Fig. 2. (a) XRD pattern with Rietveld analysis of ε-Fe₂O₃ NPs. Red dots, black lines, and grey lines are the observed patterns, calculated patterns, and their differences, respectively. Red bars represent the calculated positions of the Bragg reflections of the ε-Fe₂O₃ phase (orthorhombic, Pna2₁). (b) Crystal structure of ε-Fe₂O₃. Blue and red balls indicate Fe and O atoms, respectively. (c) Distribution of hydrodynamic diameters, D_H, from dynamic light scattering (DLS) measurements of coated and uncoated ε-Fe₂O₃ NPs and (d) γ-Fe₂O₃ NPs. (e) TEM images of ε-Fe₂O₃ NPs and (f) γ-Fe₂O₃NPs. (g) ED patterns of ε-Fe₂O₃ NPs. (h) Particle size histograms from TEM images of ε-Fe₂O₃ NPs, in the inset HRTEM image of a single NP. (i) ED patterns of γ-Fe₂O₃ NPs. (j) Particle size histograms from TEM images of γ-Fe₂O₃ NPs. In the inset, HRTEM images of a single NP.