Fluorine Content Research Articles

Experimental Realization of Fluoroborophene.

Borophene, an anisotropic metallic Dirac material exhibits superlative physical and chemical properties. While the lack of bandgap restricts its electronic chip applications, insufficient charge carrier density and electrochemical/catalytically active sites, restricts its energy storage and catalysis applications. Fluorination of borophene can induce bandgap and yield local electron injection within its crystallographic lattice. Herein, a facile synthesis of fluoroborophene with tunable fluorine content through potassium fluoride-assisted solvothermal-sonochemical combinatorial approach is reported. Fluoroborophene monolayers with lateral dimension 50 nm-5 µm are synthesized having controlled fluorine content (12-35%). Fluoroborophene exhibits inter-twinned crystallographic structure, with fluorination-tunable visible-range bandgap ≈1.5-2.5 eV, and density functional theory calculations also corroborate it. Fluoroborophene is explored for electrocatalytic oxygen evolution reaction in an alkaline medium and bestow a good stability. Tunable bandgap, electrophilicity and molecular anchoring capability of fluoroborophene will open opportunities for novel electronic/optoelectronic/spintronic chips, energy storage devices, and in numerous catalytic applications.

Facile and Efficient Synthesis of Fluorosilicone Polymers by Using an Optimized Gradient Ring-Opening Reaction.

Fluorosilicone rubber is essential for sealing in extreme temperatures and non-polar environments due to its exceptional adaptability. However, achieving a high yield of fluorosilicone polymers with medium and high fluorine content remains a challenge. Herein, a facile gradient strategy is developed that involves modifying the method of cyclic monomer addition based on the rate of ring-opening polymerization (ROP), to improve yield and adjust fluorine content precisely. The polymerization process is designed and tailored based on the reaction rates of anionic ring-opening polymerization (AROP) and cationic ring-opening polymerization (CROP) via an efficient gradient strategy. The effects of the polymerization process on the viscosity and yield of vinyl fluorosilicone polymers and hydrofluorosilicone polymers are investigated and optimized. Notably, the as-prepared vinyl-terminated fluoromethylsilane with 60% fluorine content (FMS-Vi-60F) has a high yield (86.6%) and high viscosity (150000 mPa·s) in a short reaction time, which is superior to previous methods. Clearly, the gradient ring-opening method developed in this work provides a facile and efficient synthesis for fabricating fluorosilicone polymers with a high yield and tunable fluorine content.

The Influence of Fluoride Ions on the Forms of Lanthanide Migration in Natural and Polluted Waters of the Lovozero Massif (The Kola Peninsula)

A comprehensive study (monitoring, thermodynamic modeling) of natural and anthropogenically polluted waters of the Lovozero Massif has been carried out. A thermodynamic study of the weathering of the Lovozero Massif within the “water-rock-atmosphere” system at a temperature of 5 °C showed that the elements contained in the rocks of the studied massif influence the formation of the chemical composition of natural waters. It has been established that an increase in the degree of “water-rock” interaction leads to an increase in the concentrations of F−, Cl−, SO42−, and HCO3− in the solution. This affects the mobility of lanthanum, cerium, and other elements due to the formation of complex compounds with them. The relatively high content of fluorine, phosphorus, and HCO3− (weak and medium acids) in the solution promotes the dissolution of silicates while Si, Al, and P are released into the solution. Monitoring of water from a flooded mine in which there is an increase in the degree of interaction of water with rock showed higher pH values for the concentrations of Na, HCO3−, F−, P, Al, Si, V, U, La, and Ce. The conclusions are relevant in the context of the use of groundwater for drinking water supply purposes. The obtained information is useful to evaluate the health of the population of the region under study.

Perfluoroalkyl acid precursor or weakly fluorinated organic compound? A proof of concept for oxidative fractionation of PFAS and organofluorines.

Organofluorine mass balance approaches are increasingly applied to investigate the occurrence of per- and polyfluoroalkyl substances (PFAS) and other organofluorines in environmental samples more comprehensively. Usually, complex samples prevent the identification and quantification of every fluorine-containing molecule. Consequently, large unidentified fractions between fluorine sum parameters such as extractable organic fluorine (EOF) and the sum of quantified analytes are frequently reported. We propose using oxidative conversion to separate (unidentified) weakly fluorinated compounds (e.g., pesticides, pharmaceuticals) from PFAA-precursors (perfluoroalkyl chain lengths ≥ C6). We show with three organofluorine model substances (flufenamic acid, diflufenican, pantoprazole) that CF3-groups or aromatic fluorine can be quantitatively converted to inorganic fluoride and trifluoroacetic acid (TFA) by applying PhotoTOP oxidation (UV/TiO2). The principle of fluorine separation in mixtures is demonstrated by the oxidation of the three weakly fluorinated compounds together with the PFAA-precursor 6:2/6:2 fluorotelomer mercaptoalkyl phosphate diester (FTMAP). After oxidation, the products F- and TFA were separated from PFCAs (> C4) by SPE, and the fractions were analyzed individually. Closed mass balances both with and without the addition of organic matrix were achieved. Eventually, the fluorine balance was verified by total fluorine measurements with combustion ion chromatography (CIC). The proposed methods should be considered a proof of concept to potentially explain unidentified fractions of the EOF, especially if compounds with low fluorine content such as pesticides, pharmaceuticals, and their transformation products contribute largely to the EOF. Future studies are needed to show the applicability to the complexity of environmental samples.

Geoecological Assessment of Fluorine Contamination of Environmental Components in the Zone of Influence of an Abandoned Rare-metal Mine in the Murmansk Region

A geoecological assessment of fluorine contamination of environmental components in the zone of influence of an abandoned rare-metal mine in the Murmansk region was carried out. Samples were taken of loparite ore enrichment tailings, soils around the tailings pond and the Loparitovy, Alluaiv, Azimut creeks and the watercourse flowing through the mine after the mining impact. The content of water-soluble fluorine in the collected samples was determined. No exceedance of maximum permissible concentration (MPC) of fluorides in soil was found. Increased content of fluoride ions (up to 15 MPC) in water samples from the watercourse was recorded. It is concluded that the production facility closed more than 15 years ago has a negative impact on ecosystems.

The Effect of Fluorine and Hydrogen Concentrations on the Chain Reaction of HF Chemical Laser

A numerical investigation has been performed to examine the effect of fluorine concentration on the chain reaction mechanisms and parameters of hydrogen fluoride (HF) chemical laser. The practical difficulties associated with this type of lasers impose that an alternative route might be quite useful. Thus, particular attention was paid to develop a computer program to investigate various processes. The results of this computer simulation program proved their credibility when compared with the little published data. This computer program is called Reaction Rate Simulation Model (RRSM). An entirely new approach to emulate the reaction mechanisms has been followed. The effectiveness of reaction rates in the processes of HF laser production has been investigated. This simulation program dealt with the percentages of the forward and reverse reactions, when a large number of reactions have been considered. In addition a large number of species have been taken into account in these reactions. From the computer program (RRSM), some valuable results could be predicted with regard to the hydrogen fluoride chemical laser.

Fluorine containing diamond-like carbon coatings

Fluorine containing diamond-like carbon (DLC) coatings were obtained by CVD deposition using the destruction of gaseous hydrocarbons by a high-energy ion source with an anode layer. The chemical composition, structure, surface energy, mechano-tribological characteristics of the synthesized thin-film material were studied. It has been shown that the fluorine content in the deposited coatings reaches 31 at.%. It has been established that the presence of fluorine in the DLC coating promotes the formation of nanodispersed graphite-like structures. Fluorine containing coatings with a high content of sp2 hybridized carbon atoms and graphite fragments show a decrease in hardness. Such coatings have a very low coefficient of friction at the level of 0.03–0.07 due to the low surface energy, which can be reduced by 1.5 times compared to pure DLC. It has been established that different fluorine contents in thin-film diamond-like carbon material have different effects on the interaction of the DLC coating with polar/non-polar dielectrics. The research results can be used for the technology of producing solid lubricants in friction units of machines and mechanisms, and are also of interest for medicine, the food industry, the production of plastics, and chemical fibers as chemically inert and corrosion-resistant coatings.

Sustainable furfural bis-thymol based benzoxazines: Superhydrophobic, aggregation induced emission and corrosion resistant properties

Sustainable bis-thymol based benzoxazines have been synthesized using furfural bis-thymol (FBT) and paraformaldehyde separately with five different fluorine substituted amines through Mannich condensation process. The molecular structure of the obtained benzoxazines has been verified using spectroscopic analyses. The curing temperature of the synthesized benzoxazines are ranged between 241°C and 277°C. Among the synthesized polybenzoxazines, poly(FBT-pfa) exhibits the highest thermal stability of 52% char yield. All the polybenzoxazines exhibit the value of LOI above the threshold limit of 26 which infers the self-extinguishing property of the polymer. Poly(FBT-pfsa) showed the highest value of water contact angle of 151o, which ascertains that the increased fluorine content contributes to the superhydrophobic nature. Results from hydrophobic durability studies with poly(FBT-pfsa) using coated cotton fabric under acidic and basic conditions indicate its suitability for hydrophobic applications. The corrosion protection ability of polybenzoxazines towards mild steel surfaces was studied and the results obtained suggest that these polybenzoxazines can be used as an excellent coating material. UV-Visible and fluorescence spectroscopic analyses infer that these benzoxazines exhibit aggregation induced emission (AIE) characteristics. Data from different studies suggest that these materials can be conveniently utilized in the form of optical, superhydrophobic and corrosion-resistant coatings.

A new aspect of the effect of fluorine doping on structural and superconducting properties in the Bi2Sr1.6La0.4CuO5+δ(O1-xFx) ceramic system

In this study, ceramic samples with the nominal composition Bi2Sr1.6La0.4CuO5+δ(O1-xFx) (where x = 0, 0.2 and 0.4) were synthesized using the solid-state reaction method to investigate the effects of fluorine anionic doping on the Bi-2201 system's structural, microstructural, and superconducting properties. X-ray diffraction analysis (XRD) confirmed the Bi-2201 phase in all samples and total incorporation of fluorine. Doping with fluorine reduced orthorhombicity, leading to an orthorhombic-tetragonal transition. Scanning electron microscopy (EDS) revealed changes in grain shape and size, while energy dispersive x-ray analysis (EDAX) confirmed fluorine incorporation. DC-electrical resistivity measurements showed that fluorine doping decreased the critical transition temperature TC (Onset), with a greater decrease observed at higher fluorine concentrations. The resistivity increase in the normal state of the sample with x = 0.4 was also noted. The conduction mechanism above TC (Onset) = 26.10 K followed the Arrhenius law, indicating thermally activated behavior due to a band gap.

Cationic fluorinated micelles for cell labeling and 19F-MR imaging

Magnetic resonance imaging (MRI) relies on appropriate contrast agents, especially for visualizing transplanted cells within host tissue. In recent years, compounds containing fluorine-19 have gained significant attention as MRI probe, particularly in dual 1H/19F-MR imaging. However, various factors affecting probe sensitivity, such as fluorine content and the equivalency of fluorine atoms, must be considered. In this study, we synthesized fluorinated micelles with adjustable surface positive charge density and investigated their physicochemical properties and MRI efficacy in phantoms and labeled cells. While the micelles exhibited clear signals in 19F-MR spectra and imaging, the concentrations required for MRI visualization of labeled cells were relatively high, adversely affecting cell viability. Despite their favourable physicochemical properties, achieving higher labeling rates without compromising cell viability during labeling remains a challenge for potential in vivo applications.

Removal and recovery of phosphorus and fluorine in process water from water based direct physical lithium-ion battery recycling

In the present work, the recovery of phosphorus and fluorine from process water generated in a water based direct physical recycling process of Li-ion batteries has been studied. The recycling process considered in this work produces significant amounts of process water, which is generated during the opening of the batteries by means of electro-hydraulic fragmentation and the subsequent sorting of the components in aqueous solution. This process produces between 21.6 L and 30.3 L of process water per kg of batteries with a total phosphorus and a total fluorine concentration of 60–85 mg/L and 120–470 mg/L, respectively. Currently, the process water has to be disposed of as hazardous waste. The goal is to discharge the wastewater into the sewer system. For this the total phosphorus and total fluorine concentration must be reduced. The process water is mainly contaminated by the released electrolyte consisting of organic carbonates and conducting salts. 31-P and 19-F NMR shows conclusively that no hydrolysis takes place in this process water. The phosphorus is present exclusively in the form of the complex anion PF6- and fluorine as F-, namely as FSI- from the conducting salt LiFSI and PF6- from the conducting salt LiPF6. In order to meet the regulatory requirements for discharge into the sewage system, 70.4% of the phosphorus and 89.3% of the fluorine must be removed. The conducting salts are hydrolyzed by adding acid and thereby phosphate and fluoride are precipitated. After critical and valuable materials are recovered the process water can be discharged into the sewer system.

Mechanisms of Atomic Oxygen Erosion in Fluorinated Polyimides Investigated by Molecular Dynamics Simulations.

Traditional polyimides have highly conjugated structures, causing significant coloration under visible light. Fluorinated colorless polyimides, known for their light weight and excellent optical properties, are considered ideal for future aerospace optical lenses. However, their lifespan in low Earth orbit is severely limited by high-density atomic oxygen (AO) erosion, and the degradation behavior of fluorinated polyimides under AO exposure is not well understood. This study uses reactive molecular dynamics simulations to model two fluorinated polyimides, PMDA-TFMB and 6FDA-TFMB, with different fluorine contents, to explore their degradation mechanisms under varying AO concentrations. The results indicate that 6FDA-TFMB has slightly better resistance to erosion than PMDA-TFMB, mainly due to the enhanced chemical stability from its -CF3 groups. As AO concentration increases, widespread degradation of the polyimides occurs, with AO-induced cleavage and temperature-driven pyrolysis happening simultaneously, producing CO and OH as the main degradation products. This study uncovers the molecular-level degradation mechanisms of fluorinated polyimides, offering new insights for the design of AO erosion protection systems.

N‐heterocyclic carbene copper complexes catalyze the C1 polymerization of substituted diazomethanes

AbstractThe C1 polymerization of substituted diazomethanes, including diazoethane and 2,2,2‐trifluoromethyl diazomethane, are reported. N‐heterocyclic carbene copper complexes were employed as catalysts for the polymerization reactions and afforded the corresponding persubstituted polymers containing methyl or trifluoromethyl units along the backbones of the polymer products. The polymers were characterized using size exclusion chromatography, a variety of spectroscopic and thermal techniques, and contact angle measurements. Polymers prepared using the C1 polymerization methodology described herein are more hydrophobic than related polymers that were obtained using a standard C2 polymerization method and the fluorinated polymers were determined to be more hydrophobic than their hydrogenated analogues. The relationship between fluorine content and wettability of persubstituted polymers was quantified.

Heat-Excitation-Based Triboelectric Charge Promotion Strategy.

The surface charge decay is observed at high temperatures due to thermionic emission, which, however, may not be the only mechanism contributing to the surface charge variation. Here, a triboelectric charge promotion strategy due to the heat-excitation effect of hot electrons near the fermi level is demonstrated, while the final charge is determined by the balance between thermionic emission and the heat-excitation effect. It is demonstrated that metals with lower work function exhibit a better heat excitation capability, and polymers with lower fluorine content in molecule chains further boost the charge output, where metal/Kapton pairs demonstrated a charge promotion of over 2 times at the temperature of 383K with good durability during 90min measurement. The heat-excitation effect and charge durability in sliding freestanding-triboelectric-layer (SFT) mode triboelectric nanogenerator (TENG) is demonstrated as well, where the energy is promoted by over 3 times and the capacitor charging speed is doubled as well, with an energy promotion from 109.34 to 373µJ per cycle to successfully trigger a discharger. This work suggests a promising future of the heat-excitation effect as a new charge promotion strategy for TENG toward different applications in high-temperature environments.

Preparation and Characterization of Fluorinated Acrylate and Epoxy Co-Modified Waterborne Polyurethane.

Conventional waterborne polyurethane (WPU) has poor water resistance and poor overall performance, which limits its application in outdoor coatings. A solution to this problem is urgently needed. The introduction of fluorine-containing groups can effectively improve the water resistance of WPU. In this study, a new fluorinated chain extender (HFBMA-HPA) synthesized by free radical copolymerization and epoxy resin (E-44) were used to co-modify WPU, and five waterborne fluorinated polyurethane (WFPU) emulsions with different fluorine contents were prepared by the self-emulsification method. The effects of HFBMA-HPA content on the emulsion particle properties, coating surface properties, mechanical properties, water resistance, thermal stability, and corrosion resistance were investigated. The results showed that the WFPU coating had excellent thermal stability, corrosion resistance, and mechanical properties. As the content of HFBMA-HPA increased from 0 wt% to 14 wt%, the water resistance of the WFPU coating gradually increased, the water contact angle (WCA) increased from 73° to 98°, the water absorption decreased from 7.847% to 3.062%, and the surface energy decreased from 32.8 mN/m to 22.6 mN/m. The coatings also showed impressive performances in the adhesion and flexibility tests in extreme conditions. This study provides a waterborne fluorinated polyurethane material with excellent comprehensive performance that has potential application value in the field of outdoor waterproof and anticorrosion coatings.

Aggregation-Induced Emission Enhancement and Solid-State Photoswitching of Crystalline Carbazole N-Salicylidene Anilines.

The development of fluorescent stimuli-responsive organic materials has attracted substantial interest due to their increasing optoelectronic applications. This study systematically introduces fluorine atoms on one end of carbazole-based N-salicylidene anilines 5a-5f to elucidate the impact in their solution and solid-state photophysics. The addition of fluorine atoms at one end of the molecule induced significant changes, for example, a reduction in the quantum yield (QY) fluorescence emission in solution, going from QY near unity in compound 5a (QY ∼ 100%) to a negligible emission in 5f (QY < 1%). Similarly, compound 5a showed a very strong aggregation-induced enhancement emission behavior, whereas compounds with a higher fluorine content were almost quenched. Furthermore, the crystalline solid-state photoisomerization in N-salicylidene anilines is not trivial, and only compounds with three (5e) and five fluorine atoms (5f) exhibited reversible solid-state photoisomerization under 405 nm light source irradiation. We propose that the presence of the arene-perfluoroarene interaction in the crystalline array facilitates the latter behavior. Our findings present a comprehensive study of crystal engineering for the obtention of photoswitchable crystalline materials and adjustable photophysics response, paving the way for its implementation in other systems.

Thermodynamic implications of size, hydrophilicity, and fluorine content on perfluoroalkyl adsorption in NU‐1000

Thermodynamic implications of size, hydrophilicity, and fluorine content on perfluoroalkyl adsorption in <scp>NU</scp>‐1000

Effect of elemental composition and phase transformation on lithium leaching behavior of micas in calcination-acid leaching process

Lithium (Li)-bearing clays have emerged as new types of Li resources. The structure and elemental composition of clay minerals play a crucial role in determining the Li leaching efficiency. The elemental composition and structural transformation of Li-bearing mica from Inner Mongolia (IMS) and Jiangxi (JS), China, were studied during the calcination-leaching process by using X-ray diffraction (XRD), Fourier Transform infrared spectroscopy (FTIR) and electron microprobe analysis (EMPA). The findings indicate that Mica is the predominant Li-bearing mineral in both IMS and JS. Notably, the IMS mica contains a significantly higher concentration of fluorine compared to the JS mica. Fluorine exerts a minor inhibitory effect on Li leaching, whereas the hydroxyl group (OH) significantly inhibits the leaching of Li from mica. The removal of residual oxygen atoms post-dehydroxylation is crucial to extract Li from mica. Both defluorination and dehydroxylation reactions occur within the temperature range of 800 °C to 900 °C. When calcined at 900 °C, the IMS mica was transformed into sanidine, while the JS mica was transformed into microcline. The acid leaching of products calcined at this temperature represents a process that further disrupts the residual mica structure and facilitates a cation exchange reaction.

Toward Water and Oil Repellent Coating: Synthesis of Fluorinated Methacrylate-Glycidyl Methacrylate Copolymers.

The development of durable and eco-friendly coatings with excellent adhesion and remarkable surface properties remains a critical pursuit in various industries. This study introduces an innovative methodology for the synthesis of glycidyl methacrylate-co-fluorinated methacrylate (P(GMA-co-FMA)) random copolymers with variable fluorine contents derived from GMA and FMA monomers. The copolymerization of these constituents yields coatings with enhanced durability and unique surface characteristics. Particularly, the incorporation of FMA introduces novel surface functionalities, leading to high water and oil repellent properties. The copolymer-coated surfaces exhibited impressive water contact angles ranging from 105° to 125° and decane contact angles ranging from 50° to 85°. The wettability of the P(GMA-co-FMA) coatings demonstrated a strong dependence on the fluorine content in the copolymers, with higher fluorine content resulting in superior water and oil repellency. Through a comprehensive characterization, we demonstrate the exceptional adhesion and self-cleaning capabilities of the fabricated films. Notably, the self-cleaning efficacy of P(GMA-co-FMA)-coated surfaces persists even following a prolonged duration of 6 months. Furthermore, our investigation reveals the influence of copolymer composition on surface wettability and contact angle hysteresis, providing valuable insights for tailoring coating properties. Overall, the novelty of this study lies in the synthesis of P(GMA-co-FMA) copolymer coatings with superior adhesion and self-cleaning properties. These advancements present promising applications in various fields, including electronics, textiles, and medical supplies, where such durable and functional coatings can significantly enhance product performance and longevity.

Biochar from paddy field - A solution to reduce PFAS pollution in the environment

Generally, activated carbons demonstrated a notable ability to capture long-chain PFAS, but exhibited relatively lower effectiveness for short-chain PFAS. Thirteen commercially available activated carbons in Japan underwent testing for their adsorption capacity of PFAS in water. The activated carbon derived from rice husk, Triporous™-PFAS, exhibited the highest adsorption capacity (over 95%) for PFAS from ultrashort-chain (perfluorocarbon chain: C1 for perfluorocarboxylic acid (PFCA) and C2 for perfluoroalkane sulfonic acid (PFSA)) to long-chain PFAS (C13 for PFCA and C10 for PFSA). An earlier lysimeter study highlighted Andosol, representative soil in Japan, as a potential medium for removing PFAS from irrigation water. Considering cultivating rice on Andosol fields and producing biochar from rice husks and rice straw, a new rice cultivation system is proposed. This system aims to facilitate continuous removal of PFAS from the environment in Asia. Japanese rice cultivation system produces not only rice but also biochar to remove PFAS from water circulation system. The total fluorine content in the tested activated carbon materials ranged from 0.18 to 38 μg g−1 F. Based on the results from background F blank and adsorption capacity, TriporousTM-PFAS-F was shown to be an option to lower the method detection limit for a proposed international standard method for measuring total PFAS.