Extended Data Fig. 9: Head-group optimization by tuning the bridge length.
From: Designer phospholipid capping ligands for soft metal halide nanocrystals
a–c, Lead iodide perovskites have a larger distance between A and X surface sites than bromides. Positive-to-negative moieties distance in the zwitterion thus has a pronounced effect on the ligand binding. Mixed halide CsPb(Br/I)3 NCs (without anti-solvent purification, synthesis details in Supplementary Table 7) capped with phosphoalkylamine ligands featuring different distances between ammonium and phosphate functionalities (a): PEA, PPA, and PBA. After the first purification step with anti-solvent (b), PEA-capped NCs drop in PLQY from 95% to 42%, while longer-bridge PPA and PBA ligands retain high PLQY and NCs shape (c). d–g, In general, PEA ligands better suit Br-rich compositions, while PPA ligands make for a better choice for I-rich compositions. h,i, Mixed halide CsPb(Br/I)3 NCs capped with 3-ammoniopropyl (2-octyl-1-dodecyl) phosphate (PPA-R6) display remarkable spectral stability during purification cycles with antisolvent (ethyl acetate:acetonitrile).