Unraveling Photoinduced\nDesorption Dynamics of π‑Conjugated\nLigands in ZnS Nanocrystals via Pump–Push–Probe Spectroscopy

The photoinduced ligand desorption\nfrom nanocrystal (NC)\nsurfaces\nplays a critical role in the diverse functionalities of NCs. However,\nthis reaction is inherently complex because photophysical and photochemical\nreactions are involved, and many aspects remain elusive. In this study,\nusing ZnS NCs coordinated with perylenebisimide (PBI) ligands as a\nmodel system, we revealed that pump–push–probe spectroscopy\nprovides detailed insights into the transient species following photoinduced\nligand desorption reactions. This method successfully isolated the\nsignal of the PBI radical anion, generated by photoinduced charge\nseparation, which was difficult to identify by conventional pump–probe\nspectroscopy. Furthermore, pump–push–probe spectroscopy\nalso revealed that the transiently formed aggregation of PBI after\n PBI desorption is the H-type aggregate. This research is expected\nto contribute to the analysis of complex photochemical reaction processes\nin composite nanomaterials and is important for the development of\nhighly efficient NC photocatalysts and photodurable NCs.