Total Photoelectron Research Articles

Microbial desulfurization of SBR ground rubber by Sphingomonas sp . and its utilization as filler in NR compounds

Microbial desulfurization of waste tyre rubber has been investigated with great efforts since 1990s, because waste rubber has created serious ecological and environmental problems. A microbial desulfurization technique for SBR ground rubber has been developed by a novel sulfur-oxidizing bacterium Sphingomonas sp. The adaptability of Sphingomonas sp. with SBR ground rubber was tested with the amounts of SBR ground rubber varying from 0.5 to 4% g/l. The sol fraction of desulfurized SBR ground rubber increased 70%, compared with SBR ground rubber without desulfurization. Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR) spectrum and X-ray photoelectron spectroscopy (XPS) analysis of the desulfurized surface of vulcanized SBR flakes revealed that not only the oxidation of crosslinked SS and SC bonds, but also the rupture of CC double bonds had happened to SBR vulcanizates during microbial desulfurization. The cure characteristics, such as scorch time and optimum cure time of natural rubber (NR) vulcanizates filled, were found to decrease with increasing contents of desulfurized SBR ground rubber, due to some reactive groups on its surface. NR vulcanizates filled with desulfurized SBR ground rubber had lower crosslink density and hardness, higher tensile strength and elongation at break, compared with those filled with SBR ground rubber of the same amount. Dynamic mechanical properties indicated that there were better crosslink distribution and stronger interfacial bonding between NR matrix and desulfurized SBR ground rubber. Scanning electron microscope (SEM) photographs showed that the fracture surfaces of NR vulcanizates filled with desulfurized SBR ground rubber had more smooth morphologies. Copyright © 2010 John Wiley & Sons, Ltd.

Stimuli–responsive networks grafted onto polypropylene for the sustained delivery of NSAIDs

Co-polymers of N-isopropyl acrylamide (NIPAAm) and N-(3-aminopropyl) methacrylamide hydrochloride (APMA) were grafted on polypropylene (PP) films by means of a γ-ray pre-irradiation method, with the aim of developing medical devices able to load non-steroidal anti-inflammatory drugs (NSAIDs) and to control their release under physiological conditions. The NIPAAm/APMA molar ratios in the grafts, estimated by Fourier transform infrared attenuated total reflection spectroscopy and X-ray photoelectron spectroscopy analysis, were 4.76 and 1.23 for PP-g-(1M NIPAAm-r-0.5M APMA) and PP-g-(1M NIPAAm-r-1M APMA), respectively. By varying the reaction time, different degrees of grafting were achieved, while the monomer ratio was kept constant. PP-g-(NIPAAm-r-APMA) films showed temperature-responsive swelling, smaller friction coefficients, hemolysis and thrombogenicity and higher cell compatibility, did not elicit secretion of cytokines, and took up remarkable amounts of diclofenac and ibuprofen and sustained delivery for several hours in phosphate buffer, pH 7.4. Coating with carboxymethyl dextran of diclofenac-loaded PP-g-(NIPAAm-r-APMA) films caused a minor discharge of the drug but did not alter the drug release rate.

Study of the Photodissociation Process of ClC(O)SCH3 Using both Synchrotron Radiation and HeI Photoelectron Spectroscopy in the Valence Region

The simultaneous evaluation of the PES and valence synchrotron photoionization studies complemented by the results of quantum chemical calculations offers unusually detailed insights into the valence ionization processes of small covalent molecules. Thus, methyl thiochloroformate, ClC(O)SCH(3), has been investigated by using results from both photoelectron spectroscopy (PES) and synchrotron radiation in the valence energy range. In an additional series of experiments, total ion yield (TIY) and photoelectron-photoion coincidence (PEPICO) spectra have been recorded. Furthermore, the relative yields for ionic fragments have been determined as a function of the photon energy. Vibronic structure has been observed in the TIY spectrum recorded in the synchrotron experiments. The photodissociation behavior of ClC(O)SCH(3) can be divided into two well-defined energy regions.

Extreme durability of wettability changes on polyolefin surfaces by atmospheric pressure plasma torch

In the present work three common polyolefins: high density polyethylene (HDPE), low density polyethylene (LDPE) and polypropylene (PP) have been treated with an atmospheric pressure air plasma torch (APPT) in order to improve their wettability properties. The variations in surface energy (γ s), as well as the durability of the treatment are determined by means of contact angle measurements for different aging times after plasma exposure (up to 270 days) using five test liquids which cover a wide range of polarities. The introduction of new polar moieties (carbonyl, amine or hydroxyl) is confirmed by Fourier transform infrared spectroscopy in attenuated total multiple reflection mode (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). Furthermore, scanning electron microscopy (SEM) provides information on the morphological changes and variation on surface roughness, revealing that smoother, lamellar and semispheric micrometric structures are created on the LDPE, HDPE and PP surfaces, respectively. Results show that APPT treatment enhances both the total and polar components of the γ s under study, with an unprecedent stability (> 8 months) in time.

Preparation of high density polyethylene/polyethylene-block-poly(ethylene glycol) copolymer blend porous membranes via thermally induced phase separation process and their properties

High density polyethylene (HDPE)/polyethylene-block-poly(ethylene glycol) (PE-b-PEG) blend porous membranes were prepared via thermally induced phase separation (TIPS) process using diphenyl ether (DPE) as diluent. The phase diagrams of HDPE/PE-b-PEG/DPE systems were determined by optical microscopy and differential scanning calorimetry (DSC). By varying the content of PE-b-PEG, the effects of PE-b-PEG copolymer on morphology and crystalline structure of membranes were studied by scanning electron microscopy (SEM) and wide angle X-ray diffraction (WAXD). The chemical compositions of whole membranes and surface layers were characterized by elementary analysis, Fourier transform infrared spectroscopy-attenuated total reflection (FTIR-ATR) and X-ray photoelectron spectroscopy (XPS). Water contact angle, static protein adsorption and water flux experiments were used to evaluate the hydrophilicity, antifouling and water permeation properties of the membranes. It was found that the addition of PE-b-PEG increased the pore size of the obtained blend membranes. In the investigated range of PE-b-PEG content, the PEG blocks could not aggregate into obviously separated domains in membrane matrix. More importantly, PE-b-PEG could not only be retained stably in the membrane matrix during membrane formation, but also enrich at the membrane surface layer. Such stability and surface enrichment of PE-b-PEG endowed the blend membranes with improved hydrophilicity, protein absorption resistance and water permeation properties, which would be substantially beneficial to HDPE membranes for water treatment application.

Micropatterning of conducting polymer tracks on plasma treated flexible substrate using vapor phase polymerization-mediated inkjet printing

A facile strategy to pattern a conducting polymer on various flexible substrates is reported using vapor phase polymerization-mediated inkjet printing. Complex polypyrrole patterns were obtained via oxidation polymerization of vaporized monomer on the inkjet-printed oxidant patterns. The patterned lines are readily controlled by inkjet printing with the high resolution of micrometer scale. FT-IR attenuated total reflection analysis and X-ray photoelectron spectroscopy were conducted in order to confirm the polymerization of pyrrole monomer. This process provided highly conductive polymer patterns of polypyrrole with the sheet resistance of 2.8 × 10 3 Ω/□, the minimum line width of ca. 60 μm and the film thickness of ca. 450 nm. Furthermore, metallic copper pattern was prepared on previously patterned polypyrrole architectures by electroless plating as a practical application.

The effect of thermal oxidation on laser-induced photoelectron emission during tensile deformation of polycrystalline aluminum

Many metals emit electrons when exposed to UV radiation (photon energies 4 to 8 eV). Deformation can significantly affect the intensity of these emissions. In the case of reactive metals, these emissions are also altered by the presence of surface oxides. We have characterized the effect of thermal oxides on laser-induced photoelectron emission from commercially pure polycrystalline aluminum with a view toward using these emissions as a probe of deformation processes. The thickness of oxides produced by a range of annealing treatments in air was determined by x-ray photoelectron spectroscopy. Time-of-flight measurements on photoelectrons from these surfaces under 248 nm irradiation (5 eV photons) show two peaks: a fast peak which we attributed to electrons from metallic aluminum, and a slower peak, which may be due to electrons from interface states. Surface oxide films of sufficient thickness attenuate both peaks. We show that the sensitivity of the photoelectron signals to deformation varies with thermal oxidation pretreatments and oxide film thickness and that with the appropriate oxide thickness the total photoelectron intensity becomes a sensitive probe of deformation-related processes during tensile testing.

Competing ultrafast intersystem crossing and internal conversion in the “channel 3” region of benzene

We report new, detailed, femtosecond time-resolved photoelectron spectroscopy experiments and calculations investigating the competition between ultrafast internal conversion and ultrafast intersystem crossing in electronically and vibrationally excited benzene at the onset of "channel 3". Using different probe energies to record the total photoelectron yield as a function of pump-probe delay we are able to confirm that S(1), T(1) and T(2) electronic states are involved in the excited state dynamics. Time-resolved photoelectron spectroscopy measurements then allow us to unravel the evolution of the S(1), T(1) and T(2) components of the excited state population and, together with complementary quantum chemistry and quantum dynamics calculations, support our earlier proposal that ultrafast intersystem crossing competes with internal conversion (Chem. Phys. Lett., 2009, 469, 43).

Preparation of hydrophilic and fouling resistant poly(vinylidene fluoride) hollow fiber membranes

Amphiphilic brush-like copolymer P(MMA-r-PEGMA) was synthesized by a radical polymerization method. The copolymer was characterized by the nuclear magnetic resonance proton spectra ( 1H NMR) and gel permeation chromatography (GPC). Poly(vinylidene fluoride) (PVDF) hollow fiber membrane was then prepared by the phase inversion method using the copolymer as the macromolecular additive. The effect of P(MMA-r-PEGMA) on the phase inversion process was investigated using a light transmission experiment. The surface enrichment of amphiphilic copolymer in the PVDF hollow fiber was characterized by Fourier transform infrared attenuated total reflection spectroscopy (FTIR-ATR) and X-ray photoelectron spectroscopy (XPS). Morphological structures of both dry and wet membranes were observed by scanning electron microscopy (SEM). The hydrophilicity, water permeation flux, anti-fouling and carbon ink rejection performance of the hollow fiber were characterized respectively. All these results demonstrated that PVDF hollow fibers fabricated by the single-step method showed high permeation flux, good hydrophilicity and fouling resistance.

Synchrotron radiation photoelectron studies for primary radiation effects using a liquid water jet in vacuum: Total and partial photoelectron yields for liquid water near the oxygen [formula omitted]-edge

A new spectroscopy to identify the hydration structure playing important role in liquid-phase radiation damage is in progress using a laminar liquid water jet sample in vacuum in combination with soft X-ray synchrotron radiation. We present the total and partial electron yields for liquid water using a photoelectron spectroscopy. Partial electron yields for the K - 1 1 b 1 1 b 1 Auger transition are obtained for the first time by measuring the electrostatically dispersed electron kinetic energy spectra as a function of photon energy of synchrotron radiation.

Modification of polytetrafluoroethylene porous membranes by electron beam initiated surface grafting of binary monomers

Polytetrafluoroethylene (PTFE) porous membranes were pre-irradiated by electron beam in vacuum. And then the hydrophilic sulfonate groups were introduced by the single step grafting method with binary monomer solution of acrylic acid (AAc) and sodium 4-styrenesulfonate (SSS). The effect of monomer concentration and irradiation dose on degree of grafting, the surface morphological and chemical changes after grafting reaction, as well as the surface hydrophilicity of the modified membrane, were investigated. The surface chemical change was determined by Fourier transform infrared attenuated total reflection spectroscopy (FTIR-ATR) and X-ray photoelectron spectroscopy (XPS). Morphological changes on the film surface were described using field emitting scanning electron microscopy (SEM). The surface hydrophilicity of the modified film was characterized through water contact angle measurement. The degree of grafting changed with different AAc contents in binary monomers and irradiation doses, and the water contact angle of the film surface reduced significantly when compared with the original one. These results indicated that the grafted polymer layer introduced hydrophilic groups to PTFE membrane and improved the hydrophilicity of the porous membrane.

Multiphoton ionization through the triplet states of Mg by linearly and circularly polarized laser pulses

We theoretically study multiphoton ionization through the triplet states of Mg by linearly polarized and circularly polarized fs laser pulses. After the construction of the atomic basis using the frozen-core Hartree-Fock potential as well as the model potential approaches for both singlet and triplet series which show rather good agreements with the existing data in terms of state energies and dipole matrix elements, we solve time-dependent Schr\"odinger equations with $3s3p$ $^{3}P_{1}$ as an initial state, and calculate the total ionization yield and photoelectron energy spectra.

Cross sections and asymmetry parameters for photoionization of [formula omitted] in the VUV region

Calculated cross sections and asymmetry parameters for photoionization of the three outermost valence orbitals of CH 3 F for photon energies from near threshold to 50 eV are reported. The photoelectron continuum orbitals are obtained using the Schwinger variational method at the level of static-exchange plus correlation potential. Our results are compared with other theoretical and experimental results showing a good quantitative agreement. Correlation effects do not significantly affect the computed total cross sections and photoelectron asymmetry parameters. The broader structure that appears in the experimental cross section are well described. However, the narrow resonant features near threshold are not found in the present one-electron treatment of the photoionization process.

Poly(N‐isopropylacrylamide) surface‐grafted chitosan membranes as a new substrate for cell sheet engineering and manipulation

The immobilization of poly(N-isopropylacrylamide) (PNIPAAm) on chitosan membranes was performed in order to render membranes with thermo-responsive surface properties. The aim was to create membranes suitable for cell culture and in which confluent cell sheets can be recovered by simply lowering the temperature. The chitosan membranes were immersed in a solution of the monomer that was polymerized via radical initiation. The composition of the polymerization reaction solvent, which was a mixture of a chitosan non-solvent (isopropanol) and a solvent (water), provided a tight control over the chitosan membranes swelling capability. The different swelling ratio, obtained at different solvent composition of the reaction mixture, drives simultaneously the monomer solubility and diffusion into the polymeric matrix, the polymerization reaction rate, as well as the eventual chain transfer to the side substituents of the pyranosyl groups of chitosan. A combined analysis of the modified membranes chemistry by proton nuclear magnetic resonance ((1)H-NMR), Fourier transform spectroscopy with attenuated total reflection (FTIR-ATR) and X-ray photoelectron spectroscopy (XPS) showed that it was possible to control the chitosan modification yield and depth in the solvent composition range between 75% and 100% of isopropanol. Plasma treatment was also applied to the original chitosan membranes in order to improve cell adhesion and proliferation. Chitosan membranes, which had been previously subjected to oxygen plasma treatment, were then modified by means of the previously described methodology. A human fetal lung fibroblast cell line was cultured until confluence on the plasma-treated thermo-responsive chitosan membranes and cell sheets were harvested lowering the temperature.

A solubility and surface complexation study of a non-stoichiometric hydroxyapatite

The dissolution and surface complexation of a non-stoichiometric hydroxyapatite (Ca 8.4(HPO 4) 1.6(PO 4) 4.4(OH) 0.4), (HAP) was studied in the pH range 3.5–10.5, at 25 °C in 0.1 M Na(Cl). The results from well-equilibrated batch experiments, potentiometric titrations, and zeta-potential measurements were combined with information provided by Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectroscopy and X-ray Photoelectron Spectroscopy (XPS). The information from the analyses was used to design an equilibration model that takes into account dissolution, surface potential, solution and surface complexation, as well as possible phase transformations. The results from the XPS measurements clearly show that the surface of the mineral has a different composition than the bulk and that the Ca/P ratio of the surface layer is 1.4 ± 0.1. This ratio was also found in solution in the batches equilibrated at low pH where the dominating reaction is dissolution. In the batches equilibrated at near neutral pH values, however, the Ca/P ratio in solution attains values as high as 25, which is due to re-adsorption of phosphate ions to the HAP surface. The total concentration of protons as well as the total concentration of dissolved calcium and phosphate in solution were used to calculate a model for the dissolution and surface complexation of HAP. The constant capacitance model was applied in designing the following surface complexation model: CaOH + H + ⇋ CaOH 2 + log β ( intr . ) = 8.41 ± 0.16 OPO 3 H 2 ⇋ OPO 3 H - + H + log β ( intr . ) = - 1.11 ± 0.13 CaOH + HPO 4 2 - + H + ⇋ CaOPO 3 H - + H 2 O log β ( intr . ) = 11.63 ± 0.15 OPO 3 H 2 + Na + ⇋ OPO 3 Na - + 2 H + log β ( intr . ) = - 11.08 ± 0.12 In addition a solubility product with log β = −23.27 ± 0.29 was obtained: Ca 8.4 ( HPO 4 ) 1.6 ( PO 4 ) 4.4 ( OH ) 0.4 ( s ) + 4.8 H + ⇋ 8.4 Ca 2 + + 6 HPO 4 2 - + 0.4 H 2 O Furthermore, this model predicts a pH zpc = 7.9, which is in agreement with pH iep = 8.1 obtained from zeta potential measurements. This model can be used as a helpful tool to predict the reactivity of HAP in different aquatic environments.

Studies on surface grafting of AAc/SSS binary monomers onto polytetrafluoroethylene by dielectric barrier discharge initiation

Polytetrafluoroethylene (PTFE) films were pre-treated by dielectric barrier discharge in atmospheric pressure with air as carrier gas. And then the hydrophilic sulfonate groups were introduced by the single step grafting method with binary monomer solution of acrylic acid (AAc) and sodium 4-styrenesulfonate (SSS). The effects of binary monomer ratio, reaction solution concentration and polymerization time on the degree of grafting were investigated. The surface chemical change was determined by Fourier transform infrared attenuated total reflection spectroscopy (FTIR-ATR) and X-ray photoelectron spectroscopy (XPS). Morphological changes on the film surface were described using field emitting scanning electron microscopy (SEM) and atomic force microscopy (AFM). The surface hydrophilicity of the modified film was characterized through water contact angle measurement. It was found that the water contact angle of the film surface reduced significantly when compared with the original one, indicating the introduction of hydrophilic groups and improvement of the surface hydrophilicity.

X-ray absorption spectrum for guanosine- [formula omitted]-monophosphate in water solution in the vicinity of the nitrogen K-edge observed in free liquid jet in vacuum

A new spectroscopy for direct effect of radiation damage to nucleic acids such as DNA and RNA is underway using a liquid beam sample in vacuum combined with soft-X-ray synchrotron radiation. We show the X-ray absorption spectrum (XANES) of liquid phase water at X-ray photon energy in the vicinity of oxygen K-shell absorption edge obtained from total photoelectron yields ejected from a pure water beam. We confirm a “liquid sample in vacuum” for the present experiment by the measurements of the temperature dependence of the XANES spectrum for a liquid beam of pure water. Shown is the first measurement of the XANES spectrum for guanosine- 5 ′ -monophosphate (GMP), which is one of the fundamental nucleotide unit for RNA, in water solution at X-ray photon energy in the vicinity of nitrogen K-shell absorption edge involved in the ‘water-window’ region, which corresponds to a selective excitation of guanine site.

Enhanced hydrolysis resistance of biodegradable polymers and bio-composites

This study investigated the hydrolysis of biodegradable polymers and bio-composites at 50 °C and 90% relative humidity (RH). With increasing hydrolysis time, the mechanical properties of the biodegradable polymers and bio-composites significantly decreased due to the easy hydrolytic degradation of the ester linkage of the biodegradable polymers. With increasing hydrolysis time, the tensile strength of the polybutylene succinate (PBS) treated with anti-hydrolysis agent or with trimethylolpropane triacrylate (TMPTA) significantly increased compared to the non-treated PBS. The same results were observed for the PBS-based bio-composites. This result was confirmed by the Fourier transform infrared-attenuated total reflectance (FTIR-ATR) and X-ray photoelectron spectroscopy (XPS) spectra, which exhibited a less eroded surface, small cracks and fewer holes due to the reduced surface hydrolysis and erosion under high humidity condition.

Electron emission suppression from hydrogen-terminated n-type diamond

By total photoelectron yield spectroscopy (TPYS), we have found a thermal instability of a negative electron affinity in hydrogen-terminated n-type diamond films, which has never been observed for intrinsic and p-type diamond films. Experimentally, we have succeeded in detecting surface defect states and surface valence band extended states on the same n-type sample after soft annealing from 100 to 300 °C, which allowed us to evaluate the surface Fermi level and surface band bending using phosphorus doping parameters. Our results show that “quasi-positive” electron affinity prevents electron emission from an n-type diamond film even though its surface has a negative electron affinity.

Probing Wave Packet Dynamics of I2− Anions with Pump–Probe Femtosecond Spectroscopy

The wave packet dynamics of I2− anions is studied by using the time-dependent wave packet method. Two conclusions can be drawn from the calculations. First, the period of the total photoelectron signal oscillating with the propagation of delay time is about 750 fs. Second, the photoionization of I2− anions begin at the time 600 fs, and the time needed for the population of the electronic state of I2 neutral molecule to reach the maximum becomes shorter with the increasing delay time.