Theoretical Modeling and Spectroscopical Characterisation of Molecular Organic Materials
The present project will be dedicated to the study of novel organic molecular materials with biotechnological applications in different fields ranging from heterogeneous catalysis to dye sensitized and polymer solar cells, and to gas sensors and molecular magnets. The focus will be the modeling and theoretical generation of soft X-ray spectra by means of Density Functional Theory (DFT) aiming at obtaining a fundamental description of the electronic and morphological structures of these systems at the atomic/molecular level. This will be achieved by the computation of soft X-ray spectra like X-ray Absorption and Emission Spectroscopy (XAS and XES), Photo-Electron Spectroscopy (PES), as well as by Scanning Tunneling Microscopy (STM). Among the most remarkable characteristics of these techniques there are the elemental selectivity, and the selection rules involved in the excitation/de-excitation mechanisms, which provide specific information about symmetry and character of the electronic orbitals. The theoretical modeling plays a crucial role, being able to provide a detailed description at the atomic/molecular level of the experiments. Electronic structure calculations for the simulation of the spectra will be performed in plane wave and in gaussian formalism. A class of targets for these studies are organic macrocycles like metal phthalocyanine or porphyrins and their derivatives adsorbed on semiconductor surfaces, or double decker Pc's molecules. For practical applications, these molecules need to be deposited on a substrate, where they in most cases organize in an ordered fashion (self assembling). The understanding of the substrate/adsorbate interaction, meaning how it affects the electronic and geometrical structure of the adsorbed molecules, is clearly one of the determining factors to understand the functionality of the molecular materials, i.e. their chemical and physical properties. Part of the project is dedicated to the modeling of the adsorption of organic molecules on different types of substrates and to study the interactions that take place in the interlayer region between the organic films and the surfaces. For example thin films of Pc's in the form of films are important candidates for applications as gas sensors, specifically the double-decker rare earth phthalocyanines (or bisphthalocyanines derivatives), formed by sandwich Pc’s structures with an atom of the lanthanide group in between, which can be arranged in a sensing layer on a substrate. The interaction between the molecules and different gases will be studied, as well as the characteristics of the double decker rare earth Pc films, for which many basic aspects are still to be understood. Another important target of the project will be fullerene type materials which are used as acceptors in organic photovoltaics. Moreover, part of the project will be dedicated to the study of organic molecules in aqueous solutions. Organic molecules have a tendency to build up hydrogen bond nets in liquid solution, influencing the way they assemble together and their behaviour. This can be studied in detail by analysing the structure of organic molecules in liquid solutions, which is the environment where most of the biological processes occur.