104 / 2021-10-23 11:46:40

A double layer laminated film of cellulose nanocrystals and dye displaying vibrant circularly polarized light

Cellulose nanocrystals; Dye; Tunable circularly polarized light; Selective reflection; light absorption

Circularly polarized light materials with tunable properties are of importance in photonic technologies. In this work, we demonstrate that a double layer laminated film consisted of luminophore-embedded left-handed chiral nematic cellulose nanocrystals and a dye, denoted as CNC/luminophore||dye, produces fresh and vibrant circularly polarized light. We show that the right-handed circularly polarized luminescence enabled by CNC/luminophore can be transformed to a rich palette of circularly polarized light with tunable peak wavelength, peak g_lum and handedness upon propagating through a layer of non-fluorescent dye. This is achieved by controlling the level of overlapping between selective light absorption band of the non-fluorescent dye and the right-handed circularly polarized luminescence.



The mechanistic insight of this unique optical phenomenon is presented.



For example, when the right-handed circularly polarized luminescence from CNC/luminophore propagated through the dye layer can be partially absorbed while the remaining light toward both sides of the film then. One of the intrinsic circular polarization properties of CNC photonic crystal film is that it selectively reflects left-handed circularly polarized light and transmits right-handed circularly polarized light. Therefore, left-oriented circularly polarized luminescence transmits right-handed circularly polarized light when it encounters cellulose film, while left-handed circularly polarized light is not affected and is received by the detector. Right-oriented circularly polarized luminescence enters the detector directly. Therefore, the part of right-handed circularly polarized light is lost during dye manipulation. We believe that the selective light absorption, selective reflection of left-handed circularly polarized light and selective transmission of right-handed circularly polarized light are at work in a defect-embedded left-handed chiral nematic structure. Our method is simple for execution, easy for implementation and offers a facile method for generation of circularly polarized light with wide-ranging tunable band wavelengths, peak g_lum values and on-demand handedness. Our work provides a new method for synthetic construction of wavelength and handedness tunable circularly polarized light active materials that may be of significance in developing new information and display technologies.