Synergistic enhancement of rhodamine 6G fluorescence by photonic crystals and β-cyclodextrin for sensitive detection of EGCG

A Rhodamine 6G fluorescence sensor was developed through synergistic enhancement combining β-cyclodextrin host–guest regulation with hollow-sphere photonic crystals amplification. • The sensor enabled ultrasensitive detection of (-)-epigallocatechin gallate with an ultra-low theoretical detection limit of 5.1 × 10 -16 mol·L -1 and a broad concentration-dependent fluorescence response • The sensing platform exhibited excellent reproducibility and strong anti-interference capability, demonstrating reliable performance in complex sample matrices. (−)-Epigallocatechin gallate (EGCG) is one of the most abundant bioactive polyphenols in tea, and its rapid and sensitive determination is of great importance for food quality control and safety evaluation. Herein, a highly sensitive fluorescence sensing platform based on the synergistic enhancement of hollow-sphere photonic crystals (HSPCs) and β-cyclodextrin (β-CD) is developed for the quantitative detection of EGCG. The photonic band-edge effect and light localization effect of HSPCs, combined with microenvironment regulation induced by the host–guest inclusion interaction of β-CD, synergistically amplify the fluorescence emission intensity of rhodamine 6G (Rh6G). Under acidic conditions, EGCG reacts with ammonium molybdate to form molybdate ester complexes, which induce selective fluorescence quenching of Rh6G, enabling an indirect sensing strategy with a good linear response. Benefiting from the synergistic contribution of structural optical field modulation and molecular microenvironment engineering, the proposed sensor achieves a theoretical limit of detection (LOD) of 5.1 × 10 −16  mol·L −1 , together with good selectivity, anti-interference capability, and reusability. In practical tea sample analysis, satisfactory recoveries are obtained, confirming the accuracy and reliability of the method. This study demonstrates that synergistic fluorescence amplification provides an effective strategy for the sensitive detection of bioactive small molecules in complex food matrices. Download: Download high-res image (139KB) Download: Download full-size image