD value presented minor abruptions of about 1.2 to 1.3 Å and superimposed structures of selected derivatives complexes with Monkeypox target protein at 0 ns and 100 ns presented minor fluctuation in the native and bounded conformation. Slight instability is noted from the peaks in graphs of RMSD, RMSF, hydrogen bonds (HBs), beta factor (BF), and solvent-accessible surface area (SASA). Based on promising results, we proposed that Pinocembrin derivatives may serve as novel therapeutic agents against Monkeypox infections. Therefore, strongly advocate for further experimental validation through chemical laboratory testing. Such endeavors could pave the way for the development of effective treatments to mitigate the impact of Monkey-Pox disease.

Substitution of heating systems in the Italian buildings panorama and potential for energy, environmental and economic efficiency improvement

In many countries, old inefficient generators are used for heating purposes. A way to improve energy efficiency in those countries can be the choice of the most suitable heating generators to replace the current ones, without the inconveniences caused by other retrofit measures. In this context, we present a methodology to choose the most appropriate generator through dynamic simulations applied to building stock energy models. Economic, energetic, and environmental parameters guide the choice. The methodology is applied in the Italian residential building scenario, where the most widespread heating device is traditional boiler. Three options are considered: condensing boiler, heat pump, and hybrid heat pump (an alternative-working system with a condensing boiler and heat pump). For a detailed analysis, a white-box bottom-up building stock energy model is defined, through a statistical analysis, consisting of four building typologies in three different external climates. An hourly dynamic building-system simulation has been performed to obtain energy performance, emissions, and operational costs. The results have demonstrated that condensing boiler allows limited economic, environmental, and energy savings (8-14%), compared to traditional boiler. The highest economic savings are obtained with the hybrid heat pump (20%), while the heat pump alone leads to higher costs, but the highest savings in emissions and non-renewable primary energy (25-50%). The flexibility offered by the hybrid heat pump allows to obtain high savings in different cost scenarios, but also to further reduce CO2 emissions by implementing an environmental-based control strategy.

Synergetic, steric, and energetic properties of exfoliated kaolinite and its methanol hybridized structure during the adsorption of bisphenol-A residuals from the aqueous environment

The adsorption potentiality of exfoliated kaolinite (EK) and its methanol hybridized product (MX.EK) for bisphenol-A (BSP-A) were assessed in synergetic studies to investigate the impact of the modification processes. The adsorption properties were illustrated based on the steric and energetic parameters of the applied advanced equilibrium modeling (monolayer model of one energy). The methanol hybridization process induced the adsorption properties of BSP-A significantly to 228.8 mg/g as compared to EK (160 mg/g) and raw kaolinite (K) (111.7 mg/g) during the saturation state. The steric investigation suggested a notable increase in the quantities of the active sites after the exfoliation process (Nm = 30.6 mg/g) and methanol functionalization (Nm = 49.2 mg/g) which illustrate enhancement in the BSP-A uptake capacity of MX.EK. Moreover, each active site of MX.EK can absorb about 8 molecules of BSP-A which occur in a vertical orientation. The energetic studies including Gaussian energy (˂ 8 KJ/mol) and adsorption energy (˂ 40 KJ/mol) demonstrate the physical uptake of BSP-A which might involve co-operated dipole bonding forces (2–29 kJ/mol) and hydrogen bonding (˂ 30 kJ/mol). The behaviors and values of entropy, intern energy, and free enthalpy as the assessed thermodynamic functions validate the exothermic and spontaneous properties of the BSP-A adsorption by EK and MX.EK composite.

Automated Generation of Microkinetics for Heterogeneously Catalyzed Reactions Considering Correlated Uncertainties.

The study presents an ab-initio based framework for the automated construction of microkinetic mechanisms considering correlated uncertainties in all energetic parameters and estimation routines. 2000 unique microkinetic models were generated within the uncertainty space of the BEEF-vdW functional for the oxidation reactions of representative exhaust gas emissions from stoichiometric combustion engines over Pt(111) and compared to experiments through multiscale modeling. The ensemble of simulations stresses the importance of considering uncertainties. Within this set of first-principles-based models, it is possible to identify a microkinetic mechanism that agrees with experimental data. This mechanism can be traced back to a single exchange-correlation functional, and it suggests that Pt(111) could be the active site for the oxidation of light hydrocarbons. The study provides a universal framework for the automated construction of reaction mechanisms with correlated uncertainty quantification, enabling a DFT-constrained microkinetic model optimization for other heterogeneously catalyzed systems.

Automatisierte Generierung von Mikrokinetiken für heterogen katalysierte Reaktionen unter Berücksichtigung korrelierter Unsicherheiten**

AbstractDie Studie stellt eine ab initio basierte Methode für die automatische Konstruktion von detaillierten Mikrokinetiken vor, welche korrelierte Unsicherheiten in allen energetischen Parametern und Schätzroutinen berücksichtigt. Hierfür wurden innerhalb des Unsicherheitsraums des BEEF‐vdW Funktionals 2000 Mikrokinetiken für die Oxidationsreaktionen repräsentativer Abgasemissionen von stöchiometrischen Verbrennungsmotoren auf Pt(111) generiert und durch Multiskalenmodellierung mit Experimenten verglichen. Das Ensemble der Simulationsergebnisse unterstreicht die Bedeutung der Berücksichtigung von Unsicherheiten. Innerhalb dieses Ensembles ist es möglich, eine Mikrokinetik zu identifizieren, welche mit den experimentellen Daten übereinstimmt. Diese Mikrokinetik lässt sich auf ein einziges Austausch‐Korrelations‐Funktional zurückführen und legt nahe, dass Pt(111) das aktive Zentrum für die Oxidation leichter Kohlenwasserstoffe sein könnte. Die Studie bietet einen universellen Rahmen für die automatisierte Konstruktion von Reaktionsmechanismen unter Berücksichtigung korrelierter Unsicherheiten und ermöglicht eine DFT‐basierte Optimierung der Mikrokinetik auch für andere heterogen katalysierte Systeme.

Nano‐sized Co(II), Ni(II), and Zr(IV) complexes of quinaldine‐based azo dye for promising therapeutic and catalytic applications: Synthesis, characterization, density functional theory studies and molecular docking

Novel azo dye containing the heterocyclic quinaldine nucleus, 3‐((2‐methylquinolin‐4‐yl)diazenyl)naphthalen‐2‐ol HL, and its Co(II), Ni(II) and Zr(IV) nano‐sized metal chelates have been synthesized and fully characterized by alternative analytical and spectral techniques. The finding indicated that the ligand coordinated as a monobasic bidentate via azo nitrogen and hydroxyl oxygen atom, resulting in octahedral geometry towards Co(II) and Zr(IV) complexes, and square planer geometry towards Ni(II) metal ion. Theoretical studies by DFT/B3LYP/6‐311+G(d,p)/LANLDZ including energetic parameters, geometrical optimization, dipole moment, and HOMO–LUMO energy gap were applied to support the geometrical arrangement of the complexes. The produced complexes were generated at the nanoscale, as evidenced by the average particle size from TEM. The average particle size calculated from TEM images for Co(II), Ni(II), and Zr(IV) complexes is 6.0, 12.0, and 5.5 nm, respectively. The antibacterial activity of the ligand compared with its metal complexes shows enhanced activity over the metal complexes against different types of bacteria. Antitumor efficacy of the compounds was tested against A‐549 and PANC‐1 cells, compared with the vinblastine standard. The cytotoxic efficiency of both Co(II) and Ni(II) complexes exceeded that of vinblastine. The anticancer activity of the Zr complex was then studied using molecular docking to determine the interactions between this molecule and PANC‐1. Docking studies revealed that the Zr complex produces four hydrogen bond contacts with the active amino acid residues Arg 136 and Asp 140, two hydrophobic interactions with Val 50 and Leu 147, and two electrostatic interactions with Arg 136. Also, the catalytic property of the free ligand and nanocomplexes were tested on the oxidative degradation of methyl violet 2B dye in the presence of H2O2. The following arrangement was observed for the pseudo‐first‐order rate constants: Co(II) complex (0.068 min−1) &gt; Ni(II) complex (0.066 min−1) &gt; Zr(IV) complex (0.061 min−1) &gt; HL (0.037 min−1).

Does alkyl chain unsaturation affect tunability of the aryl alkyl imidazolium‐based ion pairs?

AbstractThree series of functionalized ion pairs composed of ethyl phenyl imidazolium [PhIM(C2H5)]+, (vinyl) ethenyl phenyl imidazolium [PhIM(C2H3)]+and ethynyl phenyl imidazolium [PhIM(C2H)]+cations and acetate ([Y1]−), nitrate ([Y2]−), tetrafluoroborate ([Y3]−) and perchlorate ([Y4]−) anions were designed and their physical and chemical properties were analyzed at M06‐2X‐GD3/AUG‐cc‐pVDZ level of theory. The effect of alkyl chain unsaturation on structural characteristics, energetic parameters, electronic and topological properties, and the global reactivity parameters and also on some physical and chemical properties such as dipole moment, melting point, and electrochemical window of the introduced IPs was discussed. Based on electrochemical window values, the studied IPs including alkyl chain unsaturation in the cation and [Y1‐2]−anions have no suitable electrochemical stability for use in electrochemical devices.

The influence of hydrogen and oxygen (HHO) gas on engine characteristics under the effect of the lean mixtures of gasoline and bioethanol

Along with the imposed stricter ecological requirements, the new manners of reducing the emitted pollutants are extensively researched. One of the requisites is the focus on the absence or the use of an extremely low count of carbon-based fuels as an option for the internal combustion engine. The conducted research demonstrates the perspective of applying bioethanol containing hydrogen and oxygen (HHO) gas as a fuel additive to stoichiometric (λ = 1.0) and lean (λ = 1.1; 1.2; 1.3; 1.4) mixtures for gasoline employing the spark ignition engine considering changes in ignition timing in the range from 16° to 42° BTDC. Ecological (CO, CO2, HC, NOx) and energetic (torque, fuel consumption, break thermal efficiency) parameters have been measured using gasoline and bioethanol (fuels E10 and E70) enriched with HHO gas. Hydrogen and oxygen gases are produced using a HHO gas generator, which is a mobile electrolysis unit. It has been concluded that a higher concentration of ethanol in fuel and the HHO additive result in higher torque for all evaluated air/fuel ratios. The rate of the analysed heat release has showed that HHO gas increases combustion speed, shortens combustion duration and has the highest positive effect of thermal efficiency when the mixtures are lean and have a higher concentration of ethanol. The use of the HHO additive has increased NOx emissions, although CO, CH and CO2 have remained lower. The regulation of the excess air ratio and ignition timing allows for selecting the most energetically-efficient adjustment parameters and to objectively evaluate the possibilities of improving energetic and ecological indicators for engines replacing gasoline with bioethanol and additionally supplying HHO gas.

Microstructure of TiAl Capsules Processed by Electron Beam Powder Bed Fusion Followed by Post-Hot Isostatic Pressing.

The microstructures of intermetallic γ-titanium aluminide (TiAl) alloys are subjected to a certain degree of Al evaporation when processed by electron beam powder bed fusion (EB-PBF). The magnitude of the Al-loss is mainly correlated with the process parameters, and highly energetic parameters produce significant Al evaporation. The Al-loss leads to different microstructures, including the formation of inhomogeneous banded structures, thus negatively affecting its mechanical performance. For this reason, the current work deals with creating EB-PBFed TiAl capsules with the inner part produced using only the pre-heating step and melting parameters with low energetic parameters applying high beam speed from 5000 to 3000 mm/s. This approach is investigated to reduce the Al-loss and microstructure inhomogeneity after hot isostatic pressing (HIP). The results showed that the HIP treatment effectively densified the capsules obtaining a relative density of around 100%. After HIP, the capsules produced with the inner part melted at 3000 mm/s presented a lower area shrinkage (around 6.6%) compared to the capsules produced using only the pre-heating step in the core part (around 20.7%). The different magnitudes of shrinkage derived from different levels of residual porosity consolidated during the HIP process. The HIPed capsules exhibited the presence of previous particle boundaries (PPBs), covered by α2 phases. Notably, applying low energetic parameters to melt the core partially eliminates the particles' surface, thus reducing the PPBs formation. In this case, the capsules melted with low energetic parameters (3000 mm/s) exhibited α2 concentration of 3.5% and an average size of 13 µm compared to the capsules produced with the pre-heating step in the inner part with an α2 around 5.7% and an average size around 23 µm. Moreover, the Al-loss of the capsules was drastically limited, as determined by X-ray fluorescence (XRF) analysis. More in detail, the capsules produced with the pre-heating step reported an atomic percentage of Al of 48.75, while using low energetic melting parameters led to 48.36. This result was interesting, considering that the massive samples produced with standard parameters (so more energetic ones) revealed atomic Al percentage from 48.04 to 47.70. Finally, the recycled small particles showed a higher fraction of α2 phases with respect to the coarse particles, as determined by X-ray diffraction (XRD).

Structural Determinants of Redox Conduction Favor Robustness over Tunability in Microbial Cytochrome Nanowires.

Structural determinants of a 103-fold variation in electrical conductivity for helical homopolymers of tetra-, hexa-, and octa-heme cytochromes (named Omc- E, S, and Z, respectively) from Geobacter sulfurreducens are investigated with the Pathways model for electron tunneling, classical molecular dynamics, and hybrid quantum/classical molecular mechanics. Thermally averaged electronic couplings for through-space heme-to-heme electron transfer in the "nanowires" computed with density functional theory are ≤0.015 eV. Pathways analyses also indicate that couplings match within a factor of 5 for all "nanowires", but some alternative tunneling routes are found involving covalent protein backbone bonds (Omc- S and Z) or propionic acid-ligating His H-bonds on adjacent hemes (OmcZ). Reorganization energies computed from electrostatic vertical energy gaps or a version of the Marcus continuum expression parameterized on the total (donor + acceptor) solvent-accessible surface area typically agree within 20% and fall within the range 0.48-0.98 eV. Reaction free energies in all three "nanowires" are ≤|0.28| eV, even though Coulombic interactions primarily tune the site redox energies by 0.7-1.2 eV. Given the conserved energetic parameters, redox conductivity differs by < 103-fold among the cytochrome "nanowires". Redox currents do not exceed 3.0 × 10-3 pA at a physiologically relevant 0.1 V bias, with the slowest electron transfers being on a (μs) timescale much faster than typical (ms) enzymatic turnovers. Thus, the "nanowires" are proposed to be functionally robust to variations in structure that provide a habitat-customized protein interface. The 30 pA to 30 nA variation in conductivity previously reported from atomic force microscopy experiments is not intrinsic to the structures and/or does not result from the physiologically relevant redox conduction mechanism.

Abstract P3173: Exposure Of Mitochondria Isolated From Left Ventricular Myocardium Of Dogs With Moderate Heart Failure To 4-hydroxy-2-nonenal (4-hne) Worsens Existing Mitochondrial Dysfunction

Background: Reactive oxygen species (ROS) generated by dysfunction of mitochondria (MITO) of the failing heart plays an important role in lipid peroxidation of polyunsaturated fatty acids in cell and MITO membranes resulting in the production of aldehydes, such as malondialdehyde and 4-hydroxy-2-nonenal (4-HNE). MITO aldehyde dehydrogenase-2 (mALDH2) is a key enzyme for the detoxification of endogenous aldehyde substrates through NAD dependent oxidation. We previously showed that mALDH2 expression and activity are markedly reduced in MITO of failing LV cardiomyocytes, a maladaptation that can lead to considerable accumulation of 4-HNE in MITO. It is unclear whether such an accumulation of 4-HNE can further exacerbate MITO dysfunction resulting in further limitation to ATP formation via oxidative phosphorylation. Hypothesis: This study tested the hypothesis that exposure of MITO isolated from failing hearts to exogenous 4-HNE can result in further deterioration of MITO function. Methods: Freshly isolated MITO from LV myocardium of dogs with moderate heart failure (HF, LV ejection fraction ~40%) were incubated for 1 hour in absence (baseline) and presence of 4-HNE at concentrations of 3 and 30 μM. MITO energetic parameters namely ADP-stimulated respiration (ADPresp), maximal respiratory capacity (MRC) and ATP-linked respiration (ATPresp) were evaluated using an XFe96 analyzer (Seahorse Biosciences). Results: Compared to baseline, exposure of MITO to 3 μM 4-HNE has no significant effects on any of the MITO energetic measures. However, exposure of MITO to 30 μM 4-HNE resulted in significant reduction of ADPresp (490 ± 37 vs. 179 ± 7 OCR pmols/O 2 /min, p&lt;0.05), significant reduction of MRC (334 ± 56 vs. 124 ± 18 OCR pmols/O 2 /min, p&lt;0.05), and significant reduction of ATPresp (48 ± 10 vs. 20 ± 12 OCR pmols/O 2 /min, p&lt;0.05). Conclusions: Exposure of MITO from failing myocardium to elevated levels of 4-HNE can lead to marked deterioration of MITO function that can result in a further reduction of ATP leading to progression of LV dysfunction. Limiting the accumulation of 4-HNE through pharmacologic normalization of ALDH2 activity can potentially represent a therapeutic target for retarding the progression of LV dysfunction toward intractable HF.

Experimental and Theoretical Studies of Hydrogen Storage in LaNi4.4Al0.3Fe0.3 Hydride Bed.

In this article, the experimental measurements of the absorption/desorption P-C-T isotherms of hydrogen in the LaNi4.4Fe0.3Al0.3 alloy at different temperatures and constant hydrogen pressure have been studied using a numerical model. The mathematics equations of this model contain parameters, such as the two terms, nα and nβ, representing the numbers of hydrogen atoms per site; Nmα and Nmβ are the receptor sites' densities, and the energetic parameters are Pα and Pβ. All these parameters are derived by numerically adjusting the experimental data. The profiles of these parameters during the absorption/desorption process are studied as a function of temperature. Thereafter, we examined the evolution of the internal energy versus temperature, which typically ranges between 138 and 181 kJmol-1 for the absorption process and between 140 and 179 kJmol-1 for the desorption process. The evolution of thermodynamic functions with pressure, for example, entropy, Gibbs free energy (G), and internal energy, are determined from the experimental data of the hydrogen absorption and desorption isotherms of the LaNi4.4Al0.3Fe0.3 alloy.

Establishing an orbital-level understanding of active origins of heteroatom-coordinated single-atom catalysts: The case of N2 reduction

Heteroatom-coordinated single-atom catalysts (SACs) supported by porous graphene exhibit high activity in electrochemical reduction reactions. However, the underlying active origins are complex and puzzling, hindering the development of efficient catalysts. Herein, we investigate the active origins of heteroatom-coordinated Fe-XmYn SACs (X, Y = B, C, N, O, m + n = 4) toward nitrogen reduction reaction (NRR) as a model reaction, through comprehensive analysis of structural, energetic, and electronic parameters. Specifically, the number and arrangement of heteroatoms are found to significantly affect the degree of d-orbital splitting and magnetic moment of the Fe center. Moreover, d-orbital splitting energy (dSE), rather than the conventional d-band theory, explains the adsorption behavior of intermediates in multi-step electron–proton coupling (EPC) reactions. In addition, both s- and d-orbitals of Fe are found to be important for Fe–N bonding, which promotes charge transfer (CT) and N2 activation. Importantly, CT is thought to influence the Pauli repulsion and orbital interaction. Correspondingly, relationships are unveiled between limiting potential (Ulimit) and adsorption energy ΔE(*NNH), dSE, CT, Fe–N bond. In all, this work provides orbital-level insights into the active origins of Fe-XmYn SACs, contributing to the understanding of intrinsic mechanism and the design of electrocatalysts for multi-step EPC reactions.

Influence of 24-Epibrassinolide on the Energetic Parameters and Early Stages of Growth and Development in Seedlings of Two Maize (Zea mays L.) Genotypes

Brassinosteroids (BRs) are a class of plant hormones that play important roles in regulating various physiological and developmental processes in plants. One of the most effective BRs involved in modulating crop growth is 24-epibrassinolide (24-EBL). The effects of different concentrations of 24-EBL on various biochemical and biophysical parameters critical to early growth stages and seedling development were investigated using two maize hybrids, ‘ZP 434’ (a new-generation hybrid) and ‘ZP 704’ (an older-generation hybrid). The evaluation of results is based on measurements of germination percentage, morphometric parameters, redox status, comparative analysis of thermodynamic parameters (such as Gibbs free energy, enthalpy, entropy), and the concentration of specific sugars in different parts of maize seedlings. The results indicate that the germination and initial growth of maize seedlings are influenced by the flow of crucial sugars from the remaining seed (as a source of nutrients) towards the plumule and radicle (as sink organs). Furthermore, alterations in Gibbs free energy play a significant role in these sugar transfers within the maize seedlings. The seed germination was most affected by the highest concentrations of 24-EBL, showing inhibitory effects, whereas lower and moderate concentrations of exogenously added 24-EBL exhibited a beneficial influence on the initial phases of seedling growth. The mentioned approach gives new insights into source–sink relationships and can be used as a quantitative measure of the germination energy, which until now has been a qualitative criterion in seed science.

Geometries, Electronic Structures, and Energetic Parameters of the first-row transition metal doped aluminum clusters Al16M

A theoretical study of geometry, stability, electronic structure, and magnetic property of neutral Al16M clusters with M being a first-row 3d transition metal atom, including Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn, are investigated in this theoretical study using quantum chemical approaches. The neutral Al16M clusters favor three kind of structures based on pure Al17 framework, including two exohedral doped isomers and one endohedral doped structure. There is a competition between the endoheral and the exohedral structures of Al16M with M being Ni, Cu, and Zn. The thermodynamic stability of encapsulated structure Al16Ni is confirm by the calculated average binding energy and embedded energy values. DFT calculation, however, indicate that the transition metal doping reduces the ionization potential of the pure aluminum clusters. Based on NBO calculations, a comprehensive picture of magnetic behavior is shown for Al16M clusters. Remarkably, the magnetism of the encapsualated Ni dopant is quenched in Al16 cage. Moreover, NBO calculations found that the 50-electron shells are completely preserved in both clusters Al16Sc and Al­16Ti and the remaining unpaired electron(s) localize(s) mainly on 3d atomic orbitals of the transition metal dopant.

Interpreting of the carbon dioxide adsorption on high surface area zeolitic imidazolate Framework-8 (ZIF-8) nanoparticles using a statistical physics model

The objective of this paper was to study CO2 adsorption on the extremely porous ZIF-8 (Zn(mIm)2 with mIm = 2-methylimidazolate). The ZIF-8 was characterized via X-ray diffraction, scanning electron microscopy, TGA analysis and N2 adsorption-desorption isotherms. The adsorption isotherms were generated at different temperatures, namely, 273 K, 298 K, 323 K, and 353 K. Based on the experimental result, a new model was simulated and interpreted using a multilayer model with saturation. The physicochemical parameters that described the CO2 adsorption process were determined by physical statistical formalism. The characteristic parameters of the CO2 adsorption isotherm such as the number of carbon dioxide molecules per site (nCO2), the receptor site densities (DZIF-8), and the energetic parameters (ΔE1a, ΔE2a) were investigated. In addition, the thermodynamic functions that governed the adsorption process such as the internal energy (Eint), entropy (Sad) and Gibbs free energy (Gad) were determined by a statistical physics model. Thus, the results showed that CO2 adsorption on ZIF-8 was spontaneous and exothermic in nature.