Dresden 2014 – scientific programme

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O: Fachverband Oberflächenphysik

O 36: Posters: Bio/organic Molecules on Surfaces, Graphene, Solid/liquid interfaces, Metal Substrates, Electronic Structure Theory

O 36.61: Poster

Tuesday, April 1, 2014, 18:30–22:00, P1

Total Internal Reflection Ellipsometry to detect ultrathin adsorbed films — •Lei Wang, Igor Siretanu, Michèl Duits, and Frieder Mugele — Physics of Complex Fluids, MESA+ Institute for Nanotechnology, University of Twente P.O. Box 217, 7500 AE Enschede, The Netherlands

To understand the adsorption/desorption of polar components of crude oil (model "asphaltene") onto polar (model "rock") substrates, is of great importance for optimizing the enhanced oil recovery (EOR) process via low salinity water flooding. However, much is still unknown from the molecular aspects about this process, and many components have to been screened. Total Internal Reflection Ellipsometry (TIRE) is capable of detecting ions or small molecules adsorbed at solid-liquid interfaces. In this work, the TIRE setup integrated with combinatorial microfluidics, enables parallel measurements on one substrate, making it a fast screening technique. Detection limit of this setup is 0.2 ng/cm2, and the sensitivity is demonstrated via the adsorption of Ca2+ at silica-water interfaces. Experimental evidences show that these adsorbed calcium ions enable the adsorption of Hexanoic Acid (HA), and the adsorbed HA film desorbs gradually when decreasing the salinity of flooding solutions, which is in consistent with the observations in EOR.