Control of interparticle spacing in stable aggregates of gold nanoparticles by light irradiation

This study describes the modulation of interparticle distances in aggregates of gold nanoparticles by light irradiation. Stable aggregates of a series of imidazolium-presenting gold nanoparticles were obtained via a photo-responsive mono-carboxylate linker. In the first step, the mono-carboxylate linker attracted the gold nanoparticles to form water-dispersive aggregates of gold nanoparticles with hydrophobic surface properties. By irradiating the aggregates with ultraviolet, the photo-responsive linker was transformed, leading to the generation of another carboxyl group. As a result, the gold nanoparticles were tightly bound via the dicarboxylate linkers. These changes decreased the interparticle distances in the aggregates, as verified by microscopic observations, and can induce significant changes in their optical characteristics. To the best of our knowledge, this is the first example of a light-driven manipulation system for the distribution of nanoparticles in an aggregate.