Hybrid Nanostructures of Fe 3 O 4 and Au Prepared via Coprecipitation and Ultrasonic Spray Pyrolysis.

The coupled processes of coprecipitation and ultrasonic spray pyrolysis (USP) were used to synthesize Fe₃O₄-Au hybrid nanostructures. The first coprecipitation method enabled the synthesis of Fe₃O₄ nanoparticles by mixing iron salts' ions (Fe²⁺ and Fe³⁺) and ammonia as the base, and USP was used as the coating process of the Fe₃O₄ nanoparticles with Au. The formatted hybrid nanostructures consist of Fe₃O₄ nanoparticles that have Au on their surface in the form of gold nanoparticles (AuNPs). AuNPs have a crystalline structure and range in size from 10 to 200 nm. Additional characterization techniques, including ICP-OES, TEM, SEM, EDS, DLS, zeta potential, and room temperature magnetic hysteresis loops, were used to determine the chemical, physical, and magnetic properties of the Fe₃O₄ nanoparticles and hybrid nanostructures. It was found that USP produces separate AuNPs too (not just on the Fe₃O₄ surface), suggesting a bimodal formation of AuNPs. The zeta potential of the Fe₃O₄ nanoparticles showed poor stability (−15 mV), indicating a high tendency to aggregate, and the zeta potential of the hybrid nanostructures was also very low (≅0), which, comparatively means even worse stability. The saturation magnetization of the Fe₃O₄ nanoparticles was 35 emu/g, which is relatively lower than that of bulk Fe₃O₄, while the saturation magnetization of the hybrid nanostructures was significantly lower (0.1 emu/g) compared to the Fe₃O₄ nanoparticles. [ABSTRACT FROM AUTHOR]