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The nature and structure of occupied and empty valence electronic states (molecular orbitals, MOs) of the [Ni(Salen)] molecular complex (NiO2N2C16H14) have been studied by X-ray photoemission and absorption spectroscopy combined with density functional theory (DFT) calculations. As a result, the composition of the high-lying occupied and low-lying unoccupied electronic states has been identified. In particular, the highest occupied molecular orbital (HOMO) of the complex is found to be predominantly located on the phenyl rings of the salen ligand, while the states associated with the occupied Ni 3d-derived molecular orbitals (MOs) are at higher binding energies. The lowest unoccupied molecular orbital (LUMO) is also located on the salen ligand and is formed by the 2pπ orbitals of carbon atoms in phenyl groups of the salen macrocycle. The unoccupied MOs above the LUMO reflect σ- and π-bonding between Ni and its nearest neighbours. All valence states have highly mixed character. The specific nature of the unoccupied Ni 3d-derived σ-MO is a consequence of donor-acceptor chemical bonding in [Ni(Salen)].

The valence band photoemission (VB PE) spectra of the [Ni(Salen)] molecular complex were measured by ultraviolet, soft X-ray and resonant photoemission (ResPE) using photons with energies ranging from 21.2 eV to 860 eV. It was found that the Ni 3d atomic orbitals’ (AOs) contributions are most significant for molecular orbitals (MOs), which are responsible for the low-energy PE band at a binding energy of 3.8 eV in the VB PE spectra. In turn, the PE bands in the binding energies range of 8–16 eV are due to the photoionization of the MOs of the [Ni(Salen)] complex with dominant contributions from C 2p AOs. A detailed consideration was made for the ResPE spectra obtained using photons with absorption resonance energies in the Ni 2p3/2, N 1s, and O 1s Near-Edge X-ray Absorption Fine Structure (NEXAFS) spectra. A strong increase in the intensity of the PE band ab was found when using photons with an energy 854.4 eV in the Ni 2p3/2 NEXAFS spectrum. This finding is due to the high probability of the participator-Auger decay of the Ni 2p3/2−13d9 excitation and confirms the relationship between the PE band ab with the Ni 3d-derived MOs.

The results of the research of a composite based on multi-walled carbon nanotubes (MWCNTs) decorated with CuO/Cu2O/Cu nanoparticles deposited by the cupric formate pyrolysis are discussed. The study used a complementary set of methods, including scanning and transmission electron microscopy, X-ray diffractometry, Raman, and ultrasoft X-ray spectroscopy. The investigation results show the good adhesion between the copper nanoparticles coating and the MWCNT surface through the oxygen atom bridge formation between the carbon atoms of the MWCNT outer graphene layer and the oxygen atoms of CuO and Cu2O oxides. The formation of the Cu–O–C bond between the coating layer and the outer nanotube surface is clearly confirmed by the results of the O 1s near edge X-ray absorption fine structure (NEXAFS) and X-ray photoelectron spectroscopy (XPS) of the Cu/MWCNTs nanocomposite. The XPS measurements were performed using a laboratory spectrometer with sample charge compensation, and the NEXAFS studies were carried out using the synchrotron radiation of the Russian–German dipole beamline at BESSY-II (Berlin, Germany) and the NanoPES station at the Kurchatov Center for Synchrotron Radiation and Nanotechnology (Moscow, Russia).

A great variety of two-dimensional (2D) boron allotropes (borophenes) were extensively studied in the past decade in the quest for graphene-like materials with potential for advanced technological applications. Among them, the 2D honeycomb boron is of specific interest as a structural analogue of graphene. Recently it has been synthesized on the Al(111) substrate; however it remains unknown to what extent does honeycomb boron behave like graphene. Here we elucidate the structural and electronic properties of this unusual 2D material with a combination of core-level X-ray spectroscopies, scanning tunneling microscopy, and DFT calculations. We demonstrate that in contrast to graphene on lattice-mismatched metal surfaces, honeycomb boron cannot wiggle like a blanket on Al(111), but rather induces reconstruction of the top metal layer, forming a stoichiometric AlB2 sheet on top of Al. Our conclusions from theoretical modeling are fully supported by X-ray absorption spectra showing strong similarity in the electronic structure of honeycomb boron on Al(111) and thick AlB2 films. On the other hand, a clear separation of the electronic states of the honeycomb boron into π- and σ-subsystems indicates an essentially 2D nature of the electronic system in both one-layer AlB2 and bulk AlB2.

Using a set of microscopic, spectroscopic, and electrochemical methods, a detailed study of the interrelation between the structural and electrochemical properties of the as-prepared nitrogen-containing multi-walled carbon nanotubes (N-MWCNTs) and their modified derivatives is carried out. It was found that after treatment of nanotubes with hydrochloric acid, their structure is improved by removing amorphous carbon from the outer layers of N-MWCNTs. On the contrary, ion bombardment leads to the formation of vacancy-type structural defects both on the surface and in the bulk of N-MWCNTs. It is shown that the treated nanotubes have an increased specific capacitance (up to 27 F·g−1) compared to the as-prepared nanotubes (13 F·g−1). This is due to an increase in the redox capacitance. It is associated with the reversible Faraday reactions with the participation of electrochemically active pyridinic and pyrrolic nitrogen inclusions and oxygen-containing functional groups (OCFG). Based on the comparison between cyclic voltammograms of N-MWCNTs treated in HCl and with an ion beam, the peaks on these curves were separated and assigned to specific nitrogen inclusions and OCFGs. It is shown that the rate of redox reactions with the participation of OCFGs is significantly higher than that of reactions with nitrogen inclusions in the pyridinic and pyrrolic forms. Moreover, it was established that treatment of N-MWCNTs in HCl is accompanied by a significant increase in the activity of nitrogen centers, which, in turn, leads to an increase in the rate of redox reactions involving OCFGs. Due to the significant contribution of redox capacitance, the obtained results can be used to develop supercapacitors with increased total specific capacitance.

Currently, X-ray photoelectron spectroscopy (XPS) is widely used to characterize the nanostructured material surface. The ability to determine the atom distribution and chemical state with depth without the sample destruction is important for studying the internal structure of the coating layer several nanometers thick, and makes XPS the preferable tool for the non-destructive testing of nanostructured systems. In this work, ultra-soft X-ray spectroscopy methods are used to study hidden layers and interfaces of pyrolytic tungsten carbide nanoscale coatings on the multi-walled carbon nanotube (MWCNT) surfaces. XPS measurements were performed using laboratory spectrometers with sample charge compensation, and Near Edge X-ray Absorption Fine Structure (NEXAFS) studies using the Russian&ndash, German dipole beamline (RGBL) synchrotron radiation at BESSY-II. The studied samples were tested by scanning and transmission electron microscopy, X-ray diffractometry, Raman scattering and NEXAFS spectroscopy. It was shown that the interface between MWCNT and the pyrolytic coating of tungsten carbide has a three-layer structure: (i) an interface layer consisting of the outer graphene layer carbon atoms, forming bonds with oxygen atoms from the oxides adsorbed on the MWCNT surface, and tungsten atoms from the coating layer, (ii) a non-stoichiometric tungsten carbide WC1-x nanoscale particles layer, (iii) a 3.3 nm thick non-stoichiometric tungsten oxide WO3-x layer on the WC1-x/MWCNT nanocomposite outer surface, formed in air. The tungsten carbide nanosized particle&rsquo, s adhesion to the nanotube outer surface is ensured by the formation of a chemical bond between the carbon atoms from the MWCNT upper layer and the tungsten atoms from the coating layer.

Energy distributions and properties of the occupied and empty electronic states for a planar complex of nickel porphyrin NiP are studied by X-ray photoemission and absorption spectroscopy techniques. As a result of the analysis of the experimental spectra of valence photoemission, the nature and energy positions of the highest occupied electronic states were determined: the highest occupied state is formed mostly by atomic states of the porphine ligand; the following two states are associated with 3d states of the nickel atom. It was found that the lowest empty state is specific and is described by the σ-type b1g MO formed by empty \(Ni3{d_{{x^2} - {y^2}}}\)-states and occupied 2p-states of lone electron pairs of nitrogen atoms. This specific nature of the lowest empty state is a consequence of the donor–acceptor chemical bond in NiP.

The thermal stability and the structural evolution of graphene grown on Fe(110) has been studied upon annealing in ultra-high vacuum conditions (UHV, P ≤ 10−9 mbar) and in the presence of gaseous ethylene at a pressure of ∼10−6 mbar by grazing incidence X-ray diffraction. It was observed that upon annealing at temperatures below 630 °C, graphene on Fe is thermally stable. Exposure to ethylene at these temperatures promotes the formation of graphene while inhibiting its deterioration. Annealing graphene/Fe(110) at temperatures above 630 °C results in a fast degradation of graphene followed by carburization of the sample, that is the irreversible formation of various iron carbides, with the most common phases being Fe3C (cementite) and Fe7C3 (Eckstrom-Adcock carbide). Annealing of the carburized sample does not result in the formation of a detectable graphitic structure.

Artificial two-dimensional (2D) materials, which host electronic or spatial structure and properties not typical for their bulk allotropes, can be grown epitaxially on atomically flat surfaces; the design and investigation of these materials are thus at the forefront of current research. Here we report the formation of borophene, a planar boron allotrope, on the surface of Ir(111) by exposing it to the flux of elemental boron and consequent annealing. By means of scanning tunneling microscopy and density functional theory calculations, we reveal the complex structure of this borophene, different from all planar boron allotropes reported earlier. This structure forms as a single phase on iridium substrate in a wide range of experimental conditions and may be then decoupled from the substrate via intercalation. These findings allow for production of large, defect-free borophene sheets and advance theoretical understanding of polymorphism in borophene.

For practical electronic device applications of graphene nanoribbons (GNRs), it is essential to have abrupt and well-defined contacts between the ribbon and the adjacent metal lead. By analogy with graphene, these contacts can induce electron or hole doping, which may significantly affect the I/V characteristics of the device. Cu is among the most popular metals of choice for contact materials. In this study, we investigate the effect of in situ intercalation of Cu on the electronic structure of atomically precise, spatially aligned armchair GNRs of width N = 7 (7-AGNRs) fabricated via a bottom-up method on the Au(788) surface. Scanning tunneling microscopy data reveal that the complete intercalation of about one monolayer of Cu under 7-AGNRs can be facilitated by gentle annealing of the sample at 80 °C. Angle-resolved photoemission spectroscopy (ARPES) data clearly reflect the one-dimensional character of the 7-AGNR band dispersion before and after intercalation. Moreover, ARPES and core-level photoemission results show that intercalation of Cu leads to significant electron injection into the nanoribbons, which causes a pronounced downshift of the valence and conduction bands of the GNR with respect to the Fermi energy (ΔE ~ 0.5 eV). As demonstrated by ARPES and X-ray absorption spectroscopy measurements, the effect of Cu intercalation is restricted to n-doping only, without considerable modification of the band structure of the GNRs. Post-annealing of the 7-AGNRs/Cu/Au(788) system at 200 °C activates the diffusion of Cu into Au and the formation of a Cu-rich surface Au layer. Alloying of intercalated Cu leads to the recovery of the initial position of GNR-related bands with respect to the Fermi energy (EF), thus, proving the tunability of the induced n-doping. [Figure not available: see fulltext.] (Less)

The energy distributions and the properties of the lower vacant electronic states in cobalt and nickel tetraphenylporphyrin complexes CoTPP and NiTPP are studied by X-ray absorption spectroscopy. Quasimolecular analysis of the experimental absorption spectra measured in the region of the 2p and 1s ionization thresholds of complexing metal atoms, as well as the 1s thresholds of ligand atoms (nitrogen and carbon), is based on the comparison of the corresponding spectra with each other and with the spectra of the simplest nickel porphyrin NiP. It has been established that, despite a general similarity of the spectra of nitrogen and carbon in CoTPP and NiTPP, the fine structure of the 2p and 1s absorption spectra of cobalt and nickel atoms are radically different. The observed differences in the spectra of cobalt and nickel are associated with the features of the energy distribution of vacant 3d electron states. The presence in CoTPP of the partially filled valence 3db2g molecular orbital (MO) results in the appearance in the cobalt spectra of a low-energy band, which is absent in the spectrum of nickel in NiTPP and leads to a doublet structure of transitions to b1g and eg MOs due to the exchange interaction between 3d electrons in partially filled 3db2g and 3db1g or 3deg MOs. The spectrum of vacant states in CoTPP differs from that in NiTPP also due to the smaller energy distance between 3db1g and eg MOs and the different positions of nonbonding MOs with the C2p character of the porphine ligand.

We investigate the bottom-up growth of N = 7 armchair graphene nanoribbons (7-AGNRs) from the 10,10′-dibromo-9,9′-bianthracene (DBBA) molecules on Ag(111) with the focus on the role of the organometallic (OM) intermediates. It is demonstrated that DBBA molecules on Ag(111) are partially debrominated at room temperature and lose all bromine atoms at elevated temperatures. Similar to DBBA on Cu(111), debrominated molecules form OM chains on Ag(111). Nevertheless, in contrast with the Cu(111) substrate, formation of polyanthracene chains from OM intermediates via an Ullmann-type reaction is feasible on Ag(111). Cleavage of C–Ag bonds occurs before the thermal threshold for the surface-catalyzed activation of C–H bonds on Ag(111) is reached, while on Cu(111) activation of C–H bonds occurs in parallel with the cleavage of the stronger C–Cu bonds. Consequently, while OM intermediates obstruct the Ullmann reaction between DBBA molecules on the Cu(111) substrate, they are required for the formation of polyanthracene chains on Ag(111). If the Ullmann-type reaction on Ag(111) is inhibited, heating of the OM chains produces nanographenes instead. Heating of the polyanthracene chains produces 7-AGNRs, while heating of nanographenes causes the formation of the disordered structures with the possible admixture of short GNRs.

Comment on "Bottom-Up Graphene-Nanoribbon Fabrication Reveals Chiral Edges and Enantioselectivity"

When used as cathode in primary lithium batteries, fluorinated carbons allow the control of the discharge potential according to the versatility of the C F bonding. High energy density may be obtained. If the atomic ratio F/C is lower than 1, the subfluorinated carbons contain both electrochemical active C F bonds (in insulating parts) and conductive nonfluorinated carbon atoms, which favor the electron flux during the discharge. Such dispersion results in high power density. The control at the nanoscale of the structure allows the performances to be further enhanced. Subfluorination is then optimized by adequate mixture of fluorinated and nonfluorinated parts into nanocarbons. Moreover, fluorinated nanotubes may be used to increase the discharge potential, thanks to a curvature effect of the carbon lattice on C F bonding. Finally, LiF particles formed during the discharge are better dispersed on the high specific surface of fluorinated nanocarbons; that avoids the partial exfoliation and losses of active material. This chapter focuses on those strategies.

International audience; Various 4–50 nm in size diamond nanoparticles prepared by different synthesis methods and their fluorinated derivatives were studied by NEXAFS, solid state NMR and FTIR spectroscopy. C 1s and F 1s NEXAFS spectra of as-prepared and fluorinated nanodiamonds (NDs and F-NDs) were analyzed based on a comparison with the known ones of reference compounds (graphitized carbon nanodiscs, phenol and amino acid molecules, graphite oxide and monofluoride). It has been found that all the studied diamond nanoparticles have crystalline diamond cores and their surfaces are covered with graphite-like carbon clusters. These clusters are partially amorphized and oxidized with the formation of functional groups C–OH, C═O, or O═C–OH and the properties of these surface shells depend on the synthesis method of nanodiamonds. The fluorination of diamond nanoparticles has a purely superficial character; it almost completely cleans the NDs particles from carbon clusters and saturates dangling bonds on the surface of the diamond nanoparticles with F atoms forming covalent σ(C–F) bonds. NEXAFS data are further supported by NMR and FTIR spectroscopy, leading to similar conclusions concerning the properties of various NDs and the chemical bonding between C and F atoms in F-NDs. A combination of NEXAFS, solid state NMR and FTIR spectroscopy is demonstrated to be very efficient in investigating various NDs and their functionalized derivatives

Atomically precise graphene nanoribbons (GNRs) can be fabricated via thermally induced polymerization of halogen containing molecular precursors on metal surfaces. In this paper the effect of substrate reactivity on the growth and structure of armchair GNRs (AGNRs) grown on inert Au(111) and active Cu(111) surfaces has been systematically studied by a combination of core-level X-ray spectroscopies and scanning tunneling microscopy. It is demonstrated that the activation threshold for the dehalogenation process decreases with increasing catalytic activity of the substrate. At room temperature the 10,10′-dibromo-9,9′-bianthracene (DBBA) precursor molecules on Au(111) remain intact, while on Cu(111) a complete surface-assisted dehalogenation takes place. Dehalogenation of precursor molecules on Au(111) only starts at around 80 °C and completes at 200 °C, leading to the formation of linear polymer chains. On Cu(111) tilted polymer chains appear readily at room temperature or slightly elevated temperatures. An...

Graphite fluorides with different structural types (CyF)(n) (y = 2.5, 2, and 1) and room temperature graphite fluorides were studied by solid state,NMR and NEXAFS. Data extracted from those two techniques are complementary, providing information about the C-F bonding and the hybridization character of the carbon atom valence states. The comparison of data obtained by different methods such as NMR, Raman, and X-ray absorption leads to similar conclusions regarding the chemical bonding in fluorographites. Several major configurations of fluorinated graphites are discussed, that is, planar sheets with mainly sp(2) hybridization in room temperature graphite fluorides and corrugated sheets with sp(3) hybridization in covalent high temperature graphite fluoride. Different references such as highly oriented pyrolytic graphite (HOPG), graphitized carbon nanodiscs (graph-CNDs) and nanodiamonds (NDs) have also been investigated for comparison.

The energy distributions of the occupied and unoccupied electronic states for copper halides CuCl and CuI have been investigated using X-ray photoemission and absorption spectroscopy with a highenergy resolution on the equipment of the Russian-German beamline for outlet and monochromatization of synchrotron radiation from the electron storage ring BESSY II. A quasi-molecular analysis of the obtained experimental spectra has revealed that there is a fundamental similarity of the energy structures of the valence band and the conduction band of copper halides CuX (X = Cl, I) due to the identical atomic structure of the studied compounds. The differences in the positions of individual energy subbands in the valence band and the conduction band of CuX and in their intensities in the spectra are associated with different degrees of hybridization of the Cu 3d, 4s and X(n + 1)s, np valence states, as well as with different sizes of structural units (CuCl4 and CuI4 quasi-molecules) of the studied crystals.

The metal atom 2p core excitations in 3d-metal phthalocyanines (MPc's, M = Ni, Co, Fe) have been studied via a combination of near edge X-ray absorption fine structure (NEXAFS) and resonant photoemission (ResPE) spectroscopy. On the basis of comparison of the corresponding spectra of NiPc, CoPc and FePc it has been shown that the presence of a partly filled molecular orbital (MO) dramatically affects the formation and decay processes of the M 2p core excitation in CoPc and, to a greater extend, in FePc due to the significant 3d-3d exchange interaction. It has been found that the low-lying unoccupied electronic states of NiPc, CoPc and FePc are strongly localized within the MN4 quasi-molecule and have nearly pure 3d character. Moreover, mainly 3d metallic character of the high-lying occupied MOs of NiPc, CoPc and FePc has been proved. (C) 2012 Elsevier B. V. All rights reserved. (Less)

In order to achieve the selective detection of NO2 in the environment, a chemical filter is added to a semiconductor gas sensor that is very sensitive to oxidizing gases in the gas flow. The aim is to remove ozone (O3), the main interfering oxidizing gas for NO2 detection before its measurement by a phthalocyanine sensor. The first parameter for the carbon material as a filter is the specific surface area (SSA), which should be high enough to ensure interaction with O3 and low enough to avoid interaction with NO2. The key role of surface oxygenated groups and dangling bonds was underlined by NEXAFS and EPR, respectively. A mixture of nanocones/nanodiscs (20/70% w/w) with SSA of 30 m2 g−1 with both structural and electronic defects is found to be the most efficient filter and was used upstream of a phthalocyanine sensor. The lifetime of the chemical filter was investigated and a strategy to increase it is described. Raman spectroscopy, EPR and NEXAFS allow the reactivity of the carbon with NO2 and O3 in the 10–1000 ppb concentration range to be studied.

CuX@SWCNT (X = Cl, Br, I) nanostructures were prepared by capillary filling of 1.4‐1.6 nm single-walled carbon nanotubes (SWCNT) with copper halides. The structure of CuX@SWCNT (X = Cl, Br, I) represents a distorted two-layer hcp of halogen atoms arranged along the SWCNT. The EXAFS and the high angle angular dark field (HAADF) HRTEM data indicate that Cu is partially coordinated by C. According to the optical absorption, valence band photoemission spectroscopy and work function measurements, a Fermi level (FL) downshift as compared with the initial value for the nanotubes and a corresponding charge transfer from the nanotubes to the 1D crystals is observed for CuX@SWCNT nanostructures. The FL shift increases in the sequence CuI < CuBr < CuCl due to an increase of the electron affinity for the halogen atoms. The XPS data confirm the acceptor effect of copper halides and indicate that metallic and semiconducting nanotubes behave differently. Raman spectroscopy performed under electrochemical charging allowed estimation of the value of charge transfer between the nanotube walls and the intercalated 1D crystal. The X-ray absorption and emission spectra for carbon and copper thresholds revealed a new energy level composed of the carbon 2pz and copper 3d-orbitals. This indicates the

The effect of atomic oxygen adsorption on the structure and electronic properties of monolayer hexagonal boron nitride (h-BN) grown on Ir(111) has been studied using near edge X-ray absorption fine ...

The Cu 2p, I 3d, and C 1sX-ray absorption spectra of the CuI@SWCNT nanocomposite prepared by filling single-walled carbon nanotubes (SWCNTs) with the CuI melt by the capillary technique have been measured with a high-energy resolution using the equipment of the Russian-German beamline at the BESSY electron storage ring. In order to characterize the electronic structure of the nanocomposite and possible changes in the atomic and electronic structures of CuI and SWCNTs in the CuI@SWCNT nanocomposite, the spectra obtained have been analyzed in the framework of the quasi-molecular approach by comparing with the spectra of the pristine (CuI and SWCNT) and reference (CuO) systems. It has been revealed that the encapsulation of the CuI compound inside SWCNTs is accompanied by changes in the electronic structure of CuI and SWCNTs due to the chemical interaction between the filler and carbon nanotubes and the change in the atomic structure of CuI.

High-resolution resonant F KLL Auger spectra from solid TiF3 and F-MWCNTs have been measured using photon energies in the vicinity of the F K(1s) edge. The spectra obtained show considerable changes in intensities and energy positions of main bands when photon energy passing through first low-energy absorption peak. These findings are explained in terms of hybridized nature and space localization of free electron states near the bottom of conduction band which are responsible for the first absorption band. The conclusions on the hybridization character of low-energy free electron states agree well with results obtained previously for F-MWCNTs with x-ray absorption.

The present study is aimed to characterize the possible chemical interaction between CuI and SWCNTs in CuI@SWCNT and electronic structure of the latter with X-ray absorption spectroscopy. Comparative analysis of C1s and Cu2p absorption spectra for CuI@SWCNT and reference samples in the framework of the quasi-molecular approach shows that encapsulation of CuI into SWCNTs is accompanied by the changes in electronic structure of CuI due to the ones in atomic structure of CuI in the composite and the chemical interaction between the filler and carbon nanotubes.

The paper presents the results of combined investigation of the chemical bond formation in fluorinated single-walled carbon nanotubes using X-ray absorption and photoelectron spectroscopy. All measurements were performed with the use of synchrotron radiation at the BESSY II. The C1s and F1s absorption and photoelectron spectra point to formation of covalent chemical bonding between the fluorine and carbon atoms in F-SWCNTs.

One-dimensional silver halide crystals were grown within single-walled nanotube (SWCNT) channels from the melt using a “molten media method”. Atomic structures of the AgX@SWCNT hybrids were proposed based on high-resolution transmission electron microscopy images. It was found that AgCl intercalation results in amorphous filling of the SWCNT channels. 1D AgBr and AgI crystals intercalated into 1.34 nm SWCNTs possess the structure of a two-layer hcp of halogen atoms arranged laterally with respect to the SWCNT axis. Electronic properties and chemical bonding in AgX@SWСNTs have been investigated by high-resolution X-ray photoelectron and near edge X-ray absorption fine structure spectroscopy (BESSY, Germany), optical absorption and Raman spectroscopy. Optical absorption spectroscopy indicates disappearance of E 11 S transitions between van-Hove singularities, which is caused by an effective electron exchange between AgX and the SWCNT. C 1s X-ray absorption spectra indicate a new empty level (S1) induced by charge transfer. Multi-component structure of photoemission spectra can be explained both by the variation of the work function of AgX@SWCNT hybrids and local interactions between halogen ions and carbon atoms. Raman spectroscopy performed under electrochemical charging clearly and directly demonstrated the acceptor behavior of AgX with respect to SWCNTs. Based on a whole dataset, a self-consistent picture of the AgX-SWCNT interactions is derived.

Thermal dependence of mineralized bone structure is examined both experimentally by measuring the near edge x-ray absorption fine structure (NEXAFS) and theoretically by applying the 3DSL model to clarify relationship between the local electronic and atomic structure and hierarchical organization of skeleton. The high energy resolution NEXAFS spectra are acquired near the Ca 2p edges in native bone heated from RT up to 450 °C and hydroxyapatite (Ca10(PO4)6(OH)2, OH-Ap) to understand the interplay of short-, long- and super-range order parameters of bone matter. Our focus is on the thermal changes of spectral distribution of oscillator strength for Ca 2p1/2,3/2 → 3d transition in bone and OH-Ap. The investigations have confirmed the assignment of the OH-Ap-to-bone spectral changes to the predicted hierarchy effect on electronic and atomic structure of mineralized bone. At RT the OH-Ap-to-bone red shift δE3dof the transition energy is found equal ≈ 0.2 eV and ≈ 0.1 eV for mature and young bone respectively. We stated that the shift behaves irregular and its magnitude varies from 0.1 eV up to 0.3 eV when the heating temperature grows. Two mechanisms associated with the thermal-induced dehydration of the inter-nanocrystallite spaces and with the subsequent atomic restructuring of the nanocrystallite interface in mineralized phase are revealed. We have detected that the OH-Ap-to-bone red shifts of the Ca 2p → 3d transition in young bone are smaller than those of in mature bone. The origin of the age differences is discussed.

FeCl2@OCHT, FeBr2@OCHT, and FeI2@OCHT nanocomposites were obtained by capillary filling of the channels of carbon single-walled nanotubes (SWNTs) with melts of iron halogenides. The composites were studied by high resolution transmission electron microscopy (HRTEM), the capillary condensation of nitrogen at 77K, Raman spectroscopy, optical absorption spectroscopy, X-ray absorption spectroscopy, X-ray photoelectron spectroscopy, and Moessbauer spectroscopy. Substantial distinctions in the combination scattering spectra of SWNTs and nanocomposites in the region of radial modes and in the region of longitudinal and tangential oscillations were revealed. The presence of electron transfer between the nanocrystal and the SWNT wall was established in the nanocomposites. For the FeCl2@OCHT nanocomposite, two states of Fe+2 were found: the first is characterized by electron transfer from the nanotube to the nanocrystal, which leads to the electron structure of the SWNT and FeCl2 changing; the second corresponds to the strained intercalated state resulting from the mechanical effect of the small SWNT diameter on the FeCl2 nanocrystal.

The C 1s and F 1s X-ray photoelectron spectra of fluorinated multiwalled carbon nanotubes with different fluorine contents have been measured using the equipment of the Russian-German beamline at the BESSY storage ring by varying the energy of exciting photons. It has been established that two fluorocarbon phases in which the chemical bonding is characterized by a different electron transfer from carbon atoms to fluorine atoms are formed in the near-surface region of nanotubes with fluorine concentrations of 10–39 wt %. The content of the dominant first phase with a large electron transfer in nanotubes remains unchanged with an increase in the probing depth. This phase is identified as a bulk phase formed as a result of the covalent attachment of fluorine atoms to graphene layers of the graphite skeleton without its destruction. The second phase with a small electron transfer is a near-surface phase, because it is predominantly located within two or three upper graphene monolayers and its contribution considerably decreases with an increase in the probing depth of fluorinated multiwalled carbon nanotubes.

The optimum conditions for the fluorination of single-walled carbon nanotubes (SWCNT) in the atmosphere of gaseous fluorine with the nanotube structure remaining intact up to a stoichiometry of CF x , x ∼ 0.5 were determined. The kinetics of fluorination was examined. The fluorinated SWCNTs were characterized by various methods, including transmission electron microscopy, measurements of specific surface area and accessible internal volume, NMR spectroscopy, IR spectroscopy, X-ray absorption and photoelectron spectroscopies, thermal stability, and analysis of gaseous products by mass-spectrometry. The structure of fluorinated SWCNT was preserved up to brutto-composition CF0.5 but degree of fluorination of SWCNT bundles was decreased with distance from the SWCNT surface to its core. Such a decrease becomes evident at ∼1.5 nm distance. It means that the degree of fluorination depends on the degree of its dispersion.

Special features of the synthesis (constructing) of highly organized quasi-one-dimensional organoiron nanostructures were considered. For the first time magnetic properties of ferromagnetic nanostructures with a specified topology based on quasi-one-dimensional organometallic structures (of “pile“ type) fixed on an inorganic matrix were studied. The presence of an uncompensated antiferromagnetism arisen on plotting organoiron groups on a silica surface was experimentally found, and the obtained data showed the study of quasi-one-dimensional organometallic nanostructures fixed on a support to be promising for the spin electronics engineering.

The combined investigation of the chemical bond formation in fluorinated multiwalled carbon nanotubes with 15 wt.% fluorine concentrations (MWCNTs + F 15 wt.%) using X-ray absorption, emission and photoelectron spectroscopy at C 1s and F 1s thresholds is presented. All measurements were performed at BESSY II. The analysis of the soft X-ray and photoelectron spectra point to the formation of covalent chemical bonding between fluorine and carbon atoms in the fluorinated nanotubes. Based on results of this combined study the depth dependent effects are discussed.

The results of the detailed investigation of the chemical bonding and electronic structure features for the series of fluorinated multi‐walled carbon nanotubes (F‐MWCNTs) with different fluorine concentrations (5–55%) using X‐ray absorption and photoelectron spectroscopy are outlined. All measurements were performed with the use of synchrotron radiation at the BESSY II. The C1s and F1s absorption and photoelectron spectra point to formation of covalent chemical bonding between the fluorine and carbon atoms in F‐MWCNTs.

The near edge X‐ray absorption fine structure (NEXAFS) spectra of polymethylmetacrylate (PMMA)‐fullerene (Fu) C60 and PMMA‐multiwall nanotubes (MWNT) composites treated at different temperatures are compared to the thermal desorption (TD) mass‐spectrometric (MS) spectra.

The structure and formation of an ultrathin hexagonal boron nitride (h-BN) film on Pt(111) has been studied by a combination of scanning tunneling microscopy, low energy electron diffraction, low ...

Sub-monolayers of gold have been grown at room temperature on the hexagonal boron nitride (h-BN) nanomesh formed on Rh(111), and studied systematically with core level and angle-resolved valence band photoelectron spectroscopy. The results are compared with those for the Au/Rh(111) and Au/h-BN/Pt(111) interfaces. It has been found that on clean Rh(111) substrate gold starts to grow two-dimensionally (2D), while in the presence of a h-BN interlayer it forms islands from the very beginning. In the case of flat h-BN monolayer (on Pt) these islands are essentially three-dimensional (3D) and irregular in size. In contrast, on the h-BN nanomesh (on Rh) gold grows initially as regular islands (predominantly 2D), probably filling the pores of the nanomesh. In addition, the evolution of the Au islands in h-BN/Rh(111) upon annealing has been investigated with core level photoemission and X-ray absorption. The annealing at temperatures between RT and 300 C does not affect the 2D character of Au islands, while further increase in temperature results in formation of 3D islands. At higher temperatures (above 500 C), the gold atoms diffuse through h-BN into the Rh substrate and/or desorb from the surface. However, they do not influence the chemical bond between rhodium and h-BN at any stage of annealing: the nanomesh remains intact. (Less)

The C 1s and F 1s x-ray absorption spectra of fluorinated multiwalled carbon nanotubes with different fluorine contents and reference compounds (highly oriented pyrolytic graphite crystals and “white” graphite fluoride) were measured using the equipment of the Russian-German beamline at the BESSY II storage ring with a high energy resolution. The spectra obtained were analyzed with the aim of characterizing multiwalled carbon nanotubes and their products formed upon treatment of the nanotubes with fluorine at a temperature of 420°C. It was established that, within the probing depth (∼15 nm) of carbon nanotubes, the process of fluorination occurs uniformly and does not depend on the fluorine concentration. The interaction of fluorine atoms with multiwalled carbon nanotubes in this case proceeds through the covalent attachment of fluorine atoms to graphene layers of the graphite skeleton and is accompanied by a change in the hybridization of the 2s and 2p valence electron states of the carbon atom from the trigonal (sp 2) to tetrahedral (sp 3) hybridization.

Electronic and atomic structure of hexagonal boron nitride (h-BN) on lattice-mismatched transition metal surfaces has been studied systematically by X-ray absorption and photoelectron spectroscopy and diffraction. The strength of interfacial chemical interaction between h-BN and the substrates is rising in the row Pt(111)-Ir(111)-Rh(111)-Ru(0001). This rise directly correlates with a growing corrugation of the h-BN monolayer. In particular, the h-BN nanomesh has larger pores on Ru(0001) than on the less reactive Rh(111) substrate. Our experiments provide strong evidence for the single-layer model of the nanomesh structure. (C) 2007 Elsevier B.V. All rights reserved.

Spectral dependences of the total absorption cross sections in the region of the 1s ionization threshold of molecular nitrogen are determined for the first time with a high energy resolution using synchrotron radiation from the Russian-German channel of the BESSY II electron storage ring and continuous radiation from an x-ray tube. For N2, partial N1s absorption cross sections are derived and the oscillator strengths for the vibrational and Rydberg transition series are evaluated from the measurements carried out with due account of the background and instrumental distortions.

Investigations of chemical bonding and electronic structure features for polycrystalline Ni(II) phthalocyanine (NiPc), Ni(II) tetrabenzoporphyrin (NiTBP), Ni(II) 2,3,7,8,12,13,17,18-octaethylporphyrin (NiOEP), Ni(II) 5,10,15,20-tetraisobutylporphyrin (NiTiBuP), Ni(II) 5,15-diphenylporphyrin (NidPP) and Ni(II) 5,15-diisobutylporphyrin (NidiBuP) have been performed by means of high-resolution soft X-ray absorption spectroscopy. It has been found that the low-lying unoccupied electron states in nickel porphyrins are mainly generated by the NiN4 quasi-molecule: the lowest empty state is the weakly antibonding molecular orbital (MO) of sigma b(1g), symmetry with nearly pure Ni 3d(x2-y2) character, while the next empty state is the e(g) MO, which has a hybridized Ni 3d pi-N 2p pi character and reflects pi chemical bonding (pi-back-donation) between nickel and neighbouring nitrogen atoms of the pyrrole rings. The differences observed in the Ni 2p spectra of nickel porphyrins and phthalocyanines indicate a limited usefulness of the NiN4 quasi-molecule and a need for its extension to the whole porphyrin (phthalocyanine) macrocycle. As a result, the differences in the Ni 2p spectra of the complexes and in their electronic structure are associated with a torsion of the opposite pyrrole ring planes (NiOEP, NiTiBuP) and the presence of N atoms in meso positions (NiPc). These conclusions are further confirmed by a comparative analysis of the Ni 2p and N Is absorption spectra for NiPc and NiOEP. (c) 2007 Elsevier B.V. All rights reserved. (Less)

The absorption cross-sections in the region of the resonance structure of the 2p ionization threshold of metal films are originally measured for the total series of 3d metals from Sc to Cu. The partial 2p absorption cross-sections are found, and the integral oscillator strengths are determined. The linear dependence of the sum of oscillator strengths in the range from 0 to 80 eV above the L3 absorption edge on the number of unfilled 3d states is established. The dependence breaks down for Cr, Fe, and Ni.