Macroscopic Self‐Assembly and Optical Characterization of Nanoparticle–Ligand Metamaterials

A self‐assembled metamaterial exhibiting a positive near‐zero index of refraction at visible wavelengths is demonstrated. The metamaterial consists of thiolene‐functionalized gold nanospheres self‐assembled into macroscopic, crosslinked, monolayers. By measuring the real and imaginary parts of the phase shift of light transmitted through the self‐assembled films the effective index of refraction is determined as a function of wavelength. These findings may pave a way to simply and efficiently self‐assemble and optically characterize multifunctional, multilayer nanoparticle–ligand metamaterials. Self‐assembly of macroscopic gold nanosphere–ligand films is demonstrated to produce optical metamaterials. Using phase separation and surface tension gradients nanoparticles are capped with thiol ligands, self‐assembled into macroscopic monolayers and transported onto non‐functionalized substrates. By measuring the real and imaginary parts of the phase shift of light transmitted through the self‐assembled films a positive near‐zero index of refraction at visible wavelengths is demonstrated.