Firstly, 0.8 g FeSO4$7H2O and 0.9 g

Firstly, 0.8 g FeSO4$7H2O and 0.9 g FeCl3$6H2O were dissolvedin mixed solution of water (200 mL) and ethanol (40 mL) underthe condition of vigorously stirring. Aer reacting for 30minutes NH3$H2O (15 mL) was added to the solution slowly asprecipitating agent. Another 15 min was needed for the reactiononce the color of the mixed solution turned black. The obtainedFe3O4 magnetic nanoparticles were washed several times withwater and then dried in vacuum for further use.Secondly, 80 mg magnetic nanoparticles were dispersed inmixed solution of water (10 mL) and ethanol (150 mL) byultrasonic for 30 minutes. Then NH3$H2O (3 mL) and TEOS (2mL) were added into the system and the pre-hydrolysis of TEOSwould last for 4 h under vigorously stirring at 30 C.Finally, the reaction performed another 4 h prior to theaddition of APTMS. Aerward the precipitate was collected,washed several times, dried in vacuum and reserved for nextstep. The whole reaction (as Scheme 1 showed) was performedunder nitrogen atmosphere.