Steric Stabilization of Core-Shell Nanoparticles in Liquid Carbon Dioxide at the Vapor Pressure

Nondilute nanoparticle dispersions were stabilized in liquid CO2 at 25 °C at pressures as low as the vapor pressure for greater than 30 min. By modifying hydrophilic silica with a trifunctional silylating agent, (heptadecafluoro-1,1,2,2-tetrahydrodecyl)triethoxy silane, a cross-linked polymer shell...

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Bibliographic Details
Published in:Langmuir 2004-10, Vol.20 (21), p.9380-9387
Main Authors: Dickson, Jasper L, Shah, Parag S, Binks, Bernard P, Johnston, Keith P
Format: Article
Language:English
Subjects:
Carbon Dioxide - chemistry
Fluorocarbons - chemistry
Molecular Structure
Nanostructures - chemistry
Nanostructures - ultrastructure
Particle Size
Pressure
Silanes - chemistry
Silicon Dioxide - chemistry
Surface Properties
Time Factors
Volatilization
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Summary:Nondilute nanoparticle dispersions were stabilized in liquid CO2 at 25 °C at pressures as low as the vapor pressure for greater than 30 min. By modifying hydrophilic silica with a trifunctional silylating agent, (heptadecafluoro-1,1,2,2-tetrahydrodecyl)triethoxy silane, a cross-linked polymer shell was formed around the silica core. The presence of the shell led to weaker Hamaker interactions between approaching fluoro-silica composite particles and enabled dispersibility at weaker solvent conditions (low pressures) than for metals with larger Hamaker constants. Steric stabilization of the nanoparticles was provided by low-molecular-weight perfluorodecane side chains at the surface of the fluoro-silica composite shell. Compared to polymeric chains, the perfluorodecane side chains are more easily solvated and thus stabilize nanoparticle dispersions in CO2 at much lower pressures, even down to the vapor pressure.
ISSN:0743-7463
1520-5827
DOI:10.1021/la048564u