Solvent effects of a fluorescent polyquinoline chemosensor for metal ions

Red shift and quenching effects of the fluorecence spectra of polyquinoline (PQH) solutions in different solvents are observed upon the addition of metal ions, which demonstrates the extraordinary solvent effects on metal-ion recognition and sensing ability (including sensitivity and selectivity) of PQH.

Alkali metal ions transfer across a water/1,2-dichloroethane interface facilitated by a novel monoaza-B15C5 derivative

In this paper, a novel monoaza-B15C5 derivative, N-(2-tosylamino)-isopentyl-monoaza-15-crown-5 (L), is used as an ionophore to facilitate alkali metal cations transfer across a water/1,2-dichloroethane (W/DCE) interface. Well-defined voltammetric behaviors are observed at the polarized W/DCE interfaces supported at micro- and nano-pipets except Cs+. The diffusion coefficient of this ionophore in the DCE phase is calculated to be equal to (3.3+/-0.2) x 10(-6) cm(2) s(-1). The experimental results indicate that a 1:1 (metal: ionophore) complex is formed at the interface with a TIC/TID mechanism. The selectivity of this ionophore towards alkali ions follows the sequence Na+ > Li+ > K+ > Rb+ > Cs+. The logarithm of the association constants (log beta(1)(0)) of the LiL+, NaL+, KL+ and RbL+ complexes in the DCE phase are calculated to be 10.6, 11.6, 9.0 and 7.1, respectively. The kinetic parameters are determined by steady-state voltammograms using nanopipets. The standard rate constants (k(0)) for Li+, Na+, K+ and Rb+ transfers facilitated by L are 0.54+/-0.05, 0.63+/-0.09, 0.51+/-0.04 and 0.46+/-0.06 cm s(-1), respectively. The pH values of aqueous solution have little effect on the electrochemical behaviors of these facilitated processes. The results predicate that this new type of ionophore might be useful to fabricate electrochemical sensor of sodium ion.

Preparation of divalent rare earth ions in air by aliovalent substitution and spectroscopic properties of Ln(2+)

When alkaline earth ions in borates, phosphates or borophosphates [SrB4O7, SrB6O10, BaB8O13, MBPO5 (M=Ca,Sr)] are substituted partially and aliovalently by trivalent rare earth ions such as Sm3+, Eu3+, these rare earth ions can be reduced to divalent state by the produced negative charge vacancy V-M". The matrices must have appropriate structure containing a rigid three-dimensional network of tetragonal AO(4) groups (A=B,P). These groups can surround and isolate the produced divalent RE2+ ions from the reaction with oxygen. Therefore, this reduction reaction can be carried out even in air at high temperature. The produced divalent rare earth ions can be detected by luminescence and XANES methods and their spectroscopic properties are discussed.

Sol-gel derived silicate oxyapatite phosphor films doped with rare earth ions

Rare-earth (Eu3+, Tb3+)-doped Ca2Y8(SiO4)(6)O-2 luminescent thin films were dip-coated on silicon and quartz glass substrates through a sol-gel route. X-ray diffraction (XRD), scanning electron microscopy (SEM) and luminescence excitation and emission spectra as well as luminescence decays were used to characterize the resultant films. The results of XRD reveal that these films remain amorphous below 700 degreesC, begin to crystallize at 800 degreesC, and crystallize completely around 1000 degreesC with an oxyapatite structure. The grain structure of the film can be seen clearly from SEM micrographs, where particles with various shape and average size of 250 nm can be resolved. The Eu3+ and Tb3+ ions show their characteristic red (D-5(0)-F-7(2)) and green (D-5(4)-F-7(5)) emission in the films with a quenching concentration of 10 and 6 mol% (of Y3+), respectively. The lifetime of Eu-3divided by increases with the heat treatment temperature front 700 to 1100 degreesC.

Phenanthroline-functionalized MCM-41 doped with europium ions

Organo-functionalized MCM-41 containing non-covalently linked 1,10-phenanthroline (denoted as Phen-MCM-41) was synthesized by template-directed co-condensation of tetraethoxysilane and the modified phenanthroline (denoted as Phen-Si). XRD, FTIR, UV/VIS spectroscopy as well as luminescence spectroscopy were employed to characterize Phen-MCM-41. No disintegration or loss of the Phen-Si during the solvent extraction procedure could be observed. When monitored by the ligand absorption wavelength (272 nm), the undoped MCM-41 produces a broad band emission centered at 450 run, whereas europium (III) doped Phen-MCM-41 displays the emission of the Eu3+, i.e., D-5(0) --> F-7(J) (J = 0, 1, 2, 3, 4) transition lines due to the energy transfer from the ligands to Eu3+ as well as a broad band emission centered at 442 nm.

VUV-UV photoluminescence spectra of strontium orthophosphate doped with rare earth ions

The measurements of VUV-UV photoluminescence emission (PL) and photoluminescence excitation (PLE) spectra of rare earth ions activated strontium orthophosphate [Sr-3(PO4)(2):RE, RE = Ce, Sm, Eu, Tb] are performed. Whenever the samples are excited by VUV or UV light, the typical emission of Ce-3+,Ce- Sm3+, Eu3+, Eu2+ and Tb3+ ions can be observed in PL spectra, respectively. The charge transfer bands (CTBs) of Sm3+ and Eu3+ are found, respectively, peaking at 206 and 230nm. The absorption bands peaking in the region of 150-160 nm are assigned to the host lattice sensitization bands, i.e., the band-to-band transitions of PO43- grouping in Sr-3(PO4)(2). It is speculated that the first f-d transitions of Sm3+ (Eu3+), and the CTB of Tb3+ are, respectively, located around 165 (14 3) and 167 urn by means of VUV-UV PLE spectra and relational empirical formula, these f-d transitions or CT bands are included in the bands with the maxima at 150-160 nm, respectively. The valence change of europium from trivalent to divalent in strontium orthophosphate prepared in air is observe by VUV-UV PL and PLE spectra.

Mechanisms of sodium and potassium ions transfer facilitated by dibenzo-15-crown-5 across the water /1,2-dichloroethane interface using micropipettes

The transfer of sodium and potassium ions facilitated by dibenzo-15-crown-5 (DB15C5) has been studied at the micro-water/1,2-dichloroethane (water/DCE) interface supported at the tip of a micropipette. Cyclic volt-ammetric measurements were performed in two limiting conditions: the bulk concentration of Na+ or K+ in the aqueous phase is much higher than that of DB15C5 in the organic phase (DB15C5 diffusion controlled process) and the reverse condition (metal ion diffusion controlled process). The mechanisms of the facilitated Na+ transfer by DB15C5 are both transfer by interfacial complexation (TIC) with 1 : 1 stoichiometry under these two conditions, and the corresponding association constants were determined at log beta(1) = 8.97 +/- 0.05 or log beta(1) = 8.63 +/- 0.03. However, the transfers of K+ facilitated by DB15C5 show different behavior. In the former case it is a TIC process and its stoichiometry is 1 : 2, whereas in the latter case two peaks during the forward scan were observed, the first of which was confirmed as the formation of K (DB15C5)(2) at the interface by a TIC mechanism, while the second one may be another TIC process with 1 : 1 stoichiometry in the more positive potential. The relevant association constants calculated for the complexed ion, K+(DB15C5)(2), in the organic phase in two cases, logbeta(2), are 13.64 +/- 0.03 and 11.34 +/- 0.24, respectively.

The interaction of aldolase with the cytoplasmic domain of human erythrocyte band 3 inhibited by lanthanum ions

The effect of lanthanum ions on the activity of the cytoplasmic domain of human erythrocyte band 3 (CDB3), which was measured according to the inhibition to aldolase, was studied. In the presence of low concentration of lanthanum ions, the function of CDB3 to inhibit aldolase activity decreased significantly. It indicated that lanthanum ions in the erythrocyte would change the conformation of CDB3 and influence the control on aldolase activity.

Study of the interaction between lanthanide ions and a supported bilayer lipid membrane by cyclic voltammetry and ac impedance

The interaction of lanthanide ions with a supported bilayer lipid (1,2-dimyristoyl-sn-glycero-3-phosphatidylcholine) membrane (sBLM) was investigated by cyclic voltammetry and ac impedance spectroscopy in this paper, Lanthanide can affect the conformation of the supported bilayer lipid membrane and cause pore formation. Through the pores, Fe(CN)(6)(3) (4) can reach the electrode surface and show its redox behaviour. Furthermore the redox currents or Fe(CN)(6)(3) (4) increased with increasing concentration of lanthanides and leveled off at 1.2 muM for Eu3+. The interaction ability of three lanthanides with sBLM follows the sequence: Eu3+ > Tb3+ > La3+.

Promoter effects of rare earth ions on electrocatalytic oxidation of methanol

The promoter effects of rare earth ions on the electrocatalytic oxidation of methanol at the Pt electrode were studied using the cyclic voltammetry and stable polarization techniques. It was found for the first time that Eu, Ho, Dy ions could accelerate the electrocatalytic oxidation of methanol at the Pt electrode, while Lu, Pr, Yb, Sm ions showed inhibitor effects.

Sol-gel deposition and luminescent properties of oxyapatite Ca-2(Y,Gd)(8)(SiO4)(6)O-2 phosphor films doped with rare earth and lead ions

Rare-earth and lead ions (Eu3+, Tb3+, Dy3+, Pb2+) doped Ca2Y8 (SiO4)(6)O-2 and Ca2Gd8(SiO4)(6)O-2 thin films have been dip- coated on silicon and quartz glass substrates through the sol- gel route. X- Ray diffraction (XRD), TG- DTA, scanning electron microscopy (SEM), atomic force microscopy (AFM), FT- IR and luminescence excitation and emission spectra as well as luminescence decays were used to characterize the resulting films. The results of XRD reveal that these films remain amorphous below 700 degreesC, begin to crystallize at 800 degreesC and crystallize completely around 1000 degreesC with an oxyapatite structure. The grain structure of the film can be seen clearly from SEM and AFM micrographs, where particles with various shapes and average size of 250 nm can be resolved. Eu3+ and Tb3+ show their characteristic red (D-5(0)-F-7(2)) and green (D-5(4) - F-7(5)) emission in the films with a quenching concentration of 10 and 6 mol% (of Y3+), respectively. The lifetime and emission intensity of Eu3+ increase with the temperature treatment from 700 to 1100 degreesC, while those of Tb3+ show a maximum at 800 degreesC. Energy transfer phenomena have been observed by activating the oxyapatite film host- lattice Ca2Gd8(SiO4)(6)O-2 with Tb3+ (Dy3+). In addition, Pb2+ can sensitize the Gd3+ sublattice in Ca2Gd8(SiO4)(6)O-2.

Calculation of the electrostatic energy H-e(fd) on 4f(N-1)5d configuration of lanthanide ions

In LS coupling, the energy expressions of H-e(fd) of the chief low-energy levels of 4f(N-15)d (n < 9) configuration ions are calculated. H-e(fd) can be parameterized with F-K (k=2,4) and G(K)(k=1,3,5). f(k) and g(k), which are coefficients, times the corresponding parameter FK and GK leads to the energy expressions of H-e(fd).

Novel trichromatic phosphor codoped with two rare earth ions in a single matrix

The luminescence properties of CaBPO5: Eu, Tb phosphor and the sensitization of Ce3+ were investigated. The CaBPO5: Eu, Tb phosphors were synthesized in the ambient air and the emission spectra of Eu3+, Tb3+ and Eu2+ were Observed in the phosphor. The result shows that there is electron transfer between conjugate rare earth ions. Sensitization of Ce3+ can improve the intensity of emission of Tb3+ and Eu2+. A novel trichromatic lamp phosphor codoped with Eu3+-Tb3+ in matrix CaBPO5 is then predicted.

Networks with hexagonal circuits in co-ordination polymers of metal ions (Zn-II, Cd-II) with 1,1 '-(1,4-butanediyl)bis(imidazole)

Three new compounds, [ZnL1.5(H2O)(SO4)]. 6H(2)O 1, [ZnL1.5(H2O)(2)][NO3](2). 2H(2)O 2 and [CdL1.5(H2O)(2)(SO4)]. 4H(2)O 3 were obtained from self-assembly of the corresponding metal salts with 1,1'-(1,4-butanediyl)bis(imidazole) (L). In both 1 and 2 zinc ion is five-co-ordinated, showing a less-common trigonal bipyramidal co-ordination polyhedron, while cadmium ion of 3 is six-co-ordinated with a common octahedral arrangement. The sulfate ions of 1 and 3 are co-ordinated, however the nitrate ions of 2 are not. Each of the three compounds is composed of a (6, 3) network with the hexagonal smallest circuit containing six metal ions and six L; each L is co-ordinated to two metal ions, acting as a bridging ligand. In 1 the 2-D sheet of (6, 3) networks is interpenetrated in an inclined mode by symmetry related, identical sheets to give an interlocked 3-D structure, while the (6, 3) networks of both 2 and 3 stack in a parallel fashion to construct frameworks having channels.