Jahn-Teller distorted Cu_1-xNi_xCr₂O₄(x = 0, 0.5, 1) nanoparticles

In this report, x-ray photoelectron spectroscopy data for three types of Cu-doped nickel chromite nanoparticles are presented. CuCr2O4, Cu0.5Ni0.5Cr2O4, and NiCr2O4 were prepared using the citric acid-assisted sol-gel method. All samples were amorphous after the initial gel preparations were dried, but after calcination at temperatures higher than 700 °C, the samples crystallized in a spinel structure. X-ray diffraction patterns for the samples were well fitted with the I41/amd space group. Survey scans were conducted as well as detailed scans of Cu 2p, Ni 2p, Cr 2p, and O 1s levels. The O 1s core level was well-fitted with three components, including lattice oxygen (low binding energy) and two higher binding energy components, which corresponded to surface-absorbed hydroxyl groups originating from water and alcohol used in the synthesis of the particles. The line shape of the Cu 2p core level was compatible with mixed 2+ and 1+/0+ oxidation states for Cu ions in these nanoparticles. The strong intensity of the high binding energy satellite indicated that the majority of the Cu 2p ions were in 2+ oxidation state. Finally, Ni 2p showed a mixed 3+/2+ oxidation state for Ni ions in these nanoparticles.