The horizontal dashed line in Figure As a final step in the development of our synthesis, we altered the shell composition by intercalating Al³⁺ ions into the ZnO lattice, using a novel approach. Zeto et al. have successfully embedded copper and rare earth metals (Ce, Er, Nd, Tm, and Yb) into the ZnO shells of Au@doped-ZnO core@shell nanostructures. However, the synthesis of Au@AZO core@shell nanoparticles remains largely unexplored. Previous studies on ZnO nanoparticles and thin films showed that aluminum doping significantly affects the morphology of the final AZO crystallites. Scheme 1 Overview of the two experimental approaches used to dope the ZnO shell with aluminum. Procedure 1 follows the literature syntheses of AZO NPs and Au@doped ZnO core@shell NPs, in which the dopant is added with the other reactants at the beginning of the ZnO synthesis. In Procedure 2, the aluminum nitrate solution is neutralized to a pH of 6.5 and used to infuse the Au@Zn(OH)2 obtained after hydrothermal treatment.