Thursday, March 29, in ETRL 101
Refreshments served in ETRL 119 at 10:30 a.m.
Dr. Xiao-Ying Yu
Earth and Biological Sciences Directorate, PNNL
Chemical Mapping of the Evolving Material Interface in Liquids
Abstract
A vacuum compatible microfluidic reactor, SALVI (System for Analysis at the Liquid Vacuum Interface) was employed to study the evolving material interface of particles in liquids. Three case studies will be provided in this talk. The first study is a model switchable ionic liquid (SWIL) system consisting of 1,8-diazabicycloundec-7-ene (DBU) and 1-hexanol. When CO2 gas is added to the DBU and 1-hexanol mixture, the solvent polarity is known to change. 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. Clear distinctions were observed among SWILs with 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. Second, we investigated the chemical structural evolution of the metal organic framework (MOF) formed over different lengths of times using in situ liquid SIMS imaging. Zn-MOF-74 is the model system. Zn-acetate is the metal center and DHTA is the ligand linker in a DMF solvent. MOFs in solvent are analyzed to ascertain the growth mechanism and the evolution of the MOF structure. Ex situ XRD, HeIM, and TEM are used to characterize MOFs to complement the in situ analysis. MOF surface area measurement and adsorption and desorption testing illustrate that the MOF pore size becomes smaller over time yet the overall adsorption/desorption properties mprove due to the increased density of the pores. Lastly, large colloidal boehmite particles of importance in nuclear engineering and processing are studied under a variety of pH conditions. Particle morphological changes are observed using in situ liquid SEM. Moreover, the solvent and solute compositions are found to relate to the pH conditions, providing direct evidence of the solvation effect via submicron chemical mapping. The vacuum compatible microchannel in SALVI offers an Innovative perspective to study the evolving liquid-liquid and solid-liquid interface. This approach allows direct visualization of the spatial and chemical heterogeneity in complex liquids by dynamic ToF-SIMS complemented with other imaging and spectroscopy techniques and provides new insights for improved understanding of the evolving material interface.
Biography
Dr. Yu was trained as a physical chemist and kineticist at the University of Michigan, Ann Arbor, MI. She did her postdoctoral research at Brookhaven National Laboratory and Colorado State University. She has been a senior scientist at Pacific Northwest National Laboratory since 2006. She has led the development of a novel mesoscale imaging tool based on microfluidics at PNNL since 2009, which has resulted in three patents, a prestigious R&D 100 award, and a Federal Laboratory Consortium Technology Transfer Excellence Award. She has developed new concepts in aerosol sampling, led and participated in many field studies for in situ measurements of aerosols. Dr. Yu is the chair of the DOE chemical exposure working group; and leads the development of the chemical mixture methodology (CMM) for consequence assessment of toxic health effects since 2008. She was a member to the DOE Temporary Emergency Exposure Limit (TEEL) Advisory Group (TAG). Her recent research focuses on in situ mesoscale chemical imaging of soft materials in atmospheric, biology, energy, and material sciences using microfluidics.
