Ion complexation waves emerge at the curved interfaces of layered minerals

Abstract

Visualizing hydrated interfaces is of widespread interest across the physical sciences and is a particularly acute need for layered minerals, whose properties are governed by the structure of the electric double layer (EDL) where mineral and solution meet. Here, we show that cryo electron microscopy and tomography enable direct imaging of the EDL at montmorillonite interfaces in monovalent electrolytes with ångstrom resolution over micron length scales. A learning-based multiple-scattering reconstruction method for cryo electron tomography reveals ions bound asymmetrically on opposite sides of curved, exfoliated layers. We observe conserved ion-density asymmetry across stacks of interacting layers in cryo electron microscopy that is associated with configurations of inner- and outer-sphere ion-water-mineral complexes that we term complexation waves. Coherent X-ray scattering confirms that complexation waves propagate at room-temperature via a competition between ion dehydration and charge interactions that are coupled across opposing sides of a layer, driving dynamic transitions between stacked and aggregated states via layer exfoliation.

Robotic Pendant Drop: Containerless Liquid for μs-resolved, AI-executable XPCS

“…When certain conditions are met, complex fluids undergo phase separations, forming structures at mesoscopic length scales which are responsible for orders-of-magnitude changes in material properties, e.g. opacity 2,3 , diffusivity 4 , viscoelasticity 5 , and conductivity 6,7 . Precise control of the dynamic pathway of these mesoscopic structures can therefore lead to materials with tunable and even rewritable properties, offering exciting opportunities in numerous material science advances such as neuromorphic computing 8 and targeted drug delivery 9 that rely on programmable and switchable material properties with large on/off ratios.…”

Cooperative Lithium Sorption in Doped Layered Double Hydroxides Is Modulated by Colloidal (Dis)Assembly

“…Transition states between the planar and scrolled particles were observed in microscopic proximity to both of these structures throughout the suspension in hundreds of separate and specific instances (Figures and S2–S4), strongly suggesting that plates and scrolls dynamically interconvert by (un)­rolling. The process of (un)­rolling involves curvature that develops in response to asymmetric bending strain across the layers, which may be driven by heterogeneous ion exchange between layers with different degrees of misalignment, different extents of exchange (i.e., chemical heterogeneity), or different interfacial hydration states. − Furthermore, particle dimensions change dramatically as layers (un)­roll. Scrolls with lengths of hundreds of micrometers coexist with layers whose maximum dimension does not exceed a few nanometers, suggesting that scrolls (dis)­assemble from smaller plate-like units.…”

“…Importantly, the Fourier components from the 2D projection images in Figure 2b−e, such as the 4.38 Å lattice parameter in Figure 2c, are the result of diffraction phenomena that encode atomic structural information. The multi-defocus tilt series scheme 19,27,28 that was employed to reconstruct 3D volumes (as discussed in Experimental Methods) allows for the direct determination of lattice positions, free of encoded phase inversion effects. Therefore, this scheme provides a clearer picture of the true stacking sequence of Fe-LDH layers.…”

Applications of Transmission Electron Microscopy in Phase Engineering of Nanomaterials

“…Advanced image alignment methods and robust algorithms have been developed, enabling the implementation of electron tomography with fewer projections , and pushing the achievable 3D resolution down to subnanometer level. − It is important to note that (S)­TEM images can contain nonlinear signals such as diffraction contrast and Fresnel fringes, which violate the projection requirement of tomography. This can result in the formation of artifacts during reconstruction.…”