Nanopores in hematite (α-Fe2O3) nanocrystals observed by electron tomography
Nanopores in hematite (α-Fe2O3) nanocrystals observed by electron tomography
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DOI：
10.2138/am.2013.4120
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发表时间：
2013-01-01
影响因子：
3.1
通讯作者：
Hochella, Michael F., Jr.
中科院分区：
文献类型：
--
作者：
Echigo, Takuya;Monsegue, Niven;Hochella, Michael F., Jr.
我们报告的内部结构特征的菱形纳米晶体的赤铁矿（α-Fe 2 O3），特别是纳米级孔（nanopores）在这些晶体内观察到的高角度环形暗场扫描透射电子显微镜断层扫描的第一个表征。对赤铁矿纳米晶体内部结构的三维观察表明，纳米孔的形成是由于在结晶不良的前体[水铁矿的聚集体：Fe8.2O8.5（OH）（7.4）中心点3 H（2）O]的转化过程中固体体积的大幅减少，这导致在晶界之间形成孔。这种形成机制不同于以前报道的那些，如空心源于螺旋位错。我们还讨论了在抗坏血酸溶液中的赤铁矿纳米晶体的溶解实验，在其中，我们证明了纳米孔是溶解的反应位点，并通过优先蚀刻扩大。我们的研究结果是至关重要的，以了解某些晶体形态，内部结构，缺陷，和反应位点发生在纳米晶体形成从一个不良的结晶前体。
We report the first characterization of the internal structural features within rhombohedral nano-crystals of hematite (alpha-Fe2O3), 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)center dot 3H(2)O], 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.