Gold Nanowire Chiral Ultrathin Films with Ultrastrong and Broadband Optical Activity

Abstract An ultrastrong and broadband chiroptical response is key but remains challenging for many device applications. A simple and cost‐effective bottom‐up method is introduced to fabricate large‐area long‐range ordered chiral ultrathin films with the Langmuir–Schaeffer technique using gold nanowires as building blocks. Significantly, as‐prepared ultrathin films display giant optical activity across a broad wavelength range covering visible and near infrared regions with an anisotropic factor of up to 0.285, which is the record value for bottom‐up techniques. Detailed experimental result and theoretical analysis disclose that such remarkable optical activity originates from birefringence and dichroism of the well‐aligned Au nanowire layers in the ultrathin films. The universality of this facile strategy for constructing chiral ultrathin films is further demonstrated with many other one‐dimensional nanomaterials.