A Novel Dual-Ratio Optical Probe Based on Europium-Doped Carbon Dots for the Detection of Tetracycline.

In this study, a dual-ratiometric optical probe utilizing europium-doped carbon dots (Eu-CDs) was developed for simultaneous fluorescent and colorimetric detection of tetracycline (TC). The Eu-CDs complex was synthesized through a hydrothermal approach. Upon coordination with Eriochrome Black T (EBT), the Eu-CDs complex exhibits a distinct magenta coloration. Introduction of TC triggers a ligand displacement reaction, resulting in color transition from magenta to blue, resulting in ratiometric colorimetric visual detection. Meanwhile, the TC-bound EBT-CDs@Eu complex emits ratiometric fluorescence change. A ratiometric fluorescence detection method was established for TC based on the absorbance-energy transfer-emission (AETE) mechanism, culminating in the successful design of a dual-ratiometric optical probe. The colorimetric assay demonstrated a detection limit (LOD) of 20.5 nM for TC. Furthermore, the practical applicability of this sensor was validated through successful TC detection in aquaculture samples, highlighting its potential for real-world monitoring applications.