Related Experiment Video
Updated: Jun 13, 2025
Characterization of Nanocrystal Size Distribution using Raman Spectroscopy with a Multi-particle Phonon Confinement Model
Published on: August 22, 2015
Anion Size Controls Cation Wigner Crystal-Like Structures at Silica Interfaces
Ho Hong Chau1, Hua Li1,2, Rob Atkin1
1School of Molecular Sciences, The University of Western Australia, Perth, Western Australia 6009, Australia.
None:
High-resolution atomic force microscopy (AFM) images reveal that anion size systematically controls the dimensions of cation Wigner crystal-like structures (WCLS) at silica-electrolyte interfaces. Calcium halide solutions (CaCl2, CaBr2, CaI2) at pH 10.5 form hexagonally close-packed Ca2+ structures with spacings of 3.6-3.8 Å (CaCl2), 4.8 Å (CaBr2), and 5.0-5.1 Å (CaI2). The CaCl2 spacing matches the Cl- diameter, suggesting direct Ca2+-Cl- contact, whereas Br- and I- systems show consistent 0.7-0.9 Å offsets above their ionic diameters, indicating partially hydrated states. This behavior reflects the balance between ionic charge density and hydration effects. The high charge density of Cl- enables strong Ca2+ interactions sufficient to displace hydration waters, while the lower charge densities of Br- and I- lead to less strong attractions with Ca2+ and partial hydration layers are preserved. These findings demonstrate how ion size and hydration control Stern layer ion organization, providing new insights into the electrical double layer structure.
More Related Videos
16:24Controlling the Size, Shape and Stability of Supramolecular Polymers in Water
Published on: August 2, 2012
08:54Vibrational Spectra of a N719-Chromophore/Titania Interface from Empirical-Potential Molecular-Dynamics Simulation, Solvated by a Room Temperature Ionic Liquid
Published on: January 25, 2020
Related Concept Videos
02:42Ionic Crystal Structures
Most monatomic ions behave as charged spheres, and their attraction for ions of opposite charge is the same in every direction. Consequently, stable structures for ionic compounds result (1) when ions of one charge are surrounded by as many ions as possible of the opposite...
02:54Trends in Lattice Energy: Ion Size and Charge
02:54Molecular and Ionic Solids
Molecular Solids
Molecular crystalline solids, such as ice, sucrose (table sugar), and iodine, are solids that are composed of neutral molecules as their constituent units. These molecules are held together by weak intermolecular forces such as London dispersion forces, dipole-dipole interactions, or hydrogen bonds, which...
03:10Ionic Radii
02:58Crystal Field Theory - Octahedral Complexes
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
02:46Crystal Field Theory - Tetrahedral and Square Planar Complexes
Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than the dxy,...