Figure 3.

(a,b) XPS spectra of the as-synthesized CeO₂ nanostructures. The peaks in XPS spectra were fitted using Gaussian function and ascribed to Ce³⁺ and Ce⁴⁺, respectively. (c) Raman spectra of the as-synthesized CeO₂ nanostructures at the excitation wavelength of 325 nm. (d) UV-Vis spectra of the as-synthesized CeO₂ nanostructures.