Investigations of ionic liquid - solute systems by surface sensitive spectroscopic techniques - part of the initiative "Shaping micro- and macroscopic properties of ionic liquid-solute systems"

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We propose to investigate experimentally the molecular structure of the surface of ionic liquids with surface sensitive methods. The goals are to determine thermodynamic properties of ionic liquids by determining their surface structure and to validate the results of simulations. We are able to determine directly concentration depth profiles of liquid surfaces with the method neutral impact collision ion scattering spectroscopy (NICISS). The concentration depth profiles yield the surface excess of the different species. Knowing the surface tension and making use of the Gibbs equation the chemical potentials can be determined. The chemical potential is an information in general required for optimizing chemical processes. An important prerequisite for the investigations is the control of the cleanliness of the liquid surfaces. Surface sensitive methods are especially suitable for detecting the presence of surface active impurities. Measuring the surface tension of the investigated substances we will be able to gain data of systems with controlled cleanliness of the surface. Even though our project will be of general benefit for the entire priority program, it will be carried out in close cooperation between 4 groups. The project is an essential contribution for a further understanding of ionic liquid structure-property relationships in its own right, the four research groups will mutually benefit from participating in an interdisciplinary network of chemical engineers, physicists, and chemists. New methods of generating physico-chemical data are validated with existing methodology, and the large set of data obtained from ionic liquids of known purity is shared within the network, thus enabling the partners to dissect the results from a cross-section of science: fundamental and theoretical as well as technological and experimental.