*2.1. Synthesis of Mesoporous Core/Shell Structured Silica Spheres (SiO2@mSiO2 Spheres)*

Core/shell silica spheres were used as a hard template to obtain HCS using our previous reported method [12]. In a typical synthesis, ethanol (100 mL, P.P.H. Stanlab, Lublin, Poland), tetraethyl orthosilicate (TEOS, Sigma Aldrich, Beijing, China) (4 mL) and concentrated ammonia (28 wt.%, 6 mL, CHEMPUR, Piekary Slaskie, Poland) were mixed and stirred for 24 h. Then, solid SiO2 spheres were dried for further use (SiO2). To prepare the SiO2@mSiO2 spheres, 100 mg of SiO2 spheres were dispersed in water (160 mL), ethanol (80 mL) and ammonia solution (28 wt.%, 0.67 mL). Then, 80 mg of the surfactant cetyltrimethylammonium bromide (CTAB, Sigma Aldrich, Beijing, China) and 0.37 mL of TEOS were added. After stirring for 24 h, the product was dried at 80 ◦C to get SiO2@mSiO2 spheres.
