Synthesis and spectroscopic studies of endohedral metallofullerenes Tb@C-2n

Endohedral metallofullerenes Tb@C-2n were synthesized and extracted with high-yield by K-H carbon-are evaporation and an effective pyridine extraction technique at high-temperature high-pressure. Laser-desorption-ionization time-of-flight (LD-TOF) mass spectrometry, X-ray photoelectron spectroscopy (XPS), solid-state fluorescent emission spectroscopy and gas phase derivation reaction with the self-chemical ionization mass spectrometric ion system of vinyl acetate were employed for studying the electronic structures, fluorescent properties and gas phase reactivities of metallofullerenes Tb@C-2n. The experimental results suggest that endohedral metallofullerenes Tb@C-2n would have the approximate structures of Tb3+@C-2n(3-) similar to other metallofullerenes, good fluorescent emission properties and active reactivities in gas phase ion-molecular reactions.

Self-assembly of the pre-formed inclusion complexes between cyclodextrins and alkanethiols on gold electrodes

A new kind of self-assembled monolayer (SAM) formed in aqueous solution through the pre-formed inclusion complexes (abbreviated CD . C-n) between alpha-, beta-cyclodextrins (CDs) and alkanethiols (CH3(CH2)(n-1)SH, n = 10, 14 and 18) was prepared successfully on gold electrodes. High-resolution H-1 NMR was used to confirm the formation of CD . C-n. X-ray photoelectron spectroscopy, cyclic voltammetry and chronoamperometry were used to characterize the resulting SAMs (denoted as M-CD . Cn). It was found that M-CD . Cn were more stable against repeated potential cycling in 0.5 M H2SO4 than SAMs of CH3(CH2)(n-1)SH (denoted as M-Cn), with a relative sequence of Mbeta-CD . Cn > Malpha-CD . Cn > M-Cn. In addition, an order of blocking the electron transfer between gold electrodes and redox couples (both Fe(CN)(6)(3-) and Ru(NH3)(6)(3+)) in solution, M-CD . C10 > M-CD . C14 > M-CD . C18, was observed. A plausible explanation is provided to elucidate some of the observations. (C) 1997 Elsevier Science S.A.

Spontaneous assembly of the inclusion complexes of viologen-attached alkanethiols and alpha-, beta-cyclodestrin on gold electrode

Electroactive self-assembled monolayers (SAMs) with well-defined electrochemical responses were prepared by spontaneous assembly of the inclusion complexes (CD/C8VComegaSH) of viologen-attached alkanethiols (C8VComegaSH) and alpha- and beta-cyclodextrin (CD). They were characterized by X-ray photoelectron spectroscopy and cyclic voltammetry. The results demonstrate that the chemisorption process of CD/C8VComegaSH on gold substrate occurs through S-Au bonds, and that the redox sites in SAMs of CD/C8VComegaSH are in a much more uniform environment than those in SAMs of C8VComegaSH.

A novel method of electrodepositing highly dispersed nano palladium particles on glassy carbon electrode

The volumetric behavior of a chloride complex of palladium was studied at a glassy carbon electrode (GCE). The Pd-IV complex existing on the GCE surface was found, which was proposed to form an octahedral surface complex through coordination to the oxygen atom of an oxygen functional group on the pretreated GCE surface. The ferri/ferrocyanide redox couple was used as a probe to examine the activity of the GCE. X-ray photoelectron spectroscopy provided the evidence of the surface complex existing on the GCE. Highly dispersed Pd particles can be obtained when the surface complexes were reduced electrochemically to Pd atoms. The Pd particles obtained in this way were in nanometer scale and exhibit high catalytic activity towards the oxidation of hydrazine. (C) 1997 Elsevier Science Ltd.

In situ scanning tunneling microscopy studies of nanometer size palladium particles on highly oriented pyrolytic graphite

A special electrodeposition process of palladium was studied by cyclic voltammetry, X-ray photoelectron spectroscopy (XPS) and in situ scanning tunneling microscopy (STM). A kind of palladium(IV) complex was attached to the highly oriented pyrolytic graphite (HOPG) electrode surface by electro-oxidation of palladium(II) complex first, and was then reduced to palladium particles. The surface complexes and particles of palladium were both characterized by in situ STM and XPS. The Pd particles are in the nanometer range of size and exhibit electrocatalytic activity towards the oxidation of hydrazine and hydroxylamine.

Plasma modification of aromatic polyamide reverse osmosis composite membrane surface

The surface of aromatic polyamide reverse osmosis composite membrane was modified by oxygen and argon plasma. The water permeability of oxygen-plasma-modified membrane increases, and the chlorine resistance of argon-plasma-modified membrane increases. The spectra of the attenuated total reflection-Fourier transform infrared and X-ray photoelectron spectroscopy and the contact angle of the water were analyzed to explain the improvement of the two performances of the composite membrane. The carboxyl groups were introduced when modified by oxygen plasma, and cross-linking occurred when modified by argon plasma. (C) 1997 John Wiley & Sons, Inc.

Miscibility of linear low density polyethylene (LLDPE)-graft-poly(methyl methacrylate) with poly(vinylidene fluoride) (PVF2) and its application as compatibilizer LLDPE/PVF2 blends

Differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) were used to study the miscibility of blends of a graft copolymer of poly(methyl methacrylate) on linear low density polyethylene (LLDPE-g-PMMA, G-3) with poly(vinylidene fluoride)(b) (PVF2) and the compatibilization of blends of LLDPE/PVF2. The specific interaction between PMMA side chains and PVF2 in G-3/PVF2 binary blends is weaker than that between the homopolymers PMMA and PVF2. There are two states of PVF2 in the melt of a G-3/PVF2 (60/40, w/w) blend, one as pure PVF2 and the other interacting with PMMA side chains. The miscibility between PMMA side chains and PVF2 affects the crystallization of PVF2. LLDPE-g-PMMA was demonstrated to be a good compatibilizer in LLDPE/PVF2 blends, improving the interfacial adhesion and dispersion in the latter. Diffusion of PMMA side chains into PVF2 in the interfacial region reduces the crystallization rate and lowers the melting point (T-m) and the crystallization temperature (T-c) of PVF2 in the blends.

Synthesis of N-(n-octyl)-N'-(10-mercaptodecyl)-4,4'-bipyridinium dibromide and electrochemical behaviour of its monolayers on a gold electrode

A new viologen derivative of N-(n-octyl)-N'-(10-mercaptodecyl)-4,4'-bipyridinium dibromide has been prepared and characterized by elemental analysis, IR, H-1 NMR, MS and TG-DTA. X-Ray photoelectron spectroscopy, cyclic voltammetry and chronoamperometry have been used to characterize the monolayers formed by this compound on the bulk gold electrodes by self-assembly.

IONIC-CONDUCTION OF A NOVEL COMB POLYMER ELECTROLYTE BASED ON MALEIC-ANHYDRIDE COPOLYMER WITH OLIGO-OXYETHYLENE SIDE-CHAINS

A comb-shaped polymer (BM350) with oligo-oxyethylene side chains of the type -O(CH2CH2O)(7)CH3 was prepared from methyl vinyl ether/maleic anhydride copolymer. Homogeneous amorphous polymer electrolyte complexes were made from the comb polymer and LICF(3)SO(3) by solvent casting from acetone, and their conductivities were measured as a function of temperature and salt concentration. Maximum conductivity close to 5.08 X 10(-5) Scm(-1) was obtained at room temperature and at a [Li]/[EO] ratio of about 0.12. The conductivity which displayed non-Arrhenius behaviour was analyzed using the Vogel-Tammann-Fulcher equation and interpreted on the basis of the configurational entropy model. The results of mid-IR showed that the coordination of Li+ to side chains made the C-O-C band become broader and shift slightly. X-ray photoelectron spectroscopy analysis indicated that the oxygen atoms in the two situations could coordinate to Li+ and this coordination resulted in the reduction of the electron orbit binding energy of F and S.

COMPARATIVE-STUDIES ON PERIODATOCUPRATE(II, III) AND TELLURATOCUPRATE(II, III)

The crystal structures, electronic spectra, and Cu2p XPS of Cu(III) complexes Na4H[Cu(H2TeO6)(2)]. 17H(2)O and Na4K[Cu(HlO(6))(2)]. 12H(2)O have been described. The characterizations of a Cu(III) atom in a complex are as follows: (i) In a square-planar coordination, the average bond length of Cu-O is 0.183 nm, shorter than the 0.190-0.200 nm found for a Cu(II) complex. (2) The ''blue shift'' occurs for d-d transitions in the electronic spectrum of the Cu(III) complex compared to those of its related Cu(II) complex, resulting from the higher valence state. (3) Cu(III) compounds with CuO4 square-planar coordination are expected to be diamagnetic whereas Cu(II) compounds to be paramagnetic. (4) Comprehensive investigations on Cu2p XPS show that the binding energy of Cu2p(3/2) of a pure Cu(III) compound is about 2.0 eV higher than that of its corresponding Cu(II) compound: the shake-up satellites do not appear in the Cu2p XPS for a pure diamagnetic Cu(III) compound, the same as found for a diamagnetic Ni(II) compound: the FWHM of the signal of Cu2p XPS may become broader for Cu(III) compound because its core hole's lifetime shortens due to the higher valence state of copper. (C) 1995 Academic Press, Inc.

ELECTROOXIDATION OF A CHLORIDE COMPLEX OF PLATINUM(II) AT A GLASSY-CARBON ELECTRODE

The electro-oxidation of PtCl42- was studied on a glassy carbon (GC) electrode. A Pt(IV) complex was formed on the electrode surface through coordination to the oxygen atom of an oxide functional group on the electrode, which results in its deactivation. The ferri/ferrocyanide redox couple was used as a probe to examine the activity of the GC electrode. X-ray photoelectron spectroscopy was employed to characterize the platinum on the electrode surface, and showed that the oxidation state of the Pt element changes depending on the electrochemical treatment of GC electrode. The platinum complex on the surface of the GC electrode can be transformed to Pt-0 by cycling the electrode between -0.25 and +1.65 V/SCE in 0.1 M H2SO4 solution. The above procedure can be used to disperse platinum ultramicroparticles on the surface of a GC electrode.

Characterization of 1:12 Phosphomolybdic Anions Doped Polypyrrole (PMo12/PPy) Film Electrode

1:12 phosphomolybdic anion doped polypyrrole film electrode was characterized by in-situ UV-vis spectroelectrochemistry, X-ray photoelectron spectroscopy(XPS), scan electronic microscopy(SEM) and electron spin resonance(ESR) spectroscopy.

XPS STUDIES ON RADIATION-INDUCED STRUCTURAL-CHANGES IN THE COPOLYMER OF TETRAFLUOROETHYLENE AND ETHYLENE

In this work, the radiation-induced structural changes in the copolymer of tetrafluoroethylene and ethylene (F-40) were studied by X-ray photoelectron spectroscopy (XPS). During irradiation, some CF2 groups in the polymer were found to have been converted into carbon structures that bonded indirectly with fluorine atoms.

HIGH-TEMPERATURE SUPERCONDUCTOR, YBA2CU3O7-X AS ALL-SOLID-STATE LITHIUM CELL

The utility of the high-temperature superconductor, YBa2Cu3O7-x as the cathode material for an all-solid-state lithium cell has been examined. The capacity of YBa2Cu3O7-x is 223 mA h g-1 and the discharge efficiency is > 92%. Measurements of a.c. impedance show that the charge-transfer resistance at the interface of the electrolyte/cathode is very low and increases with the depth-of-discharge of the battery. Studies using X-ray photoelectron spectroscopy (XPS) reveal that the cathode becomes doped with Li+ ions as the cell discharges.

RADIATION-INDUCED CROSS-LINKING OF AROMATIC POLYMERS WITH A CARDO GROUP

The effects of irradiation on some members of the family of aromatic polymers with a cardo group, such as polyetherketone with a cardo group (PEK-C) and polyethersulfone with a cardo group (PES-C), were studied. It was found that PEK-C and PES-C can be crosslinked by irradiation under vacuum. Moreover, it was also found that the intensity of the shake-up peak of x-ray photoelectron spectroscopy (XPS) for PEK-C and PES-C varies with irradiation dose. Gelation doses (Rg) of PEK-C and PES-C were estimated from the XPS shake-up peak.