STEM-EELS was applied to explore the chemical properties of Eu. However, due to the broad peak of Zn L-edge and overlap between the Eu M4,5 edge (1131 eV) and the Zn L2,3 edge (1020 eV), only the background of the Zn pre-edge was employed for background subtraction. Figure and 4B shows the elemental distribution of Zn and Eu. The Eu-rich region being much more pronounced for the 20Eu samples as revealed with HAADF-STEM and EDX was confirmed with the STEM-EELS mapping. The electron orbital occupancy can be calculated by analyzing the integrated intensity ratio between specific peaks in the EELS spectrum, thereby allowing for determination of the chemical valence states of selected elements and composition of the material. The signals in the EELS mapping were combined to get a high signal-noise ratio for chemical analysis. Figure shows the summed EELS profiles of the 5Eu and 20Eu samples, respectively. Here the EELS spectrum was normalized using the integral intensity of Zn (ranging from 1020 -1121 eV) and compared with the relative intensity of the Eu signal. In concert with EDX data, it was found that the Eu concentration in the 5Eu sample was not as high as for the 20Eu sample. The peak shape and the strong white-line features in both spectra, indicated that the europium was present as Eu-ions, rather than pure metal which should show weaker peaks around 1130 eV. From the literature, EuO and other Eu 2+ compounds are unlikely to be present here as they are very susceptible to oxidation under the synthesis conditions used here. Also, by comparing the relative intensity ratio between the Eu M4 and M5 edges, the valence state of europium could be set as +3, which is in accordance with the literature.