Understanding colloidal transport has become increasingly important, with applications in fields from materials science to biology. However, while many of these disciplines involve nanoscale systems, much remains to be understood about the behavior of colloids under confinement. To this end, we have used resistive-pulse sensing, an electrochemical detection technique, to explore surprising material-dependent size selection in polystyrene and silica nanoparticle transport through silica nanochannels. When two different particle sizes are present in equal concentrations in solution, geometric constraints predict that smaller particles will be detected more frequently than larger ones. We find that while this behavior is indeed observed with silica particles, when the particle material is switched to polystyrene a reverse size selection is exhibited, with larger particles passing through the channel much more frequently, suggesting that surface interactions play a key role in determining transport. To further investigate these unexpected results, we have studied the influence of the following factors on particle entrance and transport: particle material, channel geometry, applied pressure, applied voltage, solution pH, and solution temperature. Determining the role of these parameters will not only enable improved separation techniques and more accurate particle characterization, but will also facilitate a better fundamental understanding of important interfacial behavior under confinement.

Exploring colloid-surface interactions and anomalous particle transport behavior in silica nanochannels

248th National Meeting (2014)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.