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Open AccessFeature PaperArticle

Mixed Mercaptocarboxylic Acid Shells Provide Stable Dispersions of InPZnS/ZnSe/ZnS Multishell Quantum Dots in Aqueous Media

1
Fraunhofer IAP, Geiselbergstraße 69, 14476 Potsdam, Germany
2
Photonics and Optoelectronics, Nano-Institute Munich and Department of Physics, Ludwig-Maximilians-Universität (LMU), Königinstraße 10, 80539 Munich, Germany
3
Department of Chemistry, Ludwig-Maximilians-Universität (LMU), Butenandtstraße 5-13 (E), 81377 Munich, Germany
4
Institute of Chemistry, University of Potsdam, 14469 Potsdam, Germany
*
Authors to whom correspondence should be addressed.
Nanomaterials 2020, 10(9), 1858; https://doi.org/10.3390/nano10091858
Received: 11 August 2020 / Revised: 9 September 2020 / Accepted: 13 September 2020 / Published: 17 September 2020
(This article belongs to the Special Issue Nanocrystals: Synthesis, Properties and Applications)
Highly luminescent indium phosphide zinc sulfide (InPZnS) quantum dots (QDs), with zinc selenide/zinc sulfide (ZnSe/ZnS) shells, were synthesized. The QDs were modified via a post-synthetic ligand exchange reaction with 3-mercaptopropionic acid (MPA) and 11-mercaptoundecanoic acid (MUA) in different MPA:MUA ratios, making this study the first investigation into the effects of mixed ligand shells on InPZnS QDs. Moreover, this article also describes an optimized method for the correlation of the QD size vs. optical absorption of the QDs. Upon ligand exchange, the QDs can be dispersed in water. Longer ligands (MUA) provide more stable dispersions than short-chain ligands. Thicker ZnSe/ZnS shells provide a better photoluminescence quantum yield (PLQY) and higher emission stability upon ligand exchange. Both the ligand exchange and the optical properties are highly reproducible between different QD batches. Before dialysis, QDs with a ZnS shell thickness of ~4.9 monolayers (ML), stabilized with a mixed MPA:MUA (mixing ratio of 1:10), showed the highest PLQY, at ~45%. After dialysis, QDs with a ZnS shell thickness of ~4.9 ML, stabilized with a mixed MPA:MUA and a ratio of 1:10 and 1:100, showed the highest PLQYs, of ~41%. The dispersions were stable up to 44 days at ambient conditions and in the dark. After 44 days, QDs with a ZnS shell thickness of ~4.9 ML, stabilized with only MUA, showed the highest PLQY, of ~34%. View Full-Text
Keywords: quantum dots; QDs; cadmium-free; Cd-free; InP; InPZnS; multishell; mercaptocarboxylic acids; 3-mercaptopropionic acid; 11-mercaptoundecanoic acid; phase transfer; ligand exchange; aqueous dispersion quantum dots; QDs; cadmium-free; Cd-free; InP; InPZnS; multishell; mercaptocarboxylic acids; 3-mercaptopropionic acid; 11-mercaptoundecanoic acid; phase transfer; ligand exchange; aqueous dispersion
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Heyne, B.; Arlt, K.; Geßner, A.; Richter, A.F.; Döblinger, M.; Feldmann, J.; Taubert, A.; Wedel, A. Mixed Mercaptocarboxylic Acid Shells Provide Stable Dispersions of InPZnS/ZnSe/ZnS Multishell Quantum Dots in Aqueous Media. Nanomaterials 2020, 10, 1858.

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