Reversible self-assembly of gold nanoparticles in response to external stimuli

Abstract

Noble metal nanoparticles are highly attractive, owing to their optical, physical, electrical and chemical properties. Specifically, ease of surface modification, exceptional plasmonic and optical properties of gold nanoparticles (Au NPs) have created increasing interest in the assembly process. Once assembly is achieved successfully, the disassembly of the Au NPs is considered to be an exciting challenge. There are different kinds of forces involved in the assembly and disassembly process of Au NPs with a great deal involving the chemistry of surfactants. These forces can be externally triggered to achieve reversible assembly and disassembly. Less effort has been devoted to collate the study and mechanism involved behind environmentally or chemically triggered reversible assembly of Au NPs. Hence, the emphasis of this review is to highlight a number of promising stimuli such as light, pH, temperature and magnetic fields that can cause the reversible assembly of Au NPs. In addition, the surfactants utilized for assembly and disassembly of Au NPs under external stimuli response are examined. Furthermore, this review gives an account of the mechanism and chemistry of reversible assembly of Au NPs, taking into account the latest published literature. Indeed, it covers many ligands, biomolecules and thiol-mediated surfactants that can be linked to the surface of Au NPs and can also respond to external stimuli, realizing reversible assembly. The emerging challenges and an outlook on future developments in this research area are also discussed. The ultimate goal of this review is to encourage synthetic chemists to use ligand functionalized Au NPs (building blocks) for complex chemical systems as it will revolutionize the organic ligand synthetic processes that are responsive to different stimuli.