| AVS 62nd International Symposium & Exhibition | |
| In-Situ Spectroscopy and Microscopy Focus Topic | Tuesday Sessions |
| Session IS+AS+SA+SS-TuM |
| Session: | In-situ Studies of Solid-liquid Interfaces |
| Presenter: | Juan Yao, Pacific Northwest National Laboratory |
| Authors: | J. Yao, Pacific Northwest National Laboratory X. Sui, Pacific Northwest National Laboratory D. Lao, Pacific Northwest National Laboratory Y. Zhou, Pacific Northwest National Laboratory S. Nune, Pacific Northwest National Laboratory D. Heldebrant, Pacific Northwest National Laboratory Z. Zhu, Pacific Northwest National Laboratory X.-Y. Yu, Pacific Northwest National Laboratory |
| Correspondent: | Click to Email |
A vacuum compatible microfluidic reactor, SALVI (System for Analysis at the Liquid Vacuum Interface) was employed for in situ chemical imaging of switchable ionic liquids (SWILs) using time-of-flight secondary ion mass spectrometry (ToF-SIMS). A model SWIL system consisting of 1,8-diazabicycloundec-7-ene (DBU) and 1-hexanol with CO2 gas to change solvent polarity was selected. A series of ionic liquids with different CO2 loading was analyzed. Spatial chemical differences were observed within the same ionic liquid, indicating inhomogeneity of the ionic liquid. Spectral principal component analysis (PCA) was conducted using both positive and negative ToF-SIMS data. Clear distinctions were observed among SWILs of different CO2 loadings. The loading plots strongly indicate that fully loaded SWILs share similar spectral components as those of the non-loaded Ils. This finding confirms the hypothesis of the biphasic structure in the fully loaded IL predicated by molecular dynamic simulation and presents the first physical evidence of the liquid microenvironment of IL determined by liquid ToF-SIMS. Various ion pairs were also observed in addition to the known SWIL chemistry of the DBU and 1-hexanol system, indicating the complexity of the ionic liquid previously unknown. The vacuum compatible microchannel in SALVI provides a new way to study ionic liquids in vacuum by sensitive surface techniques. Our approach directly visualized spatial and chemical heterogeneity within the SWILs by dynamic liquid ToF-SIMS for the first time.