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| Home > Publications database > Formation Dynamics of Nanocrystals: In-situ Observation of the Growth of CdSe NCs Via Magic-sized Clusters Intermediates. |
| Home > Publications database > Formation Dynamics of Nanocrystals: In-situ Observation of the Growth of CdSe NCs Via Magic-sized Clusters Intermediates. |
| Abstract/Book | PUBDB-2025-02042 |
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2019
Fundació Scito València
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Please use a persistent id in citations: doi:10.29363/nanoge.nfm.2019.207
Abstract: The pioneer synthesis of nanocrystals (NCs) published in 1993 opened up new routes to prepare highly monodisperse quantum dots. This, together with the outstanding electronical, optical and surface properties observed in different kinds of such semiconductor nanocrystals, has triggered an increased scientific interest on these nanomaterials. As a result, well-defined methods to synthesize and characterize NCs have been developed, and very precise control on the synthesis allows obtaining a variety of crystal structures, shapes and sizes. Despite this, usually these advances are the result of trial-mistake approaches and this is due to the lack of knowledge in the events concurring during the formation of such nanocrystals. The key point to investigate the formation dynamics of nanocrystals lies on the possibility to in-situ characterize nucleation and growth events, which take place from the millisecond to second time window.To this aim, we have designed and assembled a state-of-the-art continuous-flow device to perform the synthesis of CdSe NCs at very different reaction conditions. The addition of optical flow cells and X-ray transparent flow cells enables in-situ characterization by means of optical spectroscopy and SAXS/WAXS experiments (synchrotron radiation facilities). With this reactor we have studied the growth dynamics of CdSe nanocrystals. Our results show that CdSe magic sized clusters are formed always as intermediates in the formation of CdSe nanocrystals. Whether they can be observed or not in solution depends mainly on the reaction temperature, which is closely related to the monomer concentration and the nucleation rate. A series of experiments utilizing worked-up CdSe clusters demonstrates our proposed new growth mechanism, according to which, CdSe nanocrystals are formed subsequently to burst dissolution of small CdSe magic sized clusters and further growth into larger clusters and nanocrystals. This new growth mechanism suggests that the classical nucleation theory, as we know it, is no longer suitable to explain formation processes in nanocrystals.
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