Preparation of hollow nanoparticles with controllable diameter by one-step controlled etching of microporous silica particles using an ammonia-based etchant

Hollow silica particles with spherical morphology and controllable diameter (100–250 nm) were successfully prepared by one-step etching process using an ammonia-based etchant under mild etching conditions. First, microporous silica particles with a low degree of condensation were synthesized by modified Stöber method using low concentration of ammonia solution. Then, the microporous silica particles were coated with polydimethyldiallylammonium chloride (PDDA). The PDDA-coated particles were treated with an aqueous ammonia solution to obtain hollow silica nanospheres. In this study, the condensation degree of silica particles, PDDA concentration, ammonia etchant concentration, and etching temperature were found to have significant impact on the morphology of hollow silica nanoparticles. Adsorption studies showed that the hollow silica particles could be efficiently used for the immobilization of bovine serum albumin.