We present a sandwich liquid-core waveguide for the study of the dynamic extraction of dye molecules by ionic liquid (IL). The incident light was introduced into the core of the IL phase directly via a fused silica prism to form total reflection at the IL/cladding interface. The changes in light intensity and absorbance spectra over time were monitored during the extraction process by maintaining an optical focus on the IL/water interface. The dynamic extraction of the dye Eriochrome Black-T (EBT) by the IL 1-n-butyl-3-methylimidazolium hexafluorophosphate (BmimPF<sub>6</sub>) at different concentrations and various pH conditions was investigated. The results indicated that the accumulation of the dye at the IL/water interface and the dynamic extraction of the dye into the IL phase both contributed to the increase in absorbance. The increased signal along with the increase in pH suggests that electrostatic interaction might be the main driving force for the extraction of EBT by BmimPF<sub>6</sub>, and the micro-circumstance provided by IL also has a decisive effect on the characteristics of the spectra recorded by the waveguide system.
Xuwei Chen, Atsushi Sakurazawa, Kiichi Sato, Kin-Ichi Tsunoda, and Jianhua Wang, "A Solid-Cladding/Liquid-Core/Liquid-Cladding Sandwich Optical Waveguide for the Study of Dynamic Extraction of Dye by Ionic Liquid BmimPF6," Appl. Spectrosc. 66, 798-802 (2012)