EPR spin trapping of nucleophilic and radical reactions at colloidal metal chalcogenide quantum dot surfaces.

The participation of the surfaces of colloidal semiconductor nanocrystal quantum dots (QDs) in QD-mediated photocatalytic reactions is an important factor that distinguishes QDs from other photosensitizers ( transition metal complexes or organic dyes). Here, we probe nucleophilic and radical reactivity of surface sulfides and selenides of metal chalcogenide (CdSe, CdS, ZnSe, and PbS) QDs using chemical reactions and NMR spectroscopy. Additionally, the high sensitivity of EPR spectroscopy is adapted to study these surface-centered reactions through the use of spin traps like 5,5-dimethyl-1-pyrroline--oxide (DMPO) under photoexcitation and thermal conditions.