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Colloidal Synthesis of Monodisperse Semiconductor Nanocrystals through Saturated Ionic Layer Adsorption

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journal contribution
posted on 30.03.2016, 00:00 by Natalia Razgoniaeva, Luis Carrillo, Douglas Burchfield, Pavel Moroz, Prakash Adhikari, Priyanka Yadav, Dmitriy Khon, Mikhail Zamkov
We demonstrate a general strategy for the synthesis of colloidal semiconductor nanocrystals (NCs) exhibiting size dispersion below 5%. The present approach relies on the sequential deposition of fully saturated cationic and anionic monolayers onto small-diameter clusters, which leads to focusing of nanocrystal sizes with the increasing particle diameter. Each ionic layer is grown through a room-temperature colloidal atomic layer deposition process that employs a two-solvent mixture to separate the precursor and nanocrystal phases. As a result, unreacted precursors can be removed after each deposition cycle, preventing the secondary nucleation. By using CdS NCs as a model system, we demonstrate that a narrow size dispersion can be achieved through a sequential growth of Cd2+ and S2– layers onto starting CdS cluster “seeds”. Besides shape uniformity, the demonstrated methodology offers an excellent batch-to-batch reproducibility and an improved control over the nanocrystal surface composition. The present synthesis is amenable to other types of semiconductor nanocrystals and can potentially offer a viable alternative to traditional hot-injection strategies of the nanoparticle growth.