173625.fig.003a
(a)
173625.fig.003b
(b)
Figure 3: (a) X-ray diffraction (XRD) spectra acquired for nano-Fe3O4 and VA-Fe3O4 for the range 20–90° 2θ. (b) X-ray photoelectron spectroscopy (XPS) Fe 2p3/2 photoelectron peaks for nano-Fe3O4 and VA-Fe3O4.