QUANTITATIVE STEM-HAADF AND EDS MAPPING OF ZIF-8 NANOCRYSTALS: PARTICLE SIZE, CONTRAST SCALING, ELEMENT CO-LOCALIZATION AND STOICHIOMETRY
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Khayot Bakhronov, Majidjon Akhmadov, Elyor Eshonqulov, Mirzokhid Kokhkharov, Amirkhon Sultonov
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The elemental composition of ZIF-8 nanocrystals and its distribution over the particles were studied by scanning transmission electron microscopy with high-angle annular dark-field imaging (STEM-HAADF) and energy-dispersive X-ray spectroscopy (EDS) mapping. Particles cover 26% of the HAADF field and have a size of 220±79 nm (n=259). The HAADF contrast increases with particle size (Spearman ρ=0.51), and the integrated signal scales as d2.2. The correlation of the element maps with the HAADF image is r=0.85 for Zn, 0.71 for C, 0.61 for N and 0.04 for O. The signal density of Zn and N is 4.5 and 5.6 times higher on particles than on the background, whereas for oxygen the ratio is 1.1 (95% CI 0.96-1.30), i.e. oxygen is not associated with the particles. The large-area spectrum gives an N : Zn atomic ratio of 3.97±0.91, consistent with the expected value of 4; about 71% of the carbon is attributed to sources other than the framework.
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Authors
Khayot Bakhronov, Majidjon Akhmadov, Elyor Eshonqulov, Mirzokhid Kokhkharov, Amirkhon Sultonov
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References:
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