Solid Fluorine Research Articles

Fluorine materials scavenge excess carbon dioxide and promote Escherichia coli growth

Fluorinated solvents have been used as oxygen carriers in closed microbial cultures to sustain aerobic conditions. However, the growth-promoting effects of fluorinated solvents remain unclear. Therefore, this study aimed to elucidate the mechanism by which fluorinated solvents promote microbial growth and to explore alternative materials that can be easily isolated after culture. Escherichia coli and HFE-7200, a fluorinated solvent, were used to explore factors other than oxygen released by fluorinated solvents that promote microbial growth. E. coli growth was promoted in gas-permeable cultures, and HFE-7200 alleviated medium acidification. Gas chromatography confirmed that HFE-7200 functioned as a scavenger of carbon dioxide produced by E. coli metabolism. Because fluorinated solvents can dissolve various gases, they could scavenge metabolically produced toxic gases from microbial cultures. Furthermore, using polytetrafluoroethylene, a solid fluorine material, results in enhanced bacterial growth. Such solid materials can be easily isolated and reused for microbial culture, suggesting their potential as valuable technologies in food production and biotechnology.

Flexible fluorinated graphite foils with high contents of the (C2F)n phase for slow neutron reflectors.

In order to prepare self-standing and flexible slow neutron reflectors made of graphite fluoride (GF) with high contents of (C2F)n structural phase, graphite foils of different thicknesses were used as starting materials for gas (F2)/solid fluorination. The maximal interlayer distance of GF was obtained with this phase thanks to the stacking sequence FCCF/FCCF; this is mandatory for the efficient reflection of slow neutrons. 71 and 77% of the (C2F)n phase were achieved for graphite foils with thicknesses of 1.0 and 0.1 mm, respectively. The interlayer distances were 8.6 Å as expected. The fluorination conditions (static mode, a long duration of 24 h, annealing in pure F2 gas for 24 h, and temperatures in the 390-460 °C range) were adapted to large pieces of graphite foils (7 × 7 cm2) in order to both avoid exfoliation and achieve a homogeneous dispersion of fluorine atoms. This process was also efficient for thinner (0.01 mm thick) graphitized graphene oxide foil. 56% of the (C2F)n phase and an interlayer of 8.6 Å were achieved for this foil when fluorination was performed at 430 °C. Whatever the nature and the thickness of the foil, their flexibilities are maintained.

Intimately mixed copper, cobalt, and iron fluorides resulting from the insertion of fluorine into a LDH template.

The advancement of lithium-ion batteries (LIBs) with high performance is crucial across various sectors, notably in space exploration. This advancement hinges on the development of innovative cathode materials. Our research is dedicated to pioneering a new category of cathodes using fluorinated multimetallic materials, with a specific focus on diverging from the traditional Ni, Co, and Mn-based NMC chemistries by substituting nickel and manganese with copper and iron which are more sustainable elements. Our goal is also to enhance the robustness of cathodes upon cycling by substituting oxygen with fluorine as the metal-ligand. To achieve this, an intimate composite blend of CuF2 and FeF3, through the multi-metallic template fluorination (MMTF) methodology using a layered double hydroxide (LDH) as a precursor has been designed. Each of these components was carefully selected for its distinct attributes, including high redox potential, elevated energy density, substantial theoretical capacity, and improved cyclability. The composition denoted as (Cu1.5Co0.5)2+(Fe0.75Al0.25)3+ has been selected for fluorination because it maximizes Fe3+ and Cu2+ amount in the screened LDHs. Subsequently, this particular LDH was fluorinated through solid-gas fluorination at different temperatures (200, 350, and 500 °C) using gaseous molecular fluorine (F2). A comprehensive characterization of these materials using various techniques, including X-ray diffraction (XRD), 57Fe Mössbauer spectrometry, scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDX), and inductively coupled plasma analyses (ICP-AES) was conducted, and the evolution of LDH upon fluorination has revealed an intermediate porous texture particularly sensitive to hydration. Two original crystallographic phases are else obtained by fluorination: one formed by the hydration of the amorphous intermediate compound: Cu3Fe1.5Al0.5F12(H2O)12 an anti-perovskite structure and another stabilized through the combination of solid gas fluorination and LDH precursor yielding an original CoFeF5-type phase. Raman operando during cyclic voltammetry measurement applied on a sample fluorinated at 500 °C and used as a cathode in front of lithium metal was finally conducted to validate redox activity and mechanism.

Ground state dynamically stable phases for fluorine in the TPa pressure regime by evolutionary algorithms

In this work, we tested ab initio methods combined with evolutionary algorithms for searching stable crystalline structures for solid fluorine in the Tera-Pascal (TPa) regime. We performed several structural searches using the USPEX code, at pressures that spanned the range from 1 to 5 TPa, considering up to 16 atoms per unit-cell for selected pressures. Our findings partially support recent studies by validating the transformation of fluorine from a molecular form, Cmca, into an intermediate polymeric form before its eventual dissociation. Enthalpy comparisons between candidate structures of fluorine at high pressure show a direct transition from the molecular phase Cmca into a Pm¯3n extended structure at 2.7 TPa, the later consisting of linear chains and independent atoms, which disagrees with previous conflicting reports that proposed two other intermediate phases to also exist as stable crystalline forms close to 3 TPa at zero temperature.

Reactions and Morphologies of Mg and Mg/Teflon/Viton Particles during Oxidation

A thorough investigation on the reactions and morphologies of Mg particles and Mg/Teflon/Viton (MTV) during oxidation were conducted via thermal gravity-differential scanning calorimetry (TG-DSC) and scanning electronic microscopy. The results showed that the oxidation of Mg is fast. It merely changed the metallic luster of Mg before 550 °C, and only a few particles changed to a white irregular shape at 600 °C. However, all of the Mg particles oxidized to porous irregular shaped MgO at 650 °C. Herein, the oxidation of Mg particles ended by its melting point, and the whole process is a solid–gas-phase reaction. On the other hand, when MTV reacted in air, the reaction could be divided into two stages: the fluorination of Mg and the oxidation of the exceeded Mg. In the first stage, a dense MgF2 shell was formed by the solid–solid fluorination. The dense MgF2 shell could impede the oxidation of Mg. As a result, the oxidation of Mg began after its melting. Furthermore, liquid Mg could vaporize at higher temperature, which could burst out from the MgF2 shell and react with oxygen. The MgF2 shell exhibited a dense feature, not only protecting the Mg particles from the heterogeneous oxidation at lower temperature, but also facilitates the homogeneous oxidation at higher temperature.

Study of the content of fluorides in atmospheric air in Bokhtar region and Tursunzade city of Tajikistan

Background: The emission and presence of air pollutants such as fluorides has over burdenized the public healthcare issues. The current study aimed to determine the content of fluorides in atmospheric air in Bokhtar region and Tursunzade city of Tajikistan. Methods: Based on the direction of wind, two zones were selected in the current study: experimental and control. In the first (experimental) zone, those areas were selected where the western, northern and northeastern directions of wind was significant. Dzhura Rakhmonov was assigned to the control zone with the shortest time for the eastward winds. In general, 72 samples of atmospheric air were taken in 12 settlements of the city of Tursunzade and 90 samples of atmospheric air in the Bokhtar region of the Khatlon province. To determine fluorine in air, a potentiometric method with an ion-selective electrode was used, which makes it possible to measure the potential concentrations of fluorides in atmospheric air. Results: Compounds of gaseous (hydrogen fluoride) and solid fluorine (salts of hydrofluoric acid), which are the main emission from various sources, were found in the atmospheric air of the populated areas of the city of Tursunzade, where the aluminum plant industry is located. The maximum amount of hydrogen fluoride in the experimental zone (Jamoat and Navobod) with a western wind direction was found in the autumn, which exceeded the MPC. However, the amount of solid fluorides in the western direction of the wind ranged from 0.01 to 1.0 mg / m3, which did not exceed the MPC value and was not significant. In control zone (Dzhura Rakhmonov) the said pollutants hydrogen fluoride and solid fluorine were not significant in autumn within accordance to MPC limit. The results of the study of atmospheric air in 15 administrative cities and districts of the Bokhtar region showed a complete absence of solid fluorides in all samples of atmospheric air. Conclusion: Compounds of gaseous fluorine and salts of hydrofluoric acid were found in the atmospheric air of populated areas of the city of Tursunzade, and no significant amounts in the Bokhtar region according to MPC and control. The maximum amount of fluorine compounds was found in the experimental zone (Jamoat Navobod) of the city of Tursunzade.

Multi-Metallic Template Fluorination Mmtf for the Preparation of Ternary Metal Fluoride and Their First Use As Cathodes in Solid State Lithium Batteries

There is an urgent need in exploring new cathode materials for Lithium batteries in order to increase their capacities. Conversion type cathodes are relevant replacement candidates and especially metal fluorides such as FeF3 with a theoretical capacity of 712 mAh g-1 for three electrons at a voltage of 2.74 V vs. Li+/Li or CuF2 with a theoretical capacity of 528 mAh g-1 for two electrons at 3.55 V vs. Li+/Li. However, important voltage hysteresis, dissolution in organic electrolytes and poor reversibility hinder their use as reliable cathode materials in Lithium batteries. In this work, compatibility of fluorides with a PEO/LiTFSI (Poly Ethylene Oxide impregnated with Lithium bis(trifluoromethanesulfonyl)imide) solid electrolyte membrane is evaluated to avoid dissolution of active materials in organic liquid electrolytes often encountered with fluorides. Additionally, a general synthesis method is used to prepare ternary metal fluorides. Indeed, ternary metal fluorides were recently explored1–3 as a solution to buffer volume expansion occurring during conversion, hence greatly reducing voltage hysteresis and improving cyclability. These materials are usually prepared by planetary ball milling or by hydrofluoric acid HF-assisted fluorination, both methods not scalable for industrial purpose. In this work, we propose Multi-Metallic Template Fluorination MMTF as a general synthesis way to prepare ternary metal fluorides in a scalable way suitable for industrial applications.Prussian Blue Analogs are particularly relevant fluorination templates: these compounds can be easily prepared in great quantities by coprecipitation, enabling industrial applications. Additionally, a wide variety of compositions can be synthesized while their open structure facilitates gas solid fluorination process used. Multi Metallic Template Fluorination MMTF on PBA therefore enables the preparation of fluoride compounds with desired metallic stoichiometry by tuning it in the pristine PBA. For electrochemical applications considered in this work, Copper based Prussian Blue Analog CuPBA of general formula Cu3[Fe(CN)6]2.xH2O is chosen to combine properties of copper and iron redox centers in a ternary metal fluoride cathode. By monitoring thermal transformations of CuPBA using ThermoGravimetric Analyses coupled to Mass Spectrometry (TGA MS) and XRD, different temperature domains are identified under air, assessing that the CuPBA template can be maintained up to 170 °C while oxides are formed at 350 °C. Fluorination temperatures are selected in consequence: structures of fluorinated products are characterized by combined XAS and XRD analyses. Results indicate the formation of an anti-perovskite [Cu(H2O)4]3.(FeF6)2 phase at low temperatures, showing that Multi Metallic Template Fluorination can proceed in a topotactic manner by maintaining a Multi Metallic Template in the fluorinated product. After a severe change in the local order identified by XAS at 200 °C and especially around copper cations, a biphasic CuF2/FeF3 product is formed at high temperatures.Electrochemical signature of different CuPBA fluorination products are investigated by Cyclic Voltammetry (CV) and galvanostatic measurements with a solid electrolyte membrane. Comparisons with a mechanical milling CuF2/FeF3 reference but also with pristine CuF2 and FeF3 commercial references cycled in the same conditions are presented. Results reveal that CuPBA fluorinated at 350 °C is able to match a CuF2/FeF3 mechanical milling reference and even perform slightly better. Both materials perform much better than the mere addition of CuF2 and FeF3 signatures, confirming the superiority of ternary metal fluorides as cathode materials over binary metal fluorides stated in literature. Better performances of CuPBA Multi Metallic Template Fluorination MMTF product at high temperatures over mechanical milling reference are explained by an homogeneous dispersion of copper and iron redox centers present in the initial CuPBA template resulting in a better distribution of CuF2 and FeF3 domains in the fluorinated product at 350 °C than in the mechanical milling reference.The first discharge capacity approaches the maximum theoretical capacity of 600 mAh g-1 and highlights the possibility to dramatically increase the capacity of Lithium batteries by potentially doubling the capacity reached with classical NMC electrodes. Multi Metallic Template Fluorination therefore enables the preparation of complex fluorinated cathodes in a scalable way for industry with interesting features over a simple mechanical milling.The Multi Metallic Template Fluorination MMTF approach detailed in this work can be adapted to a wide range of multi metallic templates such as Metal Organic Frameworks and Layered Double Hydroxides for the preparation of mixed metal fluorides with unique features such as particular structures and/or morphologies depending on the desired application and in a scalable way.(1) Villa et al. ACS Appl. Mater. Interfaces 2019, 11 (1), 647–654.(2) Wang et al. Nat Commun 2015, 6 (1), 6668.(3) Ding et al. ACS Appl. Mater. Interfaces 2019, 11 (4), 3852–3860. Figure 1

High-speed solid state fluorination of Nb2O5 yields NbO2F and Nb3O7F with photocatalytic activity for oxygen evolution from water.

Solid state reactions are slow because the diffusion of atoms or ions through the reactant, intermediate and crystalline product phases is the rate-limiting step. This requires days or even weeks of high temperature treatment, and consumption of large amounts of energy. We employed spark-plasma sintering, an engineering technique that is used for high-speed consolidation of powders with a pulsed electric current passing through the sample to carry out the fluorination of niobium oxide in minute intervals. The approach saves time and large amounts of waste energy. Moreover, it allows the preparation of fluorinated niobium oxides on a gram scale using poly(tetrafluoroethylene) (®Teflon) scrap and without toxic chemicals. The synthesis can be upscaled easily to the kg range with appropriate sintering equipment. Finally, NbO2F and Nb3O7F prepared by spark plasma sintering show significant photoelectrocatalytic (PEC) oxygen evolution from water in terms of photocurrent density and incident photon-to-current efficiency (% IPCE), whereas NbO2F and Nb3O7F prepared by conventional high temperature chemistry show little to no PEC response. Our study is a proof of concept for the quick, clean and energy saving production of valuable photocatalysts from plastic waste.

The detection of solid phosphorus and fluorine in the dust from the coma of comet 67P/Churyumov–Gerasimenko

ABSTRACT Here, we report the detection of phosphorus and fluorine in solid particles collected from the inner coma of comet 67P/Churyumov–Gerasimenko measured with the COmetary Secondary Ion Mass Analyser (COSIMA) instrument on-board the Rosetta spacecraft, only a few kilometers away from the comet nucleus. We have detected phosphorus-containing minerals from the presented COSIMA mass spectra, and can rule out e.g. apatite minerals as the source of phosphorus. This result completes the detection of life-necessary CHNOPS-elements in solid cometary matter, indicating cometary delivery as a potential source of these elements to the young Earth. Fluorine was also detected with CF+ secondary ions originating from the cometary dust.

Metal-organic layers as reusable solid fluorination reagents and heterogeneous catalysts for aromatic fluorination

Reusable solid fluorination reagents and heterogeneous catalysts are ideally suited for late-stage fluorination with fast and clean conversion and simplified work-up. Here we report Pd-functionalized two-dimensional metal-organic layers (MOLs) as solid reagents and heterogeneous catalysts to efficiently fluorinate a broad scope of aromatic compounds. Site isolation in the MOLs provides a unique opportunity to stabilize highly active F-containing species for the chemical conversion. A terpyridine (TPY)- based ligand on the MOL, together with a 2-chloro-1,10-phenanthroline (phenCl) as a co-ligand, chelates PdII to form a reactive center. After treatment with Selectfluor/H2O, an (N-fluoroxy)-(2-chloro)-phenanthrolinium [N-(FO)-phenCl+] moiety is produced from the co-ligand on the Pd center. This active species serves as a stochiometric solid fluorination reagent, which shows different regioselectivities and reactivities as compared to homogeneous catalysts that involves PdIII/IV-F intermediates in catalytic cycles. The MOLs can also be used as heterogeneous catalysts for fluorination using Selectfluor. This work highlights opportunities in using MOLs to stabilize unique active sites for late-stage fluorination.

Solid State Fluorination on the Minute Scale: Synthesis of WO3−xFx with Photocatalytic Activity

AbstractSolid state reactions are notoriously slow, because the rate‐limiting step is diffusion of atoms or ions through reactant, intermediate, and product crystalline phases. This requires days or even weeks of high temperature treatment, consuming large amounts of energy. Metal oxides are particularly difficult to react, because they have high melting points. The study reports a high‐speed solid state fluorination of WO3 with Teflon to the oxyfluorides WO3–xFx on a minute (<10 min) scale by spark plasma sintering, a technique that is used typically for a high‐speed consolidation of powders. Automated electron diffraction analysis reveals an orthorhombic ReO3‐type structure of WO3–xFx with F atom disorder as demonstrated by 19F magic angle spinning nuclear magnetic resonance spectroscopy. The potential of this new approach is demonstrated by the following results. i) Mixed‐ valent tungsten oxide fluorides WO3–xFx with high F content (0 < x < 0.65) are obtained as metastable products in copious amounts within minutes. ii) The spark plasma sintering technique yields WO3–xFx nanoparticles with high photocatalytic activity, whereas the corresponding bulk phases obtained by conventional solid‐state (ampoule) reactions have no photocatalytic activity. iii) The catalytic activity is caused by the microstructure originating from the processing by spark plasma sintering.

The Crystal Structure of α-F2 : Solving a 50 Year Old Puzzle Computationally.

The cohesive energy of α-fluorine, with C2/c space group symmetry, was calculated at benchmark quality by applying the method of increments. The known experimental X-ray structure data needed to be refined, since the reported intramolecular bond length was unrealistically large. At the CCSD(T) level, including corrections for zero-point energy, the basis set superposition error, and extrapolated to the complete basis set limit, a cohesive energy of -8.72 kJ mol-1 was calculated, which agrees well with the 0 K-extrapolated experimental value of -8.35 kJ mol-1 . Comparison of the C2/c structure with a Cmca structure, isotypic to that of chlorine, bromine, and iodine reveals that the origin of the different structure of solid fluorine, compared to the heavier halogens, is the lack of significantly stabilizing σ-hole interactions. In addition, the wave numbers of the stretching mode in solid fluorine were calculated at coupled cluster level and compared to newly recorded Raman spectra of condensed fluorine. Both experiment and calculation indicate a slight up-shift for the stretching mode by 2 or 5 cm-1 , respectively, with respect to a free F2 molecule in the gas phase.

Crystal structures of solid fluorine and nitrogen trifluoride

Crystal structures of solid fluorine and nitrogen trifluoride

Synthesis, curing of hydroxyl-terminated liquid fluoroelastomer: thermal, chemical resistant and mechanical properties

A novel hydroxyl-terminated liquid fluoroelastomer (HTLF) was synthesized; FT-IR, GPC and 1H-NMR result show that HTLF was synthesized successfully. Then HTLF was cured with HDI trimer, the structure of cured product was characterized by FT-IR. Compared with traditional solid fluorine elastomer, Cured HTLF has higher char yield and faster thermal decomposition rate. It ascribed to the introduction of ring structure the cross-link structure formed in the curing process. The study of chemical resistant properties and tensile strength of cured fluoroelastomer film suggested that Cured HTLF was provided with similar mmechanical properties, chemical resistant property than solid fluorine elastomer.

Crystal structures and electronic properties of solid fluorine under high pressure**Project supported by the National Natural Science Foundation of China (Grant Nos. 51632002, 51572108, 11634004, and 11174102), Program for Changjiang Scholars and Innovative Research Team in University, China (Grant No. IRT 15R23), the National Fund for Fostering Talents of Basic Science, China (Grant No. J1103202), and the Development Program of

As the previously proposed structures of C2/m and C2/c possess similar enthalpies and x-ray diffraction patterns, the space group of fluorine at ambient pressure is in controversy. We successfully obtain its thermodynamically stable low-pressure phase, which shares the same structure as the earlier known C2/c. Further investigations on phonon spectra reveal the instability of the C2/m structure with imaginary frequency in the Brillouin zone and confirm the dynamically stable property of the C2/c structure at the same time. Compressing fluorine up to 8 GPa, the C2/c phase is found to undergo a phase transition to a new structure with a space group of Cmca. Electronic energy band structures indicate the insulating feature of C2/c and Cmca with no bands across the Fermi level. The infrared (IR) and Raman spectra of C2/c and Cmca at selected pressures are calculated to provide useful information to future experiments.

A combined quantum-chemical and matrix-isolation study on molecular manganese fluorides.

Molecular manganese fluorides were studied using quantum-chemical calculations at DFT and CCSD(T) levels and experimentally by matrix-isolation techniques. They were prepared by co-deposition of IR-laser ablated elemental manganese or manganese trifluoride with F2 in an excess of Ne, Ar, or N2 or with neat F2 at 5-12 K. New IR bands in the Mn-F stretching region are detected and assigned to matrix-isolated molecular MnFx (x = 1-3).

Polyfluorides and Neat Fluorine as Host Material in Matrix-Isolation Experiments.

The use of neat fluorine in matrix isolation is reported, as well as the formation of polyfluoride monoanions under cryogenic conditions. Purification procedures and spectroscopic data of fluorine are described, and matrix shifts of selected molecules and impurities in solid fluorine are compared to those of common matrix gases (Ar, Kr, N2 , Ne). The reaction of neat fluorine and IR-laser ablated metal atoms to yield fluorides of chromium (CrF5 ), palladium (PdF2 ), gold (AuF5 ), and praseodymium (PrF4 ) has been investigated. The fluorides have been characterized in solid fluorine by IR spectroscopy at 5 K. Also the fluorination of Kr and the photo-dismutation of XeO4 have been studied by using IR spectroscopy in neat fluorine. Formation of the [F5 ](-) ion was obtained by IR-laser ablation of platinum in the presence of fluorine and proven in a Ne matrix at 5 K by two characteristic vibrational bands of [F5 ](-) at $\tilde \nu $=850.7 and 1805.0 cm(-1) and its photo-behavior.

One-shot versus stepwise gas–solid synthesis of iron trifluoride: investigation of pure molecular F2 fluorination of chloride precursors

Iron trifluoride has been known for a long time and here we provide new insights into its detailed synthesis. Anhydrous iron trifluorides with different structures have been synthesized via one-shot and stepwise gas–solid fluorination under a gaseous flow of molecular fluorine from 150 °C. The degree of hydration of the precursors has a direct influence on the crystalline phase obtained: one-shot fluorination of FeCl2·4H2O leads to the hexagonal tungsten bronze-type FeF3 while fluorination of dehydrated iron chlorides gives the rhombohedral FeF3 with traces of oxy(hydroxy)fluorides. A stepwise procedure at 150, 250 and 350 °C tends to lead to pure phases and avoid the crystallization of oxy(hydroxy)fluorides in the final powder.

Transparent conductivity of fluorine-doped anatase TiO2 epitaxial thin films

Transparent conductive anatase TiO2−xFx(F:TiO2) epitaxial thin films were fabricated by reactive pulsed laser deposition with a solid fluorine source. F-doping as high as 1.6 × 1021 cm−3 (TiO1.95F0.05) was achieved under optimal growth conditions, and the obtained anatase TiO1.95F0.05 film had a low resistivity of 1.6 × 10−3 Ωcm and a high internal transmittance of >95%. Furthermore, the refractive index of a TiO1.95F0.05 film was >0.2 less than that of undoped TiO2. By comparing the refractive indices of F:TiO2 and Nb:TiO2, we concluded that the decreased refractive index in F:TiO2 can be attributed to a reduced electronic polarizability due to increased bond ionicity as well as doped electrons.

ChemInform Abstract: Topotactic Synthesis and Crystal Structure of a Highly Fluorinated Ruddlesden—Popper‐Type Iron Oxide, Sr3Fe2O5+xF2‐x (x ≈ 0.44).

AbstractSr3Fe2O5.44F1.56 is prepared by solid state fluorination of Sr3Fe2O6.82 (obtained from SrCO3 and Fe2O3 at 1000—1200 °C in air) using polytetrafluoroethylene as fluorinating agent (flowing Ar, 270 °C, 2 d).