Direct synthesis of three-dimensional Ag nanocrystal superlattices and their superhydrophobic films for a potential surface-enhanced Raman scattering substrate

Coinage metal nanocrystals (NCs) exhibit unique optical properties arising from localized surface plasmon resonance (LSPR) in the visible region, enabling applications in sensing and photonics. While individual NCs possess remarkable LSPR characteristics, their superlattices (SLs)-with small interparticle distances-are of greater significance for applications in electronic and plasmonic devices and optical metasurfaces. This work describes a facile one-pot synthesis of three-dimensional Ag NC SLs through van der Waals force-driven spontaneous self-assembly of NCs from precursor molecules. The resulting Ag NC SLs exhibit broad optical absorption from the visible to near-infrared regions owing to LSPR coupling and offer superhydrophobicity caused by their hydrophobic surface and micrometer-scale faceted structure, showing significant potential for molecular detection applications using Raman spectroscopy.