Fabrication of europium doped carbon dots as ratiometric probe and smartphone assisted system for rapid and extremely sensitive detection of norfloxacin

Norfloxacin (NFX) residue contained in food products like meat, milk, and other products obtained from animals causes severe human health issues, and the residue harms the environment. Hence, it is very important to develop the method for rapid and extremely sensitive detection of NFX. In this study, we used europium nitrate (III) hexahydrate, citric acid, and urea, to fabricate europium-doped carbon dots (Eu-CDs), a dual emission ratiometric probe by hydrothermal method. In this present study, NFX interact with the probe and shows dual emission fluorescence when NFX transfer the energy to probe and enhances Eu 3 + emission intensity via antenna effect. The NFX concentration range increases from 5 nM to 6000 nM (0.005 µM-6 µM) and fluorescence intensity ratio I 700 /I 431 also increases that shows the good linearity with 1.3 nM LOD. This study shows high sensitivity and selectivity. We explore the excellent recoveries in real samples such as milk in between 97.3% and 103% and in water as 97.2–99.5%. In addition, we further explored smartphone-based sensing platform that provides a cost-effective, fast, portable and quantitative analysis of NFX.