Electronic structure and intramolecular interactions in three methoxyphenol isomers.

Electronic structures and intramolecular interactions of three methoxyphenol positional isomers and their rotamers have been studied using core X-ray photoelectron spectroscopy and quantum mechanical calculations. The structural calculations are benchmarked against published calculations of enthalpy of formation and rotational constants, and published experimental data. The good agreement obtained confirms the accuracy of the results.

An experimental and theoretical study of adenine adsorption on Au(111).

A model study of adenine adsorption on the Au(111) surface is reported for molecular adlayers prepared by evaporation in vacuum and deposition from saturated aqueous solution. The electronic structure and adsorption geometry of the molecular films were studied experimentally by X-ray photoelectron spectroscopy and near edge X-ray absorption fine structure spectroscopy. Adsorption models are proposed for the adlayers arising from the different preparation methods.

PEDOT(PSS) as Solid Contact for Ion-Selective Electrodes: The Influence of the PEDOT(PSS) Film Thickness on the Equilibration Times.

To understand the rate determining processes during the equilibration of poly(3,4-ethylenedioxythiophene):polystyrenesulfonate-based (PEDOT(PSS)-based) solid contact (SC) ion-selective electrodes (ISEs), the surfaces of Pt, Au, and GC electrodes were coated with 0.1, 1.0, 2.

A Close Look at the Structure of the TiO-APTES Interface in Hybrid Nanomaterials and Its Degradation Pathway: An Experimental and Theoretical Study.

The surface functionalization of TiO-based materials with alkylsilanes is attractive in several cutting-edge applications, such as photovoltaics, sensors, and nanocarriers for the controlled release of bioactive molecules. (3-Aminopropyl)triethoxysilane (APTES) is able to self-assemble to form monolayers on TiO surfaces, but its adsorption geometry and solar-induced photodegradation pathways are not well understood. We here employ advanced experimental (XPS, NEXAFS, AFM, HR-TEM, and FT-IR) and theoretical (plane-wave DFT) tools to investigate the preferential interaction mode of APTES on anatase TiO.

Adsorption of ethylene on Sn and In terminated Si(001) surface studied by photoelectron spectroscopy and scanning tunneling microscopy.

Interaction of ethylene (C2H4) with Si(001)-Sn-2 × 2 and Si(001)-In-2 × 2 at room temperature has been studied using core level (C 1s) X-ray photoelectron spectroscopy with synchrotron radiation and scanning tunneling microscopy. Sn and In form similar dimer chains on Si(001)2 × 1, but exhibit different interaction with ethylene. While ethylene adsorbs on top of Sn dimers of the Si(001)-Sn-2 × 2 surface, the Si(001)-In-2 × 2 surface turned out to be inert.

X-ray Photoemission Spectra and Electronic Structure of Coumarin and its Derivatives.

The electronic structures of coumarin and three of its derivatives (7-amino-4-methylcoumarin, 7-amino-4-(trifluoro)methylcoumarin, and 4-hydroxycoumarin) have been studied by theoretical calculations, and compared with experimental valence and core photoelectron spectra to benchmark the predicted spectra. The outer valence band spectra of the first three compounds showed good agreement with theoretical calculations for a single isomer, whereas the spectrum of 4-hydroxycoumarin indicated the presence of more than one tautomer, consistent with published results. Calculations of core level spectra of carbon, nitrogen, oxygen, and fluorine of the first three compounds are also in satisfactory agreement with our measurements.

Evidence of double layer/capacitive charging in carbon nanomaterial-based solid contact polymeric ion-selective electrodes.

This paper presents the first direct spectroscopic evidence for double layer or capacitive charging of carbon nanomaterial-based solid contacts in all-solid-state polymeric ion-selective electrodes (ISEs). Here, we used synchrotron radiation-X-ray photoelectron spectroscopy (SR-XPS) and SR valence band (VB) spectroscopy in the elucidation of the charging mechanism of the SCs.

Electrochemical Ion Transfer with Thin Films of Poly(3-octylthiophene).

We report on the limiting conditions for ion-transfer voltammetry between an ion-exchanger doped and plasticized poly(vinyl chloride) (PVC) membrane and an electrolyte solution that was triggered via the oxidation of a poly(3-octylthiophene) (POT) solid-contact (SC), which was unexpectedly related to the thickness of the POT SC. An electropolymerized 60 nm thick film of POT coated with a plasticized PVC membrane exhibited a significant sodium transfer voltammetric signal whereas a thicker film (180 nm) did not display a measurable level of ion transfer due to a lack of oxidation of thick POT beneath the membrane film. In contrast, this peculiar phenomenon was not observed when the POT film was in direct contact with an organic solvent-based electrolyte.

Adenine adlayers on Cu(111): XPS and NEXAFS study.

The adsorption of adenine on Cu(111) was studied by photoelectron and near edge x-ray absorption fine structure spectroscopy. Disordered molecular films were deposited by means of physical vapor deposition on the substrate at room temperature. Adenine chemisorbs on the Cu(111) surface with strong rehybridization of the molecular orbitals and the Cu 3d states.

Immobilised molecular catalysts and the role of the supporting metal substrate.

This work demonstrates that immobilising molecular catalysts on metal substrates can attenuate their reactivity. In particular, the reactivity towards molecular oxygen of both ruthenium tetraphenyl porphyrin (Ru-TPP) and its Ti analogue (Ti-TPP) on Ag(111) was studied as benchmark for the interaction strength of such metal-organic complexes with possible reactants. Here, Ru-TPP proves to be completely unreactive and Ti-TPP strongly reactive towards molecular oxygen; along with comparison to work in the literature, this suggests that studies into immobilised catalysts might find fruition in considering species traditionally seen as too strongly interacting.

Functionalization of nanostructured cerium oxide films with histidine.

The surfaces of polycrystalline cerium oxide films were modified by histidine adsorption under vacuum and characterized by the synchrotron based techniques of core and valence level photoemission, resonant photoemission and near edge X-ray absorption spectroscopy, as well as atomic force microscopy. Histidine is strongly bound to the oxide surface in the anionic form through the deprotonated carboxylate group, and forms a disordered molecular adlayer. The imidazole ring and the amino side group do not form bonds with the substrate but are involved in the intermolecular hydrogen bonding which stabilizes the molecular adlayer.

Surface-assisted dehydrogenative homocoupling of porphine molecules.

The templated synthesis of porphyrin dimers, oligomers, and tapes has recently attracted considerable interest. Here, we introduce a clean, temperature-induced covalent dehydrogenative coupling mechanism between unsubstituted free-base porphine units yielding dimers, trimers, and larger oligomers directly on a Ag(111) support under ultrahigh-vacuum conditions. Our multitechnique approach, including scanning tunneling microscopy, near-edge X-ray absorption fine structure and photoelectron spectroscopy complemented by theoretical modeling, allows a comprehensive characterization of the resulting nanostructures and sheds light on the coupling mechanism.

Structures of cycloserine and 2-oxazolidinone probed by X-ray photoelectron spectroscopy: theory and experiment.

The electronic structures and properties of 2-oxazolidinone and the related compound cycloserine (CS) have been investigated using theoretical calculations and core and valence photoelectron spectroscopy. Isomerization of the central oxazolidine heterocycle and the addition of an amino group yield cycloserine. Theory correctly predicts the C, N, and O 1s core spectra, and additionally, we report theoretical natural bond orbital (NBO) charges.

Bonding of histidine to cerium oxide.

Adsorption of histidine on cerium oxide model surfaces was investigated by synchrotron radiation photoemission, resonant photoemission, and near edge X-ray absorption fine structure spectroscopies. Histidine was evaporated in a vacuum onto ordered stoichiometric CeO2(111) and partially reduced CeO1.9 thin films grown on Cu(111).

Self-terminating protocol for an interfacial complexation reaction in vacuo by metal-organic chemical vapor deposition.

The fabrication and control of coordination compounds or architectures at well-defined interfaces is a thriving research domain with promise for various research areas, including single-site catalysis, molecular magnetism, light-harvesting, and molecular rotors and machines. To date, such systems have been realized either by grafting or depositing prefabricated metal-organic complexes or by protocols combining molecular linkers and single metal atoms at the interface. Here we report a different pathway employing metal-organic chemical vapor deposition, as exemplified by the reaction of meso-tetraphenylporphyrin derivatives on atomistically clean Ag(111) with a metal carbonyl precursor (Ru3(CO)12) under vacuum conditions.

Synchrotron scanning photoemission microscopy of homogeneous and heterogeneous metal sulfide minerals.

Scanning photoemission microscopy (SPEM) has been applied to the investigation of homogeneous and heterogeneous metal sulfide mineral surfaces. Three mineral samples were investigated: homogeneous chalcopyrite, heterogeneous chalcopyrite with bornite, and heterogeneous chalcopyrite with pyrite. Sulfur, copper and iron SPEM images, i.

Chemical defects in the highly fluorescent conjugated polymer dots.

We present strong evidence for the oxidation of conjugated polymers in the formation of conjugated polymer dots (CPdots) using Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Although recent studies show that folding of the polymer chain into a compact 3D structure is involved in the formation of these nanoparticles, the process by which these intrinsically hydrophobic nanoscale particles circumvent aggregation in water is still not well understood. Zeta potential results show that these dots have a negatively charged surface at neutral pH, with a zeta potential and surface charge density of approximately -40 mV and (1.

Synchrotron PEEM and ToF-SIMS study of oxidized heterogeneous pentlandite, pyrrhotite and chalcopyrite.

Synchrotron-based photoemission electron microscopy (PEEM; probing the surface region) and time-of-flight secondary ion mass spectrometry (ToF-SIMS; probing the uppermost surface layer) have been used to image naturally heterogeneous samples containing chalcopyrite (CuFeS(2)), pentlandite [(Ni,Fe)(9)S(8)] and monoclinic pyrrhotite (Fe(7)S(8)) both freshly polished and exposed to pH 9 KOH for 30 min. PEEM images constructed from the metal L(3) absorption edges were acquired for the freshly prepared and solution-exposed mineral samples. These images were also used to produce near-edge X-ray absorption fine-structure spectra from regions of the images, allowing the chemistry of the surface of each mineral to be interrogated, and the effect of solution exposure on the mineral surface chemistry to be determined.