Convective Self-Assembly of 2D Nonclose-Packed Binary Au Nanoparticle Arrays with Tunable Optical Properties

The controllable assembly of nanoparticles into nonclose-packed (NCP) arrays exhibits unusual optical properties [e.g., surface lattice resonances (SLRs)] but are challenging to construct, especially for NCP binary arrays composed of diversified nanoparticles. Here, we show the construction of two-dimensional (2D) NCP binary Au nanoparticle arrays by modulating the convective self-assembly of colloidal nanoparticles on a templating NCP nanoparticle array. By dramatically inhibiting the coffee ring effect during convective evaporation, this convective assembly approach allows colloidal nanoparticles to stack around the templating nanoparticles, forming a "core-satellite" basic architecture. Moreover, this approach is generalized for various types, shapes, and periodicities of building nanoparticles. The assembled 2D NCP binary Au arrays attain multiple tunable optical properties, including photonic band gaps, plasmonic SLRs, and dynamic surface-enhanced Raman scattering activity, based on tunable plasmonic coupling. The anticounterfeiting application of these NCP binary arrays is demonstrated by taking advantage of their unique optical properties. This convective assembly approach can pave the way for the development of a new category of NCP binary arrays and help to explore their collective unconventional properties.