Dual-Functional Rh6g@Eu-DDB as A Fluorescence-Enhanced Ratiometric Sensor for Norfloxacin and A Fluorescence Turn-Off Sensor for Nitrofurantoin in Water and Food Samples

Abstract

Norfloxacin (NFX) and nitrofurantoin (NFT) detections are of significance due to the threat on the human health from their excessive uses. A MOF-based composite of Rh6G@Eu-DDB was prepared through one-pot synthesis of Eu(NO3)3•6H2O with 1,3-di(3',5'-dicarboxylphenyl)benzene (H4DDB) with the presence of rhodamine 6G (Rh6G). Rh6G@Eu-DDB acts as a fluorescence-enhanced ratiometric sensor for NFX and a fluorescence turn-off sensor for NFT. Sensitivity test of Rh6G@Eu-DDB sensing NFX revealed a linear fitting equation of I613/I554 = 0.0642CNFX + 3.4103 (I554 and I613 = the emission intensities at 554 and 613 nm; CNFX = NFX concentration) with LOD = 69.71 nM. NFT detection test gave a linear fitting equation of (I0-I)/I = 0.0126CNFT (CNFT = NFT concentration) with LOD = 0.85 μM. The fluorescence assays using Rh6G@Eu-DDB were applied in water and milk for NFX, egg and honey for NFT, whose measured concentrations were close to the spiked concentrations and their fluorescence recoveries were around 100% with all RSDs less than 3%. It supports the presented fluorescence assays are reliable and accurate. The smartphone-assisted method contributes the visualization detections of NFX and NFT through the green/red values vs. concentration. This work provides a facile solution to antibiotics detection.