Taming the Photonic Behavior of Laser Dyes Through Specific and Dynamic Self‐Assembly onto Cellulose Nanocrystals

Abstract

Cellulose nanocrystals are used as "attractive meeting points" to enhance the photonic signatures of laser dyes physically adsorbed onto it, or in the proximity to it, thanks to a set of unique properties, such as nanometric size, surface charge, and a giant dipole moment capable of inducing a strong Stark effect into the molecular electronic transitions. Cellulose nanocrystals (CNCs) display a set of unique properties such as surface charge, nanometric size, and giant dipole moment that have not been considered so far to tame the luminescent properties of organic dyes upon soft and hard photoexcitation. Herein, the first comprehensive analysis on the photonic behavior of laser dyes adsorbed onto CNCs through physically dynamic driving forces is reported. By systematically varying the solvent, the dye molecular structure, and dye/CNC ratios, it is shown that the dye absorption and emission signatures are drastically modified when CNCs are incorporated into the solutions. The photonic characterization, together with molecular dynamic simulations, allows to unravel the labeling interaction processes and unambiguously assigns both the physicochemical properties of the surrounding media and the giant permanent dipole moment of CNCs as the most important factors taming the photophysical and lasing properties of dyes adsorbed on it. Accordingly, a CNC‐induced Stark effect accounts for the absorption and emission spectral changes recorded upon CNC incorporation. Herein, the widely expanding applications of CNCs toward the design of advanced photoactive nanomaterials based on these renewable building blocks are opened up.