Competition-Based Two-Dimensional Photonic Crystal Dually Cross-Linked Supramolecular Hydrogel for Colorimetric and Fluorescent Dual-Mode Sensing of Bisphenol A

Bisphenol A (BPA), one of the most abundantly produced endocrine disrupting chemicals, is widely used in everyday plastic products and thus must be monitored. Multimode sensing platforms are able to combine the advantages of different strategies while solving the issues of inaccurate test results of single signal sensing. However, the exploration in this field is limited due to the compromise of sensing conditions and inevitable mutual interferences of different systems. Herein, we constructed a two-dimensional photonic crystal dually cross-linked supramolecular hydrogel (2DPCDCSH) by utilizing a host-guest pair of β-cyclodextrin (β-CD) and tert-butyl (t-Bu) as the second cross-linking for colorimetric and fluorescent dual-mode sensing of BPA. Based on the fact that BPA can act as a competitive guest to break the host-guest interaction between β-CD and t-Bu, the cross-linking density decreased and an expansion-induced structural color change occurred. Sensitive and selective BPA detection can be easily achieved by measuring the Debye diffraction ring diameter or observing the color change of 2DPC with a detection limit of 1 μg mL-1. Moreover, the formation of the β-CD/BPA complex gave a significant enhancement of the intrinsic fluorescence of BPA, obtaining a detection limit of 0.001 μg mL-1. The two sensing systems can share the same reaction condition and yield a wider dynamic response range than the single signal strategy. Overall, the proposed method presented an efficient, rapid, cost-effective, and regenerative dual-mode method for BPA analysis and shed new insights for the design of diversified sensing platforms.