Issue 45, 2023

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

Abstract

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 (e.g. 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-N-oxide (DMPO) under photoexcitation and thermal conditions. We demonstrate that DMPO likely adds to CdSe QD surfaces under thermal conditions by a nucleophilic mechanism in which the surface chalcogenides add to the double bond, followed by further oxidation of the surface-bound product. In contrast, CdS QDs more readily form surface sulfur-centered radicals that can perform reactions including alkene isomerization. These results indicate that QD surfaces should be an important consideration for the design of photocatalysis beyond simply tuning QD semiconductor band gaps.

Graphical abstract: EPR spin trapping of nucleophilic and radical reactions at colloidal metal chalcogenide quantum dot surfaces

Supplementary files

Article information

Article type
Edge Article
Submitted
06 sep 2023
Accepted
31 okt 2023
First published
01 nov 2023
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY-NC license

Chem. Sci., 2023,14, 13080-13089

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

C. J. Aschendorf, M. Degbevi, K. V. Prather and E. Y. Tsui, Chem. Sci., 2023, 14, 13080 DOI: 10.1039/D3SC04724E

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