Fluoride Ion Source Research Articles

Identifying the genetic mechanism of medium-low temperature fluoride-enriched geothermal groundwater by the self-organizing map and evaluating health risk in the Wugongshan area, southeast China.

Fluoride-enriched groundwater is a serious threat for groundwater supply around the world. The medium-low temperature fluoride-enriched geothermal groundwater resource is widely distributed in the circum-Wugongshan area. And the fluoride concentration of all geothermal samples exceeds the WHO permissible limit of 1.5mg/L. The Self-Organizing Map method, hydrochemical and isotopic analysis are used to decipher the driving factors and genetic mechanism of fluoride-enriched geothermal groundwater. A total of 19 samples collected from the circum-Wugongshan geothermal belt are divided into four clusters by the self-organizing map. Cluster I, Cluster II, Cluster III, and Cluster IV represent the geothermal groundwater with the different degree of fluoride concentration pollution, the different hydrochemical type, and the physicochemical characteristic. The high F- concentration geothermal groundwater is characterized by HCO3-Na with alkalinity environment. The δD and δ18O values indicate that the geothermal groundwater origins from the atmospheric precipitation with the recharge elevation of 1000-2100m. The dissolution of fluoride-bearing minerals is the main source of fluoride ions in geothermal water. Moreover, groundwater fluoride enrichment is also facilitated by water-rock interaction, cation exchange and alkaline environment. Additionally, the health risk assessment result reveals that the fluorine-enriched geothermal groundwater in the western part of Wugongshan area poses a more serious threat to human health than that of eastern part. The fluoride health risks of geothermal groundwater for different group show differentiation, 100% for children, 94.74% for adult females, and 68.42% for adult males, respectively. Compared with adult females and adult males, children faced the greatest health risks. The results of this study provide scientific evaluation for the utilization of geothermal groundwater and the protection of human health around the Wugongshan area.

Benzylic C(sp3)−H Alkoxylation through Visible‐Light‐Driven Oxidative Radical‐Polar Crossover

AbstractWe report a metal‐free method for benzylic C(sp3)−H alkoxylation with a silyl ether as an alkoxylating agent. The reaction is considered to proceed through a sequence consisting of hydrogen atom transfer (HAT) and oxidative radical‐polar crossover, wherein Selectfluor serves as a one‐electron oxidant, a HAT agent, and a fluoride ion source. The fluoride ion formed in situ activates the silyl ether to give the alkoxide nucleophile, which reacts with a benzyl cation intermediate to provide the benzyl ether product. The present protocol has a broad substrate scope, enabling C−H alkoxylation of primary, secondary, and tertiary benzylic C(sp3)−H bonds. Furthermore, it is applicable for late‐stage C−H alkoxylation of bioactive molecules.

Optimization of anodizing parameters for the morphological properties of TiO2 nanotubes based on response surface methodology

TiO2 nanotube (TNT) morphology is crucial for applications in a variety of fields. In this paper, response surface methodology (RSM) has been utilized to optimize the anodizing parameters i.e., electrolyte concentration (C), anodization voltage (V), and time (t) for morphology (e.g., nanotube diameter and length) of TNTs. Ethylene glycol (EG) based electrolyte has been used for anodization employing ammonium fluoride (NH4F) as a source of fluoride ion (F–) with 2.5 vol% H2O. Reliable regression models have been developed between the input variables and the corresponding responses, namely tube diameter and length with multiple regression coefficients of 0.9649 and 0.9253, respectively, revealing a trustworthy association between the actual and those predicted values using the quadratic model. The predicted values of C (0.31 wt%), V (38.44 V), and t (69.37 min) were found to be the optimum anodization condition preceding a TiO2 nanotubes diameter of 99.31 nm and length of 4572.64 nm. It was observed that the nanotubes diameter and length are more affected by anodizing voltage and time, and less sensitive to NH4F concentration. Therefore, RMS could be an appropriate technique to optimize anodizing parameters for producing TiO2 nanotubes with good morphology.

Comparison of the Fluoride Ion Release from Composite and Compomer Materials under Varying pH Conditions—Preliminary In Vitro Study

Fluoride prevents the demineralization and supports remineralization of enamel. It is important to maintain a constant low level of fluoride in the oral cavity at all times. Dental restorative materials that are used for this purpose contain NaF in their composition, which is a source of fluoride ions that diffuse into body fluids and surrounding tissues. Two such materials, the flowable composite material Wave (W) (SDI, Hamilton Parkway Itasca, Australia) and compomer material Freedom (F) (SDI, Hamilton Parkway Itasca, Australia), were studied in regards to their release of fluoride ions into various solutions imitating the oral environment: artificial saliva solution with the addition of hydrated calcium chloride (CaCl2) × 2H2O in the pH range of 4.5 and 5.5; artificial saliva free of calcium chloride in the pH range of 4.5, 5.5, 6.0, 7.0, and 7.5; deionized water; and saline solution. The results were assessed over a period of 7 days, i.e., 168 h. The Freedom (F) compomer showed the highest cumulative release of fluoride ions into artificial saliva solution at pH 4.5 (31.195 ± 10.461 μg F/mm2) and the lowest into saline solution (3.694 ± 1.115 μg F/mm2). The Wave (W) composite material revealed the highest cumulative release of fluoride ions into deionized water (7.982 ± 2.011 μg F/mm2); its lowest cumulative emission was observed in artificial saliva solution at pH 7.0 (1.391 ± 0.489 μg F/mm2). The amounts of released fluoride from the Freedom (F) compomer were considerably higher compared to the Wave (W) composite material. The ability to release the largest amounts of fluoride ions in an acidic environment results from the erosion of the surface layer. Different calcium content in available experimental and commercial artificial saliva preparations may influence the obtained results. Both the flowable Wave composite and Freedom compomer released more fluoride in an acidic environment with a pH of 4.5–5.5, but with different dynamics—Wave material had its maximum on the third day while Freedom on the first day of the experiment.

Structural Characterization of CaF2: Dy Nanoparticles Synthesized by Simple Chemical Co-Precipitation Method

In this work, nanoparticles of dysprosium doped calcium fluoride (CaF2:Dy) has been prepared by Simple Chemical Co-Precipitation Method in which 0.05 mol of CaCL2 is used as the calcium ion source and 0.05 mol of NH4F as the fluoride ion source. 1 mol% of Dy2O3was used as the dopant. The synthesized nanoparticle samples was characterized by X- ray diffraction (XRD) and the crystallite size using the dominant (111) peak was found to be 56.09 nm. SEM image shows the presence of spherical shaped nanoparticles. The PL emissions bands are observed at 479 nm (blue emission peak) and 573 nm (yellow emission peak).

α-Fluoroalkylamines, their properties and application as sources of nucleophilic fluoride ion

α-Fluoroalkylamines, their properties and application as sources of nucleophilic fluoride ion

Synthesis of bis(trifluoromethyl)alkylated trisubstituted alkenes via highly regioselective catalyzed hydrosilylation reaction of hexafluoro-2-butyne and their reactivity

Hydrosilylation reaction of hexafluoro-2-butyne 1 (HFB) with various silanes in the presence of a catalytic amount of transition-metal-catalysts was investigated. The reaction of HFB gave the corresponding bis(trifluoromethyl)containing vinylsilanes in an excellent regioselective manner in high yields. Treatment of the resulting vinylsilanes with various aldehydes and ketones in the presence of fluoride ion sources afforded the coupling products in moderate yields.

Electrochemical Fluorination of Organic Compounds Using Alkali Metal Fluoride Salt with Fluorinated Alcohol-Based Solvent System

Fluorinated alcohols, such as 1,1,1,3,3,3-hexafluoroisopropanol (HFIP) and 2,2,2-trifluoroethanol (TFE), are quite useful in organic chemistry including electrosynthesis, due to their unique features such as high oxidation tolerance, high polarity, low nucleophilicity and strong donor ability in hydrogen bonding. Fluorinated alcohols are also capable of dissolving alkali metal salt such as KF and CsF, which is one of the least expensive fluoride ion sources, in high concentration. In this research, we report the electrochemical fluorination of various organic compounds using alkali metal fluoride salt dissolved in a mixed solvent containing HFIP for the first time. Alkali metal fluorides acted both as a fluoride ion source and a supporting electrolyte to enable the electrochemical fluorination of C-H and C-S bonds efficiently.

Dentifrice Based on Fluoride-Hydrotalcite Compounds: Characterization and Release Capacity Evaluation by Novel In Vitro Methods.

Anti-caries activity of fluoride ions is due to the protection against demineralization and the enhancement of remineralization of tooth enamel. Dentifrices available on the market contain sodium fluoride, sodium monofluorophosphate, stannous fluoride, and amine fluoride as source of these ions. A new compound working both as fluoride ion source and as abrasive was projected. Hybrids based on F- ions intercalated between the lamellae of hydrotalcite-like compounds (HTlc-F), namely MgAl-HTlc-F and ZnAl-HTlc-F, were prepared and characterized. Then, three different percentages (2, 3, and 4%) of both HTlc-F compounds were assayed. After the rheological characterization, the dentifrices containing 3 and 4% of MgAl-HTlc-F and ZnAl-HTlc-F, respectively, resulted to be the most suitable ones. Two novel in vitro methods, "rotary toothbrush method" and "manual brushing method," were developed and used in order to study the F- ions release from the prepared dentifrices. The obtained results showed that the dentifrice containing ZnAl-HTlc-F (4%) was the most effective in releasing fluoride ions. The "rotary toothbrush method" resulted to be the most suitable as the simulation of the brushing movements is standardizable and reproducible.

Self‐Propagated para‐Fluoro‐Thiol Reaction

We introduce a protecting-group-free concept for the powerful para-fluoro-thiol reaction (PFTR) employing a source of fluoride ions as base. The reaction is shown to be self-propagating, with under-stoichiometric amounts of base, thus effectively foregoing the need for high base concentrations. Careful tuning of the solvent-thiol combination allows for quantitative conversion, in some cases within a short timeframe, when only minimal amounts of base are used, allowing the PFTR reaction to essentially proceed base-free.

Expanding the Balz-Schiemann Reaction: Organotrifluoroborates Serve as Competent Sources of Fluoride Ion for Fluoro-Dediazoniation.

The Balz-Schiemann reaction endures as a method for the preparation of (hetero)aryl fluorides yet is eschewed due to the need for harsh conditions or high temperatures along with the need to isolate potentially explosive diazonium salts. In a departure from these conditions, we show that various organotrifluoroborates (RBF3 - s) may serve as fluoride ion sources for solution-phase fluoro-dediazoniation in organic solvents under mild conditions. This methodology was successfully extended to a one-pot process obviating aryl diazonium salt isolation. Sterically hindered (hetero)anilines are fluorinated under unprecedentedly mild conditions in good-to-excellent yields. Taken together, this work expands the repertoire of RBF3 - s to act as fluorine ion sources in an update to the classic Balz-Schiemann reaction.

Fluoride-Catalyzed Deblocking: A Route to Polymeric Urethanes.

We report a fluoride-catalyzed deblocking of urethanes as "blocked" isocyanates. Organic and inorganic sources of fluoride ion proved effective for deblocking urethanes and for converting polyurethanes to small molecules. Distinct from conventional deblocking chemistry involving organometallic compounds and high temperatures, the method we describe is metal-free and operates at or slightly above room temperature. The use of fluorescent blocking agents enabled visual and spectroscopic monitoring of blocking/deblocking reactions, and the selected conditions proved applicable to urethanes containing a variety of blocking groups. The method additionally enabled a one pot deblocking and polymerization with α,ω-diols. Overall, this deblocking/polymerization strategy offers a convenient and efficient solution to problems that have limited the breadth of applications of polyurethane chemistry.

Fluoride‐Catalyzed Deblocking: A Route to Polymeric Urethanes

AbstractWe report a fluoride‐catalyzed deblocking of urethanes as “blocked” isocyanates. Organic and inorganic sources of fluoride ion proved effective for deblocking urethanes and for converting polyurethanes to small molecules. Distinct from conventional deblocking chemistry involving organometallic compounds and high temperatures, the method we describe is metal‐free and operates at or slightly above room temperature. The use of fluorescent blocking agents enabled visual and spectroscopic monitoring of blocking/deblocking reactions, and the selected conditions proved applicable to urethanes containing a variety of blocking groups. The method additionally enabled a one pot deblocking and polymerization with α,ω‐diols. Overall, this deblocking/polymerization strategy offers a convenient and efficient solution to problems that have limited the breadth of applications of polyurethane chemistry.

Effects of fluoride source on the characteristics of titanium dioxide nanotubes

Nanotubes were obtained from commercially pure titanium by anodization at 20 V in an aqueous solution of acetic acid (14% v/v) with three different sources of fluoride ion (HF, NaF, and NH4F). The use of the same anodization conditions allowed to study the effect of each fluoride source on the morphological characteristics of the nanotubes. The nanotubes produced had a wide variation in terms of internal diameter and polygon shape. The thickness of the porous coating produced in HF solution was around half that produced in salts (NaF and NH4F) containing electrolytes, whereas the barrier layer thickness at the pore base was the same for all the anodic coatings produced. To the best of our knowledge, for the first time, the existence of titanium suboxides in the nanotubes, both with and without heat treatment, was clearly observed by HRTEM; d-spacings were measured and correlated with the possible crystalline phases. The presence of titanium suboxides in the titanium dioxide nanotubes may improve the corrosion resistance and conductance of these materials. SAED and XRD did not show evidence of these titanium suboxides; only peaks associated with rutile and anatase phases were identified. High-resolution chemical analysis indicated that the fluoride content was higher at the nanotube base than at the nanotube tip in all coatings.

Formation of nanotubular TiO2 structures with varied surface characteristics for biomaterial applications.

Nanotubular structures were generated on the surface of titanium c.p. by anodization technique in an aqueous solution of acetic acid (14% v/v) with different sources of fluoride ion (HF, NaF, NH4 F). The aim of using these three different compounds is to study the effect of the counterion (H+ , Na+ and NH4+) on the morphology, wettability and surface free energy of the modified surface. Nanotubes were generated at 10 and 15 V for each anodizing solution. To further improve surface characteristics, the samples were heat-treated at 600°C for 4 h and at 560°C for 3 h. SEM images revealed the formation of nanotubes in all anodizing conditions, while their diameter increased proportionally to the electric potential. X-ray diffraction and micro-Raman spectroscopy results showed the presence of both anatase and rutile phases, with a higher content of rutile in the coatings obtained using NH4 F and an applied potential of 10 V. The heat-treatment significantly increased the wettability of the anodic coatings, especially for the coating obtained at 15 V with HF, which showed values < 7 degrees of contact angle. Besides, the nanotubes show a decrease in diameter due to the heat treatment, except for the nanotubes formed in NH4 F. Depending on their surface properties (e.g. low contact angle and high surface free energy), these coatings potentially have great potential in biomedical applications, sensors devices, and catalytic applications among others. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 1341-1354, 2018.

Synthesis and kinetics of disassembly for silyl-containing ethoxycarbonyls using fluoride ions.

In this study, a series of silyl-containing ethoxycarbonates and ethoxycarbamates on electron poor anilines and phenols were synthesized and their kinetics of disassembly determined in real-time upon exposure to fluoride ion sources at room temperature. The results provide a greater understanding of stability and kinetics for silyl-containing protecting groups that eliminate volatile molecules upon removal, which will allow for simplification of orthogonal protection in complex organic molecules.

Influence of fluoride ions on the structure-directing effect of organic amine in the synthesis of aluminophosphate open-frameworks

The crystallization behavior of the initial mixture with the composition of Al2O3:4.0P2O5:3.0 diethylene-triamine(DETA):xHF:153H2O was investigated at 180 °C, where 0⩽x⩽3. If x⩽1.8, three-dimensional open-framework aluminophosphate AlPO-CJ31 was obtained. If 2⩽x⩽3, a chain-like aluminophosphate(1) was obtained. The crystallization process of both compounds was investigated by means of powder X-ray diffraction(XRD) and the concentrations of Al and P in the liquid product during the crystallization process were analysed by means of inductively coupled plasma atomic emission spectroscopy(ICP-AES). The evolution of the coordination state of Al, P and F during the crystallization was monitored with 27Al, 31P and 19F MAS NMR technique. The influence of the fluoride ions and the source of fluoride ions on the structure-directing effect of DETA was discussed. It was found that the fluoride ions changed the crystallization direction of the initial mixture, i.e., the structure-directing effect of DETA, via altering the distribution or micro-structure of the inorganic fragments.

Electrochemical behaviors of Ti(III) in molten NaCl-KCl under various contents of fluoride

In order to investigate an optimal concentration of fluoride in alkali chloride melt which the Ti(III) can be reduced into metallic titanium in one step, a systematic study of the electrochemical properties of Ti(III) was carried out in molten NaCl-KCl. KF was used as a source of fluoride ions, and the molar ratio of fluoride ions and titanium ([F−]/[Tin+] ratio) was employed as a parameter to illustrate the influence of fluoride anions on the electrochemical behaviors of Ti(III). The experiments were carried out with various concentrations of fluoride ions using a glassy carbon electrode at a temperature of 1023K. Transient electrochemical techniques, such as cyclic voltammetry and square wave voltammetry, were performed to reveal the reduction steps and reduction potentials of the electroactive species. Results suggest that there are two steps for Ti(III) ion reduction in molten NaCl-KCl: Ti(III)→Ti(II) and Ti(II)→Ti. Ti(III) can be reduced directly to Ti in one step when KF was added in the melt in increasing amount.

Selective and Reversible Fluoride Complexation from Water by a Cyclic Tri(phosphonio)methanide Dication.

Tri(phosphonio)methanide dication 32+ , prepared from a trifluoromethylsulfanylphosphonium dication (12+ ) via an intramolecular electrophilic aromatic substitution reaction, is an unexpected P-based, water-resistant Lewis acid that is capable to selectively and reversibly bind fluoride ions from organic/aqueous biphasic solution. The formed complex is an unusual fluorophosphorane ([3-F]OTf). The multiple donor-acceptor interactions of 32+ that are crucial for the fluoride fixation have been elucidated by quantum chemical calculation. Compound [3-F]OTf can also be used as a convenient anhydrous fluoride ion source and was probed as a suitable catalyst of the silylotrifluoromethylation of various aldehydes.

Selective and Reversible Fluoride Complexation from Water by a Cyclic Tri(phosphonio)methanide Dication

AbstractTri(phosphonio)methanide dication 32+, prepared from a trifluoromethylsulfanylphosphonium dication (12+) via an intramolecular electrophilic aromatic substitution reaction, is an unexpected P‐based, water‐resistant Lewis acid that is capable to selectively and reversibly bind fluoride ions from organic/aqueous biphasic solution. The formed complex is an unusual fluorophosphorane ([3‐F]OTf). The multiple donor–acceptor interactions of 32+ that are crucial for the fluoride fixation have been elucidated by quantum chemical calculation. Compound [3‐F]OTf can also be used as a convenient anhydrous fluoride ion source and was probed as a suitable catalyst of the silylotrifluoromethylation of various aldehydes.