Photophysical properties of some binary and ternary complexes of rare earth ions with aminobenzoic acids and 1,10-phenanthroline

Photophysical properties (e.g. luminescence and energy transfer) of binary and ternary complexes of Gd3+, Eu3+, and Tb3+ with aminobenzoic acids and 1,10-phenanthroline were studied in connection with their spectroscopic characterization. Intramolecular energy transfer between center ions and ligands as well as between ligands is discussed in detail.

Irreversible capacity loss of graphite electrode in lithium-ion batteries

The irreversible capacity loss of the carbon electrode in lithium-ion batteries at the first cycle is caused mostly by surface film growth. We inspected an unknown irreversible capacity loss (UICL) of the natural graphite electrodes. The charge/discharge behavior of graphite and meso-phase carbon microbeads heat-treated at 2800 degrees C (MCMB28) as the materials of the carbon anode in the lithium-ion battery were compared. It was found that the capacity loss of the natural graphite electrode in the first cycle is caused not only by surface film growth, but also by irreversible lithium-ion intercalation on the new formed surface at the potential range of lithium intercalation, while the capacity loss of the MCMB28 electrode is mainly originated from surface film growth. The reason for the difference of their irreversible capacity losses of these two kinds of carbon material was explained in relation to their structural characteristics. (C) 1997 Published by Elsevier Science S.A.

Lanthanide ions for the hydrolysis of 5'-mononucleotides and 3'-mononucleotides

Cleavage of adenosine-5'-monophosphate (5'-AMP), guanosine-5'-monophosphate (5'-GMP), adenosine-3'-monophosphate (3'-AMP) and guanosine-3'-monophosphate (3'-GMP) by lanthanides was investigated by NMR and the method of measuring the liberated phosphates. Rapid cleavage of both 5'-mononucleotides and 3'-mononucleotides by Ce-III and Ce-IV under air at pH 9 and 37 degrees C was observed. Other lanthanides showed less efficiency for hydrolyzing 5'-mononucleotides but 3'-mononucleotides were catalyzed by a range of lanthanide ions. The mechanism for hydrolyzing 3'-mononucleotides by lanthanides was:investigated. The notable difference in reactivity between Ce-III and the other lanthanide ions under air was further studied showing that the cleavage is enhanced with increasing molar fraction of Ce-IV. The fast cleavage of mononucleotides by Ce-III under air at pH 9 is ascribed to the resultant Ce-IV in the reaction mixture. (C) 1997 Elsevier Science Ltd.

Luminescence and energy transfer phenomena of several rare earth ions in the CaAl2B2O7

The luminescence properties of Ce3+, Gd3+, and Tb3+ have been investigated in the compound CaAl2B2O7. The single excitation band peaking at about 320 nm and single emission band peaking at about 384 nm for Ce3+, without the characteristic doublet, are attributed to the extensive crystal-field splitting of 4f ground state. The emission of Gd3+ consists of well-known sharp lines and two weak bands around 319.5 and 325 nm. These bands are due to the coupling of Gd3+ with BO33- groups. The green emission of Tb3+ is considerably sensitized by Ce3+. Energy transfer from Ce3+ to Tb3+ in CaAl2B2O7 is efficient. (C) 1997 Elsevier Science Ltd.

A study of ion kinetic energy spectrometry of o(-), m(-), and p(-) diol benzene doubly charged ions and singly charged ions in gas phase

With Mass Analyzed Ion Kinetic Energy Spectrometry (MIKES), Collisional Induced Dissociation(CID), and Electron Capture Induced Decomposition(ECID) technigues, the doubly charged ions and singly charged ions from o(-), m(-), and p(-) diol benzene in the EI source have been studied. In terms of the values of the kinetic energy releases(T) of the charge separation reactions of the doubly charged ions and the estimated intercharge distances(R) of the exploding doubly charged ions the transition structures were proposed. Some structural information about the transition states was also obtained. It is of interest that the MIKES/CID spectra of singly charged ions [C6H6O2](+) from the three isomers are of significant differences.

Study on diffusion of electroactive species in polyelectrolyte polyethylene glycol lithium perchlorate by chronoamperometry at a microdisk electrode

The mass transport dynamics of Ferrocene in polyelectrolyte polyethylene glycol lithium perchlorate (PEG . LiClO4) was studied by using chronoamperometry at a microdisk electrode. Chronoamperometry is a powerful method for the study of mass transport in polyelectrolyte, it has many advantages over the conventional methods at a microelectrode and the steady-state method at an ultramicroelectrode. By using this method the apparent diffusion coefficient D-app and concentration C-a of the electroactive species, can be estimated from a single experiment without previous knowledge of either one. We have estimated D-app and C-a of ferrocene in PEG . LiClO4 polyelectrolyte from 25 degrees C to 75 degrees C. The dependence on the concentration of electroactive species was observed. The diffusion coefficients decrease with increasing ferrocene concentration and decreasing temperature. The mass transport mechanism is explained, by using a free volume model.

Study of ion solvation and ion association in polymer gel electrolyte with polyethylene oxide-co-polypropylene oxide as a plasticizer

Using a molal conductance method, ion solvation and ion association in polytriethylene glycol dimethacrylate (PTREGD)-LiClO4 gel electrolytes with amorphous ethylene oxide-co-propylene oxide (EO-co-PO, <(M)over bar (n)>, = 1750) as the plasticizer were investigated. It was found that the fraction of solute existing as single ions (alpha(i)) and ion pairs (alpha(p)) decreases, while that of triple ions (alpha(t)) increases linearly with increasing salt concentration. The dependence of these fractions on molecular weight of plasticizer was also examined. It was shown that alpha(i) and alpha(t) increase and alpha(p) decreases with increasing molecular weight. The result of temperature dependence of these fractions was very interesting: when the temperature is lower than 55 degrees C, alpha(i) increases while alpha(p) and alpha(t) decrease with increasing temperature; however, when the temperature is higher than 55 degrees C, the reverse is true.

2D NMR and FT-Raman spectroscopic studies on the interaction of lanthanide ions and Ln-DTPA with phospholipid bilayers

The interactions of lanthanide ions and the Ln-DTPA (DTPA = diethylenetriaminepentaacetate) complex with di palmitoylphosphatidylcholine (DPPC) and dipalmitoylphosphatidylethanolamine (DPPE) bilayers are studied by 2D NOESY and FT-Raman spectroscopy. Proton NMR spectroscopic results show that lanthanide ions combine with phosphate groups in the polar region of the outer layer of DPPC liposomes, leading to the separation in chemical shift of the proton signal of N(CH3)(3) The conformational change of the O-C-C-N+ backbone from the gauche conformer to the trans one is not found; i.e., the orientation of the polar headgroup is still parallel to the surface of the bilayers. The Ln-DTPA complex at low concentration in a pH 7.4 solution localizes far away from bilayers and thereby has little effect on the structure of bilayers. The FT-Raman spectroscopic results indicate that lanthanide ions affect strongly the fluidity of acyl chains of DPPE bilayers while the Ln-DTPA complex affects it slightly.

Lithium ion conducting polymer electrolytes based on alternating maleic anhydride copolymer with oligo-oxyethylene side chains

A comb polymer with oligo-oxyethylene side chains of the type -(CH2CB2O)(12)CH3 was prepared from methyl vinyl ether/maleic anhydride copolymer and poly (ethylene glycol) methyl ether. The polymer can dissolve LiClO4 salt to form homogeneous amorphous polymer electrolyte. The ac ion conduction was measured using the complex impedance method, and conductivities were investigated as functions of temperatures and salt concentration. The complexes were first found to have two classes of glass transition which increase with increasing salt content, The optimum conductivity attained at 25 degrees C is in the order of 5.50 x 10(-6)Scm(-1). IR spectroscopy was used to study the cation-polymer interaction.

The ion selectivity of monensin incorporated phospholipid/alkanethiol bilayers

Monensin was incorporated into phospholipid/alkanethiol bilayers on the gold electrode surface by a new, paint-freeze method to deposit a lipid monolayer on the self-assembled monolayers (SAMs) of alkanethiol. The advantages of this assembly system with a suitable function for investigating the ion selective transfer across the mimetic biomembrane are based on the characteristics of SAMs of alkanethiols and monensin. On the one hand, the SAMs of alkanethiols bring out their efficiency of packing and coverage of the metal substrate and relatively long-term stability; on the other hand, monensin improves the ion selectivity noticeably. The selectivity coefficients K-Na+,K-K+, K-Na+,K-Rb+ and K-Na+,K-Ag+ are 6 x 10(-2), 7.2 x 10(-3) and 30 respectively. However, the selectivity coefficient K-Na+,K-Li+ could not be obtained by a potentiometric method due to the specific interaction between Li+ and phospholipid and the lower degree of complexion between Li+ and monensin. The potential response of this bilayer system to monovalent ions is fairly good. For example, the slope of the response to Na+ is close to 60 mV per decade and its linearity range is from 10(-1) to 10(-5) M with a detection limit of 2 x 10(-6) M, The bilayer is stable for at least two months without changing its properties. This monensin incorporated lipid/alkanethiol bilayer is a good mimetic biomembrane system, which provides great promise for investigating the ion transfer mechanism across the biomembrane and developing a practical biosensor.

Effect of lanthanum ions on the lipid polymorphism of phosphatidylethanolamines

The influence of lanthanum ions on the polymorphic phase of egg phosphatidylethanolamine and dielaidoylphosphatidylethanolamine (PE and DEPE) has been investigated by means of P-31-nuclear magnetic resonance (P-31-NMR) and high sensitivity differential scanning calorimetry (DSC) techniques. P-31-NMR experiments show that lanthanum ions promote the formation of the hexagonal II phase at temperatures lower than those of the pure egg PE, DSC results also show that lanthanum ions induce the formation of hexagonal II phase in DEPE liposomes even al very low ion concentration, The effect of lanthanum ions on the polymorphism of PE liposomes is much greater than that of calcium.

Carbon materials for lithium ion batteries

The preliminary work indicated that passive film is the most important factor influencing cell performance of carbon anode, and the carbon and solvent used govern cell performance by forming the passive film of different properties. A in situ XRD result is also presented.

Luminescence of Pb2+ and energy transfer from Pb2+ to rare earth ions in silicate oxyapatites

The Pb2+ luminescence in a series of silicate oxyapatites Me(2)(Y, Gd)(8)(SiO4)(6)O-2, Me(4)Y(6)(SiO4)(6)O (Me = Mg: Ca, Sr) is reported and discussed in relation to the crystal structure. The maximum wavelengths of the excitation (S-1(0)-P-3(1)) and emission (P-3(1)-S-1(0)) bands of Pb2+ are independent of the Mc:Y ratio (2:8 or 4:6) but they have lower energies in MgY-oxyapatites than in CaY- and SrY-oxyapatites. The Stokes shift of Pb2+ luminescence amounts to 11 100 to 11 400 cm(-1): which does not depend strongly on the host composition. There exists a mutual energy transfer between Pb2+ and Gd3+ in Sr2Gd8(SiO4)(6)O-2. At last, the dependence of the energy transfer efficiency of Pb2+-Sm3+, Tb3+: Dy3+ in Sr-2(La: Gd)(8)(SiO4)(6)O-2 and Ca-2(Y, Gd)(8)(SiO4)(6)O-2 on their doping concentrations was studied in more detail.

NMR and FT-Raman studies on the interaction of lanthanide ions with sphingomyelin bilayers

The interactions of lanthanide ions with sphingomyelin bilayers have been studied by using 2D NOESY spectroscopy and FT-Raman spectroscopy methods. The results indicate that lanthanide ions, as well as divalent calcium, combine mainly to the phosphate group in the polar headgroup and do not change the conformation of O-C-C-N+ backbone in the choline group of sphingomyelin bilayers. The polar headgroup is still extending parallel to the bilayer surface and O-C-C-N+ group is still in its gauche conformer.