The synthesis of iron oxide nanoparticles (IONPs) with a narrow size distribution (PDI < 0.2 in DLS) with tailored physicochemical properties remains a significant challenge in the field of nanotechnology for biomedical applications. This study presents a droplet-based microfluidic platform for the continuous synthesis of Magnetite (Fe 3 O 4 ) nanoparticles through co-precipitation under strongly alkaline conditions (pH = 12.3), without the use of surfactants. By optimizing precursor concentrations (0.75% FeSO 4 ·7H 2 O and 1.2% FeCl 3 ·6H 2 O for sample C2), we successfully produced IONPs with a hydrodynamic diameter of approximately 25 nm, as confirmed by dynamic light scattering (DLS). A comprehensive characterization approach was employed, utilizing a variety of analytical techniques including X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and vibrating sample magnetometry (VSM). This multifaceted approach yielded several significant findings. First, the analysis indicated high crystallinity, characterized by narrow size distributions with a mean diameter ranging from 17 to 31 nm. Second, the study identified superparamagnetic behavior, with saturation magnetization (Ms) values between 63 and 72 emu g −1 . Sample C2 was found to exhibit a balanced trade-off between structural and magnetic characteristics, making it a promising core candidate for further functionalization and application-specific evaluation, once appropriate surface modification and functional performance testing are implemented. This microfluidic approach enhances mixing uniformity and hydrodynamic reproducibility within droplet microreactors, enabling consistent nucleation–growth conditions and scalable production of Fe 3 O 4 nanoparticles with narrow size distribution in colloidal dispersion (PDI < 0.2 by DLS).
Khoshmardan et al. (Sun,) studied this question.