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

Abstract

Nanoparticles (NPs) offer their core as well as surface for manifesting various optoelectronic properties, making them one of the prominent class of materials in modern science. Here, we have used NPs as the building blocks to choreograph a multistimuli-responsive, dynamic solvent-mediated self-assembly process. Plasmonic NPs functionalized with hydrophobic thymine thiol (Thy-AuNPs) dispersed in dimethyl sulfoxide (DMSO) were our choice of NP building blocks. The hygroscopic nature of DMSO led to the autonomous dissolution of atmospheric moisture into the DMSO dispersion of Thy-AuNPs, thereby triggering the assembling step. This led to the formation of long-term stable (for weeks) controlled aggregates of Thy-AuNPs, wherein the inherent plasmonic properties of Thy-AuNPs were well preserved. This enabled the use of core-thermoplasmonic properties of Thy-AuNPs in realizing the disassembly step. The sunlight-triggered plasmonic heat dissipated from the Thy-AuNPs in controlled aggregates was used as the thermal energy source for the evaporation of water, which further triggered the disassembly step. In this way, sunlight was coupled as a fuel into the solvent-mediated dynamic self-assembly process of plasmonic NPs. Raman studies prove that the products of the self-assembly process─controlled aggregates and densely packed plasmonic NP film─can serve as effective surface-enhanced Raman scattering (SERS) substrates for analytical applications. The concept of light-coupled solvent-mediated dynamic self-assembly was extended to plasmonic NPs of different sizes and cores, proving the generality of our approach. The ability to retain the plasmonic properties of Thy-AuNPs in the aggregated state enabled the use of the core properties of NPs in achieving the disassembly step, which in turn led to the realization of dynamicity, multistimuli-responsiveness, and substantiality in the self-assembly process of NPs.