Joseph Delhalle

Electronic structure of polyethylene: Theory and ESCA measurements

Theoretical and experimental results for the band structure of polyethylene are presented. Theoretical results are obtained from both semiempirical (CNDO/2 and extended Huckel) and nonempirical methods. The density of states is measured by the ESCA method. An energy gap of 7.5 ± 0.5 eV and a C1s line at 284.6 eV are deduced. Although CNDO/2 results appear to be unreliable, the correlation between theory and observed density of states is found to be very good for extended Huckel and ab initio results.

Large scale production of short functionalized carbon nanotubes

A simple mechano-chemical modification of multiwall carbon nanotubes is described. The use of ball-milling in specific atmosphere allows us to introduce functional groups like thiol, amine, amide, carbonyl, chlorine, etc. onto carbon nanotubes. The resulted functional groups are characterized using infrared spectroscopy and X-ray photoelectron spectroscopy.

Numerical determination of the electronic structure of atoms, diatomic and polyatomic molecules

Main Lectures.- Basic Mathematical Properties of Electronic Wave Functions in Configuration Space.- Basic Mathematical Properties of Electronic Wave Functions in Momentum Space.- The Analytical Structure of Atomic and Molecular Wavefunctions and its Impact on the Rate of Convergence of Variational Calculations.- Stochastic Methods in Quantum Mechanic.- Computational Strategies and New Applications in Greens Function Monte Carlo.- Numerical Determination of non-Relativistic and Relativistic Pair Correlation.- Fully Numerical Calculations for Diatomic Systems.- Very Accurate Calculations for Diatomic, Neutral and Anionic Systems with Numerical Orbitals.- The Development of an Efficient Numerical Orbital Algorithm for Polyatomic Systems: A Review of the Various Options.- Electronic Structure Theory in Momentum Space.- Short Contributions.- Should Numerical Orbital Calculations be done with Basis Sets?.- Quantum Chemistry by Random Walk: High Accuracy for Large Molecules.- Prolate Spheroidal Wavefunctions.- Error Estimate in Variational Calculations of Eigenvalues and Eigenvectors.- A Momentum Space Approach to Improve ab initio Hartree-Fock Results Based on the LCAO-GTF Approximation.- Isotope Shift MCHF Calculations in Strontium.- Finite Element Method for the Accurate Solution of Diatomic Molecules.- Momentum Space Coordinate Transformations and their use in Numerical Orbital Calculations.- Moller-Plesset Calculations with Explicitly Correlated Wave Functions.- On the Coulomb Sturmian Basis.- An Analytical L2 Method for Continuum and Autoionizing States.- Application of the Two-dimensional Fully-Numerical RHF Method to Open-Shell Hydrides.- Interpolation of Numerical Orbitals in Momentum Space.- On the Accuracy of the Algebraic Approximation in Relativistic Electronic Structure Calculations.- Numerical MCSCF in One and Two Dimensions.- Numerical Methods for Calculating Multicenter Integrals for Arbitrary Orbitals.- Nonlinear Sequence Transformations for the Efficient Evaluation of Auxiliary Functions for GTO Molecular Integrals.- Concluding Remarks.- List of Participants.

Polymer primary structures studied by ESCA and EHCO methods

The electronic structure (core and valence levels) of various simple polymers has been investigated by ESCA (Electron Spectroscopy for Chemical Analysis), with the aid of original EHCO (Extended H?ckel Crystalline Orbitals) calculations giving corresponding density of states and band structure schemes. Simple monosubstituted homopolymers derived from polyethylene ([CH2-CHX]n) have been chosen in order to study the influence of X substituents (X = -F, -Cl, -OH, -CH3, -CH2CH3, -C6H5, -C6H11 corresponding respectively to poly(vinyl fluoride), poly(vinyl chloride), poly(vinyl alcohol), poly(propylene), poly(1-butene), poly(styrene), and poly(vinyl cyclohexane)) through the chemical shifts measured for the core levels, and the alteration of the valence band structures. Assignment of the valence molecular orbitals is made with the aid of the theoretical calculations and with comparison of spectra recorded for molecules similar to the monomeric units. Emphasis is put on the very significant information provided by the valence band spectra for polymers containing only carbon and hydrogen atoms. Valence band data are used to calculate physical parameters (first ionization potential, energy gap, work function) of importance to deduce electrical properties for the polymers.

Electronic structure of linear fluoropolymers : theory and ESCA measurements revisited

Abstract The valence electronic structure of polyethylene and of linear fluoropolymers is reinvestigated by a LCAO-CO method. Photoionization cross-section modu

XPS and electrochemical characterisation of polycrystalline copper modified with 12-(N-pyrrolyl)-n-dodecanethiol

Abstract Copper substrates electrochemically reduced in HClO 4 (0.5 M) were successfully modified with 12-( N -pyrrolyl)- n -dodecanethiol (10 −2 M ethanolic solution). XPS, cyclovoltammetry and polarisation curves were used to show the good covering of the monolayers where the organothiol acts as an interesting corrosion inhibitor.

Preparation of a polyacrylonitrile/multi-walled carbon nanotubes composite by surface-initiated atom transfer radical polymerization on a stainless steel wire for solid-phase microextraction.

We report on the fabrication and performances of a solid-phase microextraction (SPME) fiber based on a stainless steel wire coated with a covalently attached polyacrylonitrile (PAN)/multi-walled carbon nanotubes (MWCNTs) composite. This new coating is obtained by atom transfer radical polymerization (ATRP) of acrylonitrile mixed with MWCNTs. ATRP is initiated from 11-(2-bromo-2-methylpropionyloxy)-undecyl-phosphonic acid molecules grafted on the wire surface via the phosphonic acid group. The extraction performances of the fibers are assessed on different classes of compounds (polar, non-polar, aromatic, etc.) from water solutions by headspace extraction. The optimization of the parameters affecting the extraction efficiency of the target compounds was studied as well as the reproducibility and the repeatability of the fiber. The fibers sustain more than 200 extractions during which they remain chemically stable and maintain good performances (detection limits lower than 2 microg/l, repeatability, etc.). Considering their robustness together with their easy and inexpensive fabrication, these fibers could constitute promising alternatives to existing products.

Alkanethiol-oxidized copper interface: the critical influence of concentration.

In this contribution, self-assembled monolayers of n-dodecanethiol (C(12)H(25)SH) at different concentrations on polycrystalline copper have been elaborated. Using XPS, PM-IRRAS, and electrochemical methods (cyclic voltammetry curves and cathodic desorption), the effect of the C(12)H(25)SH concentration on the reduction of the oxide layer has been studied. In all cases, a monolayer of good quality has been obtained. Results provide proof that while the concentration is increased, the thickness of the oxide layer is decreased, to a point that leads to metallic copper for the higher concentration. The results presented in this publication indicate the importance of controlling the interface when forming SAMs of organothiols on oxidizable metals.

Plane wave and orthogonalized plane wave many-body Green's function calculations of photoionization intensities

General equations for the calculation of correlated single-channel photoionization cross-sections of randomly oriented molecules are presented. These equations, employing a plane wave orthogonalized to all (occupied and virtual) bound molecular orbitals as a wavefunction for the photoelectron, are derived in a many-body Greens function framework. Several decoupling approximations for the expansion of the one-particle propagator are then used to compute angle-averaged photoionization cross-sections for a Mg Kα photon source and for a representative set of molecules: CH4, H2O, C2H2, N2, and CO. Both orthogonality corrections to the continuum orbital and many-body corrections in the description of the ionization process are shown to be important for accurate simulations of soft X-ray ionization spectra.

XPS and electrochemical evaluation of two-dimensional organic films obtained by chemical modification of self-assembled monolayers of (3-mercaptopropyl)trimethoxysilane on copper surfaces

In this study, a protective film consisting of an ultrathin two-dimensional polymer was prepared by hydrolysis of a (3-mercaptopropyl)trimethoxysilane (ethanol, 10−3 M) self-assembled monolayer grafted onto copper and a subsequent modification with 3(heptofluoroisopropoxy)propyltrichlorosilane (toluene, 10−3 M). Each stage of the preparation was characterized by X-ray photoelectron spectroscopy (XPS) while coppers corrosion-inhibitive properties were assessed by cyclic voltammetry measurements carried on in a 0.1 M NaOH medium. A remarkable enhancement of the coppers corrosion protection was obtained by the formation of lateral siloxane linkages between MPTS molecules absorbed followed by the grafting of the second molecular layer.