Light-Responsive Gold Nanoparticle Vesicles Based on Oligo(ethylene glycol)-Terminated Azophenol Ligands

We demonstrate that a tri(ethylene glycol)-terminated azophenol ligand (TrAL) can self-assemble with 10 nm gold nanoparticles into gold nanoparticle vesicles (GNVs) in tetrahydrofuran (THF) due to the solvophobic effects of surface ligands. Upon ultraviolet (UV) irradiation (365 nm), the azophenol moieties in TrAL undergo trans-to-cis photoisomerization, which alters the ligand's solvophobic interaction and dipole-dipole interaction and triggers a secondary self-assembly process, driving GNVs to form hierarchical aggregates. Remarkably, exposure to visible light (450 nm) reverses this transition by regenerating the trans isomer, thereby restoring the dispersed vesicular state. This photoswitchable behavior is attributed to TrAL's dynamic light-responsive character, which modulates interparticle interactions and enables precise, reversible control over colloidal assembly. The system exhibits excellent cyclability, retaining structural integrity over multiple UV/visible light cycles. These findings highlight the potential of TrAL-functionalized GNVs as programmable nanoscale platforms for applications such as adaptive photonics and reconfigurable soft materials, where spatiotemporal control over self-assembly is critical.