High throughput continuous synthesis of size-controlled nanoFe3O4 in segmented flow

NanoFe3O4, a magnetic nanoparticle, boasts wide-ranging applications, from magnetic separation to imaging, labeling, and remote control of targeted drug delivery. However, the conventional nanoFe3O4 synthesis in a batch reactor is time- and energy-intensive. In the currently developed continuous synthesis strategies, the complexity of the rotating packed bed reactor and the low capacity of the microfluidic chip impedes the application of these devices for the fabrication of nanoFe3O4. Hence, for the continuous synthesis of nanoFe3O4, a simple and convenient device with high throughput is urgently required. Microfluidic technology presents promising approaches that can enhance mass and heat transfer in segmented flow, surpassing the limitations of conventional methods. In this study, continuous synthesis of nanoFe3O4 was achieved in segmented flow within a microchannel, utilizing the coprecipitation method. The influence of iron concentration, reaction temperature, and the Fe2+:Fe3+ ratio on the synthesis of nanoFe3O4 were investigated thoroughly. Based on the results, analyzed through X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), this segmented flow synthesis strategy was proved to be capable of fabricating nanoFe3O4 of approximately 6 nm. Moreover, by increasing the high-speed valve frequency, thus reducing the segment length, the size distribution range of nanoparticles was reduced and uniform nanoparticles were synthesized. The continuous synthesis method developed through our research offers significant advantages over other existing technologies in terms of productivity and manufacturing cost. Therefore, it offers a promising pathway for the industrial-scale continuous synthesis of nanoFe3O4.