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Issue 14, 2019
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Unravelling the growth mechanism of the co-precipitation of iron oxide nanoparticles with the aid of synchrotron X-Ray diffraction in solution

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Abstract

Co-precipitation is the most ubiquitous method for forming iron oxide nanoparticles. For a typical co-precipitation synthesis, the pH of a ferrous and/or ferric ion solution is increased via the addition of a base. The latter can be added either slowly (a steady addition over either minutes or hours) or fast (a one-time addition) resulting in an abrupt increase in the pH. However, understanding the mechanism of particle formation is still lacking, which limits the reproducibility of the co-precipitation reaction due to intermediate phases still being present in the final product. In this work, we study in detail a co-precipitation synthesis with an abrupt increase in pH via the addition of sodium carbonate. Fast and reproducible mixing at defined precursor and base solution temperatures was achieved utilising a flow reactor. Transmission electron microscopy, electron diffraction and room temperature 57Fe Mössbauer spectroscopy showed a distinct transition from an amorphous ferrihydrite phase to a mixture of magnetite-maghemite (Fe3O4/γ-Fe2O3). Synchrotron X-ray diffraction revealed the initial formation of crystalline iron hydroxide carbonate (green rust) plates occurring before the Fe3O4/γ-Fe2O3 appeared. The ferrihydrite particles increase in size over time as the proportion of iron hydroxide carbonate plates are re-dissolved into solution, until the ferrihydrite particles crystallise into Fe3O4/γ-Fe2O3.

Graphical abstract: Unravelling the growth mechanism of the co-precipitation of iron oxide nanoparticles with the aid of synchrotron X-Ray diffraction in solution

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Publication details

The article was received on 17 Jan 2019, accepted on 08 Mar 2019 and first published on 08 Mar 2019


Article type: Paper
DOI: 10.1039/C9NR00531E
Nanoscale, 2019,11, 6620-6628
  • Open access: Creative Commons BY license
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    Unravelling the growth mechanism of the co-precipitation of iron oxide nanoparticles with the aid of synchrotron X-Ray diffraction in solution

    A. P. LaGrow, M. O. Besenhard, A. Hodzic, A. Sergides, L. K. Bogart, A. Gavriilidis and N. T. K. Thanh, Nanoscale, 2019, 11, 6620
    DOI: 10.1039/C9NR00531E

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