Facile Construction of Soft Plasmonic Sensors with Exceptional Optical Activity for Quantitative Chiral Detection

The facile construction of transmissive films with ultrabroad optical activity, spanning from deep-ultraviolet to short-wave infrared and offering convenient tunability across a wide range, is highly desirable for applications in sensing, imaging, and communication. However, achieving this remains challenging. Here, an easily applied wet-stretching method is introduced that simultaneously orients polymeric substrates and surface-coated plasmonic nanorods. Stacking two such hybrid films at an angle produces ultrastrong (ellipticity≈10⁴ mdeg, g_abs≈1) and broadband (200-2500 nm) circular dichroism (CD). The polymer's excellent strength and flexibility allow for broad-range tuning of the CD spectra by applying external force. The optical activity is sensitive to intervening medium, facilitating chiral detection of various inserted analytes in the forms of films, salt pellets, or solutions. This cost-effective and scalable fabrication strategy not only pioneers an expandable method for inducing chirality across diverse materials, but also offers a universal approach for constructing precise, non-destructive, non-contact, and reusable chiral sensors.