Extended Data Fig. 5: Synthesis of APbBr₃ NCs and testing of ligands.

a, In TOPO-DOPA synthesis³¹, PbBr₂-trioctylphosphine (TOPO) complex reacts with diisooctylphosphinic acid (DOPA) salt of the corresponding A cation at room temperature, yielding monodisperse NCs (1). TOPO and DOPA are known as “bad ligands” and can be readily exchanged for zwitterion ligands (2a). If no capping ligands are added promptly after NCs are formed, the NCs rapidly lose their colloidal and structural integrity (2b). b, To purify phospholipid-capped NCs (see also Supplementary Note 6), a suited antisolvent is added, followed by centrifugation (3), whereas a supernatant containing unreacted precursors and free ligand molecules is discarded (4). If the ligand is’ good’, the resulting NCs pellet is redispersed in a suited solvent, yielding a stable colloid (5a). With a ‘bad’ ligand, NCs redisperse incompletely, do not redisperse (5b), or lose their colloidal integrity upon storage (6). Such a purification cycle (steps 3, 4, and 5a) can be repeated several times. c,d, In this experiment, two head groups and two tails were compared. Combining a ‘bad’ head group and a ‘bad’ tail (c) leads to the worst colloidal stability, while combining a ‘bad’ head group and a ‘good’ tail might still yield long-term stable colloids (d). Similar to FAPbBr₃, MAPbBr_3, and CsPbBr₃ (c) NCs with PC head-group and a ‘bad’ hexadecyl tail precipitate after three rounds of purification, with visible deposit highlighted with a white box on the photo. CsPbBr₃ NC colloids with both PEA or PC head-groups and a ‘good’ glycerodioleyl tail (d, commercially available) yield stable colloids; however, with different ligand coverage, in agreement with MD prediction. Furthermore, PC-based surface ligation is more labile, with both “good” and “bad” tails: NCs tend to increase their mean particle size (inset TEM images, scale bars 50 nm) and acquire more irregular NC morphology with storage or several purification cycles.