Cysteine-grafted chitosan-mediated gold nanoparticle assembly: from nanochains to microcubes

Molecule-mediated nanoparticle assemblies were obtained by the rational design and modification of chitosan, and grafting it onto gold nanoparticles, providing a new way for combining the virtues of synthetic and biological polymers. Using thiolate-functionalized chitosan molecules as soft templates, gold nanoparticles were found to self-organize into 1D nanochains via specific molecular recognition, or assemble into 2D needle-like crystals and 3D flower clusters through conformational change of the template. Such clusters may further re-crystallize into gold single crystal microcubes by way of a simple dialysis method. The as-prepared nano- and microstructures were characterized and the mechanism for the gold nanoparticle assembly process and microcrystal formation was revealed. This work demonstrates a simple and novel approach for fabricating well defined gold nano- and microstructures through a controlled nanoparticle self-assembly process.