Synthesis and applications of graphite carbon sphere with uniformly distributed magnetic Fe3O4 nanoparticles (MGCSs) and MGCS@Ag, MGCS@TiO2

Magnetic graphite carbon spheres (MGCSs) with well-distributed Fe3O4 magnetic nanoparticles were synthesized via the following steps. The colloidal carbon spheres (CCSs) with uniformly dispersed Fe(II) and large numbers of hydroxyl groups were synthesized via synchronous hydrothermal reaction of glucose and ferrous gluconate. The CCSs were then converted to MGCSs via consequent thermal treatment. In addition, the hydroxyl groups of the as-prepared CCSs were also utilized to adsorb Ag+ ions or condensate with Ti-OH. Following a thermal treatment, composite MGCS@Ag or MGCS@TiO2 microspheres were fabricated. The results of SEM, TEM and XRD revealed that MGCSs with an average diameter of 1 mm were synthesized; and magnetic Fe3O4 nanoparticles with diameters from 20 to 25 nm were uniformly distributed in MGCSs, which indicated that Fe(II) in the CCSs not only changed into magnetic Fe3O4 nanoparticles, but also worked as a catalyst for the graphitization of amorphous carbon during the thermal treatment. Such a strategy gave at least two advantages. First, the protective effect on the magnetic nanoparticles and mechanical strength of the graphite carbon may improve the capability and feasibility of practical applications. Synchronously, the MGCSs not only have well adsorbing properties as carbon materials, but also possess unusual adsorbing behaviours for heavy metal ions and noble metal ions, which have significant potential applications in the treatment of polluted water and the recovery of noble metals. Second, the synthesis of composite MGCSs may further expand the scope of the applications. For example, the MGCS@Ag and MGCS@TiO2 microspheres prepared in this effort exhibited excellent antibacterial activity and selective enrichment of phosphopeptides, respectively.