Document Detail

Role of Solvent-Oxygen Ion Pairs in Photooxidation of CdSe Nanocrystal Quantum Dots.
MedLine Citation:
PMID:  22381115     Owner:  NLM     Status:  Publisher    
Understanding the mechanisms for photodegration of nanocrystal quantum dots is an important step toward their application in real-world technologies. A usual assumption is that photochemical modifications in nanocrystals such as their photooxidation are triggered by absorption of a photon in the dot itself. Here, we demonstrate that contrary to this commonly accepted picture, nanocrystal oxidation can be initiated by photoexcitation of solvent-oxygen ion pairs that relax to produce singlet oxygen, which then reacts with the nanocrystals. We make this conclusion on the basis of photolysis studies of solutions of CdSe nanocrystals. Our measurements indicate a sharp spectral onset for photooxidation, which depends on solvent identity and is 4.8 eV for hexane and 3.4 eV for toluene. Importantly, the photooxidation onset correlates with the position of a new optical absorption feature, which develops in a neat solvent upon its exposure to oxygen. This provides direct evidence that nanocrystal photooxidation is mediated by excitation of solvent-oxygen pairs and suggests that the stability of the nanocrystals is defined not only by properties of their surfaces (as has been commonly believed) but also the properties of their environment, that is, of the surrounding solvent or matrix.
Virginia W Manner; Alexey A Koposov; Paul Szymanski; Victor I Klimov; Milan Sykora
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-3-1
Journal Detail:
Title:  ACS nano     Volume:  -     ISSN:  1936-086X     ISO Abbreviation:  -     Publication Date:  2012 Mar 
Date Detail:
Created Date:  2012-3-2     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  101313589     Medline TA:  ACS Nano     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
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