Light-induced assembly of colloidal nanoparticles based on photo-controlled metal–ligand coordination

Self-assembly of colloidal nanoparticles is a promising approach for the fabrication of functional materials. Zeta potential strongly influences the self-assembly processes of nanoparticles. Light-induced zeta potential manipulation provides spatiotemporal resolution. However, current studies on photo-controllable zeta potential are based on ultraviolet (UV) light. In comparison with UV light, visible light is better suited to control the zeta potential of colloidal nanoparticles. In the present study, we applied visible light-responsive ruthenium (Ru) complexes, grafted onto the surface of silica nanoparticles (Ru-SNPs), to control their assembly. The Ru complexes were photoresponsive. Irradiation of Ru-SNPs induced the release of Ru complexes from the nanoparticle surface. The released Ru caused a decrease in the zeta potential of colloidal Ru-SNPs that further changed the assembly behavior and led to the aggregation of Ru-SNPs.