Facile Fabrication of High-Quality Plasmonic Nanoparticle Lattices and Investigation of Their Optical Properties

Abstract

Plasmonic nanoparticle lattices have emerged as promising platforms for precisely tuning light–matter interactions through collective optical modes, such as surface lattice resonances (SLRs). In this study, we demonstrate the large-area fabrication of gold nanocube lattices via a template-assisted nanoimprinting technique and systematically analyze their structural, optical, and chiroptical properties. By varying the particle size, concentration, and solvent composition, high-quality two-dimensional nanoparticle arrays were achieved. Two key strategies were implemented to enhance the quality of the lattice resonances. Ultraviolet–ozone (UVO) treatment improved the structural robustness of the lattice and selectively removed surface-bound organics, enabling accurate refractive index matching between the substrate and superstrate. As a result, the Q-factor of the SLR was enhanced by up to 53%. Finite-difference time-domain (FDTD) simulations were employed to quantitatively evaluate the effects of vertical stacking, lateral extension, and structural asymmetry within unit clusters on resonance behavior, with good agreement to experimental observations. Although individual nanocubes are geometrically achiral, circular dichroism (CD) signals were observed near the Rayleigh anomaly and SLR, attributed to subtle asymmetries in the assembled clusters. To further amplify chiroptical responses, chiral thiol-functionalized molecules were either post-adsorbed onto the lattice or embedded directly during the printing process via co-printing. While both methods enhanced CD signals, the co-printing approach yielded stronger responses, reaching up to 120 mdeg and 15 mdeg in the LSPR and SLR regions, respectively. These enhancements were particularly pronounced in nanocube-based lattices with flat facets and narrow gaps, highlighting the critical role of near-field interactions between molecules and plasmons. This work demonstrates a simple and scalable strategy that synergistically combines structural and molecular chirality. The co-printing of chiral molecules with nanocube lattices offers superior performance compared to conventional CD amplification methods, paving the way for advanced applications in chiral optical sensing and polarization-selective photonic devices.