Thermosensitive and Thermoreversible 1D Assemblies of Plasmonic Nanoparticles

Abstract

We have studied the fine-tuning of plasmonic coupling from the charged nanoparticle(NP)s in aqueous solution and revealed the thermoreversible assembly of one-dimensional structure by the temperature-dependent surface charge variation of NPs. When the linear assemblies start developing in aqueous solution by adding salt to diminish the electrostatic force, the charged NPs evade the relatively strong electrostatic repulsions of the chain sides and prefer to the chain ends, proceeding to nanochains by end-on attachment. The linear self-assembly process is reversible when nanoparticles are modified with adequately strong surfactants which bring the short-range steric repulsion by surfactant layer to counter the van der Waals attraction between NPs at high ionic strength. And the thermoresponsive assembly and disassembly were reversible by the temperature-dependent surface charge variation which directly affect the electrostatic repulsion of NPs. Interestingly, the specific temperature limited the average chain length of the linear nanostructures as a form of the temperature memory and thus, the hue differences based on temperature-dependent surface plasmonic coupling are easily discernible by the naked eye and the UV-vis spectra. This simple and cost-effective concept could represents a new strategy to development of novel functional devices in related fields of nanobiotechnology, nanoelectronics, and phononics.