A facile two-step etching method to fabricate porous hollow silica particles

[Display omitted] ► Hollow silica particles are synthesized with Stöber silica particles. ► The process is facile than the conventional templates method. ► It does not need expensive organic silica precursors. ► Large pores with an average diameter of ∼12nm can be generated on the shell. ► The hollow particles can effectively uptake protein-based biomolecules (hemoglobin). We report here the fabrication of hollow silica particles with mesopores larger than 10nm on their wall via a facile two-step etching method. Different from the conventional template method, the new method uses the silica particles as starting materials, which were synthesized using the well-known Stöber method. In the hollow silica preparation, first, we gently etch the silica particles with a NaOH solution without using template molecules to make them porous. Then, we coat the porous silica particles with poly-dimethyldiallylammonium chloride (PDDA) and treat the PDDA-coated porous silica with an ammonia solution to form the hollow silica nanospheres. In this study, we found that the NaOH dosage and ammonia concentration have significant impact on the morphology of the final products. Adsorption was also studied and results show that the hollow nanospheres can effectively uptake protein-based biomolecules (hemoglobin).