In Situ Live Observation of Nucleation and Dissolution of Sodium Chlorate Nanoparticles by Transmission Electron Microscopy

Abstract

The formation of crystals from solution requires the initial self-assembly of units of matter into stable periodic structures reaching a critical size. The early stages of this process , called nucleation, are very difficult to visualize. Here we describe a novel method that allows real time observation of the dynamics of nucleation and dissolution of sodium chlorate clusters in an ionic liquid solution using in situ transmission electron microscopy. Using ionic liquids as solvent circumvents the problem of evaporation and charging, while the nucleation frequency was reduced by using saturated solutions. We observe simultaneous formation and dissolution of prenucleation clusters, suggesting that high-density fluctuations leading to solid cluster formation exist even under equilibrium conditions. In situ electron diffraction patterns reveal the simultaneous formation of crystalline nuclei of two polymorphic structures, the stable cubic phase and the metastable monoclinic phase, during the earliest stages of nucleation. These results demonstrate that molecules in solution can form clusters of different polymorphic phases independently of their respective solubility.

Nucleation of metastable aragonite CaCO 3 in seawater

“…Quantifying how solution environments modify the relative surface energies between competing polymorphs is therefore foundational to predicting synthesis pathways toward polymorphs with desired materials properties. Recent high-resolution in situ microscopy techniques have yielded unprecedented observations of nucleation dynamics between competing polymorphs (12,13), and molecular dynamics simulations of nucleation have identified structural motifs of bulk metastable phases on the surfaces of nuclei for Lennard-Jones solids (14) and ice (15). However, the surface energy of nuclei in solution, and more subtly, the change of surface energy with solution chemistry, has remained inaccessible.…”

In situ XAFS Study of Palladium Electrodeposition at the Liquid/Liquid Interface

“…Oscillatory deposition or dissolution processes have previously been observed in electrochemical systems where one parameter (potential/current/resistance) is free to vary M a n u s c r i p t during the reaction [36,37]. Likewise in chemical systems, the reversible formation of metastable pre-nucleation clusters have been observed previously by XAFS and TEM [38][39][40].…”

A general strategy for colloidal stable ultrasmall amorphous mineral clusters in organic solvents

“…11–13 Pre-nucleation clusters have been found either experimentally or by modelling the nucleation of calcium carbonate (CaCO 3 ), 11,14 calcium phosphate, 15,16 magnetite, 17 silica, 18 amino acids, 19 quantum dots, 20,21 YVO 4 , 22 NaClO 3 , 23 1,3,5-tris(4-bromophenyl)benzene, 24 and many more. Analytical ultracentrifugation (AUC) measurements confirmed the presence of pre-nucleation clusters even in salts of simple monovalent ions like NaCl and LiI.…”