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O: Fachverband Oberflächenphysik

O 97: Wetting and Liquids at Interfaces and Surfaces I (joint session CPP/DY/O)

O 97.3: Vortrag

Donnerstag, 19. März 2020, 10:00–10:15, ZEU 255

Concentration measurements in binary liquids via Raman spectroscopy — •Alena K. Bell and Robert W. Stark — Physics of Surfaces, Materialwissenschaften, TU Darmstadt, Alarich-Weiss-Str. 16, 64287 Darmstadt, Deutschland

The optical measurement of concentration gradients in liquid mixtures plays a crucial role in understanding transport processes in various technical applications such as printing or medical technology. In particular Raman spectroscopy offers a direct approach to identify the substances and to quantify the concentration of the components in a binary liquid. In order to quantify concentration gradients confocal Raman spectroscopy can provide the necessary spatial and temporal resolution that is needed to monitor transport processes as they occur during the evaporation of binary droplets or during mixing processes in microchannels. To this end, chemically similar substances such as alcohols of different molecular weight need to be differentiated either through the analysis of the fingerprint region or through chemical labelling. However, using the weak Raman signals in fingerprint region reduces the temporal resolution drastically which makes chemical labelling much more convenient. We discuss the advantages and disadvantages of chemical labelling in order to discriminate spectroscopically between the components of a binary liquid. By using this approach concentration gradients can be calculated by comparing relative peak intensities and correlating these results with calibration curves. Thus, the temporal and spatial evolution of concentration gradients in binary mixtures of chemically similar fluids can be analysed.