Granick Research Group
University of Illinois at Urbana-Champaign


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Colloids (MOONs): Modulated Optical Nanoparticles

This novel technique enables us:

(1) to measure the rotational dynamics of colloidal particle with single-particle resolution; (2) to create geometrically symmetric but chemically asymetric materials.

Movie 1: MOONs

Fluorescence emission of a colloidal particle was modulated by making one hemisphere opaque with coated metal. This movie shows the real-time Brownian rotation of a 1 micron latex particle in water-glycerol mixture.

Movie 2: Quadramer Rotation

A rod-like quadramer was made by assembling 4 particles in a line. This movie shows the real-time rotational diffusion along the long axis of the rod.

Movie 3: Flower

In a recent breakthrough, we have created a new type of Janus particle, positively charged on one hemisphere and negatively charged on the other hemisphere. They are found to self-assemble into novel clusters, which we envision as the first step towards an end goal of assembling colloidal 'molecules.' This movie showes one typical cluster, the pentagonal dipyramid. In the movie, note that although adsorbed onto a quartz surface, it rotates freely like a flywheel.

Lipid vesicles (liposomes):

The biomolecular applications of phospholipid vesicles are currently severely impeded by their poor structural stability. They are prone to fuse with one another in suspension, forming larger vesicles and a polydisperse size distribution. When they encounter solid substrates, they form bilayers on hydrophilic surfaces and monolayers on hydrophobic surfaces -- in both cases losing their integrity. In a recent breakthrough, this research has discovered a novel, versatile, exceptionally effective strategy to stabilize phospholipid vesicles in soluton, as well as to decorate solid surfaces with intact vesicles.

Movie 1: Vesicle-12nM-fusion

This epifluorescence movie illustrates that naked (unstabilized) liposomes fuse with each other and form giant liposomes when the volume fraction exceeds 3%.

Movie 2: Vesicle+Latex-128nM

This epifluorescence movie illustrates that nanoparticle-stabilized vesicles are protected against fusion up to exceptionally high volume fractions, in this case 32%. Extensions of this strategy allow one to stabilize thousands of vesicles on solid surfaces, forming patterns with micron-scale periodicity.

Nanoparticles on lipid tubules:

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The Granick research group is an affiliated member of the Materials Research Laboratory,
the Beckman Institute, the Center for Nanoscale Science and Technology.