Structure-dependent light-responsiveness of chemically linked nanoparticle clusters

Abstract

Self-assembled colloidal nanoparticle (NP) clusters are one of the bottom-up processing products to construct complex two- and three-dimensional optical materials. We show metal NP clusters chemically linked by a light-sensitive organic ligand to build up nanophotonic hybrid structures. NPs are spheres identical in size with narrow polydispersity, enabling systematic structural modifications. Before randomly aggregating and settling down, the chemical interlinking of NPs behaves like a polymerization procedure, generating characteristic cluster structures with a specific fractal dimension (D). The absorbance in the UV-vis and THz regions is significantly modified depending on the cluster structures. In contrast with physical aggregation, the absorbance of chemically linked NPs can be blue-shifted in the UV-vis region, which is prominently beneficial for solar energy utilization. Applied electron beams modify the cluster structures and induce blue-shifts in UV-vis light absorbance. These types of chemically constructed NP clusters can be a general method for new metamaterial design useful for effective light energy use.