Journal article
Understanding voltage-induced localization of nanoparticles at a liquid-liquid interface
Journal of physics. Condensed matter, Vol.20(7), pp.073102-073102 (9)
02/20/2008
DOI: 10.1088/0953-8984/20/7/073102
Abstract
Functionalization of liquid-liquid interfaces is a hot area, driven by aspirations to build self-assembled interfacial structures with unique properties, in particular accessible to light from both sides of the interface. Adsorption of nanoparticles is an example of such functionalization. Interesting new developments take place in electrochemical liquid-liquid systems, consisting of two immiscible electrolytic solutions that form an interface impermeable to ions until a sufficiently high voltage is applied across the interface. The voltage drops across a nanoscale region near the interface due to the formation of two back-to-back electrical double layers on the two sides of the interface. This highly localized voltage drop opens a new possibility for the stabilization and control of interfacial architectures. This appears to be particularly important for metal and even semiconductor nanoparticles, because they are, in turn, 'functionalized'. They are covered by surfactants with acidic groups, some of which dissociate in water. Coverage with surfactants is required to avoid particle-particle agglomeration in the bulk. An electric field can push such nanoparticles to the interface or move them away, depending on the direction of the field. This, together with the change of the free energy of solvation of nanoparticles when they move from the bulk to the surface, are the two new decisive factors affecting their adsorption and desorption. We discuss these effects together with the more familiar ones that are known to determine interfacial localization of uncharged nanoparticles. The presented critical analysis is qualitative. Although we will try to rationalize the main effects by some simplified formulae, they should not be taken literally: they pave the way towards understanding of nanoparticle localization in these systems, rather than give exact answers. These equations will, however, help us to 'visualize' how a properly applied electric field, assisted by the interfacial tension but opposed by the line tension and the change in the free energy of hydration, causes stable localization at the interface. We show that for multiply charged nanoparticles, sustainable potential drops across the interface can give rise to deep adsorption wells with adsorption energies much larger than the thermal energy. The fine balance between adsorption and desorption forces, which depends on the particle size and charge, determines whether the particle will be localized at the interface or not and permits reasonable voltages to substantially modify their interfacial concentration.
Details
- Title: Subtitle
- Understanding voltage-induced localization of nanoparticles at a liquid-liquid interface
- Creators
- M. E. Flatte - Univ Iowa, Dept Phys & Astron, Iowa City, IA 52242 USAA. A. Kornyshev - Imperial Coll London, Dept Chem, London SW7 2AZ, EnglandM. Urbakh - Tel Aviv University
- Resource Type
- Journal article
- Publication Details
- Journal of physics. Condensed matter, Vol.20(7), pp.073102-073102 (9)
- Publisher
- Iop Publishing Ltd
- DOI
- 10.1088/0953-8984/20/7/073102
- ISSN
- 0953-8984
- eISSN
- 1361-648X
- Number of pages
- 9
- Language
- English
- Date published
- 02/20/2008
- Academic Unit
- Electrical and Computer Engineering; Physics and Astronomy
- Record Identifier
- 9984429021802771
Metrics
4 Record Views