Eco-friendly cellulosic photonic pigments with tunable structural color for anti-counterfeiting and decorative applications

Cholesteric cellulose films exhibiting an adjustable reflection wavelength across the entire visible range were obtained through the application of ultrasound treatment to a suspension of cellulose nanocrystals (CNCs) prior to casting. The influence of both low and high intensity ultrasound power on the structural color of iridescent films was systematically investigated, along with an elucidation of the mechanism behind helical pitch regulation. The findings reveal that low ultrasonic power applied to the CNC suspension has minimal impact on the structural color of the CNC film, primarily enhancing the dispersion of CNC. On the other hand, high ultrasonic power applied to the CNC suspension can effectively adjust the structural color thanks to not only improving the dispersion of CNCs suspensions, but also altering the morphology and size of the CNCs. More importantly, co-friendly cellulosic photonic pigments with tunable structural color can be easily obtained utilizing the fragility of iridescent films for applications such as anti-counterfeiting labels, nail modification and decorative coatings and so on, thereby demonstrating considerable potential for practical utilization.