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Hydrogen-bond networks in associating fluids can be extremely robust and characterize the topological properties of the liquid phase, as in the case of water, over its whole domain of stability and beyond. Here, we report on molecular dynamics simulations of hydrogen fluoride (HF), one of the strongest hydrogen-bonding molecules. HF has more limited connectivity than water but can still create long, dynamic chains, setting it apart from most other small molecular liquids. Our simulation results provide robust evidence of a second-order percolation transition of HF's hydrogen bond network occurring below the critical point. This behavior is remarkable as it underlines the presence of two different cohesive mechanisms in liquid HF, one at low temperatures characterized by a spanning network of long, entangled hydrogen-bonded polymers, as opposed to short oligomers bound by the dispersion interaction above the percolation threshold. This second-order phase transition underlines the presence of marked structural heterogeneity in the fluid, which we found in the form of two liquid populations with distinct local densities. [ABSTRACT FROM AUTHOR]

Experiments have demonstrated that vibrational strong coupling between molecular vibrations and light modes can significantly change molecular properties, such as ground-state reactivity. Theoretical studies toward the origin of this exciting observation can roughly be divided into two categories, with studies based on Hamiltonians that simply couple a molecule to a cavity mode via its ground-state dipole moment on the one hand, and on the other hand ab initio calculations that self-consistently include the effect of the cavity mode on the electronic ground state within the cavity Born-Oppenheimer (CBO) approximation; these approaches are not equivalent. The CBO approach is more rigorous, but unfortunately it requires the rewriting of electronic-structure code, and its results may sometimes be hard to physically interpret. In this work, we exploit the relation between the two approaches and demonstrate on a real molecule (hydrogen fluoride) that for realistic coupling strengths, we can recover CBO energies and spectra to high accuracy using only out-of-cavity quantities from standard electronic-structure calculations. In doing so, we discover what thephysical effects underlying the CBO results are. Our methodology can aid in incorporating more possibly important features in models, play a pivotal role in demystifying CBO results, and provide a practical and efficient alternative to full CBO calculations. [ABSTRACT FROM AUTHOR]

Anharmonic effects play a crucial role in determining thermochemical properties of liquids and gases. For such extended phases, the inclusion of anharmonicity in reliable electronic structure methods is computationally extremely demanding, and hence, anharmonic effects are often lacking in thermochemical calculations. In this study, we apply the quantum cluster equilibrium method to transfer density functional theory calculations at the cluster level to the macroscopic, liquid, and gaseous phase of hydrogen fluoride. This allows us to include anharmonicity, either via vibrational self-consistent field calculations for smaller clusters or using a regression model for larger clusters. We obtain the structural composition of the fluid phases in terms of the population of different clusters as well as isobaric heat capacities as an example for thermodynamic properties. We study the role of anharmonicities for these analyses and observe that, in particular, the dominating structural motifs are rather sensitive to the anharmonicity in vibrational frequencies. The regression model proves to be a promising way to get access to anharmonic features, and the extension to more sophisticated machine-learning models is promising. [ABSTRACT FROM AUTHOR]

Proton exchange reactions are of key importance in many processes in water. However, it is nontrivial to achieve reliable barrier heights for multiple proton exchanges and complexation energies in hydrogen-bonded systems theoretically. Performance of the fixed-node diffusion quantum Monte Carlo (FN-DMC) with the single-Slater–Jastrow trial wavefunction on total energies, barrier heights of multiple proton exchanges, and complexation energies of small water, ammonia, and hydrogen fluoride clusters is investigated in this study. Effects of basis sets and those of locality approximation (LA), T-move approximation (T-move), and determinant localization approximation (DLA) schemes in dealing with the nonlocal part of pseudopotentials on FN-DMC results are evaluated. According to our results, diffuse basis functions are important in achieving reliable barrier heights and complexation energies with FN-DMC, although the cardinal number of the basis set is more important than diffuse basis functions on total energies of these systems. Our results also show that the time step bias with DLA and LA is smaller than T-move; however, the time step bias of DMC energies with respect to time steps using the T-move is roughly linear up to 0.06 a.u., while this is not the case with LA and DLA. Barrier heights and complexation energies with FN-DMC using these three schemes are always within chemical accuracy. Taking into account the fact that T-move and DLA are typically more stable than LA, FN-DMC calculations with the T-move or DLA scheme and basis sets containing diffuse basis functions are suggested for barrier heights of multiple proton exchanges and complexation energies of hydrogen-bonded clusters. [ABSTRACT FROM AUTHOR]

This work studied the rovibrational absorption spectral line-shape parameters of the P(1)–P(10) and R(0)–R(9) lines for Hydrogen fluoride perturbed by argon in the 0–0, 1–0, and 2–0 vibrational bands at 20–1000 K. A dataset of beyond-Voigt line-shape parameters (pressure broadening and shifting parameters, their speed dependencies, and the complex Dicke parameters) has been theoretically determined for the first time from generalized spectroscopic cross-section calculated by the full quantum scattering calculations. Then these parameters were employed to predict the line shape and asymmetry based on the partially-correlated speed-dependent hard-collision and the partially-correlated quadratic-speed-dependent hard-collision profiles. The effect of each parameter on the line shape and line asymmetry was further studied, which revealed that the beyond-Voigt effects were indispensable to accurately describe the line shape contour. Our results are in good agreement with the available experimental observations and provide a comprehensive set of theoretical references for further experimental measurements. [ABSTRACT FROM AUTHOR]

This study presents a sustainable approach to extracting hydrogen fluoride (HF) from wastewater using hollow fiber membrane contactors. HF, a widely used yet hazardous chemical, requires efficient separation techniques due to its environmental and health concerns. Our research compared two operational modes, vacuum mode and liquid–liquid extraction mode, revealing the latter as more efficient for HF separation. Notably, this study introduces a novel aspect by employing a data‐driven decision‐making method, Bayesian optimization (BO) for process optimization of the liquid–liquid extraction mode, aiming to maximize HF removal efficiency at low experimental costs. Subsequent validation through a 96‐h experimental run confirms the suitability of the optimized conditions for industrial applications. This study not only demonstrates an efficient HF separation process using hollow fiber membrane contactors but also establishes a new standard for complex industrial process optimization. [ABSTRACT FROM AUTHOR]

The recombinant Cluster of Differentiation 40 Ligand (CD40L) can be expressed in various cells and is closely related to various types of cancer. This association underscores the critical need for expedited and precise measurement of CD40L levels in clinical fluid specimens. A novel optical fiber biosensor has been devised, employing single-mode fibers that are sandwiched around a coreless fiber, with the diameter refined by etching with hydrogen fluoride. This innovative configuration allows for light transmission through the evanescent field, thereby enhancing the sensor's sensitivity to changes in the surrounding refractive index. Employing chemical binding techniques, CD40 was securely immobilized onto the fiber's surface, facilitating the detection of CD40L. The sensor exhibited a sensitivity of 1.126 nm (μg mL−1)−1 and a detection limit of 0.68 nM. Furthermore, the sensor's specificity for CD40L was validated using authentic clinical serum samples spiked with artificial analytes. In addition, the specificity of CD40L of the proposed sensor was proved using natural clinical serum samples with added artificial analyte, assisted by the ELISA method, and the results ideally conformed with the detection of standard samples. With the aid of the ELISA method, the outcomes were found to be in excellent agreement with those from standard sample detection. Consequently, the findings indicate that this sensor provides a specific, label-free, and highly sensitive method for CD40L detection, showcasing its significant potential for applications in molecular biology research. [ABSTRACT FROM AUTHOR]

Sets of electrophilic probes are generally prepared using a narrow toolkit of robust reactions, which tends to limit both their structural and functional diversity. A unified synthesis of skeletally-diverse sulfonyl fluorides was developed that relied upon photoredox-catalysed dehydrogenative couplings between hetaryl sulfonyl fluorides and hydrogen donor building blocks. A set of 32 diverse probes was prepared, and then screened against Trypanosoma brucei. Four of the probes were found to have sub-micromolar anti-trypanosomal activity. A chemical proteomic approach, harnessing an alkynylated analogue and broad-spectrum fluorophosphonate tools, provided insights into the observed anti-trypanosomal activity, which likely stems from covalent modification of multiple protein targets. It is envisaged that the unified diversity-oriented approach may enable the discovery of electrophilic probes that have value in the elucidation of biological and biomedical mechanisms. Electrophilic bioactive compounds are useful chemical tools for identifying and modulating protein targets through reaction with nucleophilic amino acid side chain residues. Here, the authors report a modular synthesis of electrophilic sulfonyl fluoride probes, and evaluate their anti-trypanosomal activity using a chemoproteomics approach [ABSTRACT FROM AUTHOR]

Targeting pour point depressants of low-molecular weight and branched polyethylenes, a series of 9-[2,4-bis(benzhydryl)-6-R-phenylimino]-5,6,7,8-tetrahydro-cycloheptapyridine-nickel complexes (Ni1–Ni10) were developed as efficient precatalysts. Upon activation with either EASC or MAO, all nickel complex precatalysts exhibited high activity [up to 8.12 × 106 g PE (mol of Ni)−1 h−1] with single-site behavior toward ethylene polymerization, producing low-molecular weight and unimodal polyethylenes. The resultant polyethylenes possessed high branching with predominant methyl groups and longer chains, along with either internal vinylene or vinyl end groups. The activities of these complex precatalysts were heavily rationalized on the basis of the electronic and steric influences of their 6-R-substituents, with bromides following the order of Ni5 (F) > Ni4 (Cl) > Ni1 (Me) > Ni2 (Et) > Ni3 (iPr) and chlorides following the order of Ni10 (F) > Ni9 (Cl) > Ni6 (Me) > Ni7 (Et) > Ni8 (iPr). DFT calculations revealed the crucial role of agostic interactions (–Ni⋯H–C(Ph2)) between the nickel metal and the hydrogen atom of the ortho bulky group in achieving high catalytic activity and intramolecular hydrogen bonding with the fluoride atom in producing low Mw PE wax. Moreover, the organic compounds and nickel complexes were well characterized, including representative complexes Ni3 and Ni4, via single-crystal X-ray diffraction. [ABSTRACT FROM AUTHOR]

Purpose: Fluoride pollution in agricultural environments, particularly from industrial activities such as brick kilns, poses significant risks to crop yield and livestock health. This study investigates the impact of fluoride pollution on clover fodder, a critical feed source for livestock in the Peshawar region of Pakistan, and explores strategies to mitigate fluoride uptake using calcium amendments. Clover, specifically Persian clover (Trifolium resupinatum L.), is prone to accumulating high fluoride content, exacerbated by nearby brick kilns emitting hydrogen fluoride (HF). This accumulation poses a risk of fluorosis in livestock consuming the contaminated fodder. Methodology: A pot experiment was conducted to assess the effectiveness of adding calcium carbonate (CaCO3) at varying concentrations (0, 20, 40, and 60 µg/kg) to reduce fluoride uptake in clover. The study spanned three months, with plants harvested every four weeks to measure fluoride levels. Results: showed that increasing soil calcium significantly reduced fluoride content in clover leaves. At 60 µg/kg CaCO3, fluoride concentration decreased to 22 µg/kg from an initial 60 µg/kg at 0 µg/kg CaCO3. This reduction was consistent over 12 weeks, demonstrating the potential of calcium amendments to mitigate fluoride uptake. Additionally, a survey of farmers and agricultural extension workers in the affected areas revealed a lack of awareness and mitigation strategies for fluoride pollution. Conclusion: These findings highlight the need for policy interventions and educational programs to address fluoride pollution in agricultural systems. Implementing effective service economy strategies, such as providing subsidies for calcium amendments and conducting workshops on pollution management, can help reduce fluoride levels in fodder crops and safeguard livestock health. This study underscores the importance of collaborative efforts between government and local communities to develop sustainable solutions for managing fluoride pollution in agriculture. [ABSTRACT FROM AUTHOR]

Purpose: The natural buildup of fluoride (F) in tea leaves presents possible health hazards, despite the fact that tea is one of the most consumed beverages worldwide (Camellia sinensis (L.) O. Kuntze). Researching what causes fluoride to build up in tea leaves and coming up with long-term solutions to control the problem are the main goals of this project. In order to reduce the negative health effects of drinking too much fluoride-laced tea, this study seeks to combine theoretical understanding with real farming methods. Method: The study involved a controlled experiment where 12-month-old tea plant cuttings were cultured hydroponically and exposed to varying concentrations of selenium (Se) and calcium (Ca). The treatments included different levels of fluoride (F) and the nutrients Se and Ca. Fluoride, selenium, and calcium levels in tea leaves and roots were measured using standard analytical techniques. Data analysis was performed using one-way ANOVA and LSD tests to determine the significance of differences. Results: The results demonstrated that selenium application increased fluoride concentration in roots but significantly reduced it in tea leaves. Similarly, calcium supplementation decreased fluoride uptake in both leaves and roots. The findings suggest that Se and Ca can effectively mitigate fluoride accumulation in tea plants. The formation of Ca-F complexes and the role of Se in reducing fluoride translocation within the plant were identified as key mechanisms. Conclusion: This study highlights the critical need for managing fluoride levels in tea leaves to ensure consumer safety and product quality. By integrating scientific insights with agricultural practices, tea producers can develop sustainable strategies to control fluoride levels. Selenium and calcium supplementation, along with precision agriculture techniques, were found to be effective in reducing fluoride uptake in tea plants. Recommendations: It is recommended to focusing on developing and cultivating tea plant varieties with lower fluoride accumulation. Reducing the use of fluoride-containing pesticides and adopt integrated pest management practices. Conducting additional studies to fully understand fluoride uptake mechanisms and explore the interactions between soil amendments, water quality, and environmental factors. [ABSTRACT FROM AUTHOR]

Objective: The disadvantages of the published methods for the preparation of peptide deltorphin II and its analogues hamper thorough biological investigations of this class of molecules. Aiming to develop a more productive synthetic method we investigated an approach where Boc/Bzl solid phase peptide synthesis technique was employed without the utilization of anhydrous hydrogen fluoride. Deltorphin II and its analogues were prepared in high yields and purity using the developed method and trifluoromethane sulfonic acid as a deprotection regent. Methods: Boc/Bzl solid phase peptide synthesis using accelerated and classical coulpling protocols was employed. A few strong Lewis acids were used in the final deprotection synthesis step. Results and Discussion: The toxicity and aggressive nature of hydrogen fluoride have resulted in the development of alternative strong Lewis acid-based reagents for the final deprotection and cleavage steps in Boc/Bzl peptide synthesis. Unlike hydrogen fluoride, these acids have high boiling points; however, the favorable physicochemical properties of most peptides allow them to be quite easily isolated from the cleavage cocktails by precipitation with ether. We found that this simple procedure is not suitable for the isolation of deltorphin II peptide and its analogs and developed and successfully implemented alternative methods of synthesis, isolation, and purification of these peptides. Conclusions: The use of strong Lewis acids as an alternative to anhydrous hydrogen fluoride may complicate the isolation of hydrophobic peptides by the standard techniques. An alternative method was proposed and successfully employed in the preparation of peptide deltorphin II and its three analogs. The developed procedures can be used to purify other hydrophobic peptides. [ABSTRACT FROM AUTHOR]

Methylfluoride and hydrogen fluoride react with powerful methylating agent [SO2Me]+ in a temperature-dependent addition reaction to form methylated fluorosulfuric acid [FS(OMe)2][Sb2F11] and methylated fluorosulfuric acid methyl ester [FS(OH)(OMe)][SbF6], respectively. The obtained methylated fluorosulfinic acid and methylated fluorosulfinic acid methyl ester were characterized by single X-ray structure analysis and vibrational spectroscopy. [ABSTRACT FROM AUTHOR]

In this study, we use the UK Molecular r-matrix (ukrmol) codes in the close-coupling approximation to examine the photoionization of hydrogen halides (hydrogen fluoride, hydrogen chloride, and hydrogen bromide). This article reports the total and partial photoionization cross-sections for the |$\mathrm{X}^2 \Pi$|⁠ , |$\mathrm{A}^2 \Sigma ^{+}$|⁠ , and |$\mathrm{B}^2 \Sigma ^{+}$| ionic states of these halides. The calculated cross-sections are compared with the available literature, which does not accurately represent the effective cross-sections near the threshold region, which is dominated by the Rydberg series autoionization resonances converging to the |$\mathrm{A}^2 \Sigma ^{+}$| ionic state. There seems to have been minimal effort to investigate the Rydberg-bound states of these halides. Meanwhile, the r-matrix approaches have traditionally excelled at characterizing such studies. This indicates the effectiveness of this method for molecular photoionization as well as for understanding the resonant contribution to the photoionization cross-sections. The detailed cross-sections calculated comprise the complex autoionizing resonance structures capable of significantly contributing to the computations of total photoionization rates, which are necessary to maintain a steady state of ionization in astrophysical plasmas. Comparisons with the experimental measurements and the theoretical data generally show reasonable agreement across the reported energy range. [ABSTRACT FROM AUTHOR]

To develop more sustainable purification and recovery processes, it is critical to accurately determine inorganic impurities of natural graphite (NG) and valuable elements present in low concentrations in steelmaking slag. This study applied three microwave-assisted acid digestion methods for basic oxygen furnace (BOF) slag, NG, and NG ash. Nitric acid (HNO3), hydrochloric acid (HCl), and hydrogen fluoride (HF) were used in method 1. In method 2, method 1 was followed by microwave-assisted boric acid (H3BO3) digestion. In method 3, acids (HNO3, HCl, HF, and H3BO3) were added simultaneously. Concentrations were measured using inductively coupled plasma–optical emission spectrometry. Analytical performance was evaluated using spiking recovery tests (NG) and certified reference (slag) material (CRM). Spiking recoveries for Al, Ca, Fe, K, Mg, Na, and Si were between 5% and 116% (method 1) and 94%–116% (methods 2 and 3). CRM recoveries for Al, Ca, Fe, Mg, Mn, P, Si, Ti, and V were between 2% and 102% (method 1) and 92%–103% (methods 2 and 3). The unsuitability of method 1 was evident due to the low recoveries. Methods 2 and 3 digested Ca- and Si-containing BOF slag completely without visible residue. The sufficient recoveries verified the adequacy of the methods. The suitability of method 3 probably depended on the phases of samples, as quartz was not completely digested from the NG. Method 2 completely digested the inorganic material of NG, and the spiking test showed no loss of volatile silicon compounds. These methods have not been published for NG or NG ash and validated for slag before. [ABSTRACT FROM AUTHOR]

K4[(IF5)6(HF2)4] was obtained from the reaction of K[HF2] with liquid IF5. The compound was analyzed by single crystal and powder X‐ray diffraction, Raman spectroscopy, and quantum‐chemical calculations. It contains the largest molecular IF5/HF2− complex anion known so far. Surprisingly, the crystal structure of the A4B compound can be related to the Hg4Pt structure type. [ABSTRACT FROM AUTHOR]

K4[(IF5)6(HF2)4] was obtained from the reaction of K[HF2] with liquid IF5. The compound was analyzed by single crystal and powder X‐ray diffraction, Raman spectroscopy, and quantum‐chemical calculations. It contains the largest molecular IF5/HF2− complex anion known so far. Surprisingly, the crystal structure of the A4B compound can be related to the Hg4Pt structure type. [ABSTRACT FROM AUTHOR]

Teaching hydrogen bridges (H-bridges) in introductory chemistry courses is either oversimplified or dogmatically taught; the heuristic that 'only fluorine, oxygen and nitrogen (FON) form H-bridges' is commonly used, for example. This rule limits choices, does not match reality, and does not clarify the difference between H-bridge donors (HBD) and H-bridge acceptors (HBA) nor intermolecular versus intramolecular cases. Hydrogen fluoride is a significant HBD but a poor HBA. Oxygen is not always an HBD or HBA. Ammonia is a significant HBA but a poor HBD. There are many examples of H-bridges that do not contain these three elements. All examples of H-bridges should be shown in a way to provide symbolic and molecular structures. Is it necessary to 'explain' H-bridges in introductory classes? We conclude not, but it might be necessary to increase the total amount of time to present the material so that students do not rely on superficial rules. [ABSTRACT FROM AUTHOR]

Atomic layer deposition (ALD) and atomic layer etching (ALE) techniques were used to control the ZrO2 shell thickness on TiO2/ZrO2 core/shell nanoparticles. ALD and ALE were performed at 200 °C while the nanoparticles were agitated using a rotary reactor. To increase the ZrO2 shell thickness, ZrO2 ALD films were deposited using sequential exposures of tetrakis(dimethylamino) zirconium and H2O. Ex situ analysis using transmission electron microscopy (TEM) observed the growth of the ZrO2 shells. The ZrO2 ALD led to more spherical ZrO2 shells on the crystalline and irregular TiO2 cores. The ZrO2 ALD on the nanoparticles had a growth rate of 0.9 ± 0.1 Å/cycle. Tunable ZrO2 coatings were observed with thicknesses ranging from 5.9 to 27.1 nm after 240 ZrO2 ALD cycles. To demonstrate the decrease in the ZrO2 shell thickness, the ZrO2 film was then etched using sequential hydrogen fluoride (HF) and TiCl4 exposures. Quadrupole mass spectrometry experiments performed in a separate reactor identified the volatile products during ZrO2 ALE. H2O was monitored during HF exposures, and ZrCl4 etch products and TiFxCly ligand-exchange products were observed during TiCl4 exposures. Ex situ TEM studies revealed that the ZrO2 shells remained spherical during ZrO2 ALE. The ZrO2 ALE on the nanoparticles had an etch rate of 6.5 ± 0.2 Å/cycle. Tunable ZrO2 coatings were produced from 27.1 down to 7.6 nm using 30 ZrO2 ALE cycles. This study demonstrated that ZrO2 ALD and ZrO2 ALE can control the thickness of ZrO2 shells on TiO2/ZrO2 core/shell nanoparticles without inducing nanoparticle agglomeration. [ABSTRACT FROM AUTHOR]

Classical optimizers play a crucial role in determining the accuracy and convergence of variational quantum algorithms; leading algorithms use a near-term quantum computer to solve the ground state properties of molecules, simulate dynamics of different quantum systems, and so on. In the literature, many optimizers, each having its own architecture, have been employed expediently for different applications. In this work, we consider a few popular and efficacious optimizers and assess their performance in variational quantum algorithms for applications in quantum chemistry in a realistic noisy setting. We benchmark the optimizers with critical analysis based on quantum simulations of simple molecules, such as hydrogen, lithium hydride, beryllium hydride, water, and hydrogen fluoride. The errors in the ground state energy, dissociation energy, and dipole moment are the parameters used as yardsticks. All the simulations were carried out with an ideal quantum circuit simulator, a noisy quantum circuit simulator, and finally a noisy simulator with noise embedded from the IBM Cairo quantum device to understand the performance of the classical optimizers in ideal and realistic quantum environments. We used the standard unitary coupled cluster ansatz for simulations, and the number of qubits varied from two starting from the hydrogen molecule to ten qubits in hydrogen fluoride. Based on the performance of these optimizers in the ideal quantum circuits, the conjugate gradient, limited-memory Broyden—Fletcher—Goldfarb—Shanno bound, and sequential least squares programming optimizers are found to be the best-performing gradient-based optimizers. While constrained optimization by linear approximation (COBYLA) and Powell's conjugate direction algorithm for unconstrained optimization (POWELL) perform most efficiently among the gradient-free methods, in noisy quantum circuit conditions, simultaneous perturbation stochastic approximation, POWELL, and COBYLA are among the best-performing optimizers. [ABSTRACT FROM AUTHOR]

Understanding the surface properties of glass during the hydrogen fluoride (HF)-based vapor etching process is essential to optimize treatment processes in semiconductor and glass industries. In this work, we investigate an etching process of fused glassy silica by HF gas with kinetic Monte Carlo (KMC) simulations. Detailed pathways of surface reactions between gas molecules and the silica surface with activation energy sets are explicitly implemented in the KMC algorithm for both dry and humid conditions. The KMC model successfully describes the etching of the silica surface with the evolution of surface morphology up to the micron regime. The simulation results show that the calculated etch rate and surface roughness are in good agreement with the experimental results, and the effect of humidity on the etch rate is also confirmed. Development of roughness is theoretically analyzed in terms of surface roughening phenomena, and it is predicted that the values of growth and roughening exponents are 0.19 and 0.33, respectively, suggesting that our model belongs to the Kardar–Parisi–Zhang universality class. Furthermore, the temporal evolution of surface chemistry, specifically surface hydroxyls and fluorine groups, is monitored. The surface density of fluorine moieties is 2.5 times higher than that of the hydroxyl groups, implying that the surface is well fluorinated during vapor etching. [ABSTRACT FROM AUTHOR]

The structure of cis‐ or trans‐bridged [GeF5]− anionic chains have been investigated [Mallouk et al. (1984). Inorg. Chem.23, 3160–3166] showing the first crystal structures of μ‐F‐bridged pentafluorogermanates. Herein, we report the second crystal structure of trans‐pentafluorogermanate anions present in the crystal structure of sodium trans‐pentafluorogermanate(IV) bis(hydrogen fluoride), Na[GeF5]·2HF. The crystal structure [orthorhombic Pca21, a = 12.3786 (3), b = 7.2189 (2), c = 11.4969 (3) Å and Z = 8] is built up from infinite chains of trans‐linked [GeF6]2− octahedra, extending along the b axis and spanning a network of pentagonal bipyramidal distorted Na‐centred polyhedra. These [NaF7] polyhedra are linked in a trans‐edge fashion via hydrogen fluoride molecules, in analogy to already known sodium hydrogen fluorides and potassium hydrogen fluorides. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study is to develop a sustainable brick that incorporates marble slurry and parthenium weed waste as additives. This innovation aims to reduce environmental pollution, lower energy consumption, and promote circular economy and sustainable agriculture. Additionally, the study involves surveying brick kiln vendors to assess their willingness to adopt these eco-friendly bricks. This research objective is to palliate 'Environmental Pollution', lessen energy usage and support sustainable agriculture and in-result promote circular economy. The review of existing literature assesses the outcomes of the study. Explores examples, from Russia, China and Uzbekistan to offer a broader perspective on the proposed solutions. Method: The study was conducted in the vicinity of brick kilns near Peshawar, Pakistan. Clay bricks were prepared with varying percentages (5% to 50%) of marble slurry and parthenium biomass. These bricks were molded, dried, and fired at 950°C. The chemical composition and mechanical strength of the bricks were analyzed. A survey was also conducted with 40 brick kiln vendors and local farmers to gauge their receptiveness to using these new bricks. Results: The results indicated that adding marble slurry and parthenium biomass to bricks can significantly reduce HF emissions, a major pollutant from brick kilns. Optimal addition of 15-20% of these additives was found to maintain sufficient mechanical strength (above 20 MPa) while reducing water absorption. Survey responses showed initial reluctance but increased interest among brick kiln vendors when presented with the environmental and economic benefits. Conclusion and Recommendations: The study concludes that incorporating marble slurry and parthenium biomass into bricks can effectively reduce HF emissions and improve environmental sustainability. It recommends further research to scale up this practice and apply it in other regions. Additionally, it suggests providing financial incentives and training to brick kiln operators to encourage the adoption of this sustainable technology, aligning with the UN Sustainable Development Goals (SDGs) 11, 12, and 13. [ABSTRACT FROM AUTHOR]

Per- and polyfluoroalkyl substances (PFAS) are a group of fluorinated synthetic chemicals that are highly recalcitrant, toxic, and bio-accumulative and have been detected in biosolids worldwide, posing potential risks to humans and the environment. Recent studies suggest that the organic C-F bond in PFAS can be destructed and potentially mineralised into inorganic fluorides during thermal treatment. This study focuses on thermodynamic equilibrium investigations and the fate of fluorine compounds post-PFAS destruction during biosolid thermal treatment. The results indicate that gas-phase fluorine compounds are mainly hydrogen fluoride (HF) and alkali fluorides, whereas solid-phase fluorine compounds include alkaline earth fluorides and their spinels. High moisture and oxygen content in the volatiles increased the concentration of HF in the gas phase. However, adding minerals reduced the emission of HF in the gas phase significantly and enhanced the capture of fluorine as CaF2 spinel in the solid phase. This study also investigates the effect of feedstock composition on the fate of fluorine. High ash content and low volatile matter in the feedstock reduced HF gas emissions and increased fluorine capture in the solid product. The findings of this work are useful in designing thermal systems with optimised operating conditions for minimising the release of fluorinated species during the thermal treatment of PFAS-containing biosolids. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of the study was to explores sustainable management strategies against hydrogen fluoride (HF) emissions from brick kilns, which are a significant source of environmental pollution in South Asia, particularly affecting peri-urban agricultural areas. Despite the reliance on traditional fuel sources that exacerbate HF release during brick production, this study investigates alternative practices that could mitigate these harmful emissions. Methods: The survey encompassed approximately 50 brick kilns, including both brick kiln owners and farmers. The current knowledge and understanding of the local farmers and community regarding the damage caused by HF and the effective strategies to reduce its impact and to devise the implementation plan for the already approved government policy in the region for air pollution from brick kilns and its impacts on agriculture Results: The study uncovered findings and outcomes regarding the previous study (Hamd et al, 2012) and revealed that the air pollution situation has not improved in last two deades. The study finds that there are no advanced filtration technologies, transitioning to cleaner fuels, and improving agricultural practices to reduce air pollution from birck kilns, with no regular monitoring and maintinence and awareness of the community and brick kiln workers about the toxic exposure of crop to HF. Conclusions: The study suggests implementing advanced filtration technologies, transitioning to cleaner fuels, and improving agricultural practices by using HFresistant crop varieties. Additionally, it emphasizes the importance of regular monitoring and maintenance of kiln operations, the establishment of buffer zones, and enhanced community and worker education to reduce exposure to HF. The findings aim to inform policy measures and promote the adoption of sustainable practices that not only reduce HF pollution but also protect the livelihoods of local farming communities. [ABSTRACT FROM AUTHOR]

Lithium (Li) is vital to the world economy as an irreplaceable element in new-generation sustainable energy applications. Quantifying Li levels in clay minerals, a key new resource, supports extensive mineralization surveys. The major limitation in these analyses is complete decomposition, which often requires the use of strong acids and is labor-intensive, particularly in batch processing. This paper presents a partial extraction strategy for quantifying Li and multiple elements, employing ammonium hydrogen fluoride to extract from clay minerals while avoiding the use of various strong acids. Following extraction, the efficiency for Li reaches 98.61%, with values ranging from 62.68% to 91.43% for multiple elements including three major elements (Ca, Fe, Mg) and eleven trace elements (Be, Co, Cr, Cu, Ga, Mn, Ni, P, Rb, Sr, V), demonstrating favorable precision (RSD below 7.34%). This approach offers a promising tool for a simple and efficient batch analysis in the survey of mineralization in Li-bearing clay deposits. [ABSTRACT FROM AUTHOR]

The surface treatment of glass-ceramic-based materials, namely, lithium disilicate glass (IPS e.max CAD), feldspar porcelain (VITABLOCS Mark II), and a polymer-infiltrated ceramic network (VITA ENAMIC), using aqueous fluoride solutions and their influence on luting agent bonding were investigated. Six experimental aqueous fluoride solutions were applied to these materials, and their effects were assessed by surface topological analysis. The obtained results were compared using non-parametric statistical analyses. Ammonium hydrogen fluoride (AHF) etchant demonstrated the greatest etching effect. Subsequent experiments focused on evaluating different concentrations of the AHF etchant for the bonding pretreatment of glass-ceramic-based materials with a luting agent (PANAVIA V5). AHF, particularly at concentrations above 5 wt%, effectively roughened the surfaces of the materials and improved the bonding performance. Notably, AHF at a concentration of 30 wt% exhibited a more pronounced effect on both etching and bonding capabilities compared to hydrofluoric acid. [ABSTRACT FROM AUTHOR]

• AZ31 alloy/CFRP joints were produced by laser joining with/without HF treatment. • NEXAFS technique demonstrated that HF treatment imparted reactive sites on the alloy surface for chemical bonding. • H-F bond through the interaction of MgF 2 and polar amide group of polymer resulted in high adhesion strength. Although hydrofluoric acid (HF) surface treatment is known to enhance the joining of metals with polymers, there is limited information on its effect on the joining of AZ31 alloy and carbon-fiber-reinforced plastics (CFRPs) through laser-assisted metal and plastic direct joining (LAMP). This study uses the LAMP technique to produce AZ31-CFRP joints. The joining process involves as-received AZ31, HF-pretreated AZ31, and thermally oxidized HF-pretreated AZ31 alloy sheets. Furthermore, the bonding strength of joints prepared with thermally oxidized AZ31 alloy sheets is examined to ascertain the combined effect of HF treatment and thermal oxidation on bonding strength. The microstructures, surface chemical interactions, and mechanical performances of joints are investigated under tensile shear loading. Various factors, such as bubble formation, CFRP resin decomposition, and mechanical interlocking considerably affect joint strength. Additionally, surface chemical interactions between the active species on metal parts and the polar amide along with carbonyl groups of polymer play a significant role in improving joint strength. Joints prepared with surface-pretreated AZ31 alloy sheets show significant improvements in bonding strength. [Display omitted] [ABSTRACT FROM AUTHOR]

In this study, SiO@graphite@C@Al2O3 (SiO@G@C@A) composites are synthesized by varying the content of Al2O3, and their morphology and structure and their electrochemical performance are investigated in detail. The results indicate that the SiO/G@C@A-2 composite exhibits a specific capacity of 977.1 mA h g−1 at a current density of 0.1 A g−1 with a coulombic efficiency of 71.15%. Even after 100 cycles at a current density of 0.5 A g−1, it retains a delithiated specific capacity of 640.7 mA h g−1 and a capacity retention rate of 73.56%. Moreover, when the current density is raised to 2 A g−1, it maintains a delithiated capacity of 568.4 mA h g−1 and a capacity retention rate of 58.51%. The excellent electrochemical performance is ascribed to the synergistic effect of different components. The inclusion of graphite enhances overall conductivity while mitigating the volume expansion of the SiO. The application of asphalt pyrolytic carbon as a coating effectively isolates the SiO from the electrolyte, further reducing volume expansion and enhancing conductivity. The introduction of Al2O3 can absorb trace amounts of hydrogen fluoride (HF) generated during charge and discharge processes. Additionally, it facilitates the formation of an AlF3 film on the particle surfaces, which hinders and decelerates electrolyte dissolution into the electrode. The prepared composites exhibit promising prospects as lithium-ion battery anode materials. [ABSTRACT FROM AUTHOR]

Owing to their adjustable optoelectronic and adsorption characteristics, graphene quantum dots (GQDs) have become a potential material to manufacture effective gas sensors. Our present work deals with the study of interaction of a pristine graphene quantum dot (GQD) and a pyridinic nitrogen-doped defective graphene quantum dot (4N-GQD) with various toxic gases such as sulfur dioxide (SO2), hydrogen fluoride (HF), hydrogen chloride (HCl), methane (CH4), and carbon monoxide (CO). The 4N-GQD system has revealed strong interaction with these toxic gases in comparison to their pristine counterpart, which is because of the formation of an active region due to charge accumulation at the nitrogen-doped site. The adsorbate–adsorbent interaction in these systems has been studied at the molecular level employing density functional theory (DFT). Our findings suggest that the 4N-GQD system would be an effective adsorbent for a variety of toxic gases. These findings will help to steer the development of gas sensors with desirable features. [ABSTRACT FROM AUTHOR]

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[Display omitted] In this study, we investigate the efficacy of 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane (ViD 4) as an electrolyte additive to enhance the electrochemical stability of Li-rich (LRO)/Li cells. The LRO/Li cell in the 1 vol% ViD4 electrolyte displays a mere 27.9 % capacity loss after 100 cycles at 0.5C (1C = 300 mAh−1), in comparison with the 66 % observed in the baseline electrolyte. Theoretical calculations reveal that ViD4 possesses a lower calculated oxidation potential than the electrolyte solution, signifying its preferential oxidation propensity. Physical characterization results demonstrate the formation of a uniform ViD4-derived film spanning 2–3 nm on the LRO cathode surface. This film enhances the stability of the cathode/electrolyte interface and safeguards the structural integrity of LRO. Moreover, ViD4 acts as a scavenger for hydrogen fluoride (HF), which is a decomposition product of LiPF 6. Theoretical calculations verify the feasibility of ViD4 in effectively eliminating HF. [ABSTRACT FROM AUTHOR]

Developing sophisticated lithium-ion batteries with high energy and power density requires using high-voltage positive electrodes. Due to its three-dimensional lithium-ion diffusion and greater nominal operating voltage, spinel LiNi 0.5 Mn 1.5 O 4 has emerged as one of lithium-ion batteries' most viable cathode materials. Electrolyte breakdown, Mn dissolution, and rapid cathode-electrolyte interface (CEI) degradation in lithium-ion cells are exacerbated by the high operating voltage of LNMO. Consequently, the long-term cycling of LNMO is hampered by such adverse side effects, making the commercialization of such a battery impractical. Here, we document the enhancement in the electrochemical performance of LNMO by surface modification utilizing a combination of Al 2 O 3 coating and Graphene enveloping employing a facile wet synthesis technique. The presence of highly crystalline spherical secondary microspheres consisting of primary nanoparticles of disordered LiNi 0.5 Mn 1.5 O 4 , the surface modification with Al 2 O 3 , and the subsequent graphene wrapping were all confirmed by structural and surface analysis techniques. The fabricated cells containing the enhanced cathode material (LNMO-Al-GO) were cycled at a C/10 rate for 100 cycles in a voltage window of 3.5–4.9 V, providing a specific discharge capacity of 134.7 ± 3.8 mAhg−1. Delivering a capacity retention of 97.7 ± 3.9% compared to the unmodified LNMO sample (84.7 ± 5.3%). Ex-situ XRD, Electrochemical Impedance Spectroscopy (EIS), and Differential Scanning Calorimetry (DSC) investigations reveal that the alumina coating protects the cathode by acting as a hydrogen fluoride (H.F.) scavenger and minimizes unfavorable phase formations at the CEI, inhibiting Mn3+ dissolution and enhancing cyclability. [ABSTRACT FROM AUTHOR]

The electrolyte concentration not only impacts the battery performance but also affects the battery cost and manufacturing. Currently, most studies focus on high‐concentration (>3 M) or localized high‐concentration electrolytes (~1 M); however, the expensive lithium salt imposes a major concern. Most recently, ultralow concentration electrolytes (<0.3 M) have emerged as intriguing alternatives for battery applications, which feature low cost, low viscosity, and extreme‐temperature operation. However, at such an early development stage, many works are urgently needed to further understand the electrolyte properties. Herein, we introduce an ultralow concentration electrolyte of 2 wt % (0.16 M) lithium difluoro(oxalato)borate (LiDFOB) in standard carbonate solvents. This electrolyte exhibits a record‐low salt/solvent mass ratio reported to date, thus pointing to a superior low cost. Furthermore, this electrolyte is highly compatible with commercial Li‐ion materials, forming stable and inorganic‐rich interphases on the lithium cobalt oxide (LiCoO2) cathode and graphite anode. Consequently, the LiCoO2‐graphite full cell demonstrates excellent cycling performance. Besides, this electrolyte is moisture‐resistant and effectively suppresses the generation of hydrogen fluoride, which will markedly facilitate the battery assembly and recycling process under ambient conditions. [ABSTRACT FROM AUTHOR]

Internal discharge and overheating faults in sulfur hexafluoride (SF6) gas-insulated electrical equipment will generate a series of characteristic gas products. Hydrogen fluoride (HF) is one of the main decomposition gases under discharge failure. Because of its extremely corrosive nature, it can react with other materials in gas-insulated switchgear (GIS), resulting in a short existence time, so it needs to be detected online. Resonant gas photoacoustic spectroscopy has the advantage of high sensitivity, fast response, and no sample gas consumption, and can be used for the online detection of flowing gas. In this paper, a simulated GIS corona discharge experimental platform was built, and the HF generated in the discharge was detected online by gas photoacoustic spectroscopy. The absorption peak of HF molecule near 1312.59 nm was selected as the absorption spectral line, and a resonant photoacoustic cell was designed. To improve the detection sensitivity of HF, wavelength modulation and second-harmonic detection technology were used. The online monitoring of HF in the simulated GIS corona discharge fault was successfully realized. The experimental results show that the sensitivity of the designed photoacoustic spectroscopy detection system for HF is 0.445 μV/(μL/L), and the limit of detection (LOD) is 0.611 μL/L. [ABSTRACT FROM AUTHOR]

We study numerically nonlinear dynamics of several types of molecular systems composed of hydrogen-bonded chains placed inside carbon nanotubes with open edges. We demonstrate that carbon nanotubes provide a stabilization mechanism for quasi-one-dimensional molecular chains via the formation of their secondary structures. In particular, a polypeptide chain (Gly) N placed inside a carbon nanotube can form a stable helical chain (3 10 -, α -, π -, and β -helix) with parallel chains of hydrogen-bonded peptide groups. A chain of hydrogen fluoride molecules ⋯ FH ⋯ FH ⋯ FH can form a hydrogen-bonded zigzag chain. Remarkably, we demonstrate that for molecular complexes (Gly) N ∈ CNT and (FH) N ∈ CNT, the hydrogen-bonded chains will remain stable even at T = 500 K. Thus, our results suggest that the use of carbon nanotubes with encapsulated hydrogen fluoride molecules may be important for the realization of high proton conductivity at high temperatures. [ABSTRACT FROM AUTHOR]

Anhydrous hydrogen fluoride (AHF), a critical raw material for industries such as aluminum, pharmaceuticals, and petroleum, has traditionally been sourced from fluorite--a non-renewable mineral. The unsustainable reliance on fluorite has catalyzed the search for alternative AHF production methods. A promising substitute is fluorosilicic acid (FSA), a byproduct of the phosphate fertilizer industry previously deemed waste. Transforming fluorosilicic acid into AHF not only yields a valuable resource but also addresses the environmental and economic challenges associated with waste management. The innovative practice of producing AHF from fluorosilicic acid signals a shift towards sustainable chemical production by capitalizing on waste, potentially diminishing reliance on fluorite and reducing the industry's environmental impact. This review thoroughly dissects the AHF synthesis process from fluorosilicic acid. Despite the acknowledged importance of fluorinated compounds in numerous industrial applications, research on their synthesis from fluorosilicic acid is limited and fragmented. This review seeks to amalgamate this scattered information by closely scrutinizing diverse industrial processing methods. Additionally, it explores the current and future landscape, economic feasibility, and strategies to navigate the obstacles inherent in synthesizing AHF from fluorosilicic acid. It also assesses the environmental impact of these methods, thereby contributing to the dialogue in this emerging field. The primary aim of this manuscript is to foster further research and promote the industrial uptake of this sustainable process. Highlighting the challenges and proposing potential improvements, the review supports the responsible reuse of waste and advocates for advancements in industrial practices. [ABSTRACT FROM AUTHOR]

Hydrofluoric acid (HF) is commonly used as an etchant for the pretreatment of dental computer-aided design/computer-aided manufacturing (CAD-CAM) materials, such as glass-ceramics and resin composites. Despite its effectiveness, the harmful and hazardous nature of HF has raised significant safety concerns. In contrast, ammonium fluoride (AF) is known for its relatively low toxicity but has limited etching capability. This study explored the potential of ammonium hydrogen sulfate (AHS), a low-toxicity and weak acid, to enhance the etching ability of aqueous AF solutions for the bonding pretreatment of CAD-CAM materials. This study investigated five types of aesthetic CAD-CAM materials: lithium disilicate glass, feldspathic porcelain, polymer-infiltrated ceramic networks, resin composites, and zirconia. Seven experimental etchants were prepared by varying the amount of AHS added to aqueous AF solutions, with each etchant used to etch the surfaces of the respective CAD-CAM materials. The treated surfaces were analyzed using scanning electron microscopy and confocal laser scanning microscopy. Additionally, the shear bond strength (SBS) of the CAD-CAM materials treated with a luting agent (resin cement) was evaluated. The results indicated that the AF1/AHS3 (weight ratio AF:AHS = 1:3) etchant had the most substantial etching effect on the surfaces of silica-containing materials (lithium disilicate glass, feldspathic porcelain, polymer-infiltrated ceramic networks, and resin composites) but not on zirconia. The SBS of the materials treated with the AF1/AHS3 etchant was comparable to that of the commercial HF etchant. Hence, an AF/AHS mixed solution could effectively etch silica-containing CAD-CAM materials, thereby enhancing their bonding capabilities. [ABSTRACT FROM AUTHOR]

This study investigates the crucial process of cleaning cold field emission electron emitters and scanning tunnel microscopy (STM) probes, particularly focusing on tungsten tips. The cleanliness of these tips is essential for maintaining optimal cathode properties, preventing impurities that can significantly affect the emission process. Various cleaning methods, including macroetching, ammonia cleaning, and hydrofluoric acid (HF) cleaning were explored and compared by scanning electron microscopy. The macroetching method, involving a mixture of hydrochloric acid, nitric acid, and hydrogen fluoride, proved to be too reactive, causing significant material removal and altering the tip's structure. Ammonia cleaning did not significantly improve or harm the samples. However, oxide islands appeared in some areas, suggesting the potential formation of ammonium tungsten oxide. HF cleaning, specifically at 20% and 50% concentrations, demonstrated effectiveness in removing tungsten oxides without damaging the tip. Pre-cleaning with water and ethanol proved beneficial for subsequent HF refinement. Results suggest that HF is the most suitable method for oxide removal but a rinse with water is essential for removing residual sodium hydroxide. To maintain optimal properties, it is crucial to apply a less reactive layer quickly or transfer the tips to a water/ethanol bath to prevent oxidation. [ABSTRACT FROM AUTHOR]

Polycrystalline diguanidinium hexafluoridogermanate (IV) was obtained by co-precipitation from solutions of diguanidinium carbonate and germanium dioxide in 48 % hydrogen fluoride. The [C(NH2)3]2[GeF6] structure was refined from single crystal X-ray diffractometer data: [C(NH2)3]2[TiF6] type, C2/m, a = 1276.67(8), b = 732.70(5), c = 616.37(5) pm, b = 114.497(5)°, wR = 0.0700, 1033 F2 values, 53 variables. The trigonal planar [C(NH2)3]+ cations and the octahedral [GeF6]2− anions are condensed to double layers through strong H⋯F hydrogen bonds (208–213 pm H⋯F). The centers of gravity of the two building units have an antifluorite-like topology. [ABSTRACT FROM AUTHOR]

As a ubiquitous phenomenon, drop impact on a liquid bath has been widely studied. This paper demonstrates a systematical study on the collision between the volatile drops and a heated liquid bath. In the experiments, water, alcohol, and hydrogen fluoride ether (HFE-7100) were used to generate drops. The experimental results vary with the impact parameters and liquid properties. Despite the common phenomena, like bouncing and coalescence, antibubble was observed at an intermediate impact velocity with the HFE-7100 drops. A regime map is built based on the experimental results. A qualitative model is proposed to elucidate the stability of the air film separating the impinging droplet and the surrounding liquid during collision. This study should stimulate further investigation on the surfactant-free antibubbles and the control of antibubble lifetime. [ABSTRACT FROM AUTHOR]

Context: The reaction between Na and HF is a typical harpooning reaction which is of great interest due to its significance in understanding the elementary chemical reaction kinetics. This work aims to investigate the detailed reaction mechanisms of sodium with hydrogen fluoride and the adsorption of HF on the resultant NaF as well as the (NaF)4 tetramer. The results suggest that the reaction between Na and HF leads to the formation of sodium fluoride salt NaF and hydrogen gas. Na interacts with HF to form a complex HF···Na, and then the approaching of F atom of HF to Na results in a transition state H···F···Na. Accompanied by the broken of H-F bond, the bond forms between F and Na atoms as NaF, then the product NaF is yielded due to the removal of H atom. The resultant NaF can further form (NaF)4 tetramer. The interaction of NaF with HF leads to the complex NaF···HF; the form I as well as II of (NaF)4 can interact with HF to produce two complexes (i.e., (NaF)4(I-1)···HF, (NaF)4(I-2)···HF, (NaF)4(II-1)···HF and (NaF)4(II-2)···HF), but the form III of (NaF)4 can interact with HF to produce only one complex (NaF)4(III)···HF. These complexes were explored in terms of noncovalent interaction (NCI) and quantum theory of atoms in molecules (QTAIM) analyses. NCI analyses confirm the existences of attractive interactions in the complexes HF···Na, NaF···HF, (NaF)4(I-1)···HF, (NaF)4(I-2)···HF, (NaF)4(II-1)···HF and (NaF)4(II-2)···HF, and (NaF)4(III)···HF. QTAIM analyses suggest that the F···Na interaction forms in the HF···Na complex while the F···H hydrogen bonds form in NaF···HF, (NaF)4(I-1)···HF, (NaF)4(I-2)···HF, (NaF)4(II-1)···HF and (NaF)4(II-2)···HF, and (NaF)4(III)···HF complexes. Natural bond orbital (NBO) analyses were also applied to analyze the intermolecular donor-acceptor orbital interactions in these complexes. These results would provide valuable insight into the chemical reaction of Na and HF and the adsorption interaction between sodium fluoride salt and HF. Methods: The calculations were carried out at the M06-L/6-311++G(2d,2p) level of theory which were performed using the Gaussian16 program. Intrinsic reaction coordinate (IRC) calculations were carried out at the same level of theory to confirm that the obtained transition state was true. The molecular surface electrostatic potential (MSEP) was employed to understand how the complex forms. Quantum theory of atoms in molecules (QTAIM) and noncovalent interaction (NCI) analysis was used to know the topology parameters at bond critical points (BCPs) and intermolecular interactions in the complex and intermediate. The topology parameters and the BCP plots were obtained by the Multiwfn software. [ABSTRACT FROM AUTHOR]

The purpose of this study was to fabricate a force sensor. A novel three-dimensional carbon-based material called a carbon nano-flake ball (CNFB) was used because it exhibits a large surface-area and high electrical conductivity. Moreover, CNFB can be easily fabricated using a one-step process via microwave plasma chemical vapor deposition. In the present study, two different methods, chemical and mechanical exfoliation, were used to fabricate the CNFB thin films. CNFEs were successfully synthesized on the silicon-based composite substrate. The substrate was constructed by the Si, SiO2, and Al2O3, where Al2O3 played the role of the substrate for the force sensor while SiO2 was the interface layer and was removed in the process by hydrogen fluoride (HF) solution to separate Al2O3 from Silicon. The experiments showed that using sol–gel catalyst coating as pretreatment precursor, results in a larger ball-size but lower deposition density of CNFB on Al2O3 substrate. By using mechanical exfoliation by polyimide (PI) tape, the CNFB grown on silicon substrate can be easily exfoliated from the substrate. PI/CNFB was successfully exfoliated from the substrate with a silver-grey color at the bottom of the CNFB which is likely to be silicon carbide (SiC) from the energy dispersive spectrometer analysis. The sheet resistance of PI/CNFB was 18.3 ± 1.0 Ω sq.−1 PI/CNFB exhibits a good force sensing performance with good stability after 10 times of loading-unloading cycles and a good sensitivity of 11.6 Ω g−1. [ABSTRACT FROM AUTHOR]

In‐field rapid and reliable identification of nerve agents is critical for the protection of Defence and National Security personnel as well as communities. Fluorescence‐based detectors can be portable and provide rapid detection of chemical threats. However, most current approaches cannot differentiate between dilute vapors of nerve agent classes and are susceptible to false positives due to the presence of common acids. Here a fluorescence‐based method is shown for rapid differentiation between the V‐series and phosphonofluoridate G‐series nerve agents and avoids false positives due to common acids. Differentiation is achieved through harnessing two different mechanisms. Detection of the V‐series is achieved using photoinduced hole transfer whereby the fluorescence of the sensing material is quenched in the presence of the V‐series agent. The G‐series is detected using a turn‐on mechanism in which a silylated excited state intramolecular proton transfer sensing molecule is selectively deprotected by hydrogen fluoride, which is typically found as a contaminant and/or breakdown product in G‐series agents such as sarin. The strategy provided discrimination between classes, as the sensor for the G‐series agent class is insensitive to the V‐series agent, and vice versa, and neither responded to common acids. [ABSTRACT FROM AUTHOR]

Sphingosine 1-phosphate (S1P) is a signaling lipid molecule involved in various cellular processes. It is important to develop a quantitative method for S1P to determine endogenous levels and to investigate its functions. As S1P is a tiny lipid component of most biological samples, highly sensitive analysis by LC-MS/MS is required. The main challenge in S1P analysis by chromatography is peak-broadening due to the presence of a polar phosphate and the fact that S1P is indeed a zwitterion itself. In this study, we used hydrogen fluoride (HF) to efficiently remove a phosphate and then analyzed the surrogate, sphingosine, as a sharp peak by LC-ESI-MS/MS. We optimized the dephosphorylation reaction in terms of temperature and reaction time. Multiple reaction monitoring (MRM) for a dephosphorylated form of S1P and C17-S1P as an internal standard at m/z transition 300.4 > 282.4 (quantification ion), 300.4 > 262.4 (qualification ion), 286.3 > 268.2 (internal standard) was conducted. This method was validated by essential parameters such as specificity, linearity, range, LOQ, LOD, accuracy, precision, and repeatability. To confirm this new method, we quantified S1P levels in various serum products (100.0~284.4 nM). In the sample pretreatment conditions for extracting S1P, the concern about potential sphingosine contamination in serum was negligible. The dephosphorylation efficiency by this method was about two-fold higher than that of alkaline phosphatase (APase). To apply the method in vivo, we analyzed S1P in plasma and kidney tissues obtained from a chronic kidney disease (CKD) mouse model. S1P levels were increased only in CKD kidney tissue but not in plasma. In conclusion, by applying the dephosphorylation step with HF, we established a new, sensitive LC-MS/MS quantitative method for S1P that can be applied to biological samples. [ABSTRACT FROM AUTHOR]

The oxidation of 1,4-diiodo-2,3,5,6-tetramethylbenzene (diiododurene) and 1,4-dibromo-2,3,5,6-tetramethylbenzene (dibromodurene) with lead dioxide (PbO2) in a mixture of hydrogen fluoride and pyridine (Olahʼs reagent) and methylene chloride as co-solvent at room temperature for 96 h afforded the corresponding monofluorination products of one methyl group. This reaction is the first example of using the oxidative system PbO2–HF–Py–CH2Cl2 for the side-chain monofluorination of methylbenzenes. [ABSTRACT FROM AUTHOR]

The oxidation of 1,4-diiodo-2,3,5,6-tetramethylbenzene (diiododurene) and 1,4-dibromo-2,3,5,6-tetramethylbenzene (dibromodurene) with lead dioxide (PbO2) in a mixture of hydrogen fluoride and pyridine (Olahʼs reagent) and methylene chloride as co-solvent at room temperature for 96 h afforded the corresponding monofluorination products of one methyl group. This reaction is the first example of using the oxidative system PbO2–HF–Py–CH2Cl2 for the side-chain monofluorination of methylbenzenes. [ABSTRACT FROM AUTHOR]

Open burning of household solid waste is a large source of air pollutants worldwide, especially in the Global South. However, waste burning emissions are either missing or have large uncertainties in local, regional, or global emission inventories due to limited emission factor (EF) and activity data. Detailed particulate matter (PM) chemical speciation data are even less available. This paper reports source profiles and EFs for PM 2.5 species as well as acidic and alkali gases measured from laboratory combustion of 10 waste categories that represent open burning in South Africa. Carbonaceous materials contributed more than 70 % of PM 2.5 mass. Elemental carbon (EC) was most abundant from flaming materials (e.g., plastic bags, textiles, and combined materials), and its climate forcing exceeded the corresponding CO 2 emissions by a factor of 2–5. Chlorine had the highest EFs among elements measured by X-ray fluorescence (XRF) for all materials. Vegetation emissions showed high abundances of potassium, consistent with its use as a marker for biomass burning. Fresh PM 2.5 emitted from waste burning appeared to be acidic. Moist vegetation and food discards had the highest hydrogen fluoride (HF) and PM fluoride EFs due to fluorine accumulation in plants, while burning rubber had the highest hydrogen chloride (HCl) and PM chloride EFs due to high chlorine content in the rubber. Plastic bottles, plastic bags, rubber, and food discards had the highest EFs for polycyclic aromatic hydrocarbons (PAHs) and nitro-PAHs as well as their associated toxicities. Distinct differences between odd and even carbon preferences were found for alkanes from biological and petroleum-based materials: dry vegetation, paper, textiles, and food discards show preference for the odd-numbered alkanes, while the opposite is true for plastic bottles, plastic bags, and rubber. As phthalates are used as plasticizers, their highest EFs were found for plastic bottles and bags, rubber, and combined materials. Data from this study will be useful for health and climate impact assessments, speciated emission inventories, source-oriented dispersion models, and receptor-based source apportionment. [ABSTRACT FROM AUTHOR]