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. 2019 Dec 6;10:5599. doi: 10.1038/s41467-019-13415-8

Fig. 2.

Fig. 2

X-ray characterizations. a X-ray diffraction spectra showing the reference stick patterns of NiO (purple line, ICDD: 04-011-9039), Ni (green line, ICDD: 04-001-3331), and γ-Fe2O3 (magenta line, ICDD:01-078-6916). The peaks marked with black dots correspond to CFP substrate; X-ray photoelectron spectroscopy (XPS) of Ni–Fe NP. b Ni 2p, c Fe 2p, d O 1s.