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A miniemulsion polymerization technique for encapsulation of silicon quantum dots in polymer nanoparticles

Lookup NU author(s): Noor Harun, Dr Ben Horrocks, Professor David Fulton

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Abstract

Miniemulsion polymerization techniques were used to encapsulate luminescent alkylated silicon quantum dots (Si-QDs) within polymer nanoparticles composed of styrene and 4-vinylbenzaldehyde monomers. The polymer nanoparticles had mean diameters in the range 90-150 nm depending on the reaction conditions, however all samples showed narrow particle size distributions, as determined by dynamic light scattering and atomic force microscopy. The Si-QDs were found to have a small, but beneficial effect on the polymerization process by reducing the polydispersity of the final polymer particles, which we attribute to co-surfactant action of the undecene used to form the alkyl capping layer on the Si-QDs. Confocal microspectroscopy was used to confirm that the luminescent alkylated Si-QDs were encapsulated within the polymer nanoparticles and also provided luminescence and Raman spectra which show peaks corresponding to both alkylated Si-QDs and the polymer nanoparticles. Treatment of the polymer nanoparticles with dilute aqueous sodium hydroxide solution, which is known to corrode Si and extinguish the luminescence of alkylated Si-QDs, results in only a partial reduction in luminescence suggesting that the majority of the alkylated Si-QDs are encapsulated sufficiently deep within the polymer matrix to protect them from alkaline attack. Miniemulsion polymerization of the monomers styrene and 4-vinylbenzaldehyde affords polymer nanoparticles displaying reactive aldehyde groups upon their surfaces, which could then be decorated with a selection of molecules through imine, oxime or hydrazone condensation reactions. We speculate that polymer-SiQD composite nanoparticles whose surfaces can be further decorated will increase the utility of luminescent Si-QDs in applications such as anti-counterfeiting and as probes of biological processes.

Publication metadata

Author(s): Harun NA, Horrocks BR, Fulton DA

Publication type: Article

Publication status: Published

Journal: Nanoscale

Year: 2011

Volume: 3

Issue: 11

Pages: 4733-4741

Print publication date: 10/10/2011

ISSN (print): 2040-3364

ISSN (electronic): 2040-3372

Publisher: Royal Society of Chemistry

URL: http://dx.doi.org/10.1039/c1nr10938c

DOI: 10.1039/c1nr10938c

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