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Plasma fluorination of graphene is studied using a combination of spectroscopy and microscopy techniques, giving insight into the yield and fluorination mechanism for functionalization of supported graphene with both CF4 and SF6 gas precursors. Ion acceleration during fluorination is used to probe the effect on grafting functionalities. Adatom clustering, which occurs with CF4 plasma treatment, is suppressed when higher kinetic energy is supplied to the ions. During SF6 plasma functionalization, the sulfur atoms tend to bond to bare copper areas instead of affecting the graphene chemistry, except when the kinetic energy of the ions is restricted. Using scanning photoelectron microscopy, with a 100 nm spatial resolution, the chemical bonding environment is evaluated in the fluorinated carbon network at selected regions and the functionalization homogeneity is controlled in individual graphene flakes. [ABSTRACT FROM AUTHOR]

We investigate the oxidation mechanism of the layered model system GeAs. In situ X-ray photoelectron spectroscopy experiments performed by irradiating an individual flake with synchrotron radiation in the presence of oxygen show that while As leaves the GeAs surface upon oxidation, a Ge-rich ultrathin oxide film is being formed in the topmost layer of the flake. We develop a theoretical model that supports the layer-by-layer oxidation of GeAs, with a logarithmic kinetics. Finally, assuming that the activation energy for the oxidation process changes linearly with coverage, we estimate that the activation energy for As oxidation is almost twice that for Ge at room temperature.

Studying surface of catalyst nanoparticles in a flowing liquid is important for understanding the underlying mechanism of a reaction performed in liquid. We report the design of a reaction cell system of Si3N4 window covering the flowing liquid with an electron-transmissible membrane. By using metal nanoparticles as a catalyst dispersed in a solvent, examination of the surface of catalyst nanoparticles in a flowing liquid was demonstrated by observation of Ag 3d photoemission feature when a liquid containing Ag nanoparticles was flowing through this system.

Composite materials of titania and graphitic carbon, and their optimized synthesis are highly interesting for application in sustainable energy conversion and storage. We report on planar C/TiO2 composite films that are prepared on a polycrystalline titanium substrate by carbothermal treatment of compact anodic TiO2 with acetylene. This thin film material allows for the study of functional properties of C/TiO2 as a function of chemical composition and structure. The chemical and structural properties of the composite on top of individual Ti substrate grains are examined by scanning photoelectron microscopy and micro-Raman spectroscopy. Through comparison of these data with electron backscatter diffraction, it is found that the amount of generated carbon and the grade of anodic film crystallinity correlate with the crystallographic orientation of the Ti substrate grains. On top of Ti grains with ∼(0001) orientations the anodic TiO2 exhibits the highest grade of crystallinity, and the composite contains the highest fraction of graphitic carbon compared to Ti grains with other orientations. This indirect effect of the Ti substrate grain orientation yields new insights into the activity of TiO2 towards the decomposition of carbon precursors.

A series of novel non-symmetrically substituted mono β-aryl and β-arylethynyl (alkylsulfanyl)porphyrazines and the corresponding Ni(ii) complexes have been prepared by the Suzuki-Miyaura and Sonogashira cross-coupling reactions with the aim to investigate substituent effects on their electronic and aggregation properties. Spectroscopic, electrochemical and computational investigations show that in both aryl and arylethynyl compounds efficient electron transfer between the aryl and macrocycle moieties occurs. The highest perturbation of the porphyrazine π-electron core is provided by strong electron-donating (NMe2) and electron withdrawing (NO2) aryl substituents, which increase and decrease the macrocycle electron density, respectively. Moreover, while in most of the compounds the LUMOs and HOMOs are mainly localized on the porphyrazine ring, in the amino-substituted derivatives the HOMO is localized on the peripheral aryl moieties and the LUMO is localized on the macrocycle. Charge-transfer electronic excitations give rise to absorptions in UV-Vis spectra of both amino- and nitro-substituted compounds. In the former such excitations occur from aryl-localized to macrocycle-localized orbitals, while backward excitations occur in the latter. Therefore, the porphyrazine ring shows an ambivalent behavior, acting as an electron acceptor in the case of the NMe2-substituted compounds and as an electron donor in the NO2-substituted derivative. In these derivatives, even macrocycle mono-substitution provides unconventional "push-pull" systems suitable for NLO. Columnar discotic mesophases are also shown by thio-octyl arylethynyl derivatives, allowing us to envisage the possibility to achieve compounds both suitable for optoelectronic applications and endowed with self-aggregation properties.

Mixed-conducting perovskite-type electrodes which are used as cathodes in solid oxide fuel cells (SOFCs) exhibit pronounced performance improvement after cathodic polarization. The current in situ study addresses the mechanism of this activation process which is still unknown. We chose the new perovskite-type material La(0.75)Sr(0.25)Cr(0.5)Mn(0.5)O(3±δ) which is a potential candidate for use in symmetrical solid oxide fuel cells (SFCs). We prepared La(0.75)Sr(0.25)Cr(0.5)Mn(0.5)O(3±δ) thin film model electrodes on YSZ (111) single crystals by pulsed laser deposition (PLD). Impedance spectroscopy (EIS) measurements show that the kinetics of these electrodes can be drastically improved by applying a cathodic potential. To understand the origin of the enhanced electrocatalytic activity the surfaces of operating LSCrM electrodes were studied in situ (at low pressure) with spatially resolving X-ray photoelectron spectroscopy (μ-ESCA, SPEM) and quasi static secondary ion mass spectrometry (ToF-SIMS) after applying different electrical potentials in the SIMS chamber. We observed that the electrode surfaces which were annealed at 600 °C are enriched significantly in strontium. Subsequent cathodic polarization decreases the strontium surface concentration while anodic polarization increases the strontium accumulation at the electrode surface. We propose a mechanism based on the reversible incorporation of a passivating SrO surface phase into the LSCrM lattice to explain the observed activation/deactivation process.

Four cyclometalated Pt(IV) compounds, 1a,b and 2a,b, were successfully obtained by oxidative addition of I(2) to 2-phenylpyridinate (PhPy) and Nile Red (NR) derived Pt(II) complexes with acetylacetonate (acac) or hexafluoroacetylacetonate (hacac) ancillary ligands. Single crystal X-ray diffraction, electrochemical, photophysical and computational studies have been performed in comparison with the analogues Pt(II) compounds, shedding new light on the role of the oxidation state of the metal centre towards both the luminescence properties and the dioxygen quenching.

The presence and stability of sp hybridized atoms in free carbon nanoparticles was investigated by NEXAFS spectroscopy. The experiments show that a predominant fraction of carbon atoms is found in linear sp-chains and that conversion into sp(2) structures proceeds already at low temperature and in the gas phase.

A comparative photophysical, electrochemical and computational study of a series of Nile Red cyclopalladated and newly synthesised cycloplatinated complexes is reported. All complexes are luminescent at room temperature and the emission properties are governed by the nature of the cyclometallated dye. However, the presence of platinum(II) as metal centre decreases severely the emission quantum yield, while the electronegativity of the ancillary hexafluoroacetylacetonato ligand enhanced the emission properties of the Nile Red complexes.

A photophysical, electrochemical and computational study has been performed on a homologous series of cyclometallated Pd(II) (1a-f) and Pt(II) (2a-f) complexes of general formula [(C,N)M(O,O)]; (H(C,N) = azobenzene, 2-phenylpyridine, benzo[h]quinoline; M = Pd, Pt; H(O,O) = acetylacetone, hexafluoroacetylacetone). Experimental and computational data have shown the strong influence exerted by electronegativity of the ancillary ligand on the frontier orbitals of the complexes, such an effect being enhanced for the Pt(II) species.

This paper reports the synthesis, characterization, photophysical and structural properties of the homologous series of good emitting pentacoordinated GaQ'2L complexes 1-3, where Q' is 2-methyl-quinolin-8-olate and L is a phenolate substituted in para position with respect to the oxygen donor atom. A combined approach between the experimental structural analysis (i.e. the molecular fragments involved in intermolecular pi-pi interactions) and the computational study (i.e. the nature of the molecular orbitals residing therein) is discussed in order to compare the charge transport aptitude of complexes 1-3, in relation to the facing of their LUMO/LUMO, HOMO/HOMO and HOMO/LUMO arising from the molecular packing. The different phenolate ligands significantly change the packing characteristics of 1-3, with indirect effects on the electron hopping kinetics responsible for conduction in amorphous thin films. The observed preference for pyridyl-pyridyl stacking proves a faster electron conduction in comparison to hole conduction in the three complexes studied.

This paper reports the synthesis, characterisation and photophysical investigation of the homologous series of blue-emitting pentacoordinated AlQ'(2)L complexes 1-6, where Q' is 2-methylquinolin-8-olate and L is a phenolate substituted in para to the oxygen donor atom. Both electron attracting and electron releasing substituents have been considered. Also binuclear complexes of formula Q'(2)Al-L'-AlQ'(2), where L' = OC(6)H(4)C(6)H(4)O, OC(6)H(4)(CH(2))(3)C(6)H(4)O and OC(6)H(4)C(CH(3))(2)C(6)H(4)C(CH(3))(2)C(6)H(4)O have been synthesised and characterised. These are interesting blue-emitting materials for OLED (organic light emitting diode) fabrication. A comparison between computational and experimental results allowed the description of the absorption and fluorescence processes. A study of the frontier orbitals involved in the electric conduction and fluorescence emission has been performed. Influences of the phenolate-based ligands on the compounds spectroscopy have been particularly taken into account.

A new series of 5-(4'-substituted)phenylazo-8-hydroxyquinolines (H[L-R]; R = N(CH(3))(2), C(2)H(5), n-C(4)H(9), C(CH(3))(3), H, and F, ) has been prepared and the corresponding Zn[L-R](2) (1a-6a) and Al[L-R](3) (1b-6b) complexes successfully synthesized. These compounds have been studied in order to design new molecular materials with enhanced electron transport properties. The obtained species have been extensively characterized by absorption and emission spectra and by cyclic voltammetric measurements. Experimental and computational results show that the Zn[L-N(CH(3))(2)].2H(2)O (1a) and Al[L-N(CH(3))(2)](1b) complexes only feature luminescence (at 620 and 600 nm), respectively. The unique effects, which are induced by the N=N-C(6)H(4)-N(CH(3))(2) group, are further proved by a reversible electron transfer process detected by cyclic voltammetry. These outcomes, discussed on the basis of theoretical calculations performed on the (H[L-N(CH3)2])-, H[L-N(CH3)2] and (H[L-N(CH3)(2)])+ species, suggest that metal complexes formed by 5-(4'-N,N-dimethylamino)phenylazo-8-hydroxyquinoline should be considered as electron transport materials suitable for applications in photonic devices.

Treatment of octakis(octylthio)porphyrazine (H(2)OOSPz) with cis-bis(benzonitrile)dichloroplatinum(II) in a 1,2,4-trichlorobenzene (TCB)-n-BuOH mixture at 190 degree C affords the asymmetric porphyrazine 2H-heptakis(octylthio)porphyrazine, H(2)HOSPz, in ca. 40% yield. In the key synthetic step the two-electron reduced diprotonated porphyrazine, [H(2)OOPz(4-)(H(+))(2)](hemiporphyrazinogen), forms in nearly quantitative yield. This species undergoes nucleophilic substitution of an octylsulfide group by H(-), affording the asymmetric porphyrazine, this process being favoured by the high-temperature induced charge and structural intramolecular rearrangements. The resulting molecule shows mesomorphic behaviour. Interestingly, in the presence of sodium acetate, or in neat TCB, the asymmetric porphyrazine does not form at all. Under these conditions, a PtCl(2) molecular fragment coordinates both to a porphyrazine aza bridge and to a thioether moiety leading to the formation of the [H(2)OOSPz]PtCl(2) complex. The S,N-coordination of the PtCl(2) unit was proved by (1)H, (195)Pt[(1)H], and (13)C NMR spectroscopy, and supported by DFT (B3LYP) calculations. The complex conjugates high asymmetry with strong solvatochromism and, therefore, it is potentially interesting for nonlinear optics.