Size control of monodisperse hollow ORMOSIL particles using a self-emulsion process

•Hollow silica particles with a controlled size were synthesized without external templates via two-step methods.•ORMOSIL particles were synthesized using PTMS in a one-pot acid-base catalyzed sol–gel process.•Hollow silica particles were prepared by mild etching of the less condensed core component of ORMOSIL particles.•The particle sizes were precisely controlled by manipulating synthetic parameters.•This strategy is not only less time consuming, but also environmentally benign by not using corrosive etching chemicals.