Optoelectronic Properties of PbS Nanocrystals Preserved through L-Type Ligand Surface Reactivity

In this work, ¹H NMR and photoluminescence spectroscopies have been leveraged to identify how amine-terminated molecules react with the surface of oleate-capped PbS nanocrystals (NCs) and impact their optical properties. The alkyl amine undec-10-ene-1-amine binds weakly to the NC surface and promotes the displacement of the native Z-type ligand Pb(oleate)₂. Through systematic experiments, we deconvolute the parallel reaction mechanisms that drive this reactivity. The binding and displacement reactivity results in a net-zero change in the NC emission, attributed to preservation of the electronic structure of PbS NCs through surface restructuring. The photoluminescence of PbS NCs remains robust even when exposed to bulky chelating diamines that exclusively promote displacement of Z-type ligands, reactivity that slightly quenches NC emission by exposing undercoordinated chalcogenides and forming trap states. This work improves fundamental understanding of NC surface reactivity with L-type ligands and their potential impact in developing improved NCs.