544 research outputs found
Composition depth profiling of polystyrene/poly(vinyl ethyl ether) blend thin films by angle resolved XPS
Angle resolved XPS (ARXPS) and scanning force microscopy (SFM) are used to study polystyrene/poly(vinyl ethyl ether) 50/50 wt% blend thin films spin cast from toluene solution, as a function of polystyrene molecular weight and film thickness. ARXPS is used to investigate the composition depth profile (CDP) of the blend thin films and SFM to study their surface morphology and miscibility. The CDPs are modelled by an empirical hyperbolic tangent function with three floating parameters. These are determined by non-linear least squares regression, their uncertainties estimated and the curve fit residuals analysed to demonstrate that the hyperbolic tangent CDP is a satisfactory fit to the ARXPS data. Conclusions are drawn regarding the behaviour of the blend thin films as the thickness and polystyrene molecular weight are varied. Flory-Huggins interaction parameters (chi) for the mixtures are calculated based upon the segregation data, and suggest a value of chi = 0.05 to be appropriate for this system. (c) 2009 Elsevier B.V. All rights reserved
Nature of band-gap states in V-doped TiO2 revealed by resonant photoemission
Band-gap states in V-doped TiO2 have been studied by photoemission spectroscopy over a range of photon energies encompassing the Ti 3p and V 3p core thresholds. The states show resonant enhancement at photon energies significantly higher than found for Ti 3d states introduced into TiO2 by oxygen deficiency or alkalimetal adsorbates. This demonstrates that the gap states relate to electrons trapped on dopant V cations rather than host Ti cations
The X-ray photoelectron spectroscopy of surface films formed during the ASTM D-130/ISO 2160 copper corrosion test
This is an Author’s Accepted Manuscript of an article published in Petroleum Science & Technology [Volume 32, Issue 4, 2014 ], available online: http://www.tandfonline.com/10.1080/10916466.2011.588635The surfaces of ISO 2160 copper strips tested in iso-octane with elemental sulfur, aliphatic, cyclic and aromatic thiols, diphenyl sulfide, and diphenyl disulfide individually or in combination were studied using XPS. Aliphatic thiols bonded through the sulfur, whereas elemental sulfur formed a cuprous sulfide layer. Aromatics bonded partially through the sulfur with the rings oriented horizontally due to π orbital interactions, accounting in part for their inhibitory effects in the test. The test rating was not directly related to the sulfur concentration in solution or on the surface, and certain combinations of species resulted in higher levels of sulfur at the surface than found individually
Plasma-generated poly(allyl alcohol) antifouling coatings for cellular attachment
Conformal poly(allyl alcohol) (PAA) coatings were grown on a biomedical grade polyurethane scaffold using pulsed plasma polymerization of the allyl alcohol monomer. The creation of a continuous wave polymer primer layer increases the interfacial adhesion and stability of a subsequent pulsed plasma deposited PAA film. The resulting PAA coatings are strongly hydrophilic and stable following 7 days incubation in biological media. Films prepared through this energyefficient, two-step process promote human dermal fibroblast cell culture, while resisting E. coli biofilm formation
Experimental methods in chemical engineering: X-ray photoelectron spectroscopy-XPS
X\u2010ray photoelectron spectroscopy (XPS) is a quantitative surface analysis technique used to identify the elemental composition, empiricalformula, chemical state, and electronic state of an element. The kinetic energy of the electrons escaping from the material surface irradiated by anx\u2010ray beam produces a spectrum. XPS identifies chemical species and quantifies their content and the interactions between surface species. It isminimally destructive and is sensitive to a depth between 1\u201310 nm. The elemental sensitivity is in the order of 0.1 atomic %. It requires ultra highvacuum (1
7107 12Pa) in the analysis chamber and measurement time varies from minutes to hours per sample depending on the analyte. XPSdates back 50 years ago. New spectrometers, detectors, and variable size photon beams, reduce analysis time and increase spatial resolution. AnXPS bibliometric map of the 10 000 articles indexed by Web of Science[1]identifies five research clusters: (i) nanoparticles, thin films, and surfaces;(ii) catalysis, oxidation, reduction, stability, and oxides; (iii) nanocomposites, graphene, graphite, and electro\u2010chemistry; (iv) photocatalysis,water, visible light, andTiO2; and (v) adsorption, aqueous solutions, and waste water
Electronic structure study by means of X-ray spectroscopy and theoretical calculations of the "ferric star" single molecule magnet
The electronic structure of the single molecule magnet system
M[Fe(L)2]3*4CHCl3 (M=Fe,Cr; L=CH3N(CH2CH2O)2) has been studied using X-ray
photoelectron spectroscopy, X-ray absorption spectroscopy, soft X-ray emission
spectroscopy, and density functional calculations. There is good agreement
between theoretical calculations and experimental data. The valence band mainly
consists of three bands between 2 eV and 30 eV. Both theory and experiments
show that the top of the valence band is dominated by the hybridization between
Fe 3d and O 2p bands. From the shape of the Fe 2p spectra it is argued that Fe
in the molecule is most likely in the 2+ charge state. Its neighboring atoms
(O,N) exhibit a magnetic polarisation yielding effective spin S=5/2 per iron
atom, giving a high spin state molecule with a total S=5 effective spin for the
case of M = Fe.Comment: Fig.2 replaced as it will appear in J. Chem. Phy
A UV LED-based fast-pulsed photoelectron source for time-of-flight studies
We report on spectroscopy and time-of-flight measurements using an 18 keV
fast-pulsed photoelectron source of adjustable intensity, ranging from single
photoelectrons per pulse to 5 photoelectrons per microsecond at pulse
repetition rates of up to 10 kHz. Short pulses between 40 ns and 40
microseconds in length were produced by switching light emitting diodes with
central output wavelengths of 265 nm and 257 nm, in the deep ultraviolet (or
UV-C) regime, at kHz frequencies. Such photoelectron sources can be useful
calibration devices for testing the properties of high-resolution electrostatic
spectrometers, like the ones used in current neutrino mass searches.Comment: 16 pages, 11 figure
An X-ray photoelectron spectroscopy investigation of chromium conversion coatings and chromium compounds
Hexavalent and trivalent chromium based conversion coatings on zinc
electrodeposited steel have been investigated using X-ray photoelectron
spectroscopy (XPS) with the aim of elucidating their film chemistry. Furthermore, a
monochromatic Al Kα X-ray source was utilised and the spectra produced evaluated
using curve fitting software to elucidate oxidation state information. In addition, a
number of chromium compounds were investigated and used to complement the
curve fitting analysis for the conversion coatings.
High resolution Cr2p spectra from chromium compounds exhibited multiplet splitting
for Cr2O3. Additional satellite emissions can also be observed for Cr2O3 and Cr(OH)3.
Curve fitting of hexavalent chromium conversion coating (CCC) 2p3/2 spectra
contained both Cr(VI) and Cr(III) species with the content of the former slightly higher
when the X-ray beam take-off angle (TOA) was reduced to determine more surface
specific information. The Cr(III) content was determined to be mainly composed of
Cr(OH)3 with some Cr2O3. In comparison, trivalent CCCs were largely composed of
Cr2O3 as opposed to Cr(OH)3. Survey scans of both coatings revealed that the
trivalent CCCs had a higher relative zinc content
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