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The effects of coadsorbing the amphiphilic ruthenium-based dye Z907 (cis-bis(isothiocyanato)(2,20-bipyridyl-4,40-dicarboxylato)(4,40-dinonyl-20-bipyridyl)ruthenium(II)) with the coadsorbent DPA (n-decylphosphonic acid) and with the organic dye D35 ((E)-3-(5-(4-(bis(2′,4′-dibutoxybiphenyl-4-yl)amino)phenyl)thiophen-2-yl)-2-cyanoacrylic acid) on mesoporous TiO2 were investigated using photoelectron spectroscopy (PES). Z907 is expected to adsorb to the TiO2 surface via the carboxylic acid groups. However, Z907 also shows signs of interacting with the TiO2 via the sulfur of the thiocyanate groups, and this interaction is affected by both the addition of DPA and D35. DPA, when added, exchanges with Z907 at the TiO2 surface, and each Z907 is replaced by six DPA molecules, but it does not affect the energy level alignment between Z907 and TiO2 substantially. Adding D35 to Z907 induces changes in the adsorption configuration of Z907 by the means of suppressing the interaction of the thiocyanate ligands and the Ti...

Means to measure the temporal evolution following a photo-excitation in conjugated polymers are a key for the understanding and optimization of their function in applications such as organic solar cells. In this paper we study the electronic structure dynamics by direct pump-probe measurements of the excited electrons in such materials. Specifically, we carried out a time-resolved photoelectron spectroscopy (TRPES) study of the polymer PCPDTBT by combining an extreme ultraviolet (XUV) high harmonic generation source with a time-of-flight spectrometer. After excitation to either the 1st excited state or to a higher excited state, we follow how the electronic structure develops and relaxes on the electron binding energy scale. Specifically, we follow a less than 50 fs relaxation of the higher exited state and a 10 times slower relaxation of the 1st excited state. We corroborate the results using DFT calculations. Our study demonstrates the power of TRPES for studying photo-excited electron energetics and dynamics of solar cell materials.

Photoelectron spectroscopy (PES) has become an important tool for investigating Li-ion battery materials, in particular for analyzing interfacial structures and reactions. Since the methodology was introduced in the battery research area, PES has undergone a dramatic development regarding photon sources, sample handling and electron energy analyzers. This includes the possibility to use synchrotron radiation with increased intensity and the possibility to vary the photon energy. The aim of the present paper is to describe how PES can be used to investigate battery interfaces and specifically highlight how synchrotron based PES has been implemented to address different questions useful for the development of the Li-ion batteries. We also present some recent developments of the techniques, which have the potential to further push the limits for the use of photoelectron spectroscopy in battery research.

A new operation mode of a HPXPS (high-pressure X-ray photoelectron spectroscopy) analyzer is evaluated on a HPXPS system fitted with an Al K alpha X-ray source. A variety of metal foil samples (gol ...

Ab initio molecular dynamics (MD) simulations of the solvation of LiI3 in four different solvents (water, methanol, ethanol, and acetonitrile) are employed to investigate the molecular and electronic structure of the I-3(-) ion in relation to X-ray photoelectron spectroscopy (XPS). Simulations show that hydrogen-bond rearrangement in the solvation shell is coupled to intramolecular bond-length asymmetry in the I-3(-) ion. By a combination of charge analysis and I 4d core-level XPS measurements, the mechanism of the solvent-induced distortions has been studied, and it has been concluded that charge localization mediates intermolecular interactions and intramolecular distortion. The approach involving a synergistic combination of theory and experiment probes the solvent-dependent structure of the I-3(-) ion, and the geometric structure has been correlated with the electronic structure.

A combination of measurements using photoelectron spectroscopy and calculations using density functional theory (DFT) was applied to compare the detailed electronic structure of the organolead halide perovskites CH3NH3PbI3 and CH3NH3PbBr3. These perovskite materials are used to absorb light in mesoscopic and planar heterojunction solar cells. The Pb 4f core level is investigated to get insight into the chemistry of the two materials. Valence level measurments are also included showing a shift of the valence band edges where there is a higher binding energy of the edge for the CH3NH3PbBr3 perovskite. These changes are supported by the theoretical calculations which indicate that the differences in electronic structure are mainly caused by the nature of the halide ion rather than structural differences. The combination of photoelectron spectroscopy measurements and electronic structure calculations is essential to disentangle how the valence band edge in organolead halide perovskites is governed by the intr...

Photoelectron spectroscopy started its modern development in the fifties based on techniques for studies of nuclear decay. Since then, photoelectron spectroscopy has undergone a dramatic expansion of application and is now a prime research tool in basic and applied science. This progress has been largely due to the concomitant development of photon sources, sample handling and electron energy analyzers. The present article describes some of the salient features of modern photoelectron spectroscopy and its applications with particular emphasis on energy relevant issues.

In this experiment we used an 800 nm laser to generate high-order harmonics in a gas cell filled with Argon. Of those photons, a harmonic with 42 eV was selected by using a time-preserving grating monochromator. Employing a modified Mach–Zehnder type Fourier transform spectrometer for the VUV/XUV it was possible to measure the temporal coherence of the selected photons to about 6 fs. We demonstrated that not only could this kind of measurement be performed with a Fourier transform spectrometer, but also with some spatial resolution without modifying the XUV source or the spectrometer.

Key processes in nanostructured dye-sensitized solar cells occur at material interfaces containing, for example, oxides, dye molecules, and hole conductors. A detailed understanding of interfacial properties is therefore important for new developments and device optimization. The implementation of X-ray-based spectroscopic methods for atomic-level understanding of such properties is reviewed. Specifically, the use of the chemical and element sensitivity of photoelectron spectroscopy, hard X-ray photoelectron spectroscopy, and resonant photoelectron spectroscopy for investigating interfacial molecular and electronic properties are described; examples include energy matching, binding configurations, and molecular orbital composition. Finally, results from the complete oxide/dye/hole-conductor systems are shown and demonstrate how the assembly itself can affect the molecular and electronic structure of the materials.

Biographical item: "Prof. Carl Nordling 1931-2016 Obituary" in Journal Of Electron Spectroscopy And Related Phenomena, vol 224, Special Issue: SI, pp 107-108

In this paper, we present the HELIOS (High Energy Laser Induced Overtone Source) laboratory, an in-house high-order harmonic generation facility which generates extreme ultraviolet (XUV) photon pulses in the range of 15-70 eV with monochromatized XUV pulse lengths below 35 fs. HELIOS is a source for time-resolved pump-probe/two-color spectroscopy in the sub-50 fs range, which can be operated at 5 kHz or 10 kHz. An optical parametric amplifier is available for pump-probe experiments with wavelengths ranging from 240 nm to 20 000 nm. The produced XUV radiation is monochromatized by a grating in the so-called off-plane mount. Together with overall design parameters, first monochromatized spectra are shown with an intensity of 2 ⋅ 1010 photons/s (at 5 kHz) in the 29th harmonic, after the monochromator. The XUV pulse duration is measured to be

Dye-sensitized interfaces in photocatalytic and solar cells systems are significantly affected by the choice of electrolyte solvent. In the present work, the interface between the hydrophobic Ru-complex Z907, a commonly used dye in molecular solar cells, and TiO2 was investigated with ambient pressure photoelectron spectroscopy (AP-PES) to study the effect of water atmosphere on the chemical and electronic structure of the dye/TiO2 interface. Both laboratory-based Al K alpha as well as synchrotron-based ambient pressure measurements using hard X-ray (AP-HAXPES) were used. AP-HAXPES data were collected at pressures of up to 25 mbar (i.e., the vapor pressure of water at room temperature) showing the presence of an adsorbed water overlayer on the sample surface. Adopting a quantitative AP-HAXPES analysis methodology indicates a stable stoichiometry in the presence of the water atmosphere. However, solvation effects due to the presence of water were observed both in the valence band region and for the S 1s core level and the results were compared with DFT calculations of the dye-water complex.

Hard X-ray photoelectron spectroscopy (HAXPES) has been used to study the effects of adding Li-TFSI to hole conducting molecular thin films of 2,2′,7,7′-tetrakis(N,N′-di-p-methoxyphenylamine)-9,9′-spirobifluorene (spiro-OMeTAD). The work shows that a procedure of mixing a Li-TFSI solution into a spiro-OMeTAD solution, and subsequent spin-coating this mixture into a solid thin film causes the Fermi level of the molecular film to move closer to the HOMO level. Hence, adding the Li-TFSI gives similar effects to spiro-OMeTAD as a p-dopant. Specific effects from doping on the valence levels were also characterized. Absorbance measurements also showed that the spiro-OMeTAD film was partially oxidized when Li-TFSI was added before spin-coating. By varying the photon energy in the photoelectron spectroscopy measurements, the probe depth varies between being surface sensitive (

The new instrument for ambient-pressure X-ray photoelectron spectroscopy at the Swedish synchrotron radiation facility MAX IV Laboratory is presented. The instrument is based on the use of a retractable and exchangeable high-pressure cell, which implies that ultrahigh-vacuum conditions are retained in the analysis chamber and that dual ambient pressure and ultrahigh-vacuum use is possible., The new instrument for near-ambient-pressure X-ray photoelectron spectroscopy which has been installed at the MAX II ring of the Swedish synchrotron radiation facility MAX IV Laboratory in Lund is presented. The new instrument, which is based on a SPECS PHOIBOS 150 NAP analyser, is the first to feature the use of retractable and exchangeable high-pressure cells. This implies that clean vacuum conditions are retained in the instrument’s analysis chamber and that it is possible to swiftly change between near-ambient and ultrahigh-vacuum conditions. In this way the instrument implements a direct link between ultrahigh-vacuum and in situ studies, and the entire pressure range from ultrahigh-vacuum to near-ambient conditions is available to the user. Measurements at pressures up to 10−5 mbar are carried out in the ultrahigh-vacuum analysis chamber, while measurements at higher pressures are performed in the high-pressure cell. The installation of a mass spectrometer on the exhaust line of the reaction cell offers the users the additional dimension of simultaneous reaction data monitoring. Moreover, the chosen design approach allows the use of dedicated cells for different sample environments, rendering the Swedish ambient-pressure X-ray photoelectron spectroscopy instrument a highly versatile and flexible tool.

The influence of water on the surface electronic and molecular properties of three Ru-dyes adsorbed at nanostructured TiO2 was investigated using photoelectron spectroscopy (PES). The dyes investig ...

Different molecular layers on TiO2 were prepared by using the p-dimethylaniline triphenylamine based organic dye, D29, together with the coadsorbents decylphosphonic acid (DPA), dineohexyl bis(3,3-dimethylbutyl)phosphinic acid (DINHOP), and chenodeoxycholic acid (CDCA). The surface molecular structure of dye and coadsorbent layers on TiO2 was investigated by photoelectron spectroscopy (PES). A focus was to determine the surface molecular concentrations using characteristic photoelectron core levels. Dye-sensitized solar cells (DSCs) were prepared from the same substrate and were further characterized by photoelectrochemical methods. Together the investigation gives information on the arrangement of the mixed molecular layer and a first insight to the extent to which the coadsorbents exchange with dye molecules on the TiO2 surface for the examined conditions.

The purpose of the present paper is to experimentally map the energy levels governing the trends observed in oxidation potentials and absorption spectra of M(bpy)32+ complexes (bpy = 2,2′-bipyridine, M = Fe(II), Ru(II), and Os(II)). Molecular films of the transition metal complexes were investigated with element specific methods using photoelectron spectroscopy (PES) at high kinetic energy using hard X-rays and by X-ray absorption spectroscopy (XAS). The results were compared to electronic structure calculations on the complexes and the ligand. The approach allows us to experimentally measure and interpret the energy levels in terms of spin−orbit coupling and metal−ligand interactions. Specifically, it was verified that the anomaly in the trend in oxidation potentials could be explained by a large spin−orbit coupling for the Os(bpy)32+. The influence of the different metal ions on the state formed upon light absorption was also investigated by N 1s X-ray absorption, and from the spectra we could determine...

Thin films of TiOPc have been investigated using photoelectron spectroscopy (PES) and X-ray spectroscopy (XAS). The results are interpreted in terms of the local geometry around the metal cente ...

Photoelectron spectroscopy at high kinetic energy is a research field that receives an increasing interest due to the possibility of studying bulk properties of materials and deeply buried interfaces. Recently the high kinetic energy electron (HIKE) spectroscopy facility at BESSY in Berlin has become operative at the bending magnet beamline KMC-1. The first results show very good performance. Electron spectra have been recorded using X-ray energies from 2 keV up to 12 keV. Using back-scattering conditions in the crystal monochromator, very high-resolution has been achieved for photon energies around 2, 6 and 8 keV. In the latter case, spectra with a resolving power from the monochromator of >= 80 000 have been achieved and it has been possible to perform electron spectroscopy with resolving power of >= 60 000, yielding a total instrument resolution of about 150 meV as determined directly from spectra. This paper describes the facility and reports some of the first results. (C) 2009 Elsevier B.V. All rights reserved.

We describe a method to fill thin films of nanoporous TiO2 with solid organic hole-conducting materials and demonstrate the procedure specifically for use in the preparation of dye-sensitized solar ...

Heparin based surface coatings can be used to improve the biocompatibility of metallic surfaces such as vascular stents. Here, we report molecular dynamics simulations of a macromolecular conjugate of heparin used to prepare such surfaces. The structural properties of the heparin conjugate are investigated for different degrees of hydration, to allow comparison with spectroscopic results. The simulations show that the polymer becomes more compact with an increasing degree of inter-chain interactions as the hydration increases. This is also accompanied by changes in the interaction patterns among the heparin chains, where counter ions become looser associated with the disaccharide units and their strong interactions can be partly replaced by water molecules and heparin hydroxyl groups. The structural information that can be obtained from computer simulations of this type of coatings can be very valuable for understanding and further development of functional interfaces, since very little is known experimentally regarding their detailed structural properties.

X-ray photoelectron spectroscopy (XPS) spectra of sputter-etched nc-TiC/a-C nanocomposite thin films published in literature show an extra feature of unknown origin in the C1s region. This feature is situated between the contributions of carbide and the carbon matrix. We have used high kinetic energy XPS (HIKE-XPS) on magnetron-sputtered nc-TiC/a-C thin films to show that this feature represents a third chemical environment in the nanocomposites, besides the carbide and the amorphous carbon. Our results show that component is present in as-deposited samples, and that the intensity is strongly enhanced by Ar+-ion etching. This third chemical environment may be due to interface or disorder effects. The implications of these observations on the XPS analysis of nanocomposites are discussed in the light of overlap problems for ternary carbon based systems.

The surface electronic and molecular structure of a new organic chromophore useful for dye-sensitized nanostructured solar cells has been investigated by means of electron spectroscopy. Initially t ...

For an electronic device well-designed interfaces are critical for the performance. Studies of interfaces down to an atomic level are thus highly motivated both from a fundamental and technological point of view. In this thesis, a surface science approach has been employed to study the formation of interfaces in systems relevant for transistor and solar cell applications. Surface science methodology entails ultra high vacuum environment, single crystalline surfaces, submonolayer control of deposited material, surface sensitive spectroscopy and atomic resolution microscopy.The primary experimental method for characterization is electron spectroscopy. This is a family of very powerful experimental techniques capable of giving information on the atomic level. Additionally, studies have been performed using scanning tunnelling microscopy. Combined these two methods can provide an atomic level characterisation of the geometric and electronic properties of the surface.The emphasis of this work is placed on ultra thin TiO2 and ZrO2 films grown on silicon substrates by means of ultra-high vacuum metal-organic chemical vapour deposition. ZrO2 has also been grown on SiC and FeCrAl. Deposition has been performed with different process parameters. The interface region of each film has been characterised. The band alignment, a most important issue with regard to the development of new transistor devices, for the ZrO2/Si(100) system has been explored. Decomposition pathways of the metal organic precursors have been studied in detail. Changing process parameters is shown to alter both the precursor decomposition pathway and the nature of the interface region, thus opening the possibility to tailor the material function.The titanium dioxide films grown in situ have shown to be excellent models of nanostructured electrode materials. In this spirit, interfaces of model systems for the solid-state dye-sensitized solar cell have been studied. Links between device performance and interface structure have been elucidated.

The properties of a sol-gel prepared Mn-modified TiO2 film have been studied with X-ray absorption spectroscopy (XAS) and photoelectron spectroscopy (PES) using synchrotron radiation. The chemical composition and oxidation state of the elements have been determined. The manganese content estimated by PES of the Mn-modified film is about 10% and both Mn2+ and Mn3+ are observed. Addition of Mn is found to modify the valence band edge. The Mn 3d states are found to extend about 1 eV into the TiO2 band gap region. It is demonstrated that lithium insertion into the sol-gel film can be performed in a stepwise fashion in situ under ultrahigh vacuum (UHV) conditions. Lithium is distributed evenly throughout the entire film and leads to reduction of Mn3+ to Mn2+ followed by reduction of Ti4+ to Ti3+. The XAS and PES measurements give fully consistent results regarding the amount of inserted lithium. (Less)

The electronic structure and chemical composition of efficient CH3NH3PbI3 perovskite solar cell materials deposited onto mesoporous TiO2 were studied using photoelectron spectroscopy with hard X-rays. With this technique, it is possible to directly measure the occupied energy levels of the perovskite as well as the TiO2 buried beneath and thereby determine the energy level matching of the interface. The measurements of the valence levels were in good agreement with simulated density of states, and the investigation gives information on the character of the valence levels. We also show that two different deposition techniques give results indicating similar electronic structures.

We report a methodology for a direct investigation of the solid/liquid interface using high pressure x-ray photoelectron spectroscopy (HPXPS). The technique was demonstrated with an electrochemical system represented by a Li-ion battery using a silicon electrode and a liquid electrolyte of LiClO4 in propylene carbonate (PC) cycled versus metallic lithium. For the first time the presence of a liquid electrolyte was realized using a transfer procedure where the sample was introduced into a 2 mbar N-2 environment in the analysis chamber without an intermediate ultrahigh vacuum (UHV) step in the load lock. The procedure was characterized in detail concerning lateral drop gradients as well as stability of measurement conditions over time. The X-ray photoelectron spectroscopy (XPS) measurements demonstrate that the solid substrate and the liquid electrolyte can be observed simultaneously. The results show that the solid electrolyte interphase (SEI) composition for the wet electrode is stable within the probing time and generally agrees well with traditional UHV studies. Since the methodology can easily be adjusted to various high pressure photoelectron spectroscopy systems, extending the approach towards operando solid/liquid interface studies using liquid electrolytes seems now feasible. (C) 2015 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.

The structure of a biomimetic phosphorylcholine (PC)-functionalized poly(trimethylene carbonate) (PC-PTMC-PC), linked to a silicon substrate through an aminolysis reaction at 120 degrees C with (3-aminopropyl)trimethoxysilane (APTMS), was studied using photoelectron spectroscopy. Two chemical states were found for the unreacted APTMS amine, a neutral state and a protonated state, where the protonated amine on average was situated closer to the silicon substrate than the neutral amine. The experiments also indicated the presence of a third chemical state, where amines interact with unreacted silanol groups. The PTMC chains of the grafted films were found to consist of only 2-3 repeat units, with the grafted chains enriched in the zwitterionic end group, suggesting that these groups are attracted to the surface. This was further supported by the experiments showing that the PC groups were situated deeper within the film.

The durability and functionality of a heparin coating on artificial heart valve leaflets were evaluated with X-ray photoelectron spectroscopy (XPS) and by the coatings' capacity to bind antithrombin. Current methods for accelerated life-time testing are based on exposing leaflets to water solutions. In this paper a method is explored, in which heart valve leaflets were exposed to a continuous high shear rate (4 L/min) of human citrated plasma. It was found that the heparin coating was stable and wear resistant enough to still be present after 3 weeks and to have about the same antithrombin uptake as coatings not exposed to circulating plasma. It was, however, partly destroyed by the test as found using XPS. We suggest that heparin chains from the upper layer of heparin have been torn off from the carrier chain, in combination with loss of heparin conjugate and plasma deposition in patches. This study showed that XPS provides additional information to biological measurements such as antithrombin uptake. XPS is therefore a valuable technique not only to characterize biomaterials but also to evaluate the effect of a performance test.

Photoelectron spectroscopy (PES) has been used to characterise the surface of Li2FeSiO4 cathodes extracted from lithium-ion batteries. Pristine, uncycled, air-exposed electrodes were first analysed and found to carry significantly greater amounts of Li2CO3 on their surfaces than electrodes stored under inert atmosphere. The surface film formed on electrochemical cycling of Li2FeSiO4 electrodes at 60 °C using a LiN(SO2CF3)2 salt based electrolyte revealed high salt stability and only small amounts of solvent reaction products. These were mainly of Li-carboxylate type; neither carbonates nor LiF were found. The excellent capacity retention (

In this study, metal-free phthalocyanine has been deposited on a conducting glass surface by two methods: by spreading the molecular powder directly on the substrate in air and by vapor sublimation under ultra-high vacuum conditions (evaporation). The films have been characterized by means of core level X-ray Photoemission Spectroscopy, X-ray Absorption Spectroscopy (XAS) and Ultra Violet and Visible absorption spectroscopy (UV-Vis). Our results show that the two deposition methods produce molecular overlayers in different polymorphic phases; the UV-Vis measurements indicate that the film obtained by powder deposition is of x-phase type whereas sublimation leads to an α-polymorph structure. The XAS results show that in the powder deposited film the molecules are mainly oriented parallel to the surface. This is opposite to the case of the vapor deposited film, where the molecules mainly are oriented orthogonal to the surface.

The element specificity of photoelectron spectroscopy (PES) has been used to compare the electronic and molecular structure of the dyes Ru(tcterpy)(NCS)3 (BD) and Ru(dcbpy)2(NCS)2 adsorbed from solution onto nanostructured TiO2. Ru(dcbpy)2(NCS)2 was investigated in its acid (N3) and in its 2-fold deprotonated form (N719) having tetrabutylammonium (TBA+) as counterions. A comparison of the O1s spectra for the dyes indicates that the interactions through the carboxylate groups with the TiO2 surface are very similar for the dyes. However, we observe that some of the dye molecules also interact through the NCS groups when adsorbed at the TiO2 surface. Comparing the N719 and the N3 molecule, the fraction of NCS groups interacting through the sulfur atoms is smaller for N719 than for N3. We also note that the counterion TBA+ is coadsorbed with the N719 and BD molecules although the amount was smaller than expected from the molecular formulas. Comparing the valence levels for the dyes adsorbed on TiO2, the position of the highest occupied electronic energy level is similar for N3 and N719, while that for BD is lower by 0.25 eV relative to that of the other complexes.

Systems comprising a dense TiO2 film electrode, a ruthenium polypyridine dye and a PEDOT-PSS (poly(3,4-ethylenedioxythiophene)-poly(4-styrenesulphonate)) film were prepared. The heterojunctions wer ...

The origin of the different Li+ intercalation behavior of raw and jet-milled natural graphite has been investigated. Jet-milled graphite is found to cycle reversibly in equal solvent mixture of pro ...

Insertion of H+, Li+, Na+ and K+ into thin films prepared from silicotungstic acid - a photoelectron spectroscopy study

The influence of electrolyte additives on the thermal stability of graphite anodes in a Li-ion battery has been investigated. The selected additives are: ethyltriacetoxysilane, 1,3 benzoldioxole, tetra (ethylene glycol) dimethylether and vinylene carbonate. These compounds were added in 4% to an electrolyte consisting of 1 M LiBF4 ethylene carbonate (EC/diethyl carbonate (DEC) solvent mixture. Differential scanning calorimetry (DSC) was used to investigated the thermal stability. The electrochemical performance was investigated by galvanostatic cycling and the formed solid electrolyte interphase (SEI) was characterised by photoelectron spectroscopy (PES) using Al Ka and synchrotron radiation /SR). The onset temperature for the thermally activated reactions was found to increas for all electrodes cycled with additives compared to electordes cycled without additives. The onset temperature in creased in the order: no additive < tetra (ethylene glycole) dimethyl ether < 1,3-benzoldioxole < ethyl-triacetoxysilane < vinylene carbonate. Feature in the PES spectra found to be associated with high onset temeratures for thermally activated reactions are: (i) no discernible graphite peak, (ii) small amount of salt species of the type LiF and LixBFyOz and (iii) larger amounts of organic compounds preferably with a high oxygen content.

Resonant core spectroscopies are applied to a study of the excited electron transfer dynamics on a low-femtosecond time scale in systems of aromatic molecules (isonicotinic acid and bi-isonicotinic acid) adsorbed on a rutile TiO 2 (110) semiconductor surface. Depending on which adsorbate state is excited, the electron is either localized on the adsorbate in an excitonic effect, or delocalizes rapidly into the substrate in less than 5 fs (3 fs) for isonicotinic acid (bi-isonicotinic acid). The results are obtained by the application of a variant of resonant photoemission spectroscopy.

In order to gain insight into the molecular structure of a new heparin surface (Corline heparin surface, CHS), quartz crystal microbalance dissipation (QCM-D) and photoelectron spectroscopy (PES) were used. Two surfaces, with different surface thickness and surface concentration of heparin, were compared. QCM-D measurements provided information on the thickness of the two different heparin surfaces and confirmed that the process of formation of the two layers were virtually identical. PES showed that the thicker coating resulted in complete coverage of the substrate, whereas with the thinner coating Fe signals originating from the stainless steel substrate could be detected. Information of the molecular surface structure of the heparin coatings could be derived from the ratios at different photon energies between S2p signals from sulfonate groups in heparin and disulfide groups originating from a cross-linking unit in the heparin conjugate.

Lithium insertion into nanoporous anatase TiO2 electrodes has been studied using resonant inelastic soft-x-ray scattering spectroscopy (RIXS). We have measured Ti 2p absorption, L2,3-emission and resonant inelastic scattering spectra of pristine anatase TiO2 and Li inserted TiO2. Inelastic scattering features in RIXS spectra of pristine TiO2 are assigned to charge-transfer excitations. Low energy-loss features for Li inserted TiO2 electrodes, appearing within t2g bands, due to d–d excitations, indicate the presence of Ti3+ states. The experimental observations suggest strong electron correlation in anatase TiO2 introduced by the Li-insertion.

X-ray photoelectron spectroscopy (XPS) has been used to study the depth profile of the solid–electrolyte interphase (SEI) formed on a graphite powder electrode in a Li-ion battery. The morphology o ...

The electronic properties of TiO2 and electrochemically Li-inserted TiO2 have been studied using synchrotron radiation photoelectron spectroscopy and x-ray absorption spectroscopy (XAS) in conjunction with resonant photoelectron spectroscopy. Core level (Ti 2p) and valence level spectra show the presence of Ti3+ states in LixTiO2. The x values determined from core level peak intensities were found to be directly correlated to the inserted amount of Li+ determined electrochemically. The x-dependent width of the Ti 2p peaks is consistent with a two-phase regime at intermediate x values. Resonant photoelectron spectroscopy at the Ti 2p edge was performed for TiO2 and Li0.5TiO2 to delineate the Ti4+ and Ti3+ contributions to the XAS spectrum.

Photoelectron spectroscopy is used to measure the electronic d. of states in the band gap region of a nanostructured TiO2 film. Such nanostructured films are used in dye-sensitized solar cells, and a plain TiO2 film as well as a dye-sensitized film were examd. To simulate the electrolyte effect on the energy levels at the oxide/dye/electrolyte interface in a solar cell, the d. of states in the band gap region for an electrochem. prepd. TiO2 film inserted with Li+ was measured. The distribution and chem. nature of electron trap states in the band gap and the energy matching between the LUMO level of the adsorbed dye, cis-bis(4,4'-dicarboxy-2,2'-bipyridine)-bis(isothiocyanato)ruthenium(II), and the TiO2 conduction band edge are discussed.

Differently sized dodecanethiol capped Au and Ag nanoparticles have been investigated using synchrotron radiation based photoelectron spectroscopy (PES). Comparative measurements were also performed on self-assembled monolayers (SAMs) of dodecanethiol at vacuum evaporated Au and Ag surfaces. The series of experiments display important differences in the surface electronic and molecular structure between the different kinds of materials. Specifically, the changes measured in binding energies are discussed with respect to initial and final state effects. Also, a broadening is observed for metal-core levels in the smaller nanoparticles. Thus, surface atoms in a different chemical state than the rest of the surface atoms are detected.In valence-levelspectra,the matching between the orbitals centered at the surface-coating molecule and the orbitals centered on the core materials are discussed.

Titanium dioxide thin film growth on silicon (111) by chemical vapor deposition of titanium(IV) isopropoxide

The adsorption of the dyes bis-(2,2‘-bipyridine)-(4,4‘-dicarboxy-2,2‘-bipyridine)-ruthenium(II) and bis-(2,2‘-bipyridine)-(4,4‘-dicarboxy-2,2‘-bipyridine)-osmium(II) on nanostructured TiO2 and ZnO was investigated by photoelectron spectroscopy (PES) using synchrotron radiation. Comparison of the results gives insight into the electronic structure of the molecules, as well as to their interaction with the substrates. The identity of the central metal ion of the dye complex was found not to influence the bonding mode of the molecule on the surfaces. However, when comparing the adsorption on the two metal oxides, the chemical state of the carboxyl group was found to be different. Binding to TiO2 results in four chemically equivalent carboxyl oxygens, while the oxygens are found chemically nonequivalent for adsorption onto ZnO. In addition, information concerning the frontier electronic structure was obtained by measuring the valence band region by PES using different photon energies and the N1s near edge X-r...

The interaction between the dye cis-bis(4,4‘-dicarboxy-2,2‘-bipyridine)-bis(isothiocyanato)-ruthenium(II), Ru(dcbpyH2)2(NCS)2, and nanostructured ZnO was investigated by photoelectron spectroscopy (PES) using synchrotron radiation. The results are compared with those of nanostructured TiO2 sensitized with the same dye, which to date is the most efficient system for dye-sensitized photoelectrochemical solar cells. When comparing the two metal oxides, differences in the surface molecular structure were observed both for low and high dye coverages, as seen by comparing the oxygen, nitrogen and sulfur signals. The origin of these differences is discussed in terms of substrate-induced dye aggregation and in variations in surface bonding geometries. The measurements also provide information concerning the energy matching between the orbitals of the dye and the ZnO valence band, which is of importance in photoinduced charge transfer.

Li insertion in thin film anatase TiO2: Identification of a two-phase regime with photoelectron spectroscopy

Dye-sensitized photoelectrochem. solar cells constitute a promising candidate in the search for cost-effective and environment-friendly solar cells. The most extensively studied, and to date the most efficient systems are based on titanium dioxide. In this paper, the possibilities to use nanostructured ZnO electrodes in photoelectrochem. solar cells are investigated. Various exptl. techniques (e.g. IR, photoelectron, femtosecond and nanosecond laser spectroscopies, laser flash induced photocurrent transient measurements, two- and three-electrode photoelectrochem. measurements) show that the thermodn., kinetics and charge transport properties are comparable for ZnO and TiO2. The prepn. techniques of ZnO provide more possibilities of varying the particle size and shape compared to TiO2. However, the dye-sensitization process is more complex in case of ZnO and care needs to be taken to achieve an optimal performance of the solar cell.