Solvothermal synthesis of Co1−xNixFe2O4 nanoparticles and its application in ammonia vapors detection

Magnetic Co1−xNixFe2O4 nanoparticles (NPs) were successfully synthesized via a solvothermal method using ethylene glycol as solvent. The samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM) and gas sensing test. The experimental results showed that the magnetic Co1−xNixFe2O4 NPs were composed of single phase spinel structure and the average crystallite size in the NPs is between 5.8 and 9.8 nm; the NPs are spherical with an average particle size of about 40–90 nm; the saturation magnetization (Ms) of the Co1−xNixFe2O4 NPs decreased linearly as the contents of Ni2+ increased; and the as-prepared Co1−xNixFe2O4 NPs have a higher selectivity toward ammonia vapors and the Co0.8Ni0.2Fe2O4 has the best gas sensitivity of Co1−xNixFe2O4 (0≤x≤1) NPs at working voltage of 8 V.