The silica-coated Fe3O4 magnetic microspheres were prepared via a direct sol–gel co-condensation technique. Typically, 200 mg of Fe3O4 was uniformly dispersed into a solution containing 30 mL of EtOH and 150 mL of H2O by using a 500 W ultrasonic crasher for 15 min at room temperature. Subsequently, 2.5 mL of ammonia (28%) and 2.0 mL of TEOS were added sequentially dropwise into the above suspension. After stirring the resulting mixture for 6 h at room temperature, the solid and liquid phases were separated by applying an external magnetic field, and the obtained solid was then washed with ethanol and water for three times. The products were obtained by drying at 60 °C for 12 h in a vacuum and denoted as Fe3O4@SiO2.