Reduced coordination in 1D crystals is obviously a consequence of the sterically confined space in which the encapsulated crystals have to grow. It was interesting to investigate the differences of the one dimensional crystals in comparison with  their three-dimensional unit cell.

In our previous investigations of 1DCuI@SWCNT HRTEM revealed hexagonal, monoclinic [1] and cubic [2] modifications of copper iodide. In cases of HRTEM investigations in order to obtain the 1D crystal structure it was necessary to get sets of micrographs (about hundreds) while HAADF HRSTEM method allows to determine 1D crystal structure with a help of a few micrographs, owing to an ability to designate various atoms according to their atomic numbers. Within a framework of this study the perspectives of HRSTEM method combined with local EELS for determination of atomic and electron structure of individual nanocrystals are shown. These analytical electron microscopy methods applied together have allowed to reveal a new type of 1DCuI@SWCNT nanocomposite structure and to identify a space group of 1D CuI unit cell in the nanotube channel which appeared to be Pmmm. The results of our investigation bear evidence of the necessity of using HRSTEM in both bright field and dark field modes simultaneously (Fig. 1). A formation of chemical bond between Cu3d and C2dz orbitals of the intercalated nanocrystal and the nanotube wall is accompanied by electron density transfer of ~ 0.09 e/atom towards C. Electron microscopy is performed in JEOL ARM 200F at 80 kV in HAADF HRSTEM mode. 

Acknowledgements

The work was supported by the Ministry of Education and Science of the Russian Federation within a framework of the program “Investigation and development on priory direction of scientific-technical complex of Russia for 2014-2020” (agreement № 14.585.21.0004, unique project identification number RFMEFI58514X0004).

1. Kiselev N.A., Kumskov A.S., Zakalyukin R.M., Vasiliev A.L., Chernisheva M.V., Eliseev A.A., Krestinin A.V.,  Freitag B., Hutchison J.L. // Journal of Microscopy. 2012. V. 246. P. 3. P. 309.

2. Kumskov A.S., Zhigalina V.G., Chuvilin A.L., Verbitskiy N.I., Ryabenko A.G., Zaytsev D.D., Eliseev A.A., Kiselev N.A. // Carbon. 2012. V. 50. № 12. P. 4696.

Figures:

Fig. 1. HRSTEM-image of 1D CuI crystal structure inside SWCNT: a – bright field mode, b – dark field mode of the same part of the crystal with a computer model of several 1D CuI unit cells (Pmmm) put on HAADF image.

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