Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 5 de 5
Filtrar
Mais filtros

Tipo de documento
Intervalo de ano de publicação
1.
Phys Chem Chem Phys ; 18(19): 13604-15, 2016 05 11.
Artigo em Inglês | MEDLINE | ID: mdl-27141554

RESUMO

Photoelectron spectroscopy is usually described by a simple equation that relates the binding energy of the photoemitted electron, Ebinding, its kinetic energy, Ekinetic, the energy of the ionizing photon, Ephoton, and the work function of the spectrometer, ϕ, Ebinding = Ephoton - Ekinetic - ϕ. Behind this equation there is an extremely rich physics, which we describe here using as an example a relatively simple conjugated molecule, namely coronene. The theoretical analysis of valence band and C1s core level photoemission spectra showed that multiple excitations play an important role in determining the intensities of the final spectrum. An explicit, time-evolving model is applied, which is able to count all possible photo-excitations occurring during the photoemission process, showing that they evolve on a short time-scale, of about 10 fs. The method reveals itself to be a valid approach to reproduce photoemission spectra of polycyclic aromatic hydrocarbons (PAHs).

2.
J Am Chem Soc ; 130(46): 15678-82, 2008 Nov 19.
Artigo em Inglês | MEDLINE | ID: mdl-18950162

RESUMO

The preparation and the properties of gold nanoparticles (Au NPs) protected by perfluorinated amphiphiles are described. The thiols were devised to form a perfluorinated region close to the gold surface and to have a hydrophilic portion in contact with the bulk solvent to impart solubility in water. The monolayer protected clusters were prepared, in an homogeneous phase using sodium thiolates because of the low nucleophilicity of the alpha-perfluorinated thiols, and fully characterized with (1)H, (19)F NMR spectrometry, IR and UV-vis absorption spectroscopies, transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). Au NPs with core diameters ranging from 1.6 to 2.9 nm, depending on the reaction conditions, were obtained. Water-soluble NPs (MPC-F8-PEGs) were obtained with the thiol HS-F8-PEG ending with a short poly(ethylene glycol) unit (PEG-OMe 550), whereas thiols with shorter PEG chains give rise to NPs insoluble in water. MPC-F8-PEGs undergo an exchange reaction with amphiphilic alkyl thiols. ESR investigations, using a hydrophobic radical probe, indicate that the MPC-F8-PEG monolayer shows a greater hydrophobicity compared to the analogous hydrogenated monolayer.


Assuntos
Compostos de Flúor/química , Ouro/química , Nanopartículas Metálicas/química , Compostos de Sulfidrila/química , Água/química , Espectroscopia de Ressonância Magnética , Estrutura Molecular , Óxido Nítrico/química , Polietilenoglicóis/química , Solubilidade
3.
Chem Commun (Camb) ; 47(10): 2952-4, 2011 Mar 14.
Artigo em Inglês | MEDLINE | ID: mdl-21240448

RESUMO

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.

4.
Rev. iberoam. educ. invest. enferm.(Internet) ; 5(3): 43-55, Jul.2015. tab, graf
Artigo em Espanhol | LILACS, BDENF - enfermagem (Brasil) | ID: biblio-1035331

RESUMO

Resumen:


Objetivo: evaluar la calidad percibida de la gestión enfermera en la demanda urgente en un centro de Atención Primaria de Valladolid. Método: estudio descriptivo trasversal. Se realizó una encuesta de satisfacción a 135 usuarios y a los profesionales del centro de salud para valorar la consulta de demanda urgente. Resultados: la satisfacción media de los usuarios fue de 5,59 (Likert 1-7). Los profesionales se muestran satisfechos, con una nota media de 5,60 (enfermeras) y 6,14 (médicos) sobre 7. Conclusiones: la gestión enfermera en la demanda urgente ha supuesto una mejora asistencial. Los usuarios aprecian particularmente la rapidez de la atención y el trato recibido. Los profesionales coinciden en que este sistema de atención permite identificar rápidamente una situación de urgencia. Para conseguir un servicio más eficiente se requiere una mayor protocolización de las actuaciones y mejor coordinación entre los profesionales del centro de salud.


Assuntos
Avaliação em Enfermagem , Inquéritos e Questionários , Satisfação do Paciente , Satisfação no Emprego , Serviços de Enfermagem
5.
J Chem Phys ; 126(12): 124709, 2007 Mar 28.
Artigo em Inglês | MEDLINE | ID: mdl-17411154

RESUMO

An experimental and theoretical study of the electronic structure of copper phthalocyanine (CuPc) molecule is presented. We performed x-ray photoemission spectroscopy (XPS) and photoabsorption [x-ray absorption near-edge structure (XANES)] gas phase experiments and we compared the results with self-consistent field, density functional theory (DFT), and static-exchange theoretical calculations. In addition, ultraviolet photoelectron spectra (UPS) allowed disentangling several outer molecular orbitals. A detailed study of the two highest occupied orbitals (having a(1u) and b(1g) symmetries) is presented: the high energy resolution available for UPS measurements allowed resolving an extra feature assigned to vibrational stretching in the pyrrole rings. This observation, together with the computed DFT electron density distributions of the outer valence orbitals, suggests that the a(1u) orbital (the highest occupied molecular orbital) is mainly localized on the carbon atoms of pyrrole rings and it is doubly occupied, while the b(1g) orbital, singly occupied, is mainly localized on the Cu atom. Ab initio calculations of XPS and XANES spectra at carbon K edge of CuPc are also presented. The comparison between experiment and theory revealed that, in spite of being formally not equivalent, carbon atoms of the benzene rings experience a similar electronic environment. Carbon K-edge absorption spectra were interpreted in terms of different contributions coming from chemically shifted C 1s orbitals of the nonequivalent carbon atoms on the inner ring of the molecule formed by the sequence of CN bonds and on the benzene rings, respectively, and also in terms of different electronic distributions of the excited lowest unoccupied molecular orbital (LUMO) and LUMO+1. In particular, the degenerate LUMO appears to be mostly localized on the inner pyrrole ring.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA