RESUMO
Codeposition of two molecular species [copper phtalocyanine (CuPc, donor) and perfluoropentacene (PFP, acceptor)] on noble metal (111) surfaces leads to the self-assembly of an ordered mixed layer with a maximized donor-acceptor contact area. The main driving force behind this arrangement is assumed to be the intermolecular C-H ⯠F hydrogen-bond interactions. Such interactions would be maximized for a coplanar molecular arrangement. However, precise measurement of molecule-substrate distances in the molecular mixture reveals significantly larger adsorption heights for PFP than for CuPc. Most surprisingly, instead of leveling to increase hydrogen-bond interactions, the height difference is enhanced in the blends as compared to the heights found in single-component CuPc and PFP layers. The increased height of PFP in mixed layers points to an overall reduced interaction with the underlying substrate, and its influence on electronic properties like the interface dipole is investigated through work function measurements.
RESUMO
In-plane dislocation networks arise in both inorganic and organic films as a way of relieving the elastic strain that builds up at the substrate interface. In molecule/surface systems, supramolecular interactions are weak and more complex (compared to the atomic bonds in inorganic films), and their interplay with molecule-substrate interactions is very subtle, making it difficult to single out the driving force for a nanoscale dislocation pattern. On the basis of a combined experimental and theoretical work, we here show that periodic dislocations in a molecular PFP film are mainly driven by the optimization of molecule-substrate interactions. Compared to inorganic networks however, it implies a much lower energy imbalance, allowing a thermally induced transition from a low-energy strain dislocation pattern to a high-energy incommensurate moiré.
RESUMO
Metal-organic interfaces based on copper-phthalocyanine monolayers are studied in dependence of the metal substrate (Au versus Cu), of its symmetry [hexagonal (111) surfaces versus fourfold (100) surfaces], as well as of the donor or acceptor semiconducting character associated with the nonfluorinated or perfluorinated molecules, respectively. Comparison of the properties of these systematically varied metal-organic interfaces provides new insight into the effect of each of the previously mentioned parameters on the molecule-substrate interactions.
Assuntos
Cobre/química , Indóis/química , Ouro/química , Halogenação , Isoindóis , Membranas Artificiais , Modelos Moleculares , Estrutura Molecular , Tamanho da Partícula , Teoria Quântica , Propriedades de SuperfícieRESUMO
Los bomberos constituyen una población especialmente sensible a los factores de estrés y a sufrir sus consecuencias, por ello cobra un mayor sentido la importancia de la adaptación entre los recursos del individuo y las demandas del entorno, máxime cuando estas demandas son impredecibles, poco estructuradas y cualitativamente significativas. En el siguiente trabajo se presentan los resultados obtenidos tras administrar un instrumento de evaluación específico de las estrategias de afrontamiento a una muestra de este colectivo. El instrumento fue elaborado por el equipo investigador y proporciona una valoración del empleo de las diferentes estrategias de afrontamiento ante las situaciones de emergencia a las que se enfrenta este colectivo profesional. Los resultados obtenidos ponen de manifiesto la especificidad del estrés laboral, es decir, la existencia de perfiles de estrés específicos según grupos profesionales (modulados a su vez por variables personales del propio individuo) y, en consecuencia, la necesidad de diseñar instrumentos que permitan evaluar esta realidad. Igualmente, tras el análisis de los resultados se observa que entre las estrategias más utilizadas destacan la acción para resolver un problema, el análisis lógico y la búsqueda de apoyo, y entre las menos utilizadas la descarga emocional y la evitación cognitiva (AU)
