Abstract:

Colloidal semiconductor quantum dot nanocrystals have applications in displays, photovoltaics, and photocatalysis. In these systems, chemistry at nanocrystal surfaces, including redox processes, association/dissociation, and other structural rearrangements, has an outsize effect on the nanocrystal properties, but is challenging to study with typical spectroscopic methods. We show that organometallic fragments like transition metal carbonyl complexes can act as strongly-bound X-type or Z-type ligands to the nanocrystal surfaces, and that these species can be useful spectroscopic reporters of surface chemistry. These functionalized nanocrystals therefore enable in situ measurements of surface stoichiometry and surface charge under photoexcitation and during photocatalysis. We further study chalcogenide centered reactions at nanocrystal surfaces using a combination of reactivity studies and EPR spin trapping. We demonstrate that metal chalcogenide nanocrystal surfaces can participate both in radical-mediated mechanisms and nucleophilic addition reactions.