Concentration Gradients in Evaporating Binary Droplets Probed by Spatially Resolved Raman and NMR Spectroscopy
Abstract
Understanding the evaporation process of binary sessile droplets is essential for optimizing various technical processes, such as inkjet printing or heat transfer. Liquid mixtures whose evaporation and wetting properties may differ significantly from those of pure liquids are particularly interesting. Concentration gradients may occur in these binary droplets. The challenge is to measure concentration gradients without affecting the evaporation process. Here, spectroscopic methods with spatial resolution can discriminate between the components of a liquid mixture. We show that confocal Raman microscopy and spatially resolved nuclear magnetic resonance (NMR) spectroscopy can be used as complementary methods to measure concentration gradients in evaporating 1-butanol/1-hexanol droplets on a hydrophobic surface. Deuterating one of the liquids allows analysis of the local composition through the comparison of the intensities of the CH and CD stretching bands in Raman spectra. Spatially resolved NMR spectroscopy is used to measure the composition at different positions of the droplet. Confocal Raman and spatially resolved NMR experiments show the presence of a vertical concentration gradient as the 1-butanol/1-hexanol droplet evaporates.
Keywords
Cite
@article{arxiv.2106.15447,
title = {Concentration Gradients in Evaporating Binary Droplets Probed by Spatially Resolved Raman and NMR Spectroscopy},
author = {Alena K. Bell and Jonas Kind and Maximilian Hartmann and Benjamin Kresse and Mark V. Hoefler and Benedikt B. Straub and Guenter K. Auernhammer and Michael Vogel and Christina M. Thiele and Robert W. Stark},
journal= {arXiv preprint arXiv:2106.15447},
year = {2022}
}