Synthesis of Macroporous Titania and Inorganic Composite Materials from Coated Colloidal SpheresA Novel Route to Tune Pore Morphology

A new method for fabricating macroporous inorganic and inorganic composite materials with tailored pore morphologies (i.e., pore wall thickness and open or closed pore structure) is described. Polystyrene (PS) colloidal spheres coated with polyelectrolyte (PE) multilayers (PS−PE) or silica nanoparticle (SiO 2 )/PE hybrid multilayers (PS−SiO 2 /PE) have been used as templates to produce macroporous structures. By infiltration of a titanium dioxide (TiO 2 ) precursor, titanium (IV) isopropoxide, into templates of close-packed coated colloidal spheres, followed by removal of the organic material (PS core and PE layers) by calcination, macroporous TiO 2 and inorganic composite structures were produced. The pore morphology of the resulting macroporous structures depends on the nature of the multilayers deposited on the colloidal spheres. Open pore structures were obtained by templating close-packed assemblies of PS−PE colloidal spheres, while a closed pore structure was achieved by templating PS−SiO 2 /PE particle assemblies. The wall thickness of the resulting pores can also be tuned by altering the number of multilayers deposited on the colloidal spheres. Increasing the number of multilayers on the spheres causes an increase in the wall thickness of the macroporous structures.