Gold Nanowire Chiral Ultrathin Films with Ultrastrong and Broadband Optical Activity

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.