Microspheres with tunable refractive index by controlled assembly of nanoparticles

Microspheres with tunable functional properties are prepared by controlled aggregation of nanoparticles in emulsion droplets. In particular, complex rutile-phase morphologies are obtained by heat treatment of anatase titania aggregates. The refractive index of the microspheres can be modulated by using mixtures of silica and titania suspensions. In addition, dye doping is achieved by simply adding dye molecules into the titania suspension.