Microfluidic Multi-Scale Homogeneous Mixing With Uniform Residence Time Distribution For Rapid Production Of Various Metal Core-Shell Nanoparticles

Seed-mediated growth of core-shell nanoparticles, which is conventionally performed in a batch reactor, is successfully reproduced in a microfluidic reactor for a facile production of uniform metal core-shell nanoparticles. The proposed microfluidic design is based on the microstructure inversion for achieving multi-scale homogeneous mixing with uniform nanoparticle residence time. Simulations demonstrate that among the staggered herringbone microstructures investigated in this study, the upper herringbone (UH) structure can rapidly and homogeneously mix multiple-sized reagents and can also prevent both the irreversible trapping and long residence time of the nanoparticles inside the microfluidic channel. A wide variety of metal core-shell nanoparticles, namely Au@Ag, Au@Pd, and Au@Au with an interior nanogap, are synthesized by using the microfluidic reactor with built-in UH microstructures. The proposed microfluidic synthesis produces a more uniform shell size than the conventional batch synthesis. This work could significantly expand the practical utility of metal core-shell nanoparticles in a multitude of applications ranging from catalysis to nanomedicine.