(442b) Anomalous Dispersion of 'hedgehog' Particles

Authors: 
Bahng, J. H., University of Michigan
Yeom, B., University of Michigan
Wang, Y., University of Michigan
Tung, S. O., University of Michigan
Hoff, D., University of Michigan, Molecule Analysis in Real-Time (SMART) Center
Kotov, N., University of Michigan

Dispersion of colloids in ‘phobic’ solvents is unstable and leads to irreversible aggregation.  A stable dispersion in ‘phobic’ environment requires chemical camouflages that provides polarity matching with the environment, thereby increasing the particle-solvent affinity, and that provides steric and electrostatic effects, thereby increasing the particle-particle repulsion. Tuning such colloidal behavior by physical canopy would overcome the limitations imposed by interfacial chemical modification and also preserve the pristine properties and functionalities. In this research, we show that the ‘hedgehog’ particles with arrays of high aspect ratio ZnO nanowires coated on a surface of microsphere exhibit stable dispersion in both ‘philic’ and ‘phobic’ media. From the experimental findings and calculations, high surface corrugation leading to limited contact area and increased minimum interaction distance drastically reduces the attractive potential. Solvent-ionization at the air-water interfaces of trapped air-pockets in the nano-topography provides extra repulsive potential in the case of aqueous dispersion of hydrophobic HPs.  Low ionic strength provides longer-range repulsive potential in the case of hydrophilic HPs in non-polar organic media. The findings could lead to reduction in the use of the volatile organic compound in a wide spectrum of industries ranging from pharmaceutical to paint, enable new strategies for exotic colloidal behavior and self-assembly, and exhibit unexplored or enhanced physicochemcial properties ranging from photophysics to catalysis.