Thermoplasmonics Enable the Coupling of Light into the Solvent-Mediated Self-Assembly of Gold Nanoparticles

Nanoparticles (NPs) offer their core as well as surfacefor manifestingvarious optoelectronic properties, making them one of the prominentclass of materials in modern science. Here, we have used NPs as thebuilding blocks to choreograph a multistimuli-responsive, dynamicsolvent-mediated self-assembly process. Plasmonic NPs functionalizedwith hydrophobic thymine thiol (Thy-AuNPs) dispersed in dimethyl sulfoxide(DMSO) were our choice of NP building blocks. The hygroscopic natureof DMSO led to the autonomous dissolution of atmospheric moistureinto the DMSO dispersion of Thy-AuNPs, thereby triggering the assemblingstep. This led to the formation of long-term stable (for weeks) controlledaggregates of Thy-AuNPs, wherein the inherent plasmonic propertiesof Thy-AuNPs were well preserved. This enabled the use of core-thermoplasmonicproperties of Thy-AuNPs in realizing the disassembly step. The sunlight-triggeredplasmonic heat dissipated from the Thy-AuNPs in controlled aggregateswas used as the thermal energy source for the evaporation of water,which further triggered the disassembly step. In this way, sunlightwas coupled as a fuel into the solvent-mediated dynamic self-assemblyprocess of plasmonic NPs. Raman studies prove that the products ofthe self-assembly process controlled aggregates and denselypacked plasmonic NP film can serve as effective surface-enhancedRaman scattering (SERS) substrates for analytical applications. Theconcept of light-coupled solvent-mediated dynamic self-assembly wasextended to plasmonic NPs of different sizes and cores, proving thegenerality of our approach. The ability to retain the plasmonic propertiesof Thy-AuNPs in the aggregated state enabled the use of the core propertiesof NPs in achieving the disassembly step, which in turn led to therealization of dynamicity, multistimuli-responsiveness, and substantialityin the self-assembly process of NPs.