Effect Of Fluorination Research Articles

Effects of surface fluorination on the dyeing of polycarbonate (PC) resin

Effects of surface fluorination on the dyeing of polycarbonate (PC) resin

Data-Driven Analysis of Fluorination of Ligands of Aminergic G Protein Coupled Receptors.

Currently, G protein-coupled receptors are the targets with the highest number of drugs in many therapeutic areas. Fluorination has become a common strategy in designing highly active biological compounds, as evidenced by the steadily increasing number of newly approved fluorine-containing drugs. Herein, we identified in the ChEMBL database and analysed 1554 target-based FSAR sets (non-fluorinated compounds and their fluorinated analogues) comprising 966 unique non-fluorinated and 2457 unique fluorinated compounds active against 33 different aminergic GPCRs. Although a relatively small number of activity cliffs (defined as a pair of structurally similar compounds showing significant differences of activity −ΔpPot > 1.7) was found in FSAR sets, it is clear that appropriately introduced fluorine can increase ligand potency more than 50-fold. The analysis of matched molecular pairs (MMPs) networks indicated that the fluorination of the aromatic ring showed no clear trend towards a positive or negative effect on affinity; however, a favourable site for a positive potency effect of fluorination was the ortho position. Fluorination of aliphatic fragments more often led to a decrease in biological activity. The results may constitute the rules of thumb for fluorination of aminergic receptor ligands and provide insights into the role of fluorine substitutions in medicinal chemistry.

In Situ Observation of Ferroelastic Domain and Phase Transition in a Three‐Dimensional Molecular Crystal

Massive efforts have been devoted to designing molecular ferroic materials by molecular modification. For molecular ferroelastic, previous work is focused on the temperature-dependent ferroelastic domains, however, few are related to controlling the ferroelastic domain by the stress. Inspired by the "quasi-spherical theory" and fluorination effect, we designed a more flexible (MedabcoF)2+ (MedabcoF=1-fluoro-4-methyl-1,4-diazoniabicyclo[2.2.2]octane) cation by introducing a methyl group and a fluorine atom at the two symmetrical ends of the Dabco (1,4-diazoniabicyclo[2.2.2]octane) and synthesized a hybrid 3D perovskite (MedabcoF)Rb(BF4 )3 (1) which displays three reversible phase transitions accompanying dual ferroelastic behavior. Besides, it not only exhibits ferroelastic domains switching by the thermal stimulation, and the sensitive reaction of in situ domains under the stress of it is also realized. This work not only achieves a force-controlled ferroelastic domain but develops a more profound comprehension of the relationship between the thermal motion behavior of guest cations and the intriguing properties of materials.

Quantitative Assessment of the Development of Micromycete Colony on the Surfaces of Polymers and Polymer Composites

The need to ensure the possibility of widespread use of electronic and mobile health-saving technologies requires not only the formation of an appropriate information technology infrastructure and the development of effective algorithms for processing a large amount of personal information. Development of medical devices for recording physiological processes also involves the creation of innovative biologically compatible materials that allow sensors and medical sensors to work continuously in 24/7 mode. Taking into account the long-term positive experience of using large-capacity thermoplastics and elastomers in medical equipment, it seems promising to use the corresponding polymers as the main materials of wearable electronics for medical purposes. At the same time, to ensure the biological compatibility of the materials under discussion, it is necessary to minimize the possibility of the development of pathogenic microorganisms on surfaces in contact with living tissues. This type of pathogenic organisms (pathogens of a number of dangerous diseases – mycoses) includes some types of microscopic fungi - micromycetes (in particular, Aspergillus niger van Tiegem; Aspergillus terreus Thom; Penicillium cycopium Westling). The article examines the effect of surface modification by gas-phase fluorination on the nature and degree of development of a mixed colony of micromycetes on the surfaces of experimental samples made of several types of thermoplastics (polyvinyl chloride, polypropylene, low-density polyethylene, polyethylene terephthalate) and elastomers (butyl- and butadiene-nitrile rubbers, as well as ethylene, propylene and dicyclopentadiene copolymers). The nature and degree of development of colonies are quantitatively described using the original methodology developed earlier. The effect of fluorination on the nanotexture and chemical composition of the surface and near-surface layers of experimental samples was demonstrated using scanning electron microscopy (SEM) and IR Fourier spectroscopy (IRFS). The dynamics and efficiency of fluorination are described using a linearized hyperbolic model, the parameters of which are set by the least squares method.

Order-disorder transition in amorphous Vanadium-Phosphorus-Lithium cathode of lithium ion battery

Vanadium-based amorphous materials are an emerging category of lithium ion battery cathodes with high specific capacity and high voltage performance. In this study, we investigated the effect of fluorination on the performance of an amorphous vanadium-phosphorus-lithium (VPLi) cathode for lithium ion battery applications. Results show that the fluorinated product consists Li3VF6 and VF4 nanocrystals embedded in an amorphous phase when the V4+ content was in the range of 16.3% to 23.8%. VPFLi has an optimal specific capacity of 344.3 mAh g−1 in the first cycle and 269.7 mAh g−1 after 200 cycles at a current of 50 mA g−1 within the voltage range of 1.5–4.2 V. VPLi has an amorphous structure, and the reversible V4+/V5+ lithiation process corresponds to the conversion between V2O5 and Li2V2O5 during the charge–discharge cycle. Compared to VPLi, VF4 and Li3VF6 crystals were found to convert into LiVP2O7 in VPFLi, which led to the increased specific capacity. Simulation based on density functional theory show that fluorine for oxygen has led to the movement of Fermi level moves towards the edge of the conduction band. Charge mostly transferred from Li to O which contributed to the improved cathode stability. This study provides a new perspective towards selecting novel cathode for lithium-ion batteries.

Effects of fluorination and thermal shock on the photocatalytic activity of Bi2O3 nanopowders

Fluorinated Bi2O3 (F-Bi2O3) nanopowder was prepared via fluorination followed by thermal shock of α-Bi2O3 nanopowder. The XRD, FTIR, SEM, and DRS characterization techniques were employed to investigate the effects of fluorine (F) insertion into the α-Bi2O3 host and the thermal shock from different temperatures. The crystal structure, optical and photocatalytic properties of the F-Bi2O3 nanopowders prepared were researched. The XRD results confirmed the substitution of O2- with F-. The FTIR results revealed that the coordination of Bi atoms changed upon F- substitution. The incorporation of F into the α-Bi2O3 host and thermal shock did not influence the morphology but modified the band structure of α-Bi2O3, leading to a red-shift in the optical absorption edge. Also, the bandgap narrowed from 2.8 eV to 2.6 eV. The density functional theory calculation proved that the F 2p orbitals were positioned in the valence band (VB), resulting in broader and more spread bands for F-Bi2O3. The results suggested that the photoexcited charge carrier mobility in the valence band (VB) and conduction band (CB) are enhanced upon F insertion into α-Bi2O3. The photocatalytic efficiency of the synthesized nanopowders was assessed by the degradation of Bromocresol Green (BG) under visible light illumination. Photocatalytic activity improved upon fluorination. The F-Bi2O3 nanopowders thermally shocked from higher temperatures showed negligible photocatalytic performance. The best photocatalytic performance of 70% BG degradation was realized after 180 min visible irradiation for the F-Bi2O3 nanopowder thermal shocked from 500 °C.

Identifying the effect of fluorination on cation and anion redox activity in Mn based cation-disordered cathode

Li-rich disordered rock-salt cathode (DRX) materials with advantage of low cost, long cycle life, nature abundant resource and high power and energy density attracted a great deal of scholarly attention. However, the poor cycle stability and the unclear realization of cation and anion redox activity in low-cost element system have severely hindered the construction of high-performance DRX. Herein, a promising class of Ti-Mn based cathode materials Li1.25Mn0.25Nb0.25Ti0.25O2 and Li1.25Mn0.25Ti0.5O1.75F0.25 were designed and successfully synthesized to construct high energy density DRX and investigate the effect of fluorination on cation and anion redox activity. The results show that both fluoridized and unfluoridized DRX possess a similar structure (Fm-3 m), but distinctly different charge/discharge profiles. The fluoridized cathode shows high initial charge/discharge capacity of 317.3/283.9 mAh g−1, specific energy density of 1370.4/735.5 Wh kg−1 and stable capacity retention with a discharge capacity of 202.6 mAh g−1 after 20 cycles at 20 mA g−1. Combining relevant spectroscopic results and HRTEM images, we revealed that the excellent cyclability of Li1.25Mn0.25Ti0.5O1.75F0.25 is rooted in the weakened adverse effects of moderated oxygen redox and the reduced Jahn–Teller distortion effect resulting from Mn3+, endowing the fluoridized DRX with better structural stability and larger Mn2+/Mn4+ reservoir. The strategy of constructing low cost oxyfluoride and the understanding of the mechanism of fluorination induced cation and anion redox activity would provide reference for the development of high-performance DRX materials.

Effect of Direct Fluorination on the Transport Properties and Swelling of Polymeric Materials: A Review

Fluorine-containing polymers occupy a peculiar niche among conventional polymers due to the unique combination of physicochemical properties. Direct surface fluorination of the polymeric materials is one of the approaches for the introduction of fluorine into the chemical structure that allows one to implement advantages of fluorinated polymers in a thin layer. Current review considers the influence of the surface interaction of the polymeric materials and membranes with elemental fluorine on gas, vapor and liquid transport as well as swelling and related phenomena. The increase in direct fluorination duration and concentration of fluorine in the fluorination mixture is shown to result mostly in a reduction of all penetrants permeability to a different extent, whereas selectivity of the selected gas pairs (He-H2, H2-CH4, He-CH4, CO2-CH4, O2-N2, etc.) increases. Separation parameters for the treated polymeric films approach Robeson’s upper bounds or overcome them. The most promising results were obtained for highly permeable polymer, polytrimethylsilylpropyne (PTMSP). The surface fluorination of rubbers in printing equipment leads to an improved chemical resistance of the materials towards organic solvents, moisturizing solutions and reduce diffusion of plasticizers, photosensitizers and other components of the polymeric blends. The direct fluorination technique can be also considered one of the approaches of fabrication of fuel cell membranes from non-fluorinated polymeric precursors that improves their methanol permeability, proton conductivity and oxidative stability.

Effects of tungsten alloying and fluorination on the oxidation behavior of intermetallic titanium aluminides for aerospace applications

Current limitations to a wider use of intermetallic TiAl alloys in aircraft and automotive engines arise from an insufficient oxidation resistance at temperatures above approximately 800 °C. In this paper, the high temperature oxidation behavior of three engineering γ-TiAl-based alloys at 900 °C in air is reported. The performance of the TNM alloy (Ti-43.5Al–4Nb–1Mo-0.1B), the 4822 alloy (Ti–48Al–2Cr–2Nb), and the Nb-free IRIS alloy (Ti–48Al–2W-0.08B) is compared (all chemical compositions are given in at.%). During testing in air non-protective mixed oxide scales developed on all untreated samples, but with different compositions and thicknesses. These different oxide layers are characterized and their formation mechanisms are discussed. The presence of W in the IRIS alloy leads to a better oxidation behavior compared to untreated TNM and 4822. This behavior was changed in the direction of a protective alumina layer formation via the so-called “fluorine effect”. The above-mentioned alloys were treated with fluorine via a liquid phase process by evenly spraying a fluorine containing polymer on all faces of the specimens. The oxidation resistance of the fluorine treated samples was significantly improved compared to the untreated specimens. Due to the fluorination all treated test coupons exhibited slow oxidation kinetics. The results of isothermal as well as thermocyclic exposure tests are presented and discussed in the view of the chemical composition and processing conditioned microstructure of the three investigated γ-TiAl-based alloys.

Improving the surface flashover performance of epoxy resin by plasma treatment: a comparison of fluorination and silicon deposition under different modes

This work treats the Al2O3-ER sample surface using dielectric barrier discharge fluorination (DBD-F), DBD silicon deposition (DBD-Si), atmospheric-pressure plasma jet fluorination (APPJ-F) and APPJ silicon deposition (APPJ-Si). By comparing the surface morphology, chemical components and electrical parameters, the diverse mechanisms of different plasma modification methods used to improve flashover performance are revealed. The results show that the flashover voltage of the DBD-F samples is the largest (increased by 21.2% at most), while the APPJ-F method has the worst promotion effect. The flashover voltage of the APPJ-Si samples decreases sharply when treatment time exceeds 180 s, but the promotion effect outperforms the DBD-Si method during a short modified time. For the mechanism explanation, firstly, plasma fluorination improves the surface roughness and introduces shallow traps by etching the surface and grafting fluorine-containing groups, while plasma silicon deposition reduces the surface roughness and introduces a large number of shallow traps by coating SiO x film. Furthermore, the reaction of the DBD method is more violent, while the homogeneity of the APPJ modification is better. These characteristics influence the effects of fluorination and silicon deposition. Finally, increasing the surface roughness and introducing shallow traps accelerates surface charge dissipation and inhibits flashover, but too many shallow traps greatly increase the dissipated rate and facilitate surface flashover instead.

Probing the effect of chiral dopant fluorination on dielectric and electro-optical properties of the ferroelectric liquid crystalline mixture

In this article, fluorinated chiral dopant-assisted tuning of dielectric and electro-optical properties of a ferroelectric liquid crystal (FLC) material is presented. Five new FLC mixtures with room temperature ferroelectric phase were formulated by fluorinating the phenyl core of chiral dopant at different positions and with a different number of fluorine atoms. The dielectric and electro-optical properties of all the FLC mixtures were systematically studied. It is found that the permittivity value of ferroelectric mesogens can be tuned between 5 and 36 (at 100 Hz) with fluorination. Also, the dielectric loss factor decreases owing to fluorination of chiral dopant with a shift in phason mode relaxation towards the low-frequency side. In addition, there is a significant change in material parameters of FLC, such as phase transition temperature, response time, spontaneous polarization, and rotational viscosity due to fluorination in chiral dopant. The presence of highly electronegative fluorine acts as a source of potentially repulsive force. It partially screens the molecular chirality of the dopant, which resulted in a change in the material parameters of FLCs. Interestingly, there is no considerable change in the mesogenic structure and orientation with the addition of fluorine, which is confirmed through wide-angle X-ray scattering. These studies open up a new avenue for tailoring the dielectric and electro-optical properties of mesogens for advanced device applications based on FLCs.

Effect of fluorination on the adsorption properties of aromatic heterocycles toward methyl halides: A quantum chemical study

Despite the numerous publications describing the synthesis and electronic properties of fluorinated furan, thiophene and pyrrole, the systematic overview of their adsorption applications is still lacking. In this study, the effect of fluorination on the adsorption properties of furan (C4H4O), thiophene (C4H4S), pyrrole (C4H4NH) and benzene (C6H6) are investigated with the help of density functional theory (DFT) calculations. Herein, the adsorption energies of CH3X (X = F, Cl & Br) on C4H4O, C4H4S, C4H4NH and C6H6 and their fluorinated analogues are calculated using ωB97XD/6-31+G(d, p) level of theory. The results of the adsorption energies and symmetry adapted perturbation theory (SAPT0) reveal that the adsorption affinity of adsorbent is enhanced upon fluorination due to the increasing dispersion forces. To comprehensively investigate the variation in the electronic properties of nonfluorinated and fluorinated systems, the HOMO, LUMO orbitals and NBO charges are analyzed. The isosurfaces of orbitals show that the electron density is more localized onto the fluorinated adsorbents which are probably due to the presence of multiple electronegative fluorine atoms. Owing to the electron-withdrawing nature of fluorine, the electronic charges are transferred from CH3X to fluorinated adsorbents while the charges are shifted from nonfluorinated adsorbents to CH3X. Furthermore, the TD-DFT calculations reveal that the electronic transition energies are significantly decreased in most of the fluorinated complexes especially, CH3X@C4F4S and CH3X@C4F4NH. With these findings, it can be postulated that fluorine substitution can significantly surge the electronic and adsorption properties of sensor materials.

Halogenation at the Phenylalanine Residue of Monomethyl Auristatin F Leads to a Favorable cis/trans Equilibrium and Retained Cytotoxicity.

Halogenation can be utilized for the purposes of labeling and molecular imaging, providing a means to, e.g., follow drug distribution in an organism through positron emission tomography (PET) or study the molecular recognition events unfolding by nuclear magnetic resonance (NMR) spectroscopy. For cancer therapeutics, where often highly toxic substances are employed, it is of importance to be able to track the distribution of the drugs and their metabolites in order to ensure minimal side effects. Labeling should ideally have a negligible disruptive effect on the efficacy of a given drug. Using a combination of NMR spectroscopy and cytotoxicity assays, we identify a site susceptible to halogenation in monomethyl auristatin F (MMAF), a widely used cytotoxic agent in the antibody–drug conjugate (ADC) family of cancer drugs, and study the effects of fluorination and chlorination on the physiological solution structure of the auristatins and their cytotoxicity. We find that the cytotoxicity of the parent drug is retained, while the conformational equilibrium is shifted significantly toward the biologically active trans isomer, simultaneously decreasing the concentration of the inactive and potentially disruptive cis isomer by up to 50%. Our results may serve as a base for the future assembly of a multifunctional toolkit for the assessment of linker technologies and exploring bystander effects from the warhead perspective in auristatin-derived ADCs.

Effect of Edge Fluorination on Electronic and Transport Properties of Aarmchair Boron Nitride Nanoribbons: A First-Principles Study

We have systematically investigated the effect of edge fluorination on structural stability, electronic and transport properties of armchair boron nitride nanoribbons (ABNNRs), using first-principles calculations within the frame work of local spin-density approximation (LSDA). ABNNRs with F-passivation on only edge B atoms, regardless of their width, are found to be half-metallic and energetically most stable. For these ribbons, completely spin polarized charge transport is predicted across the Fermi level as a result of giant spin splitting. Transmission spectrum analysis also confirms the separation of spin-up and spin-down electronic channels. It is revealed that F-passivation of only edge N atoms transforms nonmagnetic bare ribbons into magnetic semiconductors whereas fluorination of both the edges does not affect the electronic and magnetic state of bare ribbons significantly. Predicted Half-metallicity projects these ABNNRs as potential candidates for inorganic spintronic devices.

Fluorine Passivation of Defects and Interfaces in Crystalline Silicon.

Defects and impurities in silicon limit carrier lifetimes and the performance of solar cells. This work explores the use of fluorine to passivate defects in silicon for solar cell applications. We present a simple method to incorporate fluorine atoms into the silicon bulk and interfaces by annealing samples coated with thin thermally evaporated fluoride overlayers. It is found that fluorine incorporation does not only improve interfaces but can also passivate bulk defects in silicon. The effect of fluorination is observed to be comparable to hydrogenation, in passivating grain boundaries in multicrystalline silicon, improving the surface passivation quality of phosphorus-doped poly-Si-based passivating contact structures, and recovering boron-oxygen-related light-induced degradation in boron-doped Czochralski-grown silicon. Our results highlight the possibility to passivate defects in silicon without using hydrogen and to combine fluorination and hydrogenation to further improve the overall passivation effect, providing new opportunities to improve solar cell performance.

Rotational Spectrum and Molecular Structures of the Binary Aggregates of 1,1,1,3,3,3-Hexafluoro-2-propanol with Ne and Ar.

The structures and binding topologies of two binary van der Waals complexes 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP)···Ne and ···Ar were investigated. The rotational spectra of these two complexes including several isotopic species containing 20Ne, 22Ne, 40Ar, 13C, and hydroxyl D were measured using a chirped pulse Fourier transform microwave spectrometer and a cavity-based Fourier transform microwave spectrometer. While HFIP was shown to exist in both the gauche and trans configurations based on previous reports, the rare gas atom is predicted to attach to HFIP in several different binding topologies, leading to a total of nine possible structural isomers for each complex. Only one isomer was detected for each species, and it corresponds to the most stable one predicted, based on the comparison of the experimental rotational constants and electric dipole moment components with the theoretical predictions and on the isotopic data. We applied quantum theory of atoms in molecules (QTAIM) and electrostatic potential calculations to examine the different rare gas binding sites and to explore the nature of the interactions in these two complexes and several previously reported alcohol···Ar complexes. The effects of fluorination are also discussed by comparison with the binary complexes of isopropanol···Ne and ···Ar.

Arene-Perfluoroarene Interactions in Solution.

A systematic study of arene-perfluoroarene interactions in solution is presented. Using a combination of NMR titration experiments, X-ray crystallography, and computational analysis, we analyze the effects of fluorination, substituents, ring size, and solvation on the arene-perfluoroarene interaction. We find that fluorination, extension of the π systems, and enhancement of solvent polarity greatly stabilize the stacking energy up to 3 orders of magnitude (Ka = <1 to 6000 M-1), with the highest Ka achieved for the interaction of water-soluble variants of perfluoronaphthalene and anthracene in buffered D2O (pD = 12). Combining computational and experimental results, we conclude that this impressive binding energy is a result of enthalpically favorable electrostatic and dispersion interactions as well as the entropically driven hydrophobic effect. The enhanced understanding of arene-perfluoroarene interactions in aqueous solution sets the stage for the implementation of this abiotic intermolecular interaction in biology and medicine.

The impact of neutron irradiation, graphite oxidation and fluorination on tritium uptake into and desorption from graphite in molten salt environments

Tritium management is necessary in both fission and fusion nuclear reactors. In fusion reactors, tritium is a fuel that needs to be produced in breeding blankets. For fission reactors, and especially Fluoride Salt-Cooled High-Temperature Reactors (FHRs) and Molten Salt Reactors (MSRs), tritium is a contaminant to be separated and removed. The current literature on high-temperature hydrogen-graphite interactions is generated predominantly by the fusion research community and does not yet cover the low-pressure interval of relevance for FHRs and MSRs. Predictions of graphite uptake capacities and uptake rates at FHR conditions of few Pa partial pressure can only be performed using extrapolations. In order to make reliable extrapolations from the available data, the impact of phenomena that take place during operation and accident scenarios, such as neutron irradiation, air oxidation and reactions with molten fluoride salts must be accounted for. This article provides a summary of hydrogen-graphite thermodynamics and kinetics of interaction and discusses the effects of irradiation, air oxidation and fluorination on uptake capacities, uptake and desorption kinetics. We find that all three phenomena increase uptake capacities in graphite. Neutron irradiation and reactions with fluoride salts are expected to reduce tritium uptake rate, while oxidation is expected to increase it. In all three cases, the changes are more pronounced at low tritium partial pressures.

Role of the Perfluoro Effect in the Selective Photochemical Isomerization of Hexafluorobenzene

Hexafluorobenzene and many of its derivatives exhibit a chemoselective photochemical isomerization, resulting in highly strained, Dewar-type bicyclohexenes. While the changes in absorption and emission associated with benzene hexafluorination have been attributed to the so-called "perfluoro effect", the resulting electronic structure and photochemical reactivity of hexafluorobenzene is still unclear. We now use a combination of ultrafast time-resolved spectroscopy, multiconfigurational computations, and non-adiabatic dynamics simulations to develop a holistic description of the absorption, emission, and photochemical dynamics of the 4π-electrocyclic ring-closing of hexafluorobenzene and the fluorination effect along the reaction coordinate. Our calculations suggest that the electron-withdrawing fluorine substituents induce a vibronic coupling between the lowest-energy 1B2u (ππ*) and 1E1g (πσ*) excited states by selectively stabilizing the σ-type states. The vibronic coupling occurs along vibrational modes of e2u symmetry which distorts the excited-state minimum geometry resulting in the experimentally broad, featureless absorption bands, and a ∼100 nm Stokes shift in fluorescence-in stark contrast to benzene. Finally, the vibronic coupling is shown to simultaneously destabilize the reaction pathway toward hexafluoro-benzvalene and promote molecular vibrations along the 4π ring-closing pathway, resulting in the chemoselectivity for hexafluoro-Dewar-benzene.

P‐19: Student Poster: Enhanced Elevated‐Metal Metal‐Oxide Thin‐Film Transistors for Gate‐Driver Circuit Fabricated on a Flexible Substrate

The effects of fluorination on amorphous indium‐gallium‐zinc oxide thin‐film transistors fabricated on polyimide (PI) at a maximal temperature of 300 °C were investigated. An excimer laser was used to lift‐off the PI from a glass‐based carrier substrate. The resulting TFTs exhibit more positive threshold voltage, steeper subthreshold swing, reduced apparent short‐channel effects, and tighter distribution of device parameters. Various test circuit blocks and a 4‐stage 15T1C gate driver were constructed to demonstrate the beneficial effects of fluorination on circuit applications.