Successful synthesis of stable MFe2O4 nanoparticles@C has been realized by applying the novel concept of using levulinic acid possessing carboxyl and carbonyl groups to facilitate the interaction with metal ions (M(2+) and Fe(3+)) and the carbon source (phloroglucinol) in the sol-gel polymerization method. All the samples have been characterized by XRD, SEM, FT-IR, TEM, HRTEM, ICP-AES, CHNS, an...