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Journal of Nanomaterials
Volume 2012, Article ID 478153, 10 pages
http://dx.doi.org/10.1155/2012/478153
Research Article

Polycation-Capped CdS Quantum Dots Synthesized in Reverse Microemulsions

Institut für Chemie, Universität Potsdam, Karl-Liebknecht-Straße 24-25, Haus 25 Golm, 14476 Potsdam, Germany

Received 21 February 2012; Accepted 21 June 2012

Academic Editor: Grégory Guisbiers

Copyright © 2012 Karina Lemke and Joachim Koetz. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

This paper is focused on the formation and recovery of cadmium sulfide (CdS) nanoparticles in two different types of polycation-modified reverse microemulsions using low molecular weight poly(diallyldimethylammonium chloride) (PDADMAC) and poly(ethyleneimine) (PEI). Both polymers were incorporated in a quaternary w/o microemulsion consisting of water, toluene-pentanol (1 : 1), and sodium dodecyl sulfate (SDS), as well as in a ternary w/o microemulsion consisting of water, heptanol, and 3-(N,N-dimethyl-dodecylammonio)-propanesulfonate (SB). UV-vis and fluorescence measurements in the microemulsion illustrate the capping effect of the polycations on the formation of the CdS quantum dots. The nanoparticles are redispersed in water and characterized by using UV-vis and fluorescence spectroscopy, in combination with dynamic light scattering. From the quaternary microemulsion, only nanoparticle aggregates of about 100 nm can be redispersed, but, from the ternary microemulsion, well-stabilized polycation-capped CdS quantum dots can be obtained. The results show that the electrostatic interactions between the polycation and the surfactant are of high relevance especially in the solvent evaporation and redispersion process. That means only that in the case of moderate polycation-surfactant interactions a redispersion of the polymer-capped CdS quantum dots without problems of aggregation is possible.