The concentration of amine ligands was selected to be 5 eq. of a required monolayer of the total surface of the used SP batch (more information in the Methods section). Using higher monolayer equivalents resulted in partial disassembly of the SPs due to a (better) stabilization of single NCs in the used solvent (Fig. ), which also confirms the successful ligand exchange. Fourier transform infrared (FTIR) spectroscopy reveals the appearance of a broad P-O-Fe peak between 1100-900 cm -1 (Fig. ) associated to bound phosphonates on iron oxide surfaces. Once the SPs surface was activated with amine moieties, the crosslinking step aiming to create a reinforcement oleate-derived network within the SPs was also applied. As can be seen in Fig. ,F, and G, the added amine modification neither changed the supercrystallographic arrangement nor the organic content of the amine-functionalized, crosslinked SPs (xSP-NH 2 ).