Dynamic Chirality in Nature-Inspired Photonic Crystal Films: Ultralong Room Temperature Phosphorescence and Stimuli-Responsive Circularly Polarized Luminescence.

Circularly polarized luminescence (CPL) systems exhibiting room-temperature phosphorescence (RTP) are attracting considerable attention for applications in information encryption and smart sensing. However, achieving ultralong circularly polarized RTP (CPRTP) with tunable chirality and stimuli-responsive CPL remains challenging. Inspired by the color-changing properties of the butterfly, we developed a cellulose nanocrystal (CNC)-based photonic crystal film with an ultralong RTP lifetime of 2.04 s. The helical pitch of photonic crystal film could be engineered by adding different amounts of glucose, leading to 3-fold and 4-fold enhancement of the phosphorescence and fluorescence quantum yields, respectively, compared to the samples without glucose. The system exhibited green afterglows lasting over 4 s and tunable photonic bandgap (PBG) that modulated chiroptical properties, achieving high values of -0.749 for fluorescence and -0.650 for phosphorescence. Additionally, the film demonstrated stimuli-responsive features such as humidity-responsive RTP and solvent-responsive CPL. Therefore, the biomimetic photonic crystal film offers promising opportunities for multilevel anticounterfeiting, information security, and smart sensing applications.