OPPORTUNITIES IN SEPARATIONS SCIENCE USING ADVANCED SYNCHROTRON XRAY

OPPORTUNITIES IN SEPARATIONS SCIENCE USING ADVANCED SYNCHROTRON X-RAY METHODS G. BRIAN STEPHENSON Materials Science Division, Argonne National Laboratory A Research Agenda for a New Era in Separations Science August 22 -23, 2018, Washington, DC

OUTLINE • Introduction – Synchrotron X-ray Opportunities • Upgrades to sources • Examples of Current Synchrotron Studies in Separations Science • X-ray reflectivity, surface fluorescence, grazingincidence scattering, small-angle scattering • New Opportunities using Coherent X-ray Methods • Nanoscale dynamics using X-ray photon correlation spectroscopy (XPCS) 2

SYNCHROTRON X-RAY CAPABILITIES: SPECTROSCOPY, SCATTERING, IMAGING § X-ray Spectroscopy: – Photon energy matches atomic energy levels and gives chemical composition – Relevant methods: EXAFS, XANES, surface fluorescence (XFNTR) § X-ray Scattering: – Short wavelength allows the atomic structure to be precisely determined – Reflectivity, small-angle scattering (SAXS), pair distribution (PDF), grazing-incidence (GIXS and GISAXS); all can be resonant – New coherent methods (XPCS, CDI) § X-ray Imaging: – Large penetration depth of hard x-rays reveals internal structure – Many imaging modes: nanoprobe, phase contrast, coherent diffraction, . . . 3

OPPORTUNITY: LIGHT SOURCE UPGRADES Revolutionary new capabilities • Upgrades are occurring at all of the US X-ray light sources • The APS Upgrade will increase its brightness by 100 to 1000 X, as big a revolution as the original building of APS in 1996 • APS-U will turn on in 2023, and we are already planning and developing the new methods enabled: • photon correlation spectroscopy (XPCS) • nanometer x-ray probes • coherent x-ray imaging Brightness as a function of x-ray energy for the current APS and new NSLS-II sources, and the future APS Upgrade 4

EXAMPLE: RESONANT X-RAY REFLECTIVITY Adsorption of chlorometalate anions Resonant X-ray reflectivity provides the total metalate adsorption in Stern layer in addition to the total electron density profile with sub-nm resolution A. Uysal, W. Rock, B. Qiao, W. Bu, and B. Lin, J. Phys. Chem. C, 121(45), 25377, 2017 5

EXAMPLE: SURFACE X-RAY FLUORESCENCE Adsorption of chlorometalate anions X-ray fluorescence near total reflection (XFNTR) provides the total metalate adsorption both in Stern layer and in diffuse layer. A. Uysal, W. Rock, B. Qiao, W. Bu, and B. Lin, J. Phys. Chem. C, 121(45), 25377, 2017 6

EXAMPLE: GRAZING INCIDENCE X-RAY SCATTERING Adsorption of chlorometalate anions Grazing incidence x-ray scattering (GIXS) provides the information about in -plane packing and tilt structure of the extractants. A. Uysal, W. Rock, B. Qiao, W. Bu, and B. Lin, J. Phys. Chem. C, 121(45), 25377, 2017 7

EXAMPLE: COMBINING X-RAY STUDIES WITH SFG MEASUREMENTS Unique interfacial water structure Three different types of water molecules can be identified around a Pt. Cl 62 - complex adsorbed at a quaternary amine monolayer at the air/water interface by using VSFG and MD simulations. While x-rays provide information about the metal ions, SFG studies elucidate the interfacial water structure. W. Rock, B. Qiao, T. Zhou, A. Clark, 8 and A. Uysal, ar. Xiv: 1801. 06114, 2018

ADDITIONAL INFORMATION USING A COHERENT BEAM scattering sample with disorder (e. g. nanostructure in a liquid) • Incoherent Beam: Diffuse Scattering • Measures average two -point correlations, e. g. average size, spacing, anisotropy • Coherent Beam: Speckle • Speckle depends on exact nanostructure arrangement • In principle, contains complete structural information • Can observe equilibrium dynamics 9

X-RAY PHOTON CORRELATION SPECTROSCOPY (XPCS) transversely coherent X-ray beam t 1 sample t 2 monochromator Intensity auto-correlation function: t 3 1 “movie” of speckle recorded by CCD Ø Intensity fluctuations of the speckle pattern reflect sample dynamics. Ø Q dependence indicates nature of dynamics (e. g. diffusive, relaxational) Review of XPCS: O. Shpyrko, J. Synchr. Rad. 21, 1057 (2014) 10

XPCS ALLOWS STUDY OF EQUILIBRIUM DYNAMICS DOWN TO THE ATOMIC SCALE • Improvements in coherent flux and detector speed are moving XPCS studies into the length and time scale ranges needed to study dynamics of complex fluids Leheny, Curr. Opin. Colloid Interface Sci. 2012, 17, 3 11

CONVERGING EXPERIMENTS, SIMULATIONS, AND SEPARATIONS SCIENCE New territories in XPCS and MD cu rre nt fu tu r sig na e sig na l li m new detector limit it l li m it te io da ns to- m es op ha se s m ic el le s MD to-date detector limit MD w ds ne tho me Leheny, Curr. Opin. Colloid Interface Sci. 2012, 17, 3 12

INITIAL XPCS STUDY OF MICELLE DYNAMICS IN COMPLEX FLUID FOR ION SEPARATION Self-assembling reverse micelles of Ce(NO 3)3 in dodecane with malomamide extractant Ce phase diagram Ellis, Antonio, Langmuir 2012, 28, 5987 • • ■ ■ ■ ■ ■ SAXS provides good characterization of structure and phase behavior XPCS wlll reveal micelle aggregation dynamics 13

APPROACHING CRITICAL POINT BY CHANGING TEMPERATURE Power-law shape of SAXS extending to low Q is typical of critical fluctuations near a second-order transition I ~ Q -1. 7 Stephenson, Antonio, et al. unpublished 2018 14

WAVENUMBER DEPENDENCE OF FLUCTUATION CORRELATION TIME • Can observe correlation times of micelle clusters down to ~10 us • Further detector and source improvements will allow study of individual micelle dynamics at ~1 ns • Q dependence supports model of micelle aggregation as Tc is approached • Opens the way for combined SAXS, XPCS and MD studies of structure and dynamics of complex fluids used in separations ~ Q -3. 0 Stephenson, Antonio, et al. unpublished 2018 15

SUMMARY • Advanced synchrotron x-ray methods are already having and impact in separations science e. g. through studies of adsorption at interfaces and complex fluid structure • The revolutionary coherent x-ray and nanoprobe capabilities provided by new sources and detectors will extend these capabilities e. g. into fast dynamics in fluids and nanoscale imaging, providing new opportunities for separations science oil water Qiao, Muntean, Olvera de la Cruz, Ellis, Langmuir 2017, 33, 6135 16