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Synthesis and Size Control of Luminescent II-VI Semiconductor Nanocrystals by a Novel Microemulsion-Gas Contacting Technique

Published online by Cambridge University Press:  01 February 2011

Georgios N. Karanikolos ,
Paschalis Alexandridis ,
Athos Petrou  and
T. J. Mountziaris
Georgios N. Karanikolos
Affiliation:
Departments of Chemical and Biological Engineering, The State University of New York, Buffalo, New York 14260, U.S.A.
Paschalis Alexandridis
Affiliation:
Departments of Chemical and Biological Engineering, The State University of New York, Buffalo, New York 14260, U.S.A.
Athos Petrou
Affiliation:
Departments of Physics, University at Buffalo, The State University of New York, Buffalo, New York 14260, U.S.A.
T. J. Mountziaris
Affiliation:
Departments of Chemical and Biological Engineering, The State University of New York, Buffalo, New York 14260, U.S.A.
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Abstract

A scalable, room-temperature technique for controlled synthesis of luminescent II-VI nanocrystals has been developed by using the dispersed phase of stable, well-characterized microemulsions as templates for nanoparticle synthesis. The microemulsions were formed by self-assembly of poly (ethylene oxide)-poly (propylene oxide)-poly (ethylene oxide) (PEO-PPO-PEO) amphiphilic block copolymer and heptane in formamide. By adjusting the surfactant to dispersed phase ratio, stable microemulsions were obtained with droplet diameter of ∼40nm. These microemulsions avoid problems or rapid droplet-droplet coalescence that hamper reverse micelles and lead to polydisperse particle populations. Luminescent ZnSe quantum dots were synthesized by reacting diethylzinc (dissolved in the heptane dispersed phase) with hydrogen selenide gas (diluted in hydrogen). The gas was bubbled through the microemulsion, dissolved in the formamide, and diffused to the nanodroplet interfaces to react with diethylzinc. The experiments indicate that a single nanocrystal is formed in each nanodroplet by coalescence of clusters (nuclei) and smaller crystals. The energy released during coalescence is sufficient to anneal the clusters into high-quality crystals. The process allows precise control of nanocrystal size by adjusting the initial concentration of diethylzinc in heptane. The “as grown” nanocrystals exhibit size-dependent luminescence, narrow and symmetric emission, good monodispersity (confirmed by TEM analysis), and excellent photochemical stability. The technique is currently being extended to the synthesis of CdSe nanocrystals with promising preliminary results.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 789 , 2003 , N15.55
Copyright
Copyright © Materials Research Society 2004

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