289 research outputs found
The reaction between Pt- and Pd-cis di-chloro complexes and 4,4'-diethynylbiphenyl: synthesis and characterization of a zig-zag metal/poly-yne polymer
No full textThe synthesis of poly-yne polymers containing transition metals inserted in the main chain has been attempted by reacting a dialkyne molecule, 4,4'-diethynylbiphenyl (or DEBP), with [PtCl2(dppe)] and [PdCl2(dppe)], the platinum- and palladium-cis square-planar dichlorine complexes containing diphenylphosphine ethane (dppe) as bidentate ligand. The aim of this work was to obtain organometallic polymers ([Pt(dppe)DEBP](n) and [Pd(dppe)DEBP](n), respectively) having an all-cis 'zigzag' structure, by formation of a sigma -acetylide bond between the transition metal complexes and the dialkyne molecule. When [PtCl2(dppe)] was reacted with DEBP, the formation of a chlorine-terminated [Pt(dppe)DEBP], oligomer was evidenced in the reaction involving the Pd(II) complex, on the other hand, [PdCl2(dppe)] seems to catalyse the polymerisation of DEBP via opening of the triple bond, producing a poly-DEBP polymer containing Pd(II) atoms inserted in the main chain
The interface formation between thin films of conjugated polymers and evaporated metals investigated by X-ray photoemission spectroscopy
No full textXPS and FT-IR spectroscopy study of albumin adsorption on the surface of a p-conjugated polymer film
No full textThe interaction between thin films of polyphenylacetylene (PPA) and bovine serum albumin (BSA) dissolved in phosphate buffer solution (PBS) was studied by x-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FT-IR) performed in reflectance mode. PPA is a semiconducting pi-conjugated polymer consisting of a polyene backbone with phenyl pending groups, that has been used in the preparation of humidity sensors; therefore, we have tried to pre-test PPA films for possible applications as biosensors.
Thin films of PPA were incubated in buffered albumin solution (BSA/PBS) for increasing exposure times (24-96 hours). BSA adsorption on the PPA film surface takes place as demonstrated by the appearance of the N 1s signal and by the modifications in the C 1s core-level signal in the XPS spectra of the samples treated with albumin solution; time-dependent adsorption is also observed. Phosphate salts are co-adsorbed on the PPA surface upon treatment with BSA/PBS solution. Albumin adsorption on the PPA surface was confirmed by FT-IR measurements
An XPS study on the covalent immobilization of adhesion peptides on the glass surface
No full textCovalent attachment of adhesive peptides to biomaterials surfaces can result in the formation of a bioactive and biomimetic surface We have demonstrated that titanium surfaces grafted with adhesion peptides reproducing sequences of fibronectin and vitronectin can increase osteoblast adhesion compared to non-treated surfaces
We now extend our investigation to peptide immobilization on glass for studying human osteoblast adhesion and spreading Silanization was used to anchor adhesion peptides to the glass surface through a selective or a non-selective immobilization Investigated samples were analysed by XPS spectroscopy Comparison between the results obtained using two different peptides and applying selective and non-selective immobilization will be discusse
A NEXAFS and XPS study of the adsorption of self-assembling peptides on TiO2: the influence of the side chains
No full textPeptides consisting of an alternation of hydrophobic and hydrophilic (positively and negatively charged) amino acids can generate extended ordered structures by self-assembling (SA) from aqueous solutions. In this paper we present XPS, near-edge X-ray absorption fine structure (NEXAFS) and Fourier transform infrared (FTIR) investigations on a series of SA peptides with the aim of determining the effect of side-chain length on molecular arrangement and orientation. Peptides were immobilised on the surface of titanium, a well-known biocompatible material, or deposited as thick films on inert gold surfaces. FTIR analysis yields information on the backbone conformation. XPS spectroscopy was used to investigate the peptide adsorption on the TiO2 surface. The orientation of the peptide chains was investigated by angular-dependent NEXAFS
XPS investigation on the structure of two dipeptides studied as models of selfassembling oligopeptides: comparison between experiments and theory
No full textThe adsorption on TiO2 surface of two dipeptides AE (L-alanine−L-glutamic acid)
and AK (L-alanine−L-lysine), that are “building blocks” of the more complex selfcomplementary
amphiphilic oligopeptides and are therefore a good model in the interpretation
of the complex peptide spectra, has been investigated both theoretically and experimentally.
The chemical structure and composition of thin films of both dipeptides on TiO2 were
investigated by XPS (X-ray photoelectron spectroscopy). Theoretical ab-initio calculations
(SCF) were also performed to simulate the spectra allowing a direct comparison between
experiment and theory
Chemical interaction at the Cu/ PPA interface: an X-ray photoemission investigation
No full textA coverage-dependent XPS investigation of the early stages of interaction between evaporated Cu and polyphenylacetylene (PPA) has been carried out. Copper films have been deposited at 300 K to a final thickness of about 5 monolayers. Overlayer and substrate core-level emission behaviour indicates the layer-by-layer growth of Cu on the PPA surface without interdiffusion. At low copper coverages a chemical interaction between the Cu adatoms and the substrate is observed by monitoring the changes occurring at the pi --> pi * satellite feature of the C1s core-level line. We observe a decrease of intensity for this satellite as the copper coverage increases, interpreted in terms of the formation of a Cu-pi complex with the phenyl ring. The Cu Auger spectra demonstrate the presence of positively charged metal atoms up to a coverage of approximately 5 angstrom. In the submonolayer region the occurrence of broadening of the C1s core level on the low binding energy side is observed together with a positive shift for the Cu2p3/2 emission. Upon completion of the first copper monolayer these phenomena are removed. The observed behaviour can be accounted for in terms of differential charging with injection and trapping of charge into the PPA film from the Cu atoms that have not yet completed the first monolayer
Organic conducting polymers: synthesis, characterization and conductivity of polyethynylfluorenol
No full textThe polymerization reactions of ethynylfluorenol (EFl) in the presence of Rh(I), Pt(II), Pd(II) and WCl6 catalysts have been investigated. The polymer (PEFl) is air stable and soluble; in solution PEFl slowly releases some of the pendent groups which are converted into 9-fluorenone. Upon doping, enhancement of the conductivity up to about 10 orders of magnitude can be achieved. X.p.s. measurements performed on I2-doped PEFl suggest that I5- is the major doping species. An interesting reversible response to relative humidity variations is found for FeCl3-doped samples
An XPS study on the covalent immobilization of adhesion peptides on a glass surface
No full textCovalent attachment of adhesive peptides to biomaterials surfaces can result in the formation of a bioactive and biomimetic surface. We have demonstrated that titanium surfaces grafted with adhesion peptides, reproducing sequences of fibronectin and vitronectin, can increase osteoblast adhesion compared to non-treated surfaces.
We now extend our investigation to peptide immobilization on glass for studying human osteoblast adhesion and spreading. Silanization was used to anchor adhesion peptides to the glass surface through a selective or a non-selective immobilization. Investigated samples were analysed by XPS spectroscopy. Comparison between the results obtained using two different peptides and applying selective and non-selective immobilization will be discussed.
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Cu/ Polyphenylacetylene interface investigated by means of XPS
No full textXPS investigation of the early stages of Cu/PPA interface formation has been performed in the range of coverage 0.5 divided-by 13angstrom Cu. Copper is found to grow in a layer-by-layer mode without interdiffusion with the substrate. Weak chemical interaction between Cu and the pi ring electrons of the phenyl groups is evidenced by monitoring the changes occurring at the C 1s secondary structure pi-->pi* shake up transition
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