Small-Angle X-Ray Scattering of Ionic Liquids

Controlling the Intermediate Structure of an Ionic Liquid for f-Block Element Separations

“…After contact with TALSPEAK simulant containing Lu(NO 3 ) 3 (defined in detail in the Supporting Information), a representative Ln(III), the SANS data displayed a scattering profile revealing a new structural formation over the q-range of 0.01−0.5 Å −1 , while a significant increase of scattering intensity was also observed at q-ranges <0.005 Å −1 , indicative of large structures such as micelle aggregates (Figure 1a). Porod analysis 27 of the data from 0.025 to 0.15 Å −1 reveals a log− log slope of approximately 1, suggestive of a rodlike shape, 28,29 and the data can be well fitted over the range of 0.008−0.53 Å −1 by a cylindrical form factor possessing dimensions of 171 Å in length and 11.7 Å in radius (Table S1).…”

“…Additionally, data for the more concentrated Lu sample displayed a slope of −4.5 over low q . This negative deviation from Porod’s law reveals a nonideal two-phase structure with continuous variation at the phase boundary, indicative of a diffuse interfacial layer at the exterior of the aggregate structure. ,, …”

“…The data from the particle scattering region, below q of 0.005 Å –1 , displays a slope of 3.5, indicating a rough interface consistent with surface fractal formation. , Unfortunately, due to instrument limitations in q range and the reciprocal relationship between q and R g , the scattering intensity below 0.005 Å –1 cannot be definitively assigned to physical structure and limited information can be gleaned regarding the volume parameters of this inhomogeneity . A coarse approximation from inspection of the q -range reveals aggregates greater than 500 Å in dimension.…”

“…28,29 Unfortunately, due to instrument limitations in q range and the reciprocal relationship between q and R g , the scattering intensity below 0.005 Å −1 cannot be definitively assigned to physical structure and limited information can be gleaned regarding the volume parameters of this inhomogeneity. 29 A coarse approximation from inspection of the q-range reveals aggregates greater than 500 Å in dimension. In contrast, SANS data of the IL system prior to contact with TALSPEAK simulant or for the constituent ILs do not display significant scattering features at any spatial range (Figure S1).…”

“…This negative deviation from Porod's law reveals a nonideal two-phase structure with continuous variation at the phase boundary, indicative of a diffuse interfacial layer at the exterior of the aggregate structure. 29,36,37 Although analysis of the SANS data suggests extraction of metal ions does not influence the microstructure, X-ray absorption fine structure (XAFS) spectroscopy was collected at the Lu L III -edge (9244 eV) to investigate IL samples contacted with TALSPEAK simulant containing 0.01 and 0.025 M Lu(NO 3 ) 3 . Comparison of the two data sets reveals that although metal concentration affects the extent of aggregate formation, the local metal environment appears largely unchanged (Figure 2e).…”