Real time imaging of two-dimensional iron oxide spherulite nanostructure formation

Wenjing Zheng, Matthew R. Hauwiller, Wen I. Liang, Colin Ophus, Peter Ercius, Emory M. Chan, Ying Hao Chu, Mark Asta, Xiwen Du*, A. Paul Alivisatos, Haimei Zheng

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

The formation of complex hierarchical nanostructures has attracted a lot of attention from both the fundamental science and potential applications point of view. Spherulite structures with radial fibrillar branches have been found in various solids; however, their growth mechanisms remain poorly understood. Here, we report real time imaging of the formation of two-dimensional (2D) iron oxide spherulite nanostructures in a liquid cell using transmission electron microscopy (TEM). By tracking the growth trajectories, we show the characteristics of the reaction front and growth kinetics. Our observations reveal that the tip of a growing branch splits as the width exceeds certain sizes (5.5–8.5 nm). The radius of a spherulite nanostructure increases linearly with time at the early stage, transitioning to nonlinear growth at the later stage. Furthermore, a thin layer of solid is accumulated at the tip and nanoparticles from secondary nucleation also appear at the growing front which later develop into fibrillar branches. The spherulite nanostructure is polycrystalline with the co-existence of ferrihydrite and Fe3O4 through-out the growth. A growth model is further established, which provides rational explanations on the linear growth at the early stage and the nonlinearity at the later stage of growth. [Figure not available: see fulltext.].

Original languageEnglish
Pages (from-to)2889-2893
Number of pages5
JournalNano Research
Volume12
Issue number11
DOIs
StatePublished - Nov 2019

Keywords

  • in situ TEM
  • iron oxide
  • liquid cell transmission electron microscopy (TEM)
  • spherulite nanostructures

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