A dual-response ratiometric fluorescent sensor by europium-doped CdTe quantum dots for visual and colorimetric detection of tetracycline.

• A europium-doped CdTe quantum dots fluorescence sensor was easily fabricated. • The sensor exhibited a dosage-sensitive and broad-chromatic detection strategy. • CdTe quantum dots enhanced the emission of europium ions by charge transfer. • Dual-response sensor offered multicolor variations for naked eyes. • The sensor visibly detected tetracycline under the maximum residue limits in milk. Residues in animal food and drinking water caused by the abuse of antibiotics lead to cell resistance and many chronic diseases in the human body. Therefore, it has become an inevitable trend to develop a fast, easy-to-use, on-site/real-time visualization method for the detection of antibiotics. Herein, we report a dual-response ratiometric fluorescence sensor which is fabricated by chelating europium ions (Eu3+) onto cadmium telluride quantum dots (CdTe QDs) for real-time and visible detection of tetracycline (TC). With the TC addition, the fluorescence of probe can be seen by the naked eye, from green to yellow and finally to red, exhibiting a dosage-sensitive and broad-chromatic detection strategy for TC. The fluorescence intensity ratio of I 616 /I 512 of Eu/CdTe QDs sensor displays a good linear relation to TC concentrations in the range of 0–80 μM with a limit of detection (LOD) of 2.2 nM. In addition, the sensor can visually detect 200 nM TC in actual samples, which is lower than the maximum residue limit (MRL) of the safety standard. The methodology reported here opens a window toward the real applications of fluorescent and shows the wide applicability in pursuing the concepts simple, rapid, visual, and real-time for food safety and environmental protection. [ABSTRACT FROM AUTHOR]