Amorphous-Phase-Mediated Crystallization of Ni Nanocrystals Revealed by High-Resolution Liquid-Phase Electron Microscopy

Abstract

Nonclassical features of crystallization in solution have been recently identified both experimentally and theoretically. Especially, amorphous phase-mediated pathway is found in various systems of crystallization as an important route, different from classical nucleation and growth model. Here, we utilize high-resolution in-situ transmission electron microscopy with graphene liquid cells to study amorphous phase-mediated formation of Ni nanocrystals. An amorphous phase is precipitated in the initial stage of the reaction. Within the amorphous particles, crystalline domains nucleate and eventually form nanocrystals. In addition, unique crystallization behaviors, such as formation of multiple domains and dislocation relaxation, are observed in amorphous phasemediated crystallization. Theoretical calculations confirm that surface interactions can induce amorphous precipitation of metal precursors, which is analogous to the surface-induced amorphous-tocrystalline transformation occurring in biomineralization. Our results imply that an unexplored nonclassical growth mechanism is important for the formation of nanocrystals. Crystallization in liquid media is ubiquitous phenomena and is fundamental to understanding the formation of many materials including colloids, biominerals, and nanocrystals. 1 In the classical

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Room-temperature formation of CdS magic-size clusters in aqueous solutions assisted by primary amines

“…The multistep model, designated by nonclassical nucleation theory, accounts for the presence of intermediates in the pre-nucleation stage . Such intermediates have been illustrated in several materials systems including calcium-based inorganics [4][5][6][7][8] , organics [9][10][11] , polymers [12][13][14] , metals [15][16][17] , and semiconductor quantum dots (QDs) [18][19][20][21][22][23][24][25][26][27][28] .…”

Liquid phase transmission electron microscopy for imaging of nanoscale processes in solution

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