Synthesis of hollow microsphere chains and their magnetic properties

Fe3O4 hollow microsphere chains with lengths of 8–11 μm have been solvothermally synthesized in the mixed solution of glycerol and water with 1 M NaOH. The hollow microspheres have diameters in the range 0.7–1 μm, and the thickness of the shells is 150–300 nm. The shell of the hollow microspheres is constructed by octahedrons of 100–170 nm. However, when the concentration of NaOH is adjusted to 3 M, the octahedron chains with lengths of 30–50 μm can be obtained. The magnetic saturation values of hollow microsphere chains and octahedron chains are 88.1 and 102.4 emu/g at room temperature, respectively.