Nanoparticles in Layered Media

Lead Research Organisation: University of Edinburgh
Department Name: Sch of Physics and Astronomy

Abstract

Nanoparticles are of great technological importance but are very difficult to manipulate and control. Good progress has been made in two areas: the first is the control of size and shape of the particles themselves. The second is a recent demonstration that the particles can be fused together by joining crystallographically equivalent facets. This implies that nanoscale building blocks can be combined like 'lego' bricks. Unfortunately progress with arranging semiconductor nanoparticles (bringing the lego bricks together) is more limited. This is an essential step to creating nanoscale electronic devices. My research will address this problem. My approach will be to manipulate the particles by dispersing them in a solvent that has ordered phases. I will specifically make use of layered phases to confine particles in two-dimensional regions. It is possible that the nanoparticles will then interact with each other via their effect on the host solvent. This could lead to the controlled aggregation of particles. A major strength of my approach is that the successful procedures are not dependent on the particular chemistry of the nanoparticle. Hence it should be possible to repeat techniques with a range of different sorts of particle. A later development will be to use non-equilibrium phenomena to assist with spatial organisation of the particles. Layered phases are novel states of matter in their own right. Consequently our research on their relationship with dispersed nanoparticles is of fundamental significance beyond nanotechnology. We anticipate creating new partially ordered phases and arrested states that will provide a challenge to theories of soft composites and membranes with inclusions.

Publications

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Herzig EM (2009) Dynamics of a colloid-stabilized cream. in Physical review. E, Statistical, nonlinear, and soft matter physics

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Van't Zand DD (2011) Hindered coarsening of a phase-separating microemulsion due to dispersed colloidal particles. in Langmuir : the ACS journal of surfaces and colloids

 
Description The samples used contained a high concentration of surfactant (soap-like) molecules. The chosen ingredients separate into two parts one concentrated in soap and the other not when they are warmed up. We found that adding small particles to these ingredients significantly alters this separation behaviour. In particular the process was radically slowed down and contained some completely new features.
Exploitation Route We used a recently developed x-ray technique to study the motion of complex samples in time. We found that the motion was dominated by occasional large rearrangements rather than by a succession of small changes. The changes we focused on are similar to "shelf life" problems that occur in many commercial products that have a gel / thick liquid consistency.
Sectors Agriculture, Food and Drink

 
Description A research project on particles in a phase separating microemulsion has implications for a widely used method for purifying or concentrating biological macromolecules. Phase separating liquids of various kinds are used to separate a desired macromolecule from a sample containing a various different components. When the liquids phase separate the desired macromolecule moves into one of the liquid domains while the unwanted components go into the other domain. The macromolecules can then be harvested easily. We used small particles as model macromolecules that are easy to see. We observed them in a phase separating system of the type that is used by biologists and other practitioners. What we found was that, in addition to the desired separation effect, the particles also significantly altered the behaviour of the liquids. Beneficiaries: Biologists and technologists who use phase separating liquids to purify or concentrate macromolecules