Type of presentation: Poster

MS-10-P-2495 Atomic resolution analysis of beam sensitive ordered porous materials

Mayoral A.¹, Anderson P. A.², Coronas J.³, Sanchez M.⁴, Diaz I.⁴

¹Laboratorio de Microscopías Avanzadas (LMA), Instituto de Nanociencia de Aragón (INA), Universidad de Zaragoza, Zaragoza, Spain, ²School of Chemistry, University of Birmingham, Edgbaston, Birmingham, United Kingdom, ³Chemical and Environmental Engineering Department and Nanoscience Institute of Aragon (INA) Universidad of Zaragoza, 50018 Zaragoza (Spain), ⁴Instituto de Catálisis y Petroleoquímica, CSIC, Madrid, Spain

amayoral@unizar.es

With the recent advances in transmission electron microscopes, mainly through the implementation of spherical aberration correctors, sub-angstrom resolution is becoming easily achievable overcoming the challenge of lateral resolution (especially for higher voltages). Our next efforts therefore, effort should now be devoted into optimizing the different modes of observations, improvement of detectors, and in-situ experiments among many others. One of the main challenges from the electron microscopy and materials science point of view is the observation of beam sensitive materials. For the cases of knock-on damage, lowering the accelerating voltage is the solution (as happens for carbon based materials). On the other hand if radiolysis causes the bond disruption there is not a straightforward approach, and thus dose as well as voltage has to be taken into account. Zeolites and zeotypes suffer from this problem and the final image resolution has always suffered from this effect. In this work, we present the data that can be acquired by using Cs-corrected STEM under various conditions. Many zeolites have been observed including the most beam sensitive one, LTA type (Si/Al = 1), figure 1a, in its bare form and loaded with silver ions, whose structure has been analyzed, figure 1b[1, 2]. Due to the benefits of ADF detectors, which provide direct observations of heavier elements, metals contained in zeolites are more easily identified, but also, structural defects can be studied more clearly through this method, as in the case of the titanosilicate ETS-10[3], figure 2.
The results presented here, prove the effectiveness of this method in acquiring true atomic-column resolution images which will provide new information on guest species within the zeolite cavities as well as observing the structural defects with unprecedented resolution. In addition, metal organic framework (MOF) materials, which have also been analysed, will be presented with virtual atomic resolution of the metals allowing for structure identification in direct space.

References

[1] A. Mayoral, T. Carey, P. A. Anderson, A. Lubk, I. Diaz, Angew. Chem. Int. Ed. 50 (2011) 11230–11233.
[2] A. Mayoral, T. Carey, P. A. Anderson, I. Diaz, Micropor. Mesopor. Mater. 166 (2013) 117-122.
[3] A. Mayoral, J. Coronas, C. Casado, C. Tellez, I. Díaz, Chem. Cat. Chem. 5 (2013) 2595–2598.

The authors would like to acknowledge the ESTEEM2 and Talem program for funding. MSS and ID acknowledge funding from MINECO (MAT2012-31127 project).

Fig. 1: Cs-corrected STEM HAADF images of a) as-synthesized Na zeolite A along the [001] with the simulated image inset. b) dehydrated Ag zeolite A with a ball and stick model inset, where silver appears in grey, oxygen in red and silicon and aluminum in dark and light blue.

Fig. 2: Cs-corrected STEM HAADF analysis of ETS-10. a) Atomic resolution image along the [110] zone axis. b) Lower magnification image along the same orientation where some defects are marked by circles. c) GPA analysis rotational map of b), where the reference area is marked by a dashed rectangle.