Droplet-Based Microfluidic Synthesis of Anisotropic Metal Nanocrystals

• Published in: Small (Weinheim an der Bergstrasse, Germany) Germany), 2009-12, Vol.5 (24), p.2828-2834
• Main Authors: Duraiswamy, Suhanya, Khan, Saif A.
• Format: Article
• Language: English
• Subjects: anisotropic materials; Anisotropy; Crystallization - methods; Droplets; Gold; Macromolecular Substances - chemistry; Materials Testing; Metals - chemistry; Microchannels; Microfluidic Analytical Techniques - methods; Microfluidics; Molecular Conformation; Nanocrystals; Nanomaterials; nanoparticles; Nanostructure; Nanostructures - chemistry; Nanostructures - ultrastructure; Nanotechnology - methods; Particle Size; Surface Properties
• ISSN: 1613-6810; 1613-6829; 1613-6829
• DOI: 10.1002/smll.200901453

A droplet‐based microfluidic method for the preparation of anisotropic gold nanocrystal dispersions is presented. Gold nanoparticle seeds and growth reagents are dispensed into monodisperse picoliter droplets within a microchannel. Confinement within small droplets prevents contact between the growing nanocrystals and the microchannel walls. The critical factors in translating macroscale flask‐based methods to a flow‐based microfluidic method are highlighted and approaches are demonstrated to flexibly fine tune nanoparticle shapes into three broad classes: spheres/spheroids, rods, and extended sharp‐edged structures, thus varying the optical resonances in the visible–near‐infrared (NIR) spectral range. A droplet‐based microfluidic method is presented for the preparation of anisotropic gold nanocrystal dispersions, and tunability of the shape and optical resonance of these dispersions is demonstrated. Gold nanoparticle seeds and growth reagents are continuously dispensed into small picoliter droplets formed at a microfluidic T‐junction (see image). The critical factors in translating macroscale flask‐based methods to a flow‐based microfluidic method are also highlighted.