Formation mechanism of CdS nanoparticles with tunable luminescence via a non-ionic microemulsion route
We investigated the synthesis of CdS nanoparticles via an optimized water-in-oil microemulsion route that used the non-ionic surfactant-based system H2O–n-octane–Brij30/1-octanol. For that purpose, a microemulsion that contained Cd(II) ions (μe1) and another microemulsion that contained S2− ions (μe2) were combined. To investigate the ways in which the non-ionic microemulsion characteristics controlled the size and emission properties of colloidal CdS quantum dots, μe1 and μe2 with tunable and robust similar structure were prepared. This requirement was fulfilled by matching the water emulsification failure boundary (wefb) of the two microemulsions and carrying out synthesis along this boundary. Dynamic light scattering and fluorescence probe techniques were used to investigate the size and interfacial organization of the microemulsion water droplets, and the CdS nanoparticles were characterized by UV–Vis and static fluorescence spectrometry, TEM and HRTEM. Nanoparticles of diameter 4.5–5.5 nm exhibiting enhanced band edge emission were produced by increasing the water content of the precursor microemulsions. The experimental results were combined with a Monte Carlo simulation approach to demonstrate that growth via coagulation of seed nuclei represented the driving mechanism for the CdS nanoparticle formation in the water-in-oil microemulsion.
KeywordsCdS nanoparticles Non-ionic microemulsions Phase behavior Photoluminescence Monte Carlo simulations
DA would like to thank the National University Research Council (CNCSIS) for financial support (Project PN-II-ID-PCE-2011-3-0328). POS-CCE O 2.2.1 Project INFRANANOCHEM-19/01.03.2009 funded by EU (ERDF) and Romanian Government is gratefully acknowledged for the light scattering equipment. DA thanks for the use of the HPC infrastructure developed under NASR Grant, Capacities Project CpI 84/2007. VST thanks to PN45N09 project.
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