ARXPS and DFT studies of thermally induced Pb surface segregation on Au/Cu alloys

Surface segregation of Pb has been studied using angle resolved X-ray Photoelectron Spectroscopy (ARXPS) and Density Functional Theory (DFT) modelling in a polycrystalline Au0.85Cu0.15 alloy. Au surface enrichment was found in the alloy surface, whereas Pb surface enrichment was detected after annealing. ARXPS depth profiles show a 23% surface coverage by Pb atoms. DFT calculations predict an approximate coverage of ¼ monolayer (ML) of Pb atoms in the first atomic layer, consistent with the experimental results. The results presented here are an example of the importance of low concentration of impurities in determining the surface composition of bulk alloys.Fil: Volker, Edgar. University of Liverpool; Reino Unido. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: Williams, Federico José. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: Jacob, Timo. Universitat Ulm; AlemaniaFil: Schiffrin, D. J.. University of Liverpool; Reino Unid

O 2 induced Cu surface segregation in Au-Cu alloys studied by angle resolved XPS and DFT modelling

Surface segregation effects on polycrystalline Au-Cu alloys (Au 0.80Cu 0.20, Au 0.85Cu 0.15 and Au 0.90Cu 0.10) were studied at room temperature by angle resolved XPS (ARXPS) and density functional theory (DFT) before and after exposure to O 2. Au surface enrichment was found as predicted from calculations showing that this process is energetically favourable, with a segregation energy for Au in a Cu matrix of -0.37 eV atom -1. Surface enrichment with Cu was observed after exposure to O 2 due to its dissociative adsorption, in agreement with DFT calculations that predicted an energy gain of -1.80 eV atom -1 for the transfer of Cu atoms to a surface containing adsorbed oxygen atoms, thus leading to an inversion in surface population.Fil: Volker, Edgar. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: Williams, Federico José. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: Calvo, Ernesto Julio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: Jacob, Timo. Universitat Ulm; AlemaniaFil: Schiffrin, David J.. University of Liverpool; Reino Unid

Organization of Alkane Amines on a Gold Surface: Structure, Surface Dipole, and Electron Transfer

Surface molecular self-assembly is a fast advancing field with broad applications in molecular electronics, sensing and advanced materials. Although a large number of practical systems utilize alkanethiols, there is increasing interest in alkylamine self-assembled monolayers (SAMs). In this article, the molecular and electronic structure of alkylamine SAMs on Au surfaces was studied. It was found that amine-terminated alkanes self-assemble, forming a compact layer with the amine headgroup interacting directly with the Au surface and the hydrocarbon backbone tilted by around 30° with respect to the surface normal. The dense layers formed substantially decrease electron tunneling across the metal/solution interface and form a dipole layer with positive charges residing at the monolayer/vacuum interface

LU135252, an endothelin(A) receptor antagonist did not prevent pulmonary vascular remodelling or lung fibrosis in a rat model of myocardial infarction

1. The early intervention with endothelin(A) (ET(A)) receptor antagonists following coronary artery ligation has been shown to reduce the development of pulmonary hypertension, despite a lack of improvement in left ventricular function. 2. The present study examined the contribution of pulmonary vascular remodelling and the progression of lung fibrosis in the development of pulmonary hypertension and the subsequent role of endothelin-1 in these processes in a rat model of myocardial infarction (MI). 3. The administration of 60 mg kg(−1) per day of the specific ET(A) receptor antagonist LU135253 ((+)-(S)-2-(4,6-dimethoxy-pyrimidin-2-yloxy)-3-methoxy-3,3-diphenyl-propionic acid) 24 h following coronary artery ligation, failed to improve left ventricular contractile indices, but reduced the extent of pulmonary hypertension, as reflected by the significant decrease in right ventricular systolic pressure. 4. The medial wall thickness of small pulmonary arteries (50–200 μm) was significantly increased 4 weeks following MI, albeit LU135253 treatment did not ameliorate this pattern of vascular remodelling. 5. The steady-state mRNA levels of collagen, fibronectin, transforming growth factor-β(1), and -β(3) were significantly increased in the lungs of MI rats. The treatment with LU135252 did not alter this pattern of gene expression. 6. Thus, these data demonstrate pulmonary vascular remodelling and the increased expression of extracellular matrix proteins represent underlying mechanisms implicated in the development of pulmonary hypertension in the MI rat. 7. Despite the amelioration of the pulmonary hypertensive state, ET(A) receptor blockade was insufficient to reverse pulmonary vascular remodelling, or the development of lung fibrosis in the MI rat

Organization of Alkane Amines on a Gold Surface: Structure, Surface Dipole, and Electron Transfer

Surface molecular self-assembly is a fast advancing field with broad applications in molecular electronics, sensing and advanced materials. Although a large number of practical systems utilize alkanethiols, there is increasing interest in alkylamine self-assembled monolayers (SAMs). In this article, the molecular and electronic structure of alkylamine SAMs on Au surfaces was studied. It was found that amine-terminated alkanes self-assemble, forming a compact layer with the amine headgroup interacting directly with the Au surface and the hydrocarbon backbone tilted by around 30° with respect to the surface normal. The dense layers formed substantially decrease electron tunneling across the metal/solution interface and form a dipole layer with positive charges residing at the monolayer/vacuum interface.Fil: de la Llave, Ezequiel Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: Clarenc, Romain. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Inorgánica, Analítica y Química Física; ArgentinaFil: Schiffrin, David J.. University of Liverpool; Reino UnidoFil: Williams, Federico José. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentin