Borazine as a sensor for fluoride ion: a computational and experimental study

The computational and experimental studies have revealed that even simple molecule like borazine can act as a sensor for fluoride ions. This study further reported the various binding modes of analytes using quantum chemical calculations and the nature of such interactions have been examined using electron density surface analysis. Total charge transfer analysis (q_CT) correlates well with the binding affinities of analytes with the borazine receptor.     

Indirect voltammetric detection of fluoride ions in toothpaste on a comb-shaped interdigitated microelectrode array

A novel technique based on dynamic electrochemistry for the detection of fluoride ions was developed. It is based on its strong complexation with ferric ion. Formed fluoroferric complex is cathodically inactive at the potential of the reduction of free ferric aquo ion. The voltammetric and amperometric response of platinum comb-shaped interdigitated microelectrode array is decreased after fluoride addition. This decrease serves for the quantification of fluoride ions added to the solution. The detection limit of 4.5 × 10⁻⁵ mol dm⁻³ was achieved when one of the segments of interdigitated microelectrode array (IDA) was used as an indicating electrode. The detection limit is about one order of magnitude lower than in the case of conventional platinum macroelectrode. In comparison with ISE electrodes this method is faster and also avoiding large error resulting from the antilogarithmization of ISE Nerstian response. The method was applied to the analysis of toothpaste.     

On-chip pre-concentration and complexation of [¹⁸F]fluoride ions via regenerable anion exchange particles for radiochemical synthesis of Positron Emission Tomography tracers

Microfluidic approaches have demonstrated a relevant impact on radiochemical reactions involving Positron Emission Tomography (PET) nuclides, due to shorter reaction times and smaller precursor quantities. However, little attention has been given to the integration of the initial pre-concentration and drying of radioactive [(18)F]fluoride ions, required for the labeling of radiotracer compounds. In this work we report the design, fabrication and implementation of a glass microfluidic device filled with recyclable anion exchange particles for the repeated recovery of [(18)F] and [(19)F]fluoride ions. The device was first tested with non radioactive [(19)F]fluoride ions and it was shown to repeatedly trap and elute >95% fluoride over 40 successive experimental runs with no decrease in efficiency. The same device was then tested for the trapping and release of [(18)F]fluoride ions over 20 experiments with no measurable decrease in performance. Finally, the [(18)F]fluoride ions were eluted as a K(18)F/K2.2.2 complex, dried by repeated dissolution in acetonitrile and evaporation of residual water, and reacted with ethyl ditosylate (EtDT) leading to the desired product ([(18)F]fluoroethyltosylate) with 96 ± 3% yield (RCY). The overall time needed for conditioning, trapping, elution and regeneration was less than 6 min. This approach will be of great benefit towards an integrated platform able to perform faster and safer radiochemical synthesis on the micro-scale.     

The chemistry of phase selectivity in the synthesis of high-silica zeolites

In this review we discuss the roles that inorganic and organic components play in the synthesis of high-silica zeolites. We discuss the effects that heteroatom identity, heteroatom substitution, and SDA shape have on synthesis products. Then we summarize recent developments in zeolite synthesis that have been made by performing syntheses in concentrated fluoride media and by using germanium as a tetravalent heteroatom. Finally, we examine the combined roles that framework stability, framework/SDA interactions, and silanol defects may have in determining phase selectivity.     

Long range enhancement of boron diffusivity by phosphorus diffusion

The effect of electron and ion beam irradiation on the Si_{L vv} Auger spectra of SiO₂, Si₃N₄ and Si-oxynitride films was measured by the relative intensity of the 92 eV signal, characteristic for the formation of “free” silicon during irradiation. While in Si-oxynitride (O/N = 0.37) the beam effects were almost negligible, some damage was found in Si₃N₄, but SiO₂ appeared to be extremely sensitive for electron and ion beam irradiation. By low energy electron loss spectroscopy (ELS) of ion bombarded SiO₂ and Si₃N₄ films new electron states due to broken Si-O and Si-N bonds could be determined within the band gap of the insulators. The measured energy losses were interpreted by means of electron energy level schemes of the amorphous films.     

Metallic Li colloids studied by 7 Li MAS NMR in electron-irradiated LiF

7 Li MAS NMR spectra of 2.5 v MeV electron-irradiated LiF crystals have been measured in a field of 9.4 v T. Besides the resonance line of the ionic compound, a second well-separated spectrum is observed in the region of the Knight shift value for metallic lithium. At room temperature, the latter can be decomposed into two components with different Knight shift and linewidth values. When the temperature is increased, line narrowing takes place at first, indicating shortening of correlation times for self-diffusion, independently in both components. Above 370 v K, both lines broaden and approach each other before collapsing into a single line. The high ppm component disappears after crossing the melting temperature of metallic lithium (454 v K). The two lines are attributed to different types of metallic Li: one to bulk-like metal, the other to Li present initially under pressure and relaxing to the former under thermal treatment.     

Catalytic Homologation-Allylboration Sequence for Diastereo- and Enantioselective Synthesis of Densely Functionalized β-Fluorohydrins with Tertiary Fluoride Stereocenters

Homologation of trisubstituted fluoroalkenes followed by allylboration of aldehyde, ketone and imine substrates is suitable for synthesis of β-fluorohydrin and amine products. In the presence of (R)-iodo-BINOL catalyst enantioselectivities up to 99 % can be achieved by formation of a single stereoisomer with adjacent stereocenters, of which one is a tertiary C−F center.     

Crystal growth and luminescent properties of Pr-doped K(Y,Lu)3F10 single crystal for scintillator application

Pr1%:K(Y_1−xLu_x)₃F₁₀ (x=0, 0.2, 0.4) single crystals were grown by the μ-PD method. All the grown crystals were greenish and perfectly transparent without any inclusions or cracks. Radioluminescence spectra and decay kinetics of the Pr1%:K(Y,Lu)₃F₁₀ crystals were measured. Emission from the Pr³⁺ 5d–4f transition, peaking around 260 nm and of the decay time of around 22 ns were observed. The 5d–4f emission intensities of the Pr1%:K(Y,Lu)₃F₁₀ crystals were higher than that of the standard BGO scintillator.     

A novel coumarin-based switching-on fluorescent and colorimetric sensor for F

A novel turn-on fluorescent and colorimetric sensor, N-(4′-nitrophenyl)-2-oxo-6-(phenylazo)-2H-chromene-3-carbohydrazide (1), for fluoride in dimethyl sulfoxide (DMSO) was designed and synthesized. The binding ability evaluated by UV-vis and fluorescence titration experiments reveals that 1 can selectively recognize fluoride. In particular, addition of F⁻ to the DMSO solution of 1 resulted in an enhancement in fluorescence intensity at 338 and 352 nm, which can provide a way of ‘naked-eye’ detection for fluorides. The spectral change of 1 is due to the anion-induced increase of the charge density in and the rigidity of the host molecule. Furthermore, the binding mode with F⁻ was investigated by ¹H NMR experiments.