Gas Phase Research Articles

On the fate of protonated chloroformates in the gas phase: a competition between forming HCl and chloroformic acid.

Chloroformates are prevalent in the atmosphere due to their utilization as fuel additives and industrial solvents. These species may undergo interactions with atmospheric water resulting in protonated chloroformates. This study delves into the gas-phase dissociation of these protonated species. Tandem mass spectrometry was employed to scrutinize the unimolecular dissociation of protonated methyl (1), ethyl (2), neopentyl (3), and phenyl chloroformate (4). Notably, 1 and 4 exhibited HCl loss, yielding CH3OCO+ and C6H5OCO+, respectively, with 1 additionally generating neutral methanol and ClCO+. 4 additionally loses CO and CO2. In contrast, 2 and 3 each only exhibit a single fragmentation channel, with 2 losing C2H4 to generate protonated chloroformic acid and 3 generating protonated 2-methylbutene by losing neutral chloroformic acid. Density functional theory at the B3LYP/6-311+G(d,p) level of theory was employed to explore minimum energy reaction pathways for each ion, and CBS-QB3 single-point energy calculations were added to provide reliable energetics. The Rice-Ramsperger-Kassel-Marcus (RRKM) calculations of the rate constants for selected competing processes were carried out to link theory and experiment. One common unimolecular process observed was the 1,3-H shift of the proton from the carbonyl oxygen to the ester oxygen before dissociation.

Comparative study on the flame retardancy, pyrolysis behavior, and flame retardant pathways of black phosphorus in polyurethane and polypropylene

Black phosphorus nanosheets (BPns) have gained widespread attention in the field of flame retardancy due to their highly efficient flame-retardant properties achieved with a low addition rate (e.g., 0.4%). However, the pyrolysis pathways of BP in polymers have not yet been elucidated. This work systematically studies the flame retardancy and pyrolysis behavior of BP in oxygen-containing (polyurethane, PU) and oxygen-free (polypropylene, PP) polymers, distinguishing between the gas-phase and the condensed-phase flame retardant effect of BP. Through slow heating and staged heating methods, the condensed phase and gas phase pyrolysis products of BP in PU and PP at different temperatures are compared in detail. The distinct flame retardant pathways of BP in PU and PP are revealed. The results indicate that the oxidation of BP commences with its reaction with atmospheric oxygen, implying that the condensed-phase flame-retardant effect of BP primarily occurs at the polymer surface. In PP, BP mainly functions as a gas-phase flame retardant. In the condensed phase, BP generates phosphate derivatives that cover the substrate surface, providing solely a physical barrier effect. In PU, while BP demonstrates an outstanding gas-phase flame-retardant effect, it also accelerates the early dehydration carbonization of alcohols within the substrate, resulting in the formation of phosphate ester compounds (P–O–C structure) to bolster the thermal stability of residual carbon. Additionally, the side reactions of BP during catalytic carbonization will decrease the thermal stability of ester bonds in PU. This work lays a theoretical foundation for the development and application of BP-based flame retardant systems.

Effect of gas pre-decomposition device on the growth of GaN epitaxial layer

In previous studies, the influence of gas phase and surface reactions on the growth of GaN was mainly calculated through simulations. In this study, a novel gas pre-decomposition device (GPDD) was designed to experimentally investigate the effects of gas phase and surface reactions on GaN growth by changing the length and height of the isolation plates (IPs). By varying the structure of the GPDD, the effects on the growth rate and thickness uniformity of the GaN films were studied. The growth rate of the GaN sample slowed with the extension of the IPs because the longer partition plates led to insufficient gas mixing and premature consumption of the precursor trimethylgallium (TMG). The use of GPDD simultaneously achieves high crystal quality and smooth surface morphology of the GaN film. Owing to the use of GPDD, the decomposition of TMG in the pyrolysis pathway was promoted, which suppressed Ga vacancies and C impurities, resulting in weak yellow luminescence bands in the photoluminescence. This study provides a comprehensive understanding of the chemical reaction mechanism of GaN and plays an important role in promoting the development of metal-organic chemical vapor deposition equipment.

Toward Designing Reactive Metal Clusters for Dinitrogen Activation: A Guideline Based on N2 Initial Adsorption.

Gas-phase metal clusters are ideal models to explore transition-metal-mediated N2 activation mechanism. However, the effective design and search of reactive clusters in N2 activation are currently hindered by the lack of clear guidelines. Inspired by the Sabatier principle, we discovered in this work that N2 initial adsorption energy (ΔEads) is an important parameter to control the N2 activation reactivity of metal clusters in the gas phase. This mechanistic insight obtained from high-level calculations rationalizes the N2 activation reactivity of many previously reported metal clusters when combined with the known factor determining the N≡N cleavage process. Furthermore, based on this guideline of ΔEads, we successfully designed several new reactive clusters for cleaving N≡N triple bond under mild conditions, including FeV2S2-, TaV2C2-, and TaV2C3-, the high N2 activation reactivity of which has been fully corroborated in our gas phase experiments employing mass spectrometry with collision-induced dissociation. The importance of ΔEads revealed in this work not only reshapes our understanding of N2 activation reactions in the gas phase but also could have implication for other N2 activation processes in the condensed phase. The more general establishment of this new perspective on N2 activation reactivity warrants future experimental and computational studies.

An ALCHEMI inspection of sulphur-bearing species towards the central molecular zone of NGC 253

Sulphur-bearing species are detected in various environments within Galactic star-forming regions and are particularly abundant in the gas phase of outflow and shocked regions in addition to photo-dissociation regions. Thanks to the powerful capabilities of millimetre interferometers, studying sulphur-bearing species and their region of emission in various extreme extra-galactic environments (e.g. starburst and active galactic nuclei) and at a high-angular resolution and sensitivity is now possible. In this work, we aim to investigate the nature of the emission from the most common sulphur-bearing species observable at millimetre wavelengths towards the nuclear starburst of the nearby galaxy NGC 253. We intend to understand which type of regions are probed by sulphur-bearing species and which process(es) dominate(s) the release of sulphur into the gas phase. We used the high-angular resolution (1.6arcsec or $ 27$ pc) observations from the ALCHEMI ALMA Large Program to image several sulphur-bearing species towards the central molecular zone (CMZ) of NGC 253. We performed local thermodynamic equilibrium (LTE) and non-LTE large velocity gradient (LVG) analyses to derive the physical conditions of the gas where the sulphur-bearing species are emitted, and their abundance ratios across the CMZ. Finally, we compared our results with previous ALCHEMI studies and a few selected Galactic environments. To reproduce the observations, we modelled two gas components for most of the sulphur-bearing species investigated in this work. We found that not all sulphur-bearing species trace the same type of gas: strong evidence indicates that H$_2$S and part of the emission of OCS, H$_2$CS, and SO are tracing shocks, whilst part of SO and CS emission rather traces the dense molecular gas. For some species, such as CCS and SO$_2$, we could not firmly conclude on their origin of emission. The present analysis indicates that the emission from most sulphur-bearing species throughout the CMZ is likely dominated by shocks associated with ongoing star formation. In the inner part of the CMZ where the presence of super star clusters was previously indicated, we could not distinguish between shocks or thermal evaporation as the main process releasing the S-bearing species.

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A suite of measurements of refractive index n(p,T90)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$n(p,\\ T_{90})$$\\end{document} is reported for gas phase ordinary water H2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document}O and heavy water D2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document}O. The methodology is optical refractive index gas metrology, operating at laser wavelength 633nm\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$633\\ \ ext {nm}$$\\end{document} and covering the range (293<T90<433)K\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$(293< T_{90} < 433)\\ \ ext {K}$$\\end{document} and p<2kPa\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$p < 2\\ \ ext {kPa}$$\\end{document}. A key output of the work is the determination of molar polarizabilities AR=3.7466(18)·[1+1.5(6)×10-6(T/K-303)]cm3·mol-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$A_{\ ext {R}} = 3.7466(18) \\cdot [1 + 1.5(6) \ imes 10^{-6} (T/\ ext {K} - 303) ]\\ \ ext{cm}^3 \\cdot \ ext{mol}^{-1}$$\\end{document} for ordinary water, and AR=3.7135(18)·[1+4.4(10)×10-6(T/K-303)]cm3·mol-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$A_{\ ext {R}} = 3.7135(18) \\cdot [1 + 4.4(10) \ imes 10^{-6} (T/\ ext {K} - 303) ]\\ \ ext{cm}^3 \\cdot \ ext{mol}^{-1}$$\\end{document} for heavy water, with the numbers in parentheses expressing standard uncertainty. For heavy water, this work appears to be only the second gas phase measurement to date. For both ordinary and heavy water, this work agrees within 0.15%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$0.15\\ \\%$$\\end{document} with recent ab initio theoretical results for AR\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$A_{\ ext {R}}$$\\end{document}, but the comparison is affected by imperfect knowledge of dispersion. For ordinary water, the close agreement between the present work and theory suggests problems at the 2%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$2\\ \\%$$\\end{document} level in the low density limit of the reference formulation for refractivity.

Formation of Methanol via Fischer-Tropsch Catalysis by Cosmic Iron Sulphide.

Chemical reactions in the gas phase of the interstellar medium face significant challenges due to its extreme conditions (i.e., low gas densities and temperatures), necessitating the presence of dust grains to facilitate the synthesis of molecules inaccessible in the gas phase. While interstellar grains are known to enhance encounter rates and dissipate energy from exothermic reactions, their potential as chemical catalysts remain less explored. Here, we present mechanistic insights into the Fischer-Tropsch-type methanol (FTT-CH3OH) synthesis by reactivity of CO with H2 and using cosmic FeS surfaces as heterogeneous catalysts. Periodic quantum chemical calculations were employed to characterize the potential energy surface of the reactions on the (011) and (001) FeS surfaces, considering different Fe coordination environments and S vacancies. Kinetic calculations were also conducted to assess catalytic capacity and allocate reaction processes within the astrochemical framework. Findings demonstrate the feasibility of FeS-based astrocatalysis in the FTT-CH3OH synthesis. The reactions and their energetics were elucidated from a mechanistic standpoint. Kinetic analysis demonstrates the temperature dependency of the simulated processes, underscoring the compulsory need of energy sources considering the astrophysical scenario. Our results provide insights into the presence of CH3OH in diverse regions where current models struggle to explain its observational quantity.

Understanding the Ageing Processes of Electrolytes in Aqueous Magnesium Batteries Using Radiation Chemistry

Manufacturing aqueous batteries based on the magnesium cations is an important step towards more sustainable and safer energy storage solutions. Thus, it is important to understand how these systems age and which species are formed throughout numerous charge/discharge cycles. To this end, we have used radiolysis to induce accelerated aging in concentrated solutions of magnesium bistriflimide Mg(TFSI)2 (also called “water‐in‐salt electrolytes” or WISEs). We demonstrate in this work that the degradation products formed, whether in the gas or liquid phase, are very similar to those formed in concentrated LiTFSI aqueous solutions. In fact, the behavior under ionizing radiation is driven by the anion/water molar ratio regardless of whether the cation is Li+ or Mg2+. This is because both cations are non‐reactive, and the bond strengths in the TFSI‐ anion do not vary with the nature of the cation. Reaction mechanisms are proposed to explain the formation of several species under ionizing radiation.

Discrimination between raw and ginger juice processed Fructus Gardeniae based on UHPLC-Q-TOF-MS and Heracles NEO ultra-fast gas phase electronic nose.

Fructus Gardeniae (ZZ), a traditional Chinese herb, has been used in treating patients with jaundice, inflammation, etc. When mixed with ginger juice and stir-baked, ginger juice-processed Fructus Gardeniae (JZZ) is produced, and the chemical compositions in ZZ would be changed by adding the ginger juice. To illuminate the differential components between ZZ and JZZ. HPLC, UHPLC-Q-TOF-MS, and Heracles NEO ultra-fast gas phase electronic nose were applied to identify the differential components between ZZ and JZZ. HPLC fingerprints of ZZ and JZZ were established, and 24 common peaks were found. The content determination results showed that the contents of shanzhiside, geniposidic acid, genipin-1-β-D-gentiobioside and geniposide increased, while the contents of crocin I and crocin II decreased in JZZ. By UHPLC-Q-TOF-MS, twenty-six possible common components were inferred, among which 11 components were different. In further investigation, eight components were identified as the possible distinctive non-volatile compounds between ZZ and JZZ. By Heracles NEO ultra-fast gas phase electronic nose, four substances were inferred as the possible distinctive volatile compounds in JZZ. Shanzhiside, caffeic acid, genipin-1-β-D-gentiobioside, geniposide, rutin, crocin I, crocin II, and 4-Sinapoyl-5-caffeoylquinic acid were identified as the possible differential non-volatile components between ZZ and JZZ. Aniline, 3-methyl-3-sulfanylbutanol-1-ol, E-3-octen-2-one, and decyl propaonate were inferred as the possible distinctive volatile compounds in JZZ. This experiment explored a simple approach with objective and stable results, which would provide new ideas for studying decoction pieces with similar morphological appearance, especially those with different odors.

Increased Absorption of Thyroxine in a Murine Model of Hypothyroidism Using Water/CO2 Nanobubbles

Thyroxine (T4) is a drug extensively utilized for the treatment of hypothyroidism. However, the oral absorption of T4 presents certain limitations. This research investigates the efficacy of CO2 nanobubbles in water as a potential oral carrier for T4 administration to C57BL/6 hypothyroid mice. Following 18 h of fasting, the formulation was administered to the mice, demonstrating that the combination of CO2 nanobubbles and T4 enhanced the drug’s absorption in blood serum by approximately 40%. To comprehend this observation at a molecular level, we explored the interaction mechanism through which T4 engages with the CO2 nanobubbles, employing molecular simulations, semi-empirical quantum mechanics, and PMF calculations. Our simulations revealed a high affinity of T4 for the water–gas interface, driven by additive interactions between the hydrophobic region of T4 and the gas phase and electrostatic interactions of the polar groups of T4 with water at the water–gas interface. Concurrently, we observed that at the water–gas interface, the cluster of T4 formed in the water region disassembles, contributing to the drug’s bioavailability. Furthermore, we examined how the gas within the nanobubbles aids in facilitating the drug’s translocation through cell membranes. This research contributes to a deeper understanding of the role of CO2 nanobubbles in drug absorption and subsequent release into the bloodstream. The findings suggest that utilizing CO2 nanobubbles could enhance T4 bioavailability and cell permeability, leading to more efficient transport into cells. Additional research opens the possibility of employing lower concentrations of this class of drugs, thereby potentially reducing the associated side effects due to poor absorption.

Dynamic response of a pipe with geometrical restriction subjected to gas-liquid internal flow

Due to the potential hazard of deepwater oil exploration, the Brazilian industry has an ever-increasing concern for reliability during hydrocarbon production. A major source of concern is mechanical failure in devices, such as safety valves, which can fail without warning, putting both the operation and the environment at risk. A possible reason for malfunction and failure could be the permanent occurrence of vibrations induced by internal two-phase flow during the extraction of fluids from the well. An experimental campaign is proposed to better understand these phenomena. Twenty two-phase flow conditions were tested, with superficial velocities ranging from 0.1 m/s to 2.0 m/s for water, and 0.33 m/s to 7.47 m/s for compressed air. The experiments were carried out in a restricted pipe and a pipe without any restriction to evaluate and compare the vibrations produced by two-phase flow (2-FIV). Three accelerometers positioned downstream of the restriction were used to collect vibrational amplitude spectral density data, 2-D acceleration magnitudes, and RMS values of acceleration. Among the main findings are the roles played by the gas volumetric fraction and the mixture velocity, which strongly influence the vibrational amplitude of both tubes, and the observation that the gas phase is the main responsible for vibrational amplitudes at low frequencies, while the liquid phase acts mainly at high frequencies. Furthermore, the flow pattern is also considered a key feature in determining the vibration level, as 20- and 12-fold increments have been observed for the same volumetric fraction when comparing elongated bubbles and severe slug patterns. Finally, it was demonstrated that the presence of an internal restriction strongly influences the structural response.

Microwave heating-assisted chemical looping dry reforming of methane

Chemical looping dry reforming of methane (CLDRM) offers a sustainable pathway to convert methane (CH4) and carbon dioxide (CO2) to syngas, i.e., a mixture of hydrogen (H2) and carbon monoxide (CO). However, carbon deposition caused by high gas temperature remains a crucial challenge for the CLDRM. We proposed microwave (MW) heating-assisted CLDRM to leverage the selective heating feature of MWs to create a thermal gradient between solid and gas phases. This thermal gradient, i.e., a higher solid temperature than the gas temperature, can promote desired reduction and oxidation (redox) reactions, while suppressing undesired gas phase reactions, in particular, CH4 decomposition. At bulk temperature of 800 °C, the MW heating-assisted CLDRM achieved a maximum CH4 conversion of 97% and H2/CO ratio of around 2. Compared to the conventionally heated CLDRM, the MW heating increased the redox extents of magnetite (the oxygen carrier) by 2.5 and 1.5 times, respectively, and suppressed carbon deposition.

The impact of gaseous degradation on the gas–particle partitioning of methylated polycyclic aromatic hydrocarbons

Abstract. The partitioning of semi-volatile organic compounds (SVOCs) between gas and particle phases plays a crucial role in their long-range transport and health risk assessment. However, the accurate prediction of the gas–particle (G–P) partitioning quotient (KP′) remains a challenge, especially for the light-molecular-weight (LMW) SVOCs due to their upward deviation from equilibrium state. In this study, the phenomenon with the influence of gaseous degradation on G–P partitioning was observed. Based on the diurnal study of concentrations and KP′ values for methylated polycyclic aromatic hydrocarbons (Me-PAHs), it was found that the KP′ values of methylated naphthalenes (Me-Naps; one type of LMW SVOC) during the daytime were higher than during the nighttime, and the regression lines of log KP′ versus log KOA (octanol–air partitioning coefficient) for daytime and nighttime were non-overlapping, which were different from other Me-PAHs. Compared with other diurnal influencing factors, the higher gaseous degradation of Me-Naps in the daytime than in the nighttime should partially explain their special diurnal variation in KP′, which provided a new explanation for the non-equilibrium behavior of KP′ for LMW SVOCs. Moreover, the influence of gaseous degradation on the deviation of KP′ from equilibrium state was deeply studied based on the steady-state G–P partitioning model considering particulate proportion in emission (ϕ0). The increasing times of KP′ influenced by the gaseous degradation deviated from equilibrium state can be calculated by 1 + 13.2ϕ0 × kdeg (kdeg, gaseous degradation rate). The increase in KP′ along with the increase in kdeg proved that higher gaseous degradation in the daytime could increase the KP′ value. Furthermore, an amplification in KP′ ranging from 1.11 to 5.58 times (90 % confidence interval: 1.01 to 14.4) under different ϕ0 values (0 to 1) in the temperature range of −50 to 50 °C was estimated by the Monte Carlo analysis. In summary, it can be concluded that the influence of gaseous degradation should also be considered in the G–P partitioning models of SVOCs, especially for the LMW SVOCs, which provided new insights into the related fields.

Boosting the Electrochemi,cal Performance of Primary and Secondary Lithium Batteries with Mn-Doped All-Fluoride Cathodes.

Transition metal fluorides are potentially high specific energy cathode materials of next-generation lithium batteries, and strategies to address their low conductivity typically involve a large amount of carbon coating, which reduces the specific energy of the electrode. In this study, MnyFe1-yF3@CFx was generated by the all-fluoride strategy, converting most of the carbon in MnyFe1-yF3@C into electrochemical active CFx through a controllable NF3 gas phase fluorination method, while still retaining a tightly bound graphite layer to provide initial conductivity, which greatly improved the energy density of the composite. This synergistic effect of nonfluorinated residual carbon (∼11%) and Mn doping ensures the electrochemical kinetics of the composite. The loading mass of the active substance had been increased to 86%. The theoretical and actual discharge capacity of MnyFe1-yF3@CFx composite was up to 765 mAh g-1 (pure FeF3 is 712 mAh g-1) and 728 mAh g-1, respectively. The discharge capacity at the high-voltage (3.0 V) platform was more than three times higher than that of the non-Mn-doped composite (FeF3@CFx).

Adsorption efficacy of acetone with zeolitic imidazolate frameworks–8: a mechanistic and kinetic insight

ABSTRACT The zeolitic imidazolate framework-8 (ZIF-8) has been investigated for the dynamic adsorption of acetone from the gas phase. In this study, ZIF-8 was synthesised using a cost-effective and environmentally friendly method and characterised using SEM, XRD, BET, and FTIR. The synthesised ZIF-8 possessed a BET surface area of 1212 m2. g−1 and a 0.64 µm particle size. The dynamic adsorption efficacy of acetone on the thermally pretreated ZIF-8 was investigated in a gas matrix under different operational factors. Increasing the acetone concentration through the adsorbate inlet from 300 to 800 ppm enhanced the adsorption capacity from 114 to 162 mg. g−1, while increasing flow rates from 100 to 200 mL. min−1 diminished the adsorption capacity from 120 to 114 mg. g−1. Additionally, increasing the relative humidity from 30 to 70% diminished the adsorption capacity from 130 to 87 mg. g−1. The acetone adsorption kinetics on ZIF-8 were investigated by the Elovich equation, pseudo-first order (PFO), and pseudo-second order (PSO) models. The statistical parameters indicated that the Elovich equation model is most suitable for representing the kinetic behaviour. In conclusion, ZIF-8 could be introduced as a sorbent with suitable potential for adsorbing acetone from the air in various environmental and occupational settings.

Impact of Surrounding Environment on Hot‐Exciton Based Organic Emitters for TADF Applications

AbstractUnderstanding thermally activated delayed fluorescence (TADF) in solid‐state environments is crucial for practical applications. However, limited research focuses on how the medium affects TADF properties of hot‐exciton‐based emitters. In our study, we calculated and compared reverse intersystem crossing, radiative, and non‐radiative decay rates of TADF emitters in gas, solvent, and solid phases. The designed emitters have a donor‐acceptor‐donor (D‐A‐D) structure, with donors such as triphenylamine (TPA) and diphenylamine thiophene (ThPA), combined with acceptors such as benzothiadiazole (BT), pyridine thiadiazole (PT) and thiadiazolobenzopyridine (NPT). We model the solvent and solid phases with the polarizable continuum model (PCM) and quantum mechanical/molecular mechanics (QM/MM) methods, respectively. Using density functional theory (DFT) and time‐dependent DFT, we analyze how TADF emitters′ geometrical, electronic, and excited‐state properties vary in these phases. Our results show that the solid‐state environment significantly influences the geometry and TADF properties of emitters. In the presence of solid medium, our study indicates that non‐radiative decay rates tend to be slower. On the other hand, radiative emission rates were found to be less influenced by the properties of the surrounding medium. Overall, our study connects emitter chemical structure and the surrounding environment‘s impact on excited‐state characteristics and photochemical properties.

Decoding the commutable first hyperpolarisability of keto–enol tautomer using DFT and AI-based soft computing method

ABSTRACT Non-linear optical (NLO) parameter of a series of donor–acceptor substituted N-salicylidene-4-benzenesulfonylaniline (SBSA) derivatives with a contrast of first hyperpolarisability has been investigated using density functional-based theory. The derivative of SBSA with both the donor and acceptor substitution (NMe2-SBSA-NO2) exhibits the highest first hyperpolarisability ( ∼ 3 × 103 a.u in gas phase) value. Frequency and solvent polarity responsive behaviours of first hyperpolarisability are utilised to demonstrate the variation of NLO as switchable electrical parameter. Each of the studied compounds displays very high NLO response at frequency corresponding to the absorption maxima of their electronic state. Likewise, the increase of solvent polarity induces a substantial increase of first hyperpolarisability. The computation of NLO responsive first hyperpolarisability by varying the frequency and solvent dielectric constant within a wide domain is very tedious and time-consuming. To overcome the lacuna, we implemented machine learning tools such as artificial neural networks (ANNs), fuzzy logic (FL) and adaptive neuro-fuzzy inference system (ANFIS) to predict the computation data of the NMe2-SBSA-NO2 and moderately good results were obtained using ANFIS as soft computing tool.

JWST detections of amorphous and crystalline HDO ice toward massive protostars

Tracing the origin and evolution of interstellar water is key to understanding many of the physical and chemical processes involved in star and planet formation. Deuterium fractionation offers a window into the physicochemical history of water due to its sensitivity to local conditions. The aim of this work is to utilize the increased sensitivity and resolution of the James Webb Space Telescope (JWST) to quantify the HDO/H$_ $O ratio in ices toward young stellar objects (YSOs) and to determine if the HDO/H$_ $O ratios measured in the gas phase toward massive YSOs (MYSOs) are representative of the ratios in their ice envelopes. Two protostars observed in the Investigating Protostellar Accretion (IPA) program using JWST NIRSpec were analyzed: HOPS 370, an intermediate-mass YSO (IMYSO), and IRAS 20126+4104, a MYSO. The HDO ice toward these sources was quantified via its 4.1 mu m band. The contributions from the CH$_ $OH combination modes to the observed optical depth in this spectral region were constrained via the CH$_ $OH 3.53 mu m band to ensure that the integrated optical depth of the HDO feature was not overestimated. H$_ $O ice was quantified via its 3 mu m band. New laboratory IR spectra of ice mixtures containing HDO, H$_ $O, CH$_ $OH, and CO were collected to aid in the fitting and chemical interpretation of the observed spectra. HDO ice is detected above the 3sigma level in both sources. It requires a minimum of two components, one amorphous and one crystalline, to obtain satisfactory fits. The H$_ $O ice band at 3 mu m similarly requires both amorphous and crystalline components. The observed peak positions of the crystalline HDO component are consistent with those of annealed laboratory ices, which could be evidence of heating and subsequent recooling of the ice envelope (i.e., thermal cycling). The CH$_ $OH 3.53 mu m band is fit best with two cold components, one consisting of pure CH$_ $OH and the other of CH$_ $OH in an H$_ $O-rich mixture. From these fits, ice HDO/H$_ $O abundance ratios of 4.6pm 1.8times 10$^ $ and 2.6pm 1.2times 10$^ $ are obtained for HOPS 370 and IRAS 20126+4104, respectively. The simultaneous detections of both crystalline HDO and crystalline H$_ $O corroborate the assignment of the observed feature at 4.1 mu m to HDO ice. The ice HDO/H$_ $O ratios are similar to the highest reported gas HDO/H$_ $O ratios measured toward MYSOs and the hot inner regions of isolated low-mass protostars, suggesting that at least some of the gas HDO/H$_ $O ratios measured toward massive hot cores are representative of the HDO/H$_ $O ratios in ices. The need for an H$_ $O-rich CH$_ $OH component in the CH$_ $OH ice analysis supports recent experimental and observational results that indicate that some CH$_ $OH ice may form prior to the CO freeze-out stage in H$_ $O-rich ice layers.

Antiaromaticity of Cycloheptatrienyl Anions: Structure, Acidity, and Magnetic Properties.

Investigations of the nature and degree of antiaromaticity of cycloheptatrienyl anion derivatives using both experimental and computational tools are presented. The ground state of cycloheptatrienyl anion in the gas phase is triplet, planar and Baird-aromatic. In DMSO, it assumes a singlet distorted allylic form with a paratropic ring current. The other derivatives in both phases assume either allylic or diallylic conformations depending on the substituent pattern. A combination of experimental and computational methods was used to determine the pKa values of 16 derivatives in DMSO, which ranged from 36 to -10.7. We revealed that the stronger stabilization of the anionic system, which correlates with acidity, does not necessarily imply a lower degree of anti-aromaticity in terms of magnetic properties. Conversely, the substitution pattern first affects the geometry of the ring through the bulkiness of the substituents and their better conjugation with a more distorted system. Consequently, the distortion reduces the cyclic conjugation in the π-system and thereby decreases the paratropic current in a magnetic field, which manifests itself as a decrease in the NICS. The triplet-state geometries and magnetic properties are nearly independent on the substitution pattern, which is typical for simple aromatic systems.

The 23–24 March 2021 lava fountain at Mt Etna, Italy

In 2021, more than 50 paroxysmal episodes occurred at the South-East Crater (SEC) of Mt Etna, Italy. The 23–24 March lava fountain was one of the longest episodes and began with weak Strombolian explosions, gradually transitioning to lava fountaining. The eruption intensity then dropped more slowly than in previous episodes, resulting in pulsating Strombolian explosions dominated by ash emission. Thirty-four tephra samples were used to reconstruct the fallout dispersal and estimate the total erupted mass. Grain size, textural, petrological and geochemical analyses indicate different features and were compared with the gas phase (SO2 and HCl) in the volcanic plume. By applying stochastic global optimization to simulations of the temporal evolution of the eruption column height and tephra dispersal and deposition, the total erupted mass retrieved (6.76 × 108 kg) matches well the total erupted mass estimation by the ground-based deposit (8.03 ± 2.38 × 108 kg), reducing the column height throughout the episode from 6.44 to 4.5 km above sea level and resulting in a mass eruption rate ranging from 1.96 × 105 to 8.18 × 103 kg/s. The unusual duration of the March episode and the characteristics of the erupted products point to the change in explosive style and magma fragmentation from fountaining to ash emission phases, associated with a slower magma supply inducing a change in magma rheology and a final, prolonged ash generation. Furthermore, this study showed that using observational data and the variation in eruption source parameters for numerical simulations can improve the accuracy of predicting the dispersal plume, thus mitigating the potential impact of longer paroxysmal episodes.