Self‐Assembled Colloidal Nanopatterns toward Unnatural Optical Meta‐Materials

Abstract 2D nanoscale patterns have been extensively investigated for various applications including information storage devices, non‐volatile memory devices, chemical or biological sensors. Recently, such nanostructured patterns have been gaining lots of attention because of their potential uses as meta‐materials or meta‐surfaces with unnatural optical properties. In particular, self‐assembled colloidal monolayers of gold nanoparticles (NPs) have been demonstrated as optical meta‐materials for unnaturally high refractive index (n_eff > 4) at optical frequency. Raspberry‐like particles or spherical assembly of NPs are also investigated for negative or near‐zero index of refraction. Thanks to the recent advance in colloidal chemistry for shaping NPs with controlling the interaction, non‐close‐packed, or even non‐periodic colloidal nanostructures can be achieved, which may be potentially useful for optical meta‐surfaces. In this article, a brief introduction of optical meta‐materials is provided and recent progress for high‐index and negative‐index meta‐materials are reviewed. In the second part, the meta‐surfaces will be briefly described including fundamental principle and some of the key potential applications. Finally, the recent experimental progress of high‐precision self‐assembly for the meta‐surface fabrication will be discussed.