TY - JOUR
T1 - Nanopores in hematite (α-Fe2O3) nanocrystals observed by electron tomography
AU - Echigo, Takuya
AU - Monsegue, Niven
AU - Aruguete, Deborah M.
AU - Murayama, Mitsuhiro
AU - Hochella, Michael F.
N1 - Funding Information:
Grants from the U.S. Department of Energy (DE-FG02-06ER15786) and Virginia Tech’s Nanoscale Characterization and Fabrication Laboratory provided financial support for this study. T.E. acknowledges supports from the Japan Society for the Promotion of Science, Research Fellowships for Young Scientists (PD20-1531), Japan Excellent Young Researcher Overseas Visit Program, Grant-in-Aid for Research Activity Start-up (no. 23840049), and Fukada Geological Institute (2011 no. 7). D.M.A. acknowledges support from National Science Foundation Grant DEB-0610373 (Postdoctoral Fellowship) during part of this work. This manuscript was completed during her current service at NSF. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation. We gratefully acknowledge the assistance of Madeleine Schreiber (Virginia Tech) in providing the anaerobic chamber used for our experiments. The authors are indebted to Martin Kunz, American Mineralogist Editor, and peer reviews from Benjamin Gilbert and an anonymous source.
PY - 2013/1
Y1 - 2013/1
N2 - We report the first characterization of the internal structural features within rhombohedral nanocrystals of hematite (α-Fe2O 3), specifically nanoscale pores (nanopores) within these crystals observed by high-angle annular dark-field scanning transmission electron microscopy tomography. Three-dimensional observations of the internal structure of hematite nanocrystals suggest that the nanopores are formed due to a large reduction in solid volume during the transformation of a poorly crystalline precursor [aggregates of ferrihydrite: Fe8.2O8.5(OH) 7.4·3H2O], which results in the formation of pores between grain boundaries. This formation mechanism is different from those previously reported, such as hollow cores originating from screw dislocations. We also discuss dissolution experiments of the hematite nanocrystals in ascorbic acid solution, in which we demonstrated that the nanopores are reactive sites for dissolution and enlarged by preferential etching. Our findings are of fundamental importance to understanding how certain crystal morphologies, internal structures, defects, and reactive sites occur in nanocrystals formed from a poorly crystalline precursor.
AB - We report the first characterization of the internal structural features within rhombohedral nanocrystals of hematite (α-Fe2O 3), specifically nanoscale pores (nanopores) within these crystals observed by high-angle annular dark-field scanning transmission electron microscopy tomography. Three-dimensional observations of the internal structure of hematite nanocrystals suggest that the nanopores are formed due to a large reduction in solid volume during the transformation of a poorly crystalline precursor [aggregates of ferrihydrite: Fe8.2O8.5(OH) 7.4·3H2O], which results in the formation of pores between grain boundaries. This formation mechanism is different from those previously reported, such as hollow cores originating from screw dislocations. We also discuss dissolution experiments of the hematite nanocrystals in ascorbic acid solution, in which we demonstrated that the nanopores are reactive sites for dissolution and enlarged by preferential etching. Our findings are of fundamental importance to understanding how certain crystal morphologies, internal structures, defects, and reactive sites occur in nanocrystals formed from a poorly crystalline precursor.
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U2 - 10.2138/am.2013.4120
DO - 10.2138/am.2013.4120
M3 - Article
AN - SCOPUS:84872051734
SN - 0003-004X
VL - 98
SP - 154
EP - 162
JO - American Mineralogist
JF - American Mineralogist
IS - 1
ER -