Panyi Xi, Yu Cao, Tanyi Tan, Xichong Ye* and Feng Liu*. J. Mater. Chem. C, 2025, DOI: 10.1039/d5tc01653c

Compared with traditional rigid chiral 2D materials, soft plasmonic films can efficiently regulate circular dichroism (CD) or circularly polarized luminescence (CPL) under external force by combining anisotropic plasmonic structures with flexible polymer matrices. In recent years, the combination of uniaxial alignment and multilayer twisted stacking has provided an expandable and efficient approach for the preparation of optically active materials. However, how to achieve highly ordered plasmonic nanostructures through the synergy of polymer structure design and efficient preparation methods remains a key challenge at present, and structural orderliness is the core factor for obtaining excellent chiral optical activity.

Figure 1. CPL performance of the multilayer chiroptical films and the signal regulation under mechanical stimulation.

Figure 2. Scheme of information encryption and decryption process based on chiroptical programmable films.

In this work, we utilized waterborne polyurethane (WPU) with an ultra-high stretch ratio (>1000%) as the substrate to composite with Tempo-oxidized cellulose nanofibers (TOCNF) and silver nanowires (AgNWs), achieving a perfect unidirectional alignment of the single-layer structure under axial tensile stress. Subsequently, the bilayer-oriented hybrid films (AgNWs@WPU/TOCNF) were assembled layer by layer at a certain deflection angle through water vapor-induced hydrogen bond reorganization. The self-healing bilayer assembled films exhibited significant optical activity, with an ellipticity exceeding 13° and an absorption asymmetry factor (g_abs) over 0.6. Furthermore, through self-healing assembly with the fluorescent layer, based on the selective absorption theory, significant CPL was obtained, with the luminescence asymmetry factor (g_lum) reaching up to 0.5. The inherent self-healing ability of the WPU matrix enables the multilayer films to fuse into a continuous integral structure, eliminating interface defects and significantly enhancing device stability and cyclability. Additionally, this flexible film can effectively regulate the positive/negative, ellipticity and wavelength of the CD/CPL signals by changing external mechanical stimuli. Finally, by taking advantage of the programmable CD characteristics of the multilayer films, a multi-level information deep encryption/decryption process was demonstrated. In summary, this work provides a multifunctional and scalable platform for constructing flexible chiroptical materials and devices, and shows broad application prospects in flexible photonics, information encryption transmission, and wearable optical devices.

First Author: Xi Panyi, doctoral candidate, Xi’an Jiaotong University

Correspondence Authors: Prof. Liu Feng, A/Prof. Ye Xichong, Xi’an Jiaotong University

Full Text Link: https://doi.org/10.1039/D5TC01653C