Time-resolved Luminescence-based Chemosensor for Fluoride Anion

A new europium complex is descried as a time-resolved luminescence-based sensor for fluoride anion. The sensor is selective even in the presence of intensive background fluorescence.

Selective coordination and localized polarization in graphene quantum dots: Detection of fluoride anions using ultra-low-field NMR relaxometry

The development of ultra-sensitive methods for detecting anions is limited by their low charge to radius ratios, microenvironment sensitivity, and p H sensitivity. In this paper, a magnetic sensor is devised that exploits the controllable and selective coordination that occurs between a magnetic graphene quantum dot(GQD) and fluoride anion(F–). The sensor is used to measure the change in relaxation time of aqueous solutions of magnetic GQDs in the presence of F–using ultra-low-field(118 μT) nuclear magnetic resonance relaxometry. The method was optimized to produce a limit of detection of 10 nmol/L and then applied to quantitatively detect F–in domestic water samples. More importantly, the key factors responsible for the change in relaxation time of the magnetic GQDs in the presence of F–are revealed to be the selective coordination that occurs between the GQDs and F–as well as the localized polarization of the water protons. This striking finding is not only significant for the development of other magnetic probes for sensing anions but also has important ramifications for the design of contrast agents with enhanced relaxivity for use in magnetic resonance imaging.

Amino-functionalized porous PDVB with high adsorption and regeneration performance for fluoride removal from water

Excessive fluoride anions in drinking water are toxic to the health of human beings.In this article,an effective fluoride removal adsorbent on the basis of amino-functionalized porous polydivinylbenzene(PDVB)was prepared through low cost processes,which included solvothermal preparation of porous PDVB and subsequent surface amino-functionalization.The obtained amino-functionalized porous PDVB(A-PDVB)has high surface area of 443 m2 g1 and high adsorption capacity towards fluoride anion up to 105.9 mg g1.Considering adsorbents surface area,the adsorption capacity per unit surface area of A-PDVB is 0.24 mg m2 which is more than 4 times of porous PDVB(0.058 mg m2).The enhanced adsorption performance of A-PDVB was due to amino groups electrostatic interaction coupled with hydrogen bond binding with fluoride anions.In addition,the aminofunctionalized porous PDVB could be regenerated in high efficiency under alkaline conditions.This work not only exhibits the possibility of A-PDVB for application as an environment-friendly adsorbent for fluoride removal but also gives an insight into understanding mechanism of the fluoride anions adsorption onto aminofunctionalized porous PDVB.

Development of aryl-containing dipyrrolyldiketone difluoroboron complexes(BONEPYs):Tune the hydrogen bond o-C—H…F for fluoride recognition

Dipyrrolyldiketone difluoroboron complexes(BONEPYs)were synthesized by condensation of the corresponding pyrroles and malonyl chloride followed by treatment with BF3·OEt2.The aryl-substituted pyrrole is introduced to form a cyclic system in order to investigate anion binding studies.In BONEPYs 1-3 the o-H of the aryl group forms hydrogen bonding with F to give a more table complex.In contrast,the intramolecular hydrogen-bonded BONEPY endo-4 is more stable than its exo isomer.While adding F,the hydrogen bonds must be broken first to give 4·(3)F.Owing to the electron-rich group(-OMe),the o-H of the phenyl group can hardly interact with F via hydrogen bonding to give the less stable complex4-(5)F.The energy diffe rences between the different conformations were calculated using DFT methods,which is consistent to the experimental observations.

Reversible Disassembly and Intercalation of 2-Ureido-4[1 H]- Pyrimidinone Quadruple Hydrogen-bonded Supramolecular Assembly by Fluoride and Lead Ions

2-Ureido-4[1H]-pyrimidinone quadruple hydrogen-bonded assembly 1,1 containing N,N-dimethylaminophenyl moiety exhibits a sensitive response to fluoride anion and lead cation. Spectroscopic studies reveal that the presence of small amount of fluoride anions and lead cations can easily disassemble and intercalate 2-ureido- 4[ 1H]-pyri mi di none hydrogen-bonded supramolecular architectures.

Fluoride removal by Al,Ti,and Fe hydroxides and coexisting ion effect

Batch experiments were conducted to evaluate fluoride removal by Al,Fe,and Ti-based coagulants and adsorbents,as well as the effects of coexisting ions and formation of aluminum–fluoride complexes on fluoride removal by co-precipitation with alum（Al_2（SO_4）_3·18H_2O）.Aluminum sulfate was more efficient than the other coagulants for fluoride removal in the pH range between 6 and 8.Nano-crystalline TiO_2 was more effective for fluoride removal than Al and Fe hydroxides in a pH range of 3–5.Coexisting anions in water decreased the removal of fluoride in the order：phosphate（2.5 mg/L） 〉 arsenate（0.1 mg/L） 〉 bicarbonate（200 mg/L） 〉sulfate（100 mg/L） = nitrate（100 mg/L） 〉 silicate（10 mg/L） at a pH of 6.0.The effect of silicate became more significant at pH 〉 7.0.Calcium and magnesium improved the removal of fluoride.Zeta-potential measurements determined that the adsorption of fluoride shifted the PZC of Al（OH）_3 precipitates from 8.9 to 8.4,indicating the chemical adsorption of fluoride at the surface.The presence of fluoride in solution significantly increased the soluble aluminum concentration at pH 〈 6.5.A Visual MINTEQ modeling study indicated that the increased aluminum solubility was caused by the formation of AlF^（2＋）,AlF^（＋2）,and AlF_3complexes.The AlF_x complexes decreased the removal of fluoride during co-precipitation with aluminum sulfate.

Dimesitylborylphenyl substituted 1,3,4-oxadiazole:Synthesis,characterization and sensitivity to F^-

A new 1,3,4-oxadiazole compound with a dimesitylboryl group was synthesized and characterized by ~1H NMR,MS,element analysis and X-ray single-crystal diffraction.It exhibits good blue emission at 425 nm and high sensitivity to fluoride anion.