A novel visual ratiometric fluorescent sensing platform for highly-sensitive visual detection of tetracyclines by a lanthanide- functionalized palygorskite nanomaterial

A palygorskite (Pal)-based ratiometric fluorescent nanoprobe is designed in order to establish a real time, on-site visual, and highly sensitive detection method for tetracyclines (TCs). The nanoprobe comprises the green emissive dye molecules embedded in the natural Pal, which serve as the internal reference signal. The potential red-emissive seed-europium (Eu 3+ ) ions are covalently bound on the surface of modified Pal, and they can act as the specific recognition element. The emission intensity of Eu 3+ ions significantly increases upon TC addition. The nanoprobe fluorescence changes from green to yellow, orange, or red, thereby accomplishing the visual ratiometric fluorescent detection. This nanoprobe exhibits a high sensitivity with a detection limit of 7.1   nM and an excellent selectivity in monitoring the levels of TCs in milk samples. In addition, this nanoprobe is useful for quantitative determination of TCs, and it is not affected with intensity fluctuations due to instrumental or environmental factors. The nanoprobe-immobilized test paper realizes real-time TCs analysis by using a smartphone with an easy-to-access color-scanning APP as the detection platform. Moreover, the reported construction of visual ratiometric detection system follows the sustainable development idea, that is, from nature, for nature, and into the nature.