Controlled growth of Cu nanoparticles by a tubular microfluidic reactor

A microfluidic reactor process (MRP) has proved to be a flexible approach in nanoparticle synthesis. A controlled-growth process for nanoparticles (NPs) production, based on a tubular microfluidic reactor, was demonstrated using copper NPs as a model. This process includes continuous mixing of the washing reagent with the preformed NP seed solution for controlled release of the surfactant around the small NP seeds in a Y-mixer. This promotes growth of seeds in a micro-tubing with inner diameter of 127 μm. Nearly monodispersed copper NPs, with critical size 135.6 ± 11.4 nm, can be obtained by this controlled-growth process in the micro-tubing. As a control experiment, NPs grown by the bottle-batched washing process show greatly increased polydispersion, as demonstrated by a dual-peak size distribution with one peak at 6.2 ± 2.6 nm and the other at 36.4 ± 14.4 nm. The two different growth procedures also endow the Cu NPs with distinct differences in their crystallinity and optical properties.