Control of particle morphology from porous to hollow by spray-drying with a two-fluid nozzle and template materials

Spray-drying with a two-fluid nozzle was used to produce composite particles consisting of silica or titania nanocolloids and template particles (polystyrene latex: PSL). Template particles were then removed from the composite particles by heating or washing with organic solvent to yield respectively porous SiO2 and TiO2 particles. The average size and standard deviation of particles prepared by spray-drying with the two-fluid nozzle were 1.31 mu m and 1.59 respectively. When the size of template particles was varied in the rage of 100-400 nm, porous particles were synthesized with template particles of 200 nm or smaller, while hollow particles were obtained with template particles of 300 nm or larger. In addition, polyethylene glycol (PEG) porous particles could be obtained by the same method.