Construction of fluorescent inverse opals by direct polymerization and their responsive behavior to solvents

Inverse opals are characterized by their continuous porous structures, which endow them with natural structural colors. The functionalization of inverse opals can be achieved either by modifying and loading functional materials onto their porous framework or by constructing them directly from materials with the desired functionalities. For fabricating fluorescent inverse opals, a common method involves adsorbing or incorporating fluorescent materials into the porous matrix. However, it relies on intermolecular forces such as electrostatic interactions and hydrogen bonding, which may sometimes lead to insufficient binding strength. Herein, fluorescent molecules are directly polymerized into the hydrogel matrix of inverse opal, achieving one-step fabrication of fluorescent inverse opal. The modification based on chemical bonds effectively ensures robust binding stability, while retaining the structural color of photonic crystals. Leveraging the hydrogel’s reversible volume changes and the varying polarity of the molecular chain groups, the resulting inverse opals exhibit responsive behavior to ethanol solutions of varying concentrations and fatty alcohols with different carbon numbers. The study paves the way for harnessing the combined effects of fluorescence and structural color of inverse opals, suggesting their potential in a range of applications including solvent detection, drug delivery, and beyond.

Graphical Abstract