(198h) Size-Controlled Silver Nanoparticle Synthesis in a Jet-Mixing Reactor

Silver nanoparticles (Ag NPs) are of interest as catalysts for organic reactions, antimicrobial, bio-sensing and bio-imaging agents, and in conductive materials. They are conventionally produced via batch processes. These result in a wide variability in product properties such as the particle size distribution (PSD), because of poor mixing. Further, the transition of nanoparticle synthesis from lab-scale testing to bulk production calls for higher throughput, which is challenging to achieve in a batch reactor. Microfluidic reactors have been explored as alternatives that counter both these disadvantages. We illustrate the use of a simple, inexpensive continuous jet-mixing reactor for room temperature Ag NP synthesis. Ag NPs were synthesized by reduction of silver nitrate by sodium borohydride, using trisodium citrate as the capping agent. Characterization was done using UV-Visible Spectroscopy (UV-Vis), Dynamic Light Scattering (DLS) and Transmission Electron Microscopy (TEM). The effect of jet flowrate on Ag NP PSD was investigated. Increasing the flowrate from 48 mL/h to 200 mL/h indicated no change in the PSD and particle size, suggesting the reaction can be scaled-up without affecting product properties. Further, the stable long-term operation of the reactor was tested. Ag NPs sampled intermittently were found to have similar properties, demonstrating successful continuous operation. We also demonstrate that a range of particle sizes can be produced by varying the residence time between addition of reducing agent and capping agent. Future work will involve characterizing the mixing dynamics of the reactor and synthesis of bimetallic and core-shell NPs at high temperature.