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131.
Tweezer-like molecular systems containing a redox-active tetrathiafulvalene vinylogue (TTFV) unit and two phenylboronate or phenylboronic acid endgroups were synthesized via the Cu-catalyzed alkyne azide coupling (i.e., click) reaction. The TTFV-phenylboronic acid derivative was found to show different differential pulse voltammetric (DPV) responses to various monosaccharides in aqueous DMSO at pH 7.41, suggesting potential use in electrochemical sensing of saccharides. Moreover, the TTFV-phenylboronate derivative exhibited strong binding to the fluoride ion, giving rise to sensitive electrochemical detection of the fluoride ion. 相似文献
132.
Three new monodimensional hybrid metal (Ti, In, Al) fluorides are synthesized with ethylenediamine (en) as a templating agent in solvothermal conditions assisted by microwave heating. All structures involve inorganic chains built up from TiO2F4 octahedra connected by two opposite O2− vertices in [H2en]·(TiOF4) (I), from InF6(H2O) pentagonal bipyramids linked by F–F edges in [H2en]·(InF4(H2O))2·H2O (II) and from (Al7F30)9− polyanions sharing two opposite AlF6 octahedra in [H2en]3·(Al6F24) (III). I is tetragonal, P4/ncc, a = 12.761(3) Å, c = 8.041(3) Å; II is orthorhombic, F2dd, a = 6.904(5) Å, b = 16.559(5) Å, c = 19.777(4) Å and III is monoclinic, P21/n, a = 9.387(2) Å, b = 6.710(2) Å, c = 21.513(6) Å, β = 97.18(3)°. 相似文献
133.
X.P. Chen Q.Y. Zhang C.H. Yang D.D. Chen C. Zhao 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2009,74(2):441-445
This paper reports on comparative investigation of structure and luminescence properties of tetragonal LiYF4 and BaYF5, and hexagonal NaYF4 phosphors codoped with Er3+/Yb3+ by a facile hydrothermal synthesis. The products were characterized by X-ray diffractometer, scanning electron microscope, and photoluminescence spectroscopy. Intense visible emissions centered at around 525, 550 and 650 nm, originated from the transitions of 2H11/2 → 4I15/2, 4S3/2 → 4I15/2, and 4F9/2 → 4I15/2 of Er3+, respectively, have been observed in all the samples upon excitation with a 980 nm laser diode, and the involved mechanisms have been explained. Based on the green up-conversion emission performance, the Yb3+ concentrations of Er3+/Yb3+-codoped LiYF4, BaYF5, and NaYF4 phosphors have been optimized to be 10, 20, and 20 mol.%, respectively. The quadratic dependence of fluorescence on excitation laser power has confirmed that two-photon contribute to up-conversion of the green–red emissions. 相似文献
134.
Junko Kimura 《Analytica chimica acta》2009,635(2):207-158
A novel chelating ligand, 2,4-[bis-(2,4-dihydroxybenzylidene)]-dihydrazinoquinazoline (DBHQ), was synthesized, and the fluorescence characteristics of its complex with metal ions were investigated.Thirty-five different metal ions were tested for the emission of fluorescence in the presence of DBHQ in aqueous solutions in a pH range of 3.0-10.5 (at a difference of 0.5 for each metal).It was observed that DBHQ fluoresces intensely at 470 nm with an excitation wavelength of 405 nm in the presence of Ga3+ or Al3+ in the pH range 3.0-4.0. The other metal ions did not show fluorescence with DBHQ. Although the presence of Cu2+, Co2+ and Fe3+ decreased the fluorescence intensity of DBHQ-Ga3+, the addition of a fluoride ion (NaF) recovered the fluorescence by masking the interfering ions. In addition, the fluoride ions were found to enhance the sensitive determination of Ga3+ because the fluorescence intensity of DBHQ-Ga3+ was further increased approximately 2.5-fold in the presence of F− (? = 0.658) from that in the absence of F− (? = 0.401). The fluoride ions also masked the Al3+ ions, which emit fluorescence on chelation with DBHQ. Therefore, a selective and sensitive detection of Ga3+ was achieved by using DBHQ in the presence of F−. The detection limit of Ga3+ was approximately 50 nmol L−1 (3.5 ppb). The proposed method was applicable to determine Ga3+ in river water. 相似文献
135.
A reagent tablet for determination of fluoride ion has been prepared using ethylenediamine-N,N,N′,N′-tetraacetate complex of zirconium (Zr-EDTA), 3-hydroxy-2′-flavone (FS) and an appropriate pH buffer. Dissolving of the tablet into water exhibits an intense blue fluorescence (λmax = 460 nm) upon excitation at 377 nm and the fluorescence intensity decreases with the presence of fluoride ion. Hence, a simple fluorescent detection procedure for fluoride ion in aqueous media was successfully constructed with this tablet. The principle of this detection system is the ligand exchange reaction of FS bound to Zr-EDTA with fluoride ion. The present system provides an easy, rapid and selective determination method of fluoride ion ranging from 5 × 10−6 to 1 × 10−3 mol dm−3. The measurement of real samples with this tablet showed the similar results as those by the common method with the Alfusone reagent. 相似文献
136.
137.
The first lanthanum fluoride borate La4B4O11F2 was obtained in a Walker-type multianvil apparatus at 6 GPa and 1300 °C. La4B4O11F2 crystallizes in the monoclinic space group P21/c with the lattice parameters a=778.1(2) pm, b=3573.3(7) pm, c=765.7(2) pm, β=113.92(3)° (Z=8), and represents a new structure type in the class of compounds with the composition RE4B4O11F2. The crystal structure contains BO4-tetrahedra interconnected with two BO3-groups via common vertices, B2O5-pyroborate units, and isolated BO3-groups. The structure shows a wave-like modulation along the b-axis. The crystal structure and properties of La4B4O11F2 are discussed and compared to Gd4B4O11F2. 相似文献
138.
A cholesteryl-based 2-(2′-hydroxyphenyl)benzoxazole (HPB) derivative 3 linked with an amide bond was prepared through an efficient synthetic pathway. The HPB, amide, and cholesteryl groups play important roles in constructing the supramolecular gel structure. UV-vis and fluorescence spectroscopy also showed that HPB and amide groups, which provide intra- and intermolecular hydrogen bonding, respectively, also contribute the recognition of fluoride anions. 相似文献
139.
140.
Summary. Gibbs energy of transfer data for LiF and NaF from water to aqueous alcohol mixtures, obtained from solubility measurements, are
examined via the Born equation. In spite of its well-known deficiencies, the simple Born model accounts for much of the observed variation of Δt
G°(MF, w→w+ROH), particularly for NaF. This unexpected success of the Born model appears to result from the fortuitous cancellation of the donor and acceptor contributions to the solvation of the
cations and anions by these closely related co-solvents. Examination of the deviations between the observed and calculated
Δt
G° values also suggests that they are partly due to uncompensated ion-pairing effects, especially for LiF.
Corresponding author. E-mail: hefter@chem.murdoch.edu.au
Received October 29, 2002; accepted November 8, 2002
Published online April 24, 2003
RID="a"
ID="a"Dedicated to Prof. Dr. Heinz Gamsj?ger on the occasion of his 70th birthday 相似文献