To confirm the incorporation of Al 3+ ions into the semiconducting shell we performed energy dispersive X-ray spectroscopy (EDX) using a line-scan across a Au@ZnO particle and a 2 at.% doped Au@AZO particle (Figure ). The blue lines, corresponding to the aluminum 𝐾𝐾 𝛼𝛼1 transition, clearly show the presence of aluminum within the doped particle. To measure the dopant percentage in the AZO shells we performed inductively coupled mass-spectrometry (ICP-MS) on washed Au@AZO NPs, as illustrated in Figure . When aiming for a nominal doping of 0, 1, 2, and 4 at.% of aluminum, ICP-MS measurements show that our samples contain 0.4, 0.9, 2.2 and 3.4 at.%, respectively. The ICP-MS data demonstrates a quantitative incorporation of Al 3+ into the ZnO shell, which we further confirm using extinction spectroscopy.