Photoinduced Ligand Displacement of Semiconductor Nanomaterials

Organic ligands at the surface of colloidal semiconductor nanocrystals (NCs) are usually assumed to remain anchored during optical processes. Recent time-resolved spectroscopic studies overturn this assumption: photoexcitation can displace ligands from the NC surface through photoinduced charge transfer. Because conventional ligand exchange is bound by thermodynamic equilibrium, such light-driven displacement offers on-demand, out-of-equilibrium control of the ligand shell, with implications for photocatalysis, photopatterning, and the photostability of NC-based devices. In this Perspective, we outline the fundamentals of NC–ligand surface chemistry and of the charge-transfer processes that trigger desorption, survey the growing experimental evidence─from time-resolved infrared studies of carboxylate ligands to our work using π-conjugated perylene bisimide ligands as sensitive optical reporters of desorption─and discuss the emerging quantum-chemical picture of the dissociation. We conclude with design rules and open questions toward photocontrolled NC surfaces.