CdS Magic-Sized Nanocrystals Exhibiting Bright Bandgap Photoemission via Thermodynamically Driven Formation

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DOIResolve DOI: http://doi.org/10.1021/nn9009455
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TypeArticle
Journal titleACS Nano
Volume3
Issue12
Pages38323838; # of pages: 7
SubjectCdS; single-sized nanocrystals; magic-sized nanocrystals (MSNs); one-pot noninjection; band gap emission; homogeneous broadening
AbstractCdS magic-sized nanocrystals (MSNs) exhibiting both band gap absorption and emission at 378 nm with a narrow bandwidth of 9 nm and quantum yield (QY) of 10% (total QY 28%, in hexane) were synthesized via a one-pot noninjection approach. This CdS MSN ensemble is termed as Family 378. It has been acknowledged that magic-sized quantum dots (MSQDs) are single-sized, and only homogeneous broadening contributes to their bandwidth. The synthetic approach developed is ready and highly reproducible. The formation of the CdS MSQDs was carried out at elevated temperatures (such as 90−140 °C) for a few hours in a reaction flask containing bis(trimethylsilyl)sulfide ((TMS)2S) and Cd(OAc)(OA) in situ made from cadmium acetate dihydrate (Cd(OAc)2·2H2O) and oleic acid (OA) in 1-octadecene (ODE). Low OA/Cd and high Cd/S feed molar ratios favor this formation, whose mechanism is proposed to be thermodynamically driven. 13C solid-state cross-polarization magic-angle spinning (CP/MAS) nuclear magnetic resonance (NMR) demonstrates that the capping ligands are firmly attached to the nanocrystal surface via carboxylate groups. With the cross-polarization from 1H of the alkyl chains to surface 113Cd, 113Cd NMR is able to distinguish the surface Cd (471 ppm) bonding to both −COO− and S and the bulk Cd (792 ppm) bonding to S only. DOSY-NMR was used to determine the size of Family 378 (1.9 nm). The present study provides strategies for the rational design of various MSNs.
Publication date
LanguageEnglish
AffiliationNational Research Council Canada; NRC Steacie Institute for Molecular Sciences; NRC Institute for Microstructural Sciences
Peer reviewedYes
NPARC number16457847
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Record identifier514740b3-37e1-4682-b872-f71079c3033b
Record created2011-02-09
Record modified2016-05-09
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