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.

Preparation of borates doped with divalent rare earth ions (RE2+) in air and spectroscopy of divalent rare earth ions (RE2+ = Sm, Eu, Tm, Yb)

The spectroscopic feature of divalent Sm2+, Eu2+, Tm2+ and Yb2+ is discussed in this paper. Especially the spectroscopic properties of some berates containing tetrahedral BO4 group such as SrB4O7, SrB6O10 and BaB8O13 doped with these divalent ions are reported. When the divalent alkaline earth ion in these berates is replaced partially by the above trivalent rare earth ion, the charge carried in the produced defects can be used as reductant to reduce the doped rare earth ion into divalent state at high temperature even in air. Therefore, a convenient and safe method is provided to prepared phosphors doped with these divalent rare earths.

Effects of rare earth ions and calmodulin on the activity of lactate dehydrogenase

In this paper, the effects of rare earth ions (La3+, Eu3+, Dy3+, Yb3+) and their complexes with calmodulin on the activity of lactate dehydrogenase (LDH) were investigated. The results reveal that whether binding with calmodulin or not, rare earth ions show a minor activation effects on LDH when their concentrations are less than 3 mu mol (.) L-1, but indicate some strong inhibitory effects on LDH activity when the concentrations are above 5 mu mol (.) L-1. Calmodulin, which is a calcium-dependent regulator, can stimulate LDH activity and release the inhibitory effects of rare earth ion. Diethylenetriamine pentaacetic acid(DTPA) and its derivatives bisdimethylamide-diethylenetriamine pentaacetic acid (DTPA-BDMA), bisisonicotinyl-diethylenetriamine pentaacetic acid (DTPA-BIN), which are often used as ligands to metal ions, inhibit LDH activity when their concentrations are above 5 mu mol (.) L-1. Calmodulin can also release their inhibitory effects at the same time.

Vibronic transitions and site substitution of Eu2+ and codoped ions in KMgF3 : Eu-X (X=Ce, Cr, Gd, Cu) system

The high-resolution emission spectra of KMgF3 : Eu and KMgF3 : Eu-X(X = Ce, Cr, Gd, Cu) single crystals were measured at 300 and 77 K. The vibronic side bands of Eu2+ were characterized and an assignment of the normal mode frequencies to particular vibrations has been made. The correlation between the vibronic frequencies of Eu2+ and the site substitution of other co-dopcd ions was first found. The relationship between vibronic intensity of Eu2+ and other doped ions concentration showed that Cr3+, Gd3+ ions competed K+ sites with Eu2+ ions. Ce3+ and Eu3+ occurred the electron transference. The introduction of Cu+ made for Eu2+ substuting for K+ sites.

Gaseous dipeptide complexes with metal ions by electrospray ionization and tandem mass spectrometry

Electrospray ionization (ESI) and tandem mass spectrometry have been used to investigate the gas-phase interactions of five metal ions and seven dipeptides. For silver ion, two complexes ([M+Ag](+) and [2M+Ag](+)) were obtained as well as the one complex ([2M+Met-H](+)) for transition-metal ions. Upon collision activation, there is an obvious difference in MS/MS data between metal ion complex and the protonated molecule. The fragment pathway of each complex is related to the structures of dipeptide and the nature of metal ion which suggest that there are several interaction between the metal ions and dipeptides in gas phase.

Study of energy transfer between rare earth ions in CaS host by photoluminescence spectra

When CaS:Sm3+, Eu2+ is excited at 476.5 nm (Ar+), the emission spectra taken at room temperature and at 77 K are different, indicating that there are two competitive energy transfer processes-Sm3+ --> Eu2+ and Eu2+ --> Sm3+ with phonon participation. So, the luminescence intensity of Sm3+ increases first, and then decreases as the concentration of Eu2+ is increasing. (C) 2001 Elsevier Science Ltd. All rights reserved.

Studies on the transport of lanthanides ions through the membrane of human erythrocyte in vitro by ICP-MS

A method was developed for the determination of lanthanum in the cytoplasm of human erythrocytes after they were incubated in lanthanum nitrate or citrate solutions. The lanthanum concentration in the cytoplasm of incubated erythrocytes is much higher than that in normal erythrocytes. It is suggested lanthanum can transport through the membrane of erythrocyte in vitro. Solutions containing chelator are unsuitable to be washing buffer in the investigation.

Scanning electrochemical microscopy study of electron transfer across the water/1,2-dichloroethane interface induced by common ions

In this work, we report the reverse electron transfer reaction between TCNQ in 1, 2-dichloroethane (DCE) and ferrocyanide in water. This process is a thermodynamic unfavorable reaction and the reverse electron transfer reaction can only be obtained by scanning electrochemical microscopy(SECM) in the presence of suitable potential-determining ions, which govern the interfacial potential difference. In our case, the potential determining ions are tetrabutylammonium ion(TBA(+)) and tetraphenylarsonium ion (TPAs+). The effects of the concentrations of TBA(+) and TPAs+ in two phases and other parameters have been studied in detail. The apparent heterogeneous rate constants(k(i)) were obtained under different values of K-p(K-p=c(i)(w)/c(i)(o)) for both cases by fitting the SECM approach curves with theoretical ones and the results showed that they were controlled by the interfacial potential differences. The relationship between apparent heterogeneous rate constants and the interfacial potential differences obeys Butler-Volmer theory.

Spectroscopic study of the photophysical properties of rare earth ions encapsulated: Water soluble functional calixresorcin[4]arene

A novel macrocyclic compound-water soluble functional calixresorcin[4]arenes-tetra para sulfo-phenylmethyl-calixresorcin[4]are was synthesized for the first time. The photophysical properties of terbium and europium ions encapsulated in the macrocyclic ligand were studied in detail. The triplet state energy of the calixresorcin[4]arene was determined to be 24400 cm(-1) by the low temperature phosphorescence spectrum and it was found that it can sensitize both terbium ion and europium ion. The possible energy transfer process between the functional calixresorcin[4]arene and the encapsulated Tb3+ and Eu3+ was discussed. The luminescence quantum efficiency of Tb3+- calixresorcin[4]arene was calculated.

Fragmentation reactions of adduct ions [M+CH3CO](+) of isomeric phenylenediamines

The dissociation routes of the adduct ions [M+CH3CO](+) formed by ion-molecule reaction of isomeric phenylenediamines with acetyl ion from acetone under chemical ionization condition were investigated by using collision-induced dissociation (CID) technique performed at ion kinetic energies of 40eV. The adduct ions are intermediate ion-neutral complexes.