Construction And Applications Of Photoelectrochemical Sensor For Agricultural Antibiotics Detection

The misuse of agricultural antibiotics has led to their residues entering aquatic systems,adversely affecting aquatic organisms,damaging ecological water quality and the water cycle,and threatening ecological balance and human health.Photoelectrochemical（PEC）sensors have shown great potential for application in the field of antibiotic detection due to their high sensitivity,ease of operation and short analysis time.In this thesis,two PEC aptamer sensors were developed for the sensitive detection of antibiotics in river water.In addition,a PEC aptamer sensor was fabricated for the detection of antibiotics in milk,using the Yudai River water in Zhenjiang,Jiangsu Province as the research target.The main research elements are as follows.1.A PEC aptamer sensor for the selective detection of sulfadimethoxine（SDM）was successfully constructed using a Bi OCl/Bi OIO₃/Bi OI ternary heterojunction with excellent photoelectric properties as the photoactive material and SDM aptamer as the specific recognition element,then the photoelectric detection signal sensing mechanism and PEC sensing mechanism were investigated.The linear range of the sensor was1×10^-4～100 ng m L^-1 and the detection limit was 3.3×10^-5 ng m L^-1.The actual detection performance of the developed sensor was investigated using the standard addition method.The results showed that the recovery of SDM ranged from 99.2 to 102.0%with a relative standard deviation（RSD）of 1.9～4.2%,indicating that the PEC aptamer sensor for the detection of SDM has some potential for wider application.2.In this thesis,we have used carbon nitride quantum dots doped Bi₄O₅Br₂（CN QDs-Bi₄O₅Br₂）as the photoelectric active material and enrofloxacin（ENR）aptamer as the specific recognition element.The experimental conditions including the ratio of composite materials and aptamer concentration were systematically optimised to successfully construct a PEC aptamer sensor with good performance for the detection of ENR.The linear range of the sensor was 1×10^-1～1×10⁶ ng m L^-1 and the detection limit was 0.033 ng m L^-1.The results showed that the recoveries were 98.0～102.0%and the RSDs were 2.9～5.2%,which demonstrated that the sensor could be used for the detection of ENR in real river water samples.3.In addition,Bi OI/Ru（bpy）₃²⁺composite microspheres were prepared by electrostatic interaction,and a highly sensitive PEC aptamer sensing method was constructed for the detection of ampicillin（AMP）in milk.Based on the excellent PEC performance of Bi OI/Ru（bpy）₃²⁺and the high specificity of the aptamer sensing,the linear range of the constructed sensor was 1×10^-7～100 n M with a detection limit as low as 3.3×10^-8 n M for the detection of AMP.The RSD ranged from 4.2～6.1%and the stability of the detection remained high after 20 days of storage.The PEC aptamer sensor designed in this work is simple,convenient and stable,and has good potential to be used in the detection of AMP.