Carbon Nanotubes DOI: 10.1002/anie.200902243 Observations of Chemical Reactions at the Atomic Scale: Dynamics of Metal-Mediated Fullerene Coalescence and Nanotube Rupture** Andrey Chuvilin,* AndreiN. Khlobystov,* Dirk Obergfell, Miroslav Haluska, Shihe Yang, Siegmar Roth, and Ute Kaiser* Single-walled carbon nanotubes (SWNTs), which are graph- itic tubular structures with single-atom-thick sidewalls and varying diameters, are effective containers for a wide variety of molecular species. [1–4] They are particularly suitable for study by transmission electron microscopy (TEM). [4] Chem- ical reactions between molecules inside nanotubes can be triggered by external stimuli (for example, the TEM electron beam), with the nanotube acting as a miniature reactor vessel, [5] thus potentially steering a chemical reaction along a new pathway towards new products. [6, 7] Nanotubes are often viewed as chemically inert containers. Although their surfaces can be involved in some chemical reactions, [8] the chemical reactivity of their interior has been considered to be very low. TEM is the only method that allows direct visualization and study of the molecules inside nanotubes. We are currently exploiting the capabilities of an aberration-corrected TEM, which can record atomic resolution images in a time much shorter than needed for the electron beam to promote structural transformations inside SWNTs. Under our imaging conditions, these transformations usually occur on a timescale of seconds, which enables us to capture atomic images of the intermediates. These images can then be combined into a movie to follow the chemical transformations as they happen. Both walls and interiors of SWNTs can be seen on TEM micrographs, such that the positions and orientations of the encapsulated molecules can be readily determined from the images (Figure 1 c). Accelerated electrons interact with the specimen and transfer their energy and momentum to the atoms of the specimen, causing knock-on damage, ionization, and/or heat-induced damage, the extent of which depends on the nature of the material. With this in mind, we carried out our TEM studies with an accelerating voltage of only 80 kV, which is well below the threshold for knock-on damage in carbon nanotubes (86 kV). [9] Under these conditions, the electron beam acts as an energy bath, promoting chemical transformations but not destroying the specimen, so that molecular dynamics and interactions can be observed in direct space at the atomic scale. It is not possible to measure the temperature of our nanotubes directly in TEM; however, provided that the nanotube has a good contact with the rest of the specimen (Supporting Information, Figure S2) the upper limit of heating by the electron beam is estimated to be 11 K above the temperature of the surroundings, [10] which is in good agreement with previous observations for nanotubes. [11] Figure 1. a) A single atom of dysprosium is encapsulated within a C 82 fullerene. The Dy 3+ atom interacts with the negatively charged carbon cage. b) Fullerenes inserted in the carbon nanotube line up in a chain. c) Aberration-corrected TEM image of Dy@C 82 inserted in the carbon nanotube. The dysprosium atoms can be seen as dark spots within the cages of fullerenes (except in the first and the second fullerenes, owing to fast rotation of these fullerenes). [*] Dr. A. Chuvilin, Prof. Dr. U. Kaiser Central Facility of Electron Microscopy University of Ulm, Albert Einstein Allee 11, 89069 Ulm (Germany) E-mail: andrey.chuvilin@uni-ulm.de ute.kaiser@uni-ulm.de Dr. A. N. Khlobystov School of Chemistry, University of Nottingham University Park, Nottingham NG7 2RD (UK) E-mail: andrei.khlobystov@nottingham.ac.uk Dr. D. Obergfell, Dr. M. Haluska, Dr. S. Roth Max Planck Institute for Solid State Research Heisenbergstrasse 1, 70569 Stuttgart (Germany) Dr. M. Haluska Micro- and Nano-Scale Engineering Eindhoven University of Technology (The Netherlands) Prof. Dr. S. Yang Department of Chemistry The Hong Kong University of Science and Technology (China) Dr. S. Roth School of Electrical Engineering, Korea University Seoul (Korea) [**] This work was supported by the European Science Foundation, EPSRC, the Royal Society (A.N.K.), the EU projects CANAPE (D.O.) and SALVE (U.K., A.C.), the Research Grant Council of Hong Kong (S.Y.), and the Korean Ministry of Education, Science and Technol- ogy (S.R.). We are grateful to Prof. Martyn Poliakoff and Dr. Matthew S. McFall for useful discussions and their help in preparation of the manuscript. Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/anie.200902243. Angewandte Chemie 1 Angew. Chem. Int. Ed. 2009, 48,1–6  2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim These are not the final page numbers! Ü Ü