Formation of Spinel Nanotubes
Abstract
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M. Zacharias, H.J. Fan, K. Nielsch, Y. Yang, D. Hesse, and M. Knez
Core-Shell nanowires can be used to prepare nanotubes. In our recent work we demonstrated the use of single crystalline ZnO nanowires with a shell of amorphous Al2O3. After spinel-forming interfacial solid-state reaction of the core–shell nanowires involving the Kirkendall effect we were able to demonstrate the formation of single crystalline ZnAl2O4 spinel nanotubes with a total diameter of 40 nm and a wall thickness of 10 nm with µm length. Even more, the formation of 3-dimensional hollow structures is possible.
For details the reader is referred to:
H. J. Fan etal., Nature Materials 5 (8), 627-631 (2006).
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MAX PLANCK SOCIETY: From Nanowires to Nanotubes
Transformation of core–shell nanowires to nanotubes by means of the Kirkendall effect. a, TEM image of an example ZnO–Al2O3 core–shell nanowire. b–e, Scanning electron microscopy (b) and TEM (c–e) images of ZnAl2O4 spinel nanotubes. Owing to their hollow interiors, the central part of the nanotubes becomes more transparent to the electron beam than the outer part, in contrast to the structure before annealing.
Microstructure and composition of the ZnAl2O4 spinel nanotubes. a,b, TEM images recorded from the body (a) and a region near the tip (b) of a nanotube. In both cases, the contrast clearly shows the hollow core and high crystallinity of the tube wall. The Au nanoparticle that catalysed the growth of the initial ZnO nanowire remains at the tip of the nanowire. Inset: an enlarged view of the tube wall in a. c, d, Atomic percentage (c) and intensity profile (d) of Zn, Al and O across one tube diameter
(inset in c). The atomic ratio of Zn:Al:O was nearly constant and averaged to be 1:1.6:6.7, in which the atomic percentage for oxygen was overestimated due to instrumental characteristics. e, Atomic-resolution TEM image of the tube wall showing the {111} and {220} planes of spinel ZnAl2O4.