1s Envelope Research Articles

Human hair, untreated, colored, bleached, and/or treated with a conditioner, by near-ambient pressure x-ray photoelectron spectroscopy

Near-ambient pressure-x-ray photoelectron spectroscopy (NAP-XPS) is a less traditional form of XPS that allows samples to be analyzed at relatively high pressures, i.e., at ca. 2500 Pa. With NAP-XPS, XPS can probe moderately volatile liquids, biological samples, porous materials, and/or polymeric materials that outgas significantly. Here, we show the NAP-XPS analysis of untreated/blank human hair, and human hair that has been colored (red) and treated with a commercial conditioner, or bleached and treated with a different conditioner. Survey spectra are shown of each material along with figures comparing their Si 2p, S 2p, and C 1s spectra. The survey spectrum of untreated hair shows S 2p, S 2s, C 1s, Ca 2p, N 1s, and O 1s peaks and corresponding O, N, and C Auger signals. The survey spectra of the colored and bleached hair show significant Si 2s and Si 2p signals and reduced or eliminated S 2p and S 2s peaks, presumably due to the deposition of dimethicone (polydimethylsiloxane) from the corresponding commercial hair treatment products. Narrow scans similarly indicate the deposition of a silicon-containing material on the two types of treated hair, with a concomitant decrease in the intensity of the sulfur signals from the hair. Upon treatment, the C 1s envelope also changes—the chemically shifted peak attributable to amide-type carbon disappears.

Poly(γ-benzyl l-glutamate), by near-ambient pressure XPS

Near-ambient pressure x-ray photoelectron spectroscopy (NAP-XPS) is a less traditional form of XPS that allows samples to be analyzed at relatively high pressures, i.e., at greater than 2500 Pa. In this study, poly(γ-benzyl l-glutamate) (PBLG) with a molar mass of 11.3 kg/mol was analyzed by NAP-XPS; here, we show the survey, C 1s, N 1s, and O 1s narrow scans of PBLG. The C 1s peak envelope was fitted in three different ways, to five, six, or seven synthetic peaks. In each fit, there was also a shake-up signal. The O 1s narrow scan was well fit with three peaks: C—O and C=O in a 1:2 ratio from the polymer, and a higher energy signal from water vapor. Hartree–Fock orbital energies of a model monomer served as a guide to an additional fit of the C 1s envelope.

Hard Italian cheese, by near-ambient pressure XPS

In this submission, we show survey, O 1s, and C 1s near ambient pressure x-ray photoelectron spectroscopy (NAP-XPS) spectra from a hard Italian cheese, a material that could not be analyzed by conventional approaches without special sample preparation. The C 1s spectrum is fit under the assumption that the surface of the cheese is primarily fat (triglyceride), which is expected to be the lowest free energy component of the material. The O 1s envelope corresponding to the cheese was well fit to two components of equal area.

Multiwalled carbon nanotube forest grown via chemical vapor deposition from iron catalyst nanoparticles by ToF-SIMS

The authors report the time-of-flight secondary ion mass spectrometry of carbon nanotubes grown catalytically from iron nanoparticles. Both positive and negative ion spectra were obtained using a cluster ion source (Bi32+ primary ions at 50 keV). The positive mode contains an intense C+ signal. The Cn− peaks in the negative ion spectrum show an odd–even effect in their intensities.

Multiwalled Carbon Nanotube Forest Grown via Chemical Vapor Deposition from Iron Catalyst Nanoparticles, by XPS

Carbon nanotubes (CNTs) have unique chemical and physical properties. Herein, we report an XPS analysis of a forest of multiwalled CNTs using monochromatic Al Kα radiation. Survey scans show essentially only one element here: carbon. The carbon 1s peak is centered at 284.5 eV. The C 1s envelope also shows the expected π→π* shake-up peak at ca. 291 eV. The valence band and carbon KVV Auger signals are presented. When patterned, the CNT forests can be used as a template for subsequent deposition of metal oxides to make thin layer chromatography plates.

Selective surface functionalization of polystyrene by inner-shell monochromatic irradiation and oxygen exposure

The surfaces of polystyrene (PS) thin films were selectively functionalized by a combination of monochromatic synchrotron radiation with oxygen exposure. By selecting specific K-shell excitation energies, it was shown that highly efficient surface functionalization can be obtained. After the treatments, several oxygen functionalities were detected by XPS and NEXAFS spectroscopy. The functionalization strongly depended on the excitation energy. C 1s → σ*C–C transitions produced an extremely efficient oxidation of the uppermost monolayer of the PS films. The COO and CO elemental contributions in the C 1s envelope at the PS surface was higher than 70%. On the contrary, other excitation energies did not introduce COO functionalities efficiently. The obtained results were explained by taking into account the known Auger stimulated desorption mechanism. The present research will open new ways to functionalize a polymer surface by a combination of monochromatic inner-shell excitation together with exposure to a reactive gas atmosphere.

XPS spectra of uranyl minerals and synthetic uranyl compounds. II: The O 1s spectrum

The O 1s spectrum is examined for 19 uranyl minerals of different composition and structure. Spectra from single crystals were measured with a Kratos Axis Ultra X-ray Photoelectron Spectrometer with a magnetic-confinement charge-compensation system. Well-resolved spectra with distinct maxima, shoulders and inflections points, in combination with reported and measured binding energies for specific O 2− species and structural data of the uranyl minerals are used to resolve the fine structure of the O 1s envelope. The resolution of the O 1s spectra includes, for the first time, different O 2− bands, which are assigned to O atoms linking uranyl with uranyl polyhedra ( U O U) and O atoms of uranyl groups ( O U O). The resolved bands in the O 1s spectrum occur at distinct ranges in binding energy: bands for ( U O U) occur at 529.6–530.4 eV, bands for ( O U O) occur at 530.6–531.4 eV, bands for O 2− in the equatorial plane of the uranyl polyhedra linking uranyl polyhedra with ( TO n ) groups ( T = Si, S, C, P, Se) ( T O) occur at 530.9–532.2 eV; bands for (OH) groups in the equatorial plane of the uranyl polyhedra ( OH) occur at 532.0–532.5 eV, bands of (H 2O) groups in the interstitial complex of the uranyl minerals ( H 2 O interst ) occur at 533.0–533.8 eV and bands of physisorbed (H 2O) groups on the surface of uranyl minerals ( H 2 O adsorb ) occur at 534.8–535.2 eV. Treatment of uranyl minerals with acidic solutions results in a decrease in U O U and an increase in OH. Differences in the ratio of OH : O U O between the surface and bulk structure is larger for uranyl minerals with a high number of U O U and T O species in the bulk structure which is explained by protonation of underbonded U O, U O U and T O terminations on the surface. The difference in the ratio of H 2 O interst : O U O between the bulk and surface structures is larger for uranyl minerals with higher percentages of H 2 O interst as well as, with a higher number of interstitial H 2O groups that are not bonded to interstitial cations, resulting in easier dehydration of interstitial H 2O groups in uranyl minerals during exposure to a vacuum.

Surface modification of polyurethane membranes using acrylic acid vapour plasma and its effects on the pervaporation processes

Acrylic acid (AA) vapour plasma treatment was used to modify the surface properties of polyurethane membranes (PU). The chemical changes produced after plasma treatment were measured mainly by X-ray photoelectron spectroscopy (XPS). AA plasma treatment increased in all the experimental conditions studied, the concentrations of carbonyl and ester groups at the PU surface compared with traditional oxygen plasma modification. The pervaporation (PV) results demonstrated that AA plasma treated PUs had much higher selectivity for the separation of methanol from methyl- t-butyl ether than untreated and O 2 treated PU membranes. This selectivity is maximum at 100 W and 1 min of AA plasma treatment time. HR-XPS spectra showed that a thin film with similar chemical properties to the poly(acrylic acid) was formed on top of the PU membrane after 5–10 W AA plasma treatments. AFM results of standard Si(1 0 0) substrates treated with AA revealed the formation of a ∼220 nm film at 5 W. However, Si substrates treated at 100 W, led to sputtering of the substrate. PU membranes treated with AA plasma at powers higher than 10 W showed a high C O content and a decrease in the COO contribution (C 1s envelope). This paper illustrates the importance of selecting the right plasma parameters to improve the efficiency of the PV process.

XPS characterisation of carbon‐coated alumina support

AbstractHybrid carbon–alumina supports, synthesised by pyrolysis of grafted 4,4′‐methylenebis‐(phenylisocyanate) moiety on the alumina surface, were characterised by X‐ray photoelectron spectroscopy. The recorded Al 2p and C 1s envelopes showed asymmetry that decreased with an increase in carbon loading. In all experimental Al 2p envelopes, the high‐energy individual components at 75.3–75.9 eV were present along with the low‐energy component at 74.0 eV typical for Al2O3. In the case of the C 1s envelope, the component around 284.3–284.4 eV and three high‐energy individual components at 285.9–286.0, 288.0–288.3 and 290.1–290.6 eV were observed. The presence of the high‐energy Al 2p components can be explained considering the occurrence of a steady‐state charging of the different parts of insulating alumina supports. The component around 284.3–284.4 eV in C 1s envelopes can be attributed to carbon, which constitutes the coating and, hence, ensures surface conductivity. The component around 285.9–286.0 eV is connected with carbon in carbonaceous surface species, which do not form the conducting layer on the alumina support. Carbonaceous surface species associated with CO, CO and OCO groups in carbon coating can be also identified due to the presence of corresponding components in XPS spectra at 285.9–286.0, 288.0–288.3 and 290.1–290.6 eV. Copyright © 2006 John Wiley & Sons, Ltd.

Poly(ethylene oxide)-modified poly(β-amino ester) nanoparticles as a pH-sensitive biodegradable system for paclitaxel delivery

The main objective of this study was to develop and characterize a pH-sensitive biodegradable polymeric nanoparticulate system for tumor-selective paclitaxel delivery. A representative hydrophobic poly(β-amino ester) (poly- 1) was synthesized by conjugate addition of 4,4′-trimethyldipiperidine with 1,4-butanediol diacrylate. Poly- 1 ( M n 10,000 daltons) nanoparticles were prepared by the controlled solvent displacement method in an ethanol–water system in the presence of Pluronic ® F-108, a poly(ethylene oxide) (PEO)-containing non-ionic surfactant. Control and PEO-modified nanoparticles were characterized by Coulter counter, scanning electron microscopy (SEM), zeta potential measurements, and electron spectroscopy for chemical analysis (ESCA). Polymer degradation studies were performed in phosphate-buffered saline (PBS, pH 7.4) at 37 °C. Paclitaxel loading capacities and efficiencies were determined and release studies were performed in Tween ®-80 (0.1%, w/v)-containing PBS at 37 °C. Control and PEO-modified nanoparticles, labeled with rhodamine-123, were incubated with BT-20 cells to examine the uptake and cellular distribution as a function of time. PEO-modified nanoparticles with an average size of 100–150 nm and a positive surface charge of 37.0 mV were prepared. SEM analysis showed distinct smooth, spherical particles. The ether (–C–O–) peak of the C 1s envelope in ESCA confirmed the surface presence of PEO chains. Polymer biodegradation studies showed that almost 85% of the starting material degraded after 6 days. The maximum paclitaxel loading efficiency attained was 97% at 1.0% (w/w) of the drug. Paclitaxel release studies showed that approximately 10% was released in the first 24 h, 80% after 3 days, and the entire content was released in approximately 5 days. After 1 h of incubation, a large fraction of the administered control and PEO-modified poly- 1 nanoparticles was internalized in BT-20 cells. Results of this study demonstrate that PEO-modified poly- 1 nanoparticles could provide increased therapeutic benefit by delivering the encapsulated drug to solid tumors.

Targeting mass-selected cluster ions for the deposition of advanced carbonaceous materials using an inductively coupled plasma

Study has been initiated of the deposition of thin films using cluster ions in differing abundances generated in a pulsed inductively coupled plasma. A pulse unit controlling the “on” and “off” timing ratio of a 13.56 MHz rf power supply is used to alter systematically the composition of the contents of the plasma. Adamantane (C10H16) vapor, in argon or nitrogen, was selected as precursor for the deposition of CxHy or CxNyHz thin films using this pulsed source. The effect of varying the relative abundances of the cluster ions present in the resultant plasmas on the films produced, by changing driving power on/off ratio, is investigated. The mass-energy diagnostic data recorded under 50/150 and 150/50 μs on/off pulse sequences showed that fragmentation of C10H16 is a function of the switching ratio selected, i.e., clusters of different sizes and abundances are thus produced. Langmuir probe data also suggest that the electrical characteristics of the plasma generated under these regimes can be monitored. Postdeposition x-ray photoelectron spectroscopy (XPS) analysis of specimen films deposited under the same on/off regimes, within a 200 μs cycle, indicate clear differences are present in these films in terms of the atomic concentration, the C 1s envelope bandwidths, and profiles. Contact angle measurements and optical data performed were found to reflect the variations in the differently deposited films already indicated in the XPS data. For example, specimens deposited under a 50/150 on/off ratio show a high contact angle (low surface energy) and lower refractive index, whereas those deposited under a 150/50 ratio exhibit a low contact angle (high surface energy). Films prepared using the same precursor streams but with the further on/off ratios, 20/180, 100/100, and 20/180 μs, were also considered. Postdeposition analyses confirmed the same tends in the fragmentation behavior of C10H16. Finally, the significance of such a cluster ions selection technique is discussed.

CrO2 by XPS: Comparison of CrO2 Powder to CrO2 Films on TiO2(110) Single Crystal Surfaces

Chromium dioxide is a ferromagnetic metallic oxide utilized in data storage applications. Here, the XP spectrum of CrO2 bulk powder is compared to a CrO2(110) film grown on a TiO2(110) single crystal surface by chemical vapor deposition. The spectra compare the Cr 2p and O 1s regions for the two materials. In both materials, the Cr 2p region (2p3/2 = 576.4 ± 0.1 eV and Cr 2p1/2 = 578.6 ± 0.1 eV) is asymmetric and broadened to the high binding energy side, consistent with metallic material. The O 1s envelope for both materials consists of two components. The lower BE component, at 529.2 ± 0.1 eV, has been assigned to the oxide and the higher binding energy component, at ∼531.5 eV, is believed to be associated with an adsorbed water or hydroxide layer.

Comparison of CxNy:H films obtained by deposition using magnetron sputtering or an inductively coupled plasma

Several CxNy:H specimens (A1–A6) were deposited using a magnetron sputtering system driven at 13.56 MHz in nitrogen with an unbiased substrate using a pure graphite target as the carbon source. For deposition in the inductively coupled plasma (ICP) rig concerned, driven at the same frequency, two source mixtures were used, i.e. either methane (CH4) or adamantane (C10H16) in nitrogen. Examination of the XPS C 1s envelope from the magnetron-deposited films shows different band shapes and two main peak positions depending on the bonding within the films. The band shapes and the energy positions of the peaks present are a function of the film composition (expressed as at.%), itself influenced by the deposition regime. The corresponding specimens deposited with the ICP rig from a CH4/N2 plasma exhibit C 1s envelopes showing clearly a significant difference in their shape (correlated with chemical shift) compared to those magnetron sputter-deposited using the pure graphite target. In the magnetron-deposited films one distinct C 1s band is observed, and its position and the contributing component lines therein change as a function of the relative abundance of C,O and N found in the films examined. The films deposited using C10H16/N2 mixtures give features for the C 1s envelope of the CxNy:H material obtained that, when compared to the data of the two sets of films alluded to above, are again different from those of the magnetron-deposited material. However, they do show similarities to the behaviour of the analogous CH4/N2 films. Comparison of specimens from these three deposition regimes indicates clearly a number of significant compositional and structural differences, depending on the route used. The details of the analogous N 1s component of the same specimens were also investigated. Finally, static SIMS of a diamond-like carbon specimen and CxNy:H films was performed, showing similarities for low m/z and differences for higher m/z, particularly with respect to the oxygen bound in the CxNy:H matrix. Copyright © 2000 John Wiley & Sons, Ltd.

XPS characterization of carbon-coated alumina support

X-ray photoelectron spectroscopy was used for identification of the structure and for monitoring the distribution of the carbon coating on an alumina surface synthesized by the pyrolysis of adsorbed acetylacetone. Owing to a difference in surface steady-state charging of the samples, it appeared possible to discriminate the carbon coating and carbonaceous deposits on the insulating alumina support. Carbonaceous surface species of carboxylate type were identified by detailed analysis of individual components in the experimental C 1s envelope. The surface C/Al ratio for the synthesized samples was calculated from the integral intensity of the C 1s component related to the carbon coating and the overall Al 2p envelope. It has been found that at low loading carbon is preferably concentrated at the internal surface of the alumina support. On increasing the carbon loading, the external surface of the alumina support appeared to be enriched with carbon. Copyright © 1999 John Wiley & Sons, Ltd.

Determining hybridization differences for amorphous carbon from the XPS C 1s envelope

Two kinds of amorphous carbon (a-C) thin film samples were synthesized, one by magnetron sputtering, the other by filtered cathodic arc deposition. X-ray photoelectron spectroscopy (XPS) showed that the C 1s envelope for each sample was primarily a convolution of three peaks which are assignable to sp 2 hybridized carbon, sp 3 hybridized carbon (shifted from the sp 2 peak by ∼ 1 eV) and an sp 2 satellite peak, possibly due to π-π ∗ transition. The satellite typically comprised just under 14% of the total sp 2 signal and was shifted from the main sp 2 peak by ∼ 2 eV. The relative amounts of each bonding type were determined by comparing the integrated areas of the sp 2 and sp 3 peaks. Auger electron spectroscopy (AES) was also performed on these samples, along with highly ordered pyrolytic graphite (100% sp 2) and natural diamond (100% sp 3) for comparison purposes. The binding energy width D between the highest maximum and lowest minimum values of the first derivative C (KLL) spectra were obtained and a linear relationship between D and the amount of sp 3 bonding assumed. When comparing sp 3 values obtained by AES and deconvoluted XPS spectra an error range within ±1.5% was found, making XPS a satisfactory method for obtaining hybridization information. It was noted that Ar + ion bombardment has a substantial effect on the surface sp 2/sp 3 ratio, as observed by XPS. These results are related to other studies of ion bombardment of graphite and diamond.

High Resolution Spectra of Hexatriacontane and Polyethylene

The C 1s photoelectron spectra are compared for the aliphatic hydrocarbons, hexatriacontane and polyethylene. An asymmetric C 1s envelope is observed regardless of sample form.

X-ray photoelectron spectroscopy study of fluorine-treated YBa2Cu3O7−δ crystals

An x-ray photoelectron-spectroscopy study of flux-grown YBa2Cu3O7−δ crystals left in moist atmospheric conditions has shown some aspects of the degradation process. Besides peaks which correspond to YO and BaO bonding in the superconducting phase, higher binding-energy components can be attributed to BaCO3, YOH, and/or YCO3 bonding. An x-ray photoreduction of the copper species is observed in the ultrahigh vacuum. Fluorine-gas treatments carried out at low temperature drastically modify the surface properties of the crystals. The peaks attributed to MO bonding (M=Y, Ba, or Cu) disappear and are substituted by MF bonding with a subsequent increase in Eb. In the F 1s region, the peak corresponding to those bondings is observed around Eb ≂684.5 eV, a value which is in agreement with those claimed for the corresponding inorganic fluorides. The signature of those surface fluorides remains, even when the samples are left for long periods in moist air. Within the F 1s envelope, chemisorbed fluoro species with Eb ≂686.5 eV are observed, especially when the fluorination process is performed at room temperature. These species are eliminated by vacuum annealing at 350 °C. In specific conditions, a high-binding-energy contribution arises (Eb ≂689 eV) which can be ascribed to the formation of surface ‘‘carbon fluoride.’’

Preparation of polyanilines doped in mixed protonic acids: Their characterization by X-ray photoelectron spectroscopy and thermogravimetry

A comparative study of polyaniline chemically prepared and simultaneously doped in protonic acid mixtures is presented. As the resultant polyaniline salts (PANI salts) are insoluble, solid-state techniques such as X-ray photoelectron spectroscopy (XPS), thermogravimetry (TG), derivative thermogravimetry (DTG) and elemental analysis have been applied to study the dopant environment as well as the electronic and chemical structure of the polymers. Both XPS and TG/DTG indicate that in the presence of competing acids, the stronger acid component is preferentially incorporated over the others. No advantage can be gained by the use of mixed-acid systems. XPS confirms that ring substitution by the dopant and the degree of protonation can be accurately measured based on the percentage of charged nitrogen in the N 1s envelope. Previous methods based on the total halogen content can lead to serious errors. TG results suggest an upper application temperature limit of about 150°C, at which point elimination of dopant occurs with loss of conductivity.

X‐ray photoelectron spectra of high Tc bismuth compounds. General trends for layer structures

AbstractAnalysis by XPS and XAES has been carried out for Bi2Sr2CaCu2O8 and Bi2Sr2CuO6 HTSC compounds. Some preliminary results are also reported for a Tl specimen with predominant Tl2Ba2CaCu2O8 stoichiometry, as well as La0.6Sr0.4CoO3 which is a “metallic” oxide, but is not superconducting above 4.2 K. Anomalous low binding energy contributions are found for the main alkaline earth envelopes (Ba 3d, Ca 2p, and Sr 3d) for all of these compounds. Likewise, two distinct contributions to the O 1s envelope are observed. The Bi and Tl 4f envelopes and binding energies are consistent with these species being subject to metallic screening. Possible implications of these observations for the electronic structure of the layered HTSC oxides are discussed in the context of a “screening” as well as a “shake‐down” model.

Relationships between X-ray photoelectron spectra, structure and superconductivity in LnBa2Cu3O7-x

X-ray photoelectron spectroscopy has been carried out on HoBa2Cu3O7-x (on abraded, fractured and ion beam reduced surfaces). These measurements show that there are only minor differences with similarly obtained results from YBa2Cu3O7-x. The spectral features of the Ln species (Y and Ho), the O 1s, and Ba 3d envelopes are considered in some detail. The low energy contribution to the O 1s envelope has been assigned in part to the effects of Ba−O bonding, either in the LnBa2Cu3O7-x material, or in BaO in minor phase regions, and in part to the effects of the electronic linkage of the Cu planes in the superconducting compound. The anomalous low binding energy contributions to the Ba 3d envelope are also specific to the electronic structure of these materials. It is likely that Ba (and Sr and Ca for the Bi-Sr-Ca-C-O system) plays an important electronic, as well as structural role, in promoting high temperature superconductivity.