Falcon 15 ml conical centrifuge tubes

To selectively remove the inner core and leave the porous shell relatively intact, Na₂CO₃ was selected as the etching agent. The synthesized core-shell silica and organosilica particles (csSPs and csOPs, respectively) were resuspended in 12.5 mL of 0.6 M Na₂CO₃ solution and stirred (500 rpm) at 80 °C for 1 h. The resulting particles were collected by centrifugation (10 min at 5000× g at room temperature in Falcon™ 15 mL conical centrifuge tubes), washed with MQ water two times and then repeated two times with ethanol. Finally, the synthesized hollow particles were resuspended in 10 mL of ethanol solution containing 10% concentrated HCl and stirred at 60 °C for 3 h to remove CTAB. The last step was repeated three times to ensure complete removal of the CTAB. The final products were resuspended in 20 mL MQ water. Different particles are named as porous hollow silica particle-160/280_xyz (pHSP-160/280-xyz) and as porous hollow organosilica particle-160/280-xyz (pHOP-160/280-xyz) based on the type of the used precursor, where the first three digits refer to the nominal diameter of the sSiO₂ core (i.e., 160 nm or 280 nm), while x, y, and z refer to the amount of precursor (TEOS or BTEE), ammonia, and surfactant (CTAB), as shown in Table 1.