HEDGEHOG PARTICLES

Physicochemical characteristics of particles are sensitive to any alterations, or even a small perturbation, in its constitutive properties, sizes and shapes. Hence, drastic property and behavioral changes may be imagined with particles architected with pronounced surface corrugation, yet is barren in previous studies. In Kotov Lab, we have created arrays of particles with high aspect-ratio interfacial nanotopography, which we christened ‘hedgehog’ particles to reflect its morphology. We are conducting fundamental studies on ‘hedgehog’ particles which have modified and reshaped the characteristic expectations of particles that have been referenced in the existing paradigm. Diverse types of ‘hedgehog’ particles have been constructed to date. The list includes composite microparticles with polymeric sphere as the core on which ZnO nano-spikes are sculpted normal to the core surface. Other types include iron diselenide and iron disulfide ‘hedgehog’ particles in the nanometer regime.

The first wave of discoveries on the behavioral changes that results from pronounced interfacial corrugation is alteration in the interaction potential between such particles that leads to dispersion stability in ‘phobic’ solvent, thereby breaking the “similarity rule”. Hydrophobic particles in water and hydrophilic particles in oil aggregate, but can form colloidal dispersions if their surfaces are chemically camouflaged to impart affinity to the solvent. We have shown that nano-topographical effect can also be used to disperse particles in a wide range of solvents without recourse to surface modification to mask the particles’ surfaces. This anomalous dispersion behavior of the hedgehog particles, overturning the notion that like dissolves like, might help to mitigate adverse environmental effects of the use of surfactants and volatile organic solvents, and deepens our understanding of interparticle interactions and nanoscale colloidal chemistry.