XPS Analysis (xp + analysis)

Distribution by Scientific Domains

Selected Abstracts

Preparation, characterization, and cellular interactions of collagen-immobilized PDMS surfaces

I. Keranov
Abstract Multistep procedure to biofunctionalization of (poly)dimethylsiloxane (PDMS) surfaces is present here, including plasma-based Ar+ beam treatment; acrylic acid grafting; and flexible PEG spacer coupling prior to the collagen immobilization by peptide synthesis reaction. The success of any step of the surface modification is controlled by XPS analysis, contact angle measurements, SEM, and AFM observations. To evaluate the effect of PEG chain length, three diNH2PEGs (2000, 6000, and 20,000 D) of relative long polymer chain were employed as a spacer, expecting that a long flexible spacer could provide more conformational freedom for the collagen molecules and fibroblast reorganization to further cellular matrix formation. Human fibroblast cells were used as a model to evaluate the biological response of the collagen-immobilized PDMS surfaces. It is found that the earlier described biofunctionalization is one more road to improvement of the cellular interaction of PDMS, the last one being the best when PEG spacer with moderate chain length, namely of 6000 D, is used. 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

Interfacial structure of poly(methyl methacrylate)/TiO2 nanocomposites prepared through photocatalytic polymerization

Jiao Wang
Abstract Poly(methyl methacrylate)/TiO2 nanocomposites have been prepared by the polymerization with photoexcited TiO2 nanoparticles as initiator. To reveal the interfacial structure, the composites obtained are investigated by FTIR and XPS analysis. The bound PMMA displays triply split IR bands attributed to the carbonyl stretching mode, meanwhile great changes also occur in the IR range closely related to the conformation of PMMA. Based on the area of the nonassociated and associated PMMA carbonyl stretching peaks in the FTIR spectrum, it is calculated out that the bound PMMA is constituted of 70% repeating units in nonassociated state and 30% units associated to TiO2 inorganic nanoparticles. Moreover, XPS analysis show that Ti2p doublet of the composites shift to lower binding energy by 1.0 eV, indicating the interaction between Ti atoms of TiO2 and oxygen atoms of PMMA. According to the observation that the interaction involves both carboxyl and carbonyl groups of PMMA, a bidentate complex is approved. In addition, compared with the extracted PMMA, certain backbone chains of bound PMMA have to change their rotational conformations from gauche to trans so as to bond to the surface active centers at TiO2 nanoparticles. 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

Thiol-ene Hybrid Organic/Inorganic Nanostructured Coatings Based on Thiol-Functionalized Zirconium Oxoclusters

Marco Sangermano
Abstract The thiol-functionalized zirconium oxocluster Zr12(3 -O)8(3 -OH)8(MP)24,,4MPA was used as inorganic nanosized building block in the thiol-ene photopolymerization of APE and TH in a 1:1 molar mixture. Transparent and crack-free coatings were obtained, and TEM analysis showed that the inorganic particles are well dispersed within the polymeric network with no significant macroscopic agglomeration. An increase of Tg values, storage modulus in the rubbery region, and thermal stability were evidenced by increasing the zirconium oxocluster content in the photocurable formulations. XPS analysis and SIMS depth profile were carried out on UV cured films and showed the presence of a homogeneously distributed zirconium oxocluster. [source]

Electrochemical preparation of MoO3 buffer layer deposited onto the anode in organic solar cells

M. Gacitua
Abstract In this work the authors have studied the advantages of using electrochemically deposited molybdenum oxide as a buffer layer in an organic bilayer heterojunction solar cell arrangement. Furthermore, it has been probed that electrochemistry provides an alternative low cost, reproducible and less laborious method to prepare thin layered deposits. The precursor solution is composed by a concentrated molybdic acid solution in a sulphuric media in order to ensure the obtainment of low reduced molybdenum species. Therefore, by means of potentiostatic techniques, ITO/molybdenum oxide transparent anodes were tested for the photovoltaic device showing improved surface properties. XDR and AFM techniques were used to characterize the morphology of the deposits. The films with optimum thickness (5,nm) are amorphous. XPS analysis indicates that the best results in solar cell performance are in hand with a heterogeneous composition of the molybdenum oxide film presenting MoV and MoVI as predominant species. The MoO3 films deposited by cyclic voltammetry are not as homogeneous as those deposited by potentiostatic technique and only MoVI species are present. These differences may justify the different behaviour of the solar cells using these different buffer layers. Only buffer layers deposited by potentiostatic technique allow improving the cells performances in the same way than those achieved by evaporation. [source]

Synthesis and characterisation of NCD films on 10 10 mm2 and deposition on 2 inch wafer using rotating substrate-holder set-up

S. Saada
Abstract In this study, we compare NCD films on 10 10 mm2 silicon substrates synthesised with high methane concentration and NCD films synthesised with prolongated bias during the growth step. Further, we performed in-situ sequential XPS analysis (carbon binding state) using an UHV surface analysis system connected to the MPCVD reactor. AFM and HRSEM were used to characterize films morphology. Using the same substrate holder, NCD films have been deposited on silicon 2 in wafers. To improve the homogeneity, a rotating substrate-holder set-up enabling biasing and heating of the stage has been developed and coupled with computer control of the process for a better reproducibility. UV-interferometry was performed to map the film thickness on 2 inches and quantify its thickness uniformity. Considering the symmetry of the system, AFM measurements were performed along the radius of the wafer to evaluate the surface homogeneity and its smoothness. The thickness uniformity of a NCD film of 1.6 m deposited on 2 inch wafer is under 10% and the RMS roughness comprised between 13 and 14 nm. ( 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Structural and spectroscopic study of the Fe doped TiO2 thin films for applications in photocatalysis

N. R. Mathews
Abstract In this work we are presenting the results of structural and optical investigations of TiO2 and Fe doped TiO2 films using XRD, XPS, UV-VIS transmittance spectroscopy, and the application of these films in photocatalysis is demonstrated. Fe-doped TiO2 films were prepared by sol-gel method. The concentration of Fe utilized for doping ranged from 0.5 to 4% by atomic weight. For lower concentrations of Fe the transformation from amorphous-to-polycrystalline occurred at 400 C. However, as the Fe concentration was increased to 4% this transformation occurred only after annealing at 600 C. The average grain size for 4% Fe doped sample was in the range of 13 nm. In the case of pure TiO2 the XPS analysis showed only the presence of Ti 4+, where the 4% Fe doped film showed the presence of two species of Ti atoms; one of unperturbed Ti atoms and another of negatively charged surface of Ti atoms due to the interaction with Fe atoms in the anatase lattice of TiO2. The optical band gap was found to decrease with Fe concentration. The resistivity was found to decrease by one order after doping. The 4% Fe doped TiO2 films showed an increased photocatalytic activity. ( 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Plasma Polymerization of HMDSO with an Atmospheric Pressure Plasma Jet for Corrosion Protection of Aluminum and Low-Adhesion Surfaces

Uwe Lommatzsch
Abstract Thin functional films were deposited on aluminum with an atmospheric pressure plasma jet using hexamethyldisiloxane (HMDSO) as precursor. A high dynamic deposition rate on the order of 450,nm,,m,,min,1 was achieved. Composition and structure of the thin films show a strong dependence on the downstream location of the precursor injection. A 4,mm downstream shift of the precursor injection increases the carbon content in the thin film by a factor of 2.5, as indicated by XPS analysis and alters the degree of cross-linking according to the FTIR spectra. The coating with the low carbon content (17 at.-%) provides corrosion resistance for aluminum 2024 unclad exposed for 96,h to a neutral salt spray test. The coating with the high carbon content reduces the adhesion of an epoxy resin to the surface and may be used as a release coating. [source]

Atmospheric Pressure Barrier Discharge Deposition of Silica-Like Films on Polymeric Substrates

Sergei Starostine
Abstract Silica-like coatings were deposited on polymer foils in APG discharge in a roll-to-roll configuration. The dependence of film structure and chemical composition on the conditions during deposition process was studied by means of SEM, ATR-FTIR, and XPS analysis. The influence of oxidant concentration on the deposited film properties is analyzed and discussed. It was observed that pulsing of the APG discharge suppresses dust formation in atmospheric plasma and, therefore, provides uniform coatings. [source]

Surface modification of silicone intraocular lens by 2-methacryloyloxyethyl phosphoryl-choline binding to reduce Staphylococcus epidermidis adherence

Xiao-Dan Huang MD
Abstract Purpose:, To analyse the in vitro adherence of Staphylococcus epidermidis to the 2-methacryloyl oxyethyl phosphorylcholine (MPC)-modified silicone intraocular lens (IOL). Methods:, The test IOLs were modified by using an air plasma treatment to bind MPC to the surface. The control IOLs were not modified. Chemical changes on the IOL surface were analysed by X-ray photoelectron spectroscopy (XPS) to confirm the covalent binding of MPC. IOL hydrophilicity was determined by measuring the water contact angle. Two different techniques, direct counting of viable adherent bacteria released by sonication, and scanning electron microscopy (SEM), were used to observe and compare the adherence of S. epidermidis to the IOLs after 1- and 18-h incubation. Results:, XPS analysis confirmed that the test IOLs were surface-modified with MPC. The hydrophilicity of the IOLs was improved by surface modification, and the MPC-modified IOLs exhibited significantly reduced adhesion of S. epidermidis (P = 0.002) after an incubation period of 1 h. The SEM results showed that the MPC modification also suppressed the accumulation of bacteria and biofilm production after 18 h incubation. Conclusions:, MPC-modified hydrophilic silicone IOLs reduce bacterial adherence and colonization, and thus may help reduce the incidence of postoperative endophthalmitis. [source]