Homogeneous polymer blend microparticles with a tunable refractive index.

We show that homogeneous polymer blend microparticles can be prepared in situ from droplets of dilute solution of codissolved polymers. Provided that the droplet of solution is small enough (<10 mum), solvent evaporation is rapid enough to inhibit phase separation. Thus the polymers that are being mixed need not be miscible, which greatly enhances the applicability of the technique.

Photonic polymers:a new class of photonic wire structure from intersecting polymer-blend microspheres.

We report a new kind of photonic wire structure made from the sequential attachment of polymer-blend microparticles. Using a linear quadrupole to manipulate the particles in space, we are able to take advantage of a modified surface structure in the blend particle to actively assemble particles in programmable two- or three-dimensional architectures. Strong resonance features in fluorescence are observed near the intersection of linked spheres that cannot be interpreted with a two-dimensional (equatorial plane) model.

Multiscale simulations of carbon nanotube nucleation and growth: electronic structure calculations.

Several first-principles surface and bulk electronic structure calculations relating to the nucleation and growth of single-wall carbon nanotubes are described. Density-functional theory in various forms is used throughout. In the surface-related calculations, a 38-atom Ni cluster and several low-index Ni surfaces are investigated using pseudopotentials and plane-wave expansions.

Three-dimensional photonic "molecules" from sequentially attached polymer-blend microparticles.

We report the observation of 3D linear or branched chains of polymer-blend microspheres generated from liquid droplets of solution where the modified surface structure of the polymer composite results in highly robust interparticle bonds. Using a linear quadrupole to precisely position particles in space, we are able to take advantage of this novel material property to actively assemble particles in programmable three-dimensional architectures. The robust interlocking nature of interparticle linkage gives rise to strongly coupled morphology-dependent resonances in bisphere and trisphere systems, suggesting the possibility of three-dimensional photonic "molecules" and microscale optical manipulation applications.