Synthesis of silver nanoparticles in a microfluidic coaxial flow reactor

The size and dispersity of nanoparticles (NPs) determine the properties that such particles display. In this study, synthesis of silver nanoparticles in a coaxial flow reactor (CFR) was investigated by confining the reaction and subsequent nucleation to an interface away from the channel wall. Silver NPs were formed at room temperature by reducing silver nitrate with sodium borohydride in the presence of sodium hydroxide, while trisodium citrate was used as the surfactant. The main parameters investigated were flow rate of reagents through the CFR and concentrations of trisodium citrate and silver nitrate. Decreasing the total flow rate resulted in the NP size and dispersity reducing from 5.4 +/- 3.4 nm to 3.1 +/- 1.6 nm. Increasing surfactant concentration reduced size and dispersity from 8.5 +/- 6.9 nm to 4.1 +/- 1.1 nm. By tuning the precursor concentration the size and dispersity could be reduced from 9.3 +/- 3 nm to 3.7 +/- 0.8 nm.