Detection Of Tetracycline With Eu/Zn-based Ratio Fluorescent Probe

As a widely used antibiotic,the abuse of Tetracyclines（TCs）can lead to environmental pollution and food safety problems,and even pose a serious threat to people’s health.Therefore,it is necessary to develop efficient,convenient,and sensitive methods for the detection of TCs.Fluorescence detection has the unique advantages of visualization,high sensitivity,and simple operation,and performs well in common detection methods.Ratiometric fluorescence sensor,as a fluorescence detection method,exhibits the ability to self-calibrate.As well as.it can reduce the interference of irrelevant factors,overcome the lack of obvious color change,and achieve highly sensitive detection of TCs.Herein,three kinds of ratiometric fluorescence sensors were developed,which were based on the specific interaction of Eu or Zn with TCs.Three ratiometric fluorescence sensors were capable of sensing TCs with high sensitivity.In addition,the mechanism of the sensors to TCs was explored,and the practical application of the sensors was tested.The main contents are as follows:（1）A ratiometric fluorescent probe based on 2-aminoterephthalic acid（ATA）and Eu³⁺-Cit（citrate）complexes(ATA-Eu³⁺-Cit)was developed to achieve highly sensitive detection of TCs.The sensing performance of single-emission fluorescence probe for TCs was compared to the ratiometric fluorescent probe,and it was confirmed that ratiometric fluorescent probes had better performance.The fluorescence emission of ATA can be quenched by TCs thanks to the inner filter effect（IFE）.Moreover,TCs can chelate Eu³⁺accompanied by the energy transfer defined as“Antenna Effect”（AE）that caused the enhanced red fluorescence of Eu³⁺.The fluorescence color of the solution system gradually changes from blue to red,with the increase of the concentration of added TCs.It can be confirmed that the linear detection range was 0.1-100μM,with limit of detection（LOD）as low as 33 n M for tetracycline hydrochloride（TCH）.Furthermore,the probe exhibited good selectivity for TCs.From the experimental results,the fluorescence sensor can achieve convenient,fast,and sensitive detection for TCs.（2）Detection of TCs based on Zn doped carbon quantum dots（Zn-CDs）via ratiometric fluorescence.Zn-CDs with bright blue fluorescence was synthesized via hydrothermal method using sodium citrate and zinc chloride as precursors.The diameter of prepared Zn-CDs was about 1.9 nm,and it had good optical stability.When TCs were present in the Zn-CDs probe,blue fluorescence of Zn-CDs was quenched and green fluorescence of TCs was enhanced,which can be attributed to inner filter effect and chelation.Moreover,it can be proved that the designed sensor had a wide detection range of 0.1-50μM,with LOD of 61.1 n M for TCH.Besides,there was a good linear relationship between the RGB of the fluorescence color of the solution and the concentration of TCs,with the assistance of smartphone.Furthermore,the Zn-CDs-based test strips were used for simple and direct visual identification of TCs successfully.According to the experimental results,the doping of Zn not only improved the fluorescence performance of CDs,but also the performance for the detection of TCs.（3）Synthesis of Luminescent metal-organic frameworks（LMOFs）Zn-TCPP and ratiometric fluorescence sensing of TCs.The red fluorescent Zn-TCPP,synthesized from Zn（NO₃）₂ and TCPP,was a lamellar structure,and had a enrichment effect on TCs.The fluorescence of the sensor gradually changed from red to yellow after the addition of TCs.The reason for the enhancement of yellow fluorescence was the complexation of Zn with TCs.Furthermore,the red fluorescence can be quenched by TCs thanks to photoinduced electron transfer（PET）.The LMOFs was confirmed to exhibit a good linearity in the range of 0.1-25μM,and the LOD was calculated to be 65 n M.Additionally,Zn-TCPP had good selectivity and practical application for TCs.As the experimental results,the detection performance made the sensor show a good application prospect.