Synthesis of size-controlled hollow Fe3O4 nanospheres and their growth mechanism

Size-controlled hollow Fe3O4 nanospheres were synthesized via a one-pot hydrothermal method as a function of reaction time and sodium citrate, polyacrylamide, and urea content. Multiple characterization techniques such as scanning and transmission electron microscopy and Raman spectroscopy were employed to investigate the crystal structure and morphology of the obtained nanospheres. The Fe3O4 nanosphere formation mechanism was elucidated from analyzing the characterization data. High levels of sodium citrate and longer reaction times were observed to increase the diameter of the nanospheres until hollow structures formed. Furthermore, polyacrylamide and urea promoted the formation of hollow structures. The hollow-structured Fe3O4 nanospheres exhibited high magnetization saturation values in the range of 48.8–58.7 emu/g. The facile synthesis method described herein, to generate size-controlled Fe3O4 nanospheres with tailored properties, demonstrates potential across a wide range of fields from drug-delivery and stealth devices, to environmental and energy applications.