Interfacial Capillary-Force-Driven Self-Assembly of Monolayer Colloidal Crystals for Supersensitive Plasmonic Sensors

Colloidal lithography technology based on monolayer colloidal crystals (MCCs) is considered as an outstanding candidate for fabricating large-area patterned functional nanostructures and devices. Although many efforts have been devoted to achieve various novel applicatons, the quality of MCCs, a key factor for the controllability and reproducibility of the patterned nanostructures, is often overlooked. In this work, an interfacial capillary-force-driven self-assembly strategy (ICFDS) is designed to realize a high-quality and highly-ordered hexagonal monolayer MCCs array by resorting the capillary effect of the interfacial water film at substrate surface as well as controlling the zeta potential of the polystyrene particles. Compared with the conventional self-assembly method, this approach can realize the reself-assembly process on the substrate surface with few colloidal aggregates, vacancy, and crystal boundary defects. Furthermore, various typical large-scale nanostructure arrays are achieved by combining reactive ion etching, metal-assisted chemical etching, and so forth. Specifically, benefiting from the as-fabricated high-quality 2D hexagonal colloidal crystals, the surface plasmon resonance (SPR) sensors achieve an excellent refractive index sensitivity value of 3497 nm RIU^-1 , which is competent for detecting bovine serum albumin with an ultralow concentration of 10^-8 m. This work opens a window to prepare high-quality MCCs for more potential applications.