A method was developed to synthesize silver nanoparticles with controlled size and Localized Surface Plasmon Resonance (LSPR) wavelength. In a microchip, droplets with high monodispersity and stability were produced. Using droplets as microreactors, seed-mediated growth approach was successfully applied for silver nanoparticles preparation. It was observed that nanoparticles size and LSPR wavelength could be optimized via adjusting synthesis conditions, such as droplets heating temperature, reaction time, and concentration of silver seeds and silver nitrate in aqueous phase. These results indicated that the proposed microdevices could provide a convenient and inexpensive approach for preparing nanoparticles with optimum properties.

The unique electrical, optical and biological properties of silver nanomaterials have attracted significant attention of many researchers. Since the size and shape of silver nanomaterials have significant effects on the properties of silver nanomaterials, extensive research has focused on synthesis and characterization of silver nanomaterials. However, almost all of the syntheses of silver nanomaterials were carried out in traditional batch reactors, which typically suffer from inhomogeneous mixing and corresponding spatial variations under reaction conditions, ultimately leading to poor quality of the final nanomaterials. Recently, the emerging microfluidic technology not only furnishes novel strategies for the synthesis of silver nanomaterials but also brings great opportunities and impetus to improve the quality and yield of silver nanomaterials due to enhanced mass and heat transfer. The current paper reviews recent achievements in the synthesis of silver nanomaterials in flow microreactors. Various strategies adopted for the synthesis of silver nanomaterials in microreactors are presented and compared, including synthesis in single-phase and multi-phase flow microreactors. In addition, the factors that affect the size and size distribution of silver nanomaterials in flow microreactors synthesis are also discussed briefly.