Researchers at the University of Illinois have discovered a fundamentally new approach for tailoring the stability of colloidal suspensions.
Colloidal suspensions are complex fluids utilised in numerous applications ranging from advanced materials to drug delivery.
Controlling the stability of these fluids can influence such characteristics as flow behaviour, structure and mechanical response, and may result in materials with improved optical and electrical properties.
Jennifer Lewis and her colleagues have devised a process that they call nanoparticle haloing.
This self-organising process imparts stability to otherwise attractive colloidal microspheres by decorating regions near their surface with highly charged nanoparticles.
‘Using this nanoparticle haloing approach, we can control the phase behaviour and structure of materials assembled from colloidal systems,’ said Lewis, a UI professor of materials science and engineering and of chemical engineering. ‘Our approach complements traditional stabilisation techniques, such as electrostatic stabilisation, by allowing systems of negligible charge or high ionic strength to be stabilised.’
Tailoring the interactions between particles is said to allow the researchers to engineer the desired degree of colloidal stability into the mixture.
‘That means we can create designer colloidal fluids, gels and even crystals,’ said Lewis. ‘Our ability to control colloidal forces and phase behaviour depends not only on the charge of the nanoparticles, but also on their size.
‘Through nanoparticle engineering, we can assemble structures with properties that would not be possible through traditional stabilisation routes.’
Lewis has teamed up with co-author Paul Braun, a UI professor of materials science and engineering, to explore the use of these nanoparticle-stabilised colloidal microsphere mixtures in assembling robust periodic templates for photonic band gap materials.