The Synthesis of Size-Adjustable Superparamagnetism Fe₃O₄ Hollow Microspheres

One hundred fifty to 300-nm-sized monodisperse iron oxide (Fe₃O₄) hollow microspheres were synthesized by the one-pot hydrothermal method. The morphology and crystal structure of the as-prepared hollow microspheres was characterized by scanning electron microscopy, X-ray diffraction, transmission electron microscopy, and high-resolution transmission electron microscopy, while the magnetic property was investigated by vibrating sample magnetometer. We found that the particle size of the hollow microspheres was related to the amount of sodium citrate, polyacrylamide (PAM), and urea. The hollow structure of Fe₃O₄ microspheres has high magnetization saturation values ranging in 49.10-75.41 emu/g.