Fabrication of complex nanostructures by colloidal chemistry

Structural control of nanomaterials is of paramount significance for nanodevice fabrication. Our group aims to develop methodologies for the synthesis of complex nanostructures by emulating the synthetic methodologies of organic chemistry. Multi-step nano-reactions will be set up so that the products of each reaction step is stabilized, recovered, and then purified for subsequent reactions. We have so far demonstrated several basic concepts for the colloidal reactions of nanoparticles, such as coupling reaction, valency control, protection schemes, and separation methods. Several novel nanostructures have been synthesized, for examples, core-shell nanoparticles with a variety of surface ligands for multiplexed surface-enhanced Raman scattering detections, high purity dimers and trimers of gold nanoparticles, Janus (two-faced) gold nanoparticles with partial polymer shell, open polymer nanochannels with two diametric openings, triple-layer and yolk-shell nanoparticles, linear chains of gold nanoparticles of variable length, and hetero-aggregates of gold nanoparticles with specific formulae AB, AB₂, AB₃ and AB₄. The current focus is to impart specific functionalities to a judiciously designed nanostructure, where the different components could coordinate to achieve a certain function. Generally speaking, solution methods are more facile, scalable, and reproducible than surface-based fabrication methods. The long-term goal is to fabricate nanodevices by multi-step colloidal self-assembly of nano-components.