Stimuli-responsive circularly polarized luminescent films with tunable emission

Circularly polarized luminescence (CPL) exhibiting materials responsive to external stimuli are attracting rapidly increasing interest for developing advanced smart photonic materials. Herein, tuning CPL emission in both intensity and wavelength is achieved by controlling fluorescence and chirality. The CPL composite film was constructed by the co-assembly of an achiral fluorescent polymer containing dansyl groups (PD) and partially desulfurated cellulose nanocrystals (CNCs). A left-handed cholesteric crystal structure was formed in the PD/CNC film. The film responded to multiple stimuli including acid/base, water content and polar solvent. CPL emission of the composite film can be tuned by controlling the fluorescence of PD and by adjusting the chirality of CNCs via external stimuli. Emitting-quenching of fluorescence emission is due to dansyl groups sensitive to acid/base, which contribute to the reversible control of CPL intensity. Varying adsorption content of water or contacting polar solvent caused the film to show a structural color change in the full wavelength range of visible light, which in turn led to a corresponding wavelength variation in CPL emission. The prepared CPL composite film demonstrates controllable and repeatable responsivity, and accordingly has great potential in developing new information and display technologies.