Understanding the mechanisms of gold shell growth onto polymer microcapsules to control shell thickness

Tasker, Alison, Hitchcock, James, Baxter, Elaine A., Cayre, Oliver J. and Biggs, Simon (2017) Understanding the mechanisms of gold shell growth onto polymer microcapsules to control shell thickness. Chemistry - An Asian Journal, 12 13: 1641-1648. doi:10.1002/asia.201700536


Author Tasker, Alison
Hitchcock, James
Baxter, Elaine A.
Cayre, Oliver J.
Biggs, Simon
Title Understanding the mechanisms of gold shell growth onto polymer microcapsules to control shell thickness
Journal name Chemistry - An Asian Journal   Check publisher's open access policy
ISSN 1861-4728
1861-471X
Publication date 2017-05-21
Year available 2017
Sub-type Article (original research)
DOI 10.1002/asia.201700536
Open Access Status Not yet assessed
Volume 12
Issue 13
Start page 1641
End page 1648
Total pages 20
Place of publication Ghaziabad, Uttar Pradesh, India
Publisher Chemic Publishing Company
Language eng
Subject 1600 Chemistry
Abstract Polymer microcapsules have been used commercially for decades, however they have an inherent flaw which renders them impractical as a carrier of small, volatile molecules. The porous nature of the polymer shell allows for diffusion of the encapsulated molecules into the bulk. The use of metal shells is an innovative way to prevent undesired loss of small molecules from the core of microcapsules, however it is important, particularly when using expensive metals to ensure that the resulting shell is as thin as possible. Here we investigate the fundamental mechanisms controlling the gold shell thickness when a fragrance oil is encapsulated in a poly(methyl methacrylate) shell. We consider the distribution of the nanoparticles on the capsule surface, and from quantification of the adsorbed nanoparticle (NP) density and resulting shell thickness, we propose mechanisms to describe the gold shell growth for systems with high and low NP surface coverage. We suggest from our observations that the gold grows to fill in the gaps between NPs. At low NP concentrations, thicker metal shells form. We postulate that this is due to the low NP density on the surface, forcing the gold clusters to grow larger before they meet the adjacent ones. Thus, to grow the thinnest possible shells a densely packed monolayer of platinum nanoparticles is required on the capsule surface.
Formatted abstract
Polymer microcapsules have been used commercially for decades, however they have an inherent flaw which renders them impractical as a carrier of small, volatile molecules. The porous nature of the polymer shell allows for diffusion of the encapsulated molecules into the bulk. The use of metal shells is an innovative way to prevent undesired loss of small molecules from the core of microcapsules, however it is important, particularly when using expensive metals to ensure that the resulting shell is as thin as possible.

Here we investigate the fundamental mechanisms controlling the gold shell thickness when a fragrance oil is encapsulated in a poly(methyl methacrylate) shell. We consider the distribution of the nanoparticles on the capsule surface, and from quantification of the adsorbed NP density and resulting shell thickness, we propose mechanisms to describe the gold shell growth for systems with high and low NP surface coverage. We suggest from our observations that the gold grows to fill in the gaps between NPs. At low NP concentrations, thicker metal shells form. We postulate that this is due to the low NP density on the surface, forcing the gold clusters to grow larger before they meet the adjacent ones. Thus, to grow the thinnest possible shells a densely packed monolayer of platinum nanoparticles is required on the capsule surface.
Keyword Polymer microcapsules
Volatile molecules
Metal shells
Gold shell thickness
Q-Index Code C1
Grant ID UQECR1609217
Institutional Status UQ

 
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Created: Fri, 26 May 2017, 14:45:56 EST by Alison Tasker on behalf of School of Chemical Engineering