Fig. 3. (a and d) TEM images and HR-TEM images before annealing and at (b and e) 300 °C and (c and f) 500 °C. (g) XRD of Au@TiO₂ nanostructures before and after annealing. (h) UV-visible spectroscopy of Au@TiO₂ nanostructures before and after annealing. (i) Raman spectroscopy of Au@TiO₂ nanostructures before and after annealing.