Toward a tetravalent chemistry of colloids

We propose coating spherical particles or droplets with anisotropic nanosized objects to allow micron-scale colloids to link or functionalize with a 4-fold valence, similar to the sp(3) hybridized chemical bonds associated with, e.g., carbon, silicon, and germanium. Candidates for such coatings include triblock copolymers, gemini lipids, metallic or semiconducting nanorods, and conventional liquid crystal compounds. We estimate the size of the relevant nematic Frank constants, discuss how to obtain other valences and analyze the thermal distortions of ground-state configurations of defects on the sphere.