Synthesis and characterization of pore size-tunable magnetic mesoporous silica nanoparticles

► We perform the pore size tuning during the mesoporous silica growth on Fe3O4 seeds. ► The interactions of auxiliary organics with seeds and reagents regulate the efficiency. ► A joint incorporation of swelling agents maximizes pore size in a controlled fashion. ► The great potential of these nanoparticles as DNA carrier is demonstrated.