Liquid Interfacial Sers For Detecting Pesticide Residues In Fruits

To date,food safety becomes more and more serious and has important influence to people's livelihood.In particular,the abuse of pesticides not only causes environmental pollution but also endangers people's health.Nowadays,the detection of pesticide residues have been realized by various techniques,such as gas chromatography(GC),high performance liquid chromatography(HPLC),gas chromatography-mass spectrometry(GC/MS),biosensors and enzyme inhibition,etc.In view of unique molecular fingerprint characteristics,high sensitivity,non-destructive and real-time detection,surface-enhanced Raman scattering(SERS)provides a new way for the detection of pesticide residues.Nevertheless,because of the complexity of the surface substance of fruits and vegetables,the simple SERS substrates cannot meet the requirements of rapid,quantitative,and practical detection.This thesis focuses on the following points:(1)we develop a fast batch preparation of self-ordered dense Au nanoparticle arrays on cyclohexane/water biphasic interface in 96-well plates with the assist of acetone as the phase-crossing inducer.The acetone can extract the pesticide molecules via a simple dipping sample peels and can rapidly capture and locate the pesticide molecule into the plasmonic hotspots.Meanwhile,this phase-crossing solvent,acetone itself,generates stable SERS signal and is used as the IS tags to calibrate the signal fluctuation.This platform presents an excellent uniformity with a relative standard deviation(RSD)of 5.9% compared to the RSD of 14.5% without the IS's correction and a good sensitivity with a limit of detection(LOD)of 1 n M thiram.This high-throughput strategy for analyzing pesticide residues at fruit peels reached detection levels of nanograms per square centimeter(ng/cm2).Combined with the 96-well plates,this platform greatly facilitates the self-assembly and multiplex sampling.The self-ordered arrays at two immiscible phases interface evidenced the detection of both the oil-soluble thiabendazole and the water-soluble thiram molecules and also realized the multiplex and two-phase detection of these two pesticides.This platform offers vast possibilities for on-site sensing of various analytes and paves a new way for the quantitative and high-throughput SERS analyzer just as convenient as the microplate reader.(2)the co-assembly of gold nanoparticles and chloroform with the help of polymers was realized by oil-in-water method,and the analyte can be directly identified and detected by metal liquid-like droplets.The sensitivity and repeatability of this three-dimensional array substrate were evaluated by using label molecule crystal violet,and its LOD was up to 2×10-10 M.Moreover,the RSD values at 1179 cm-1 and 1619 cm-1 Raman shifts were less than 10%.Different concentrations of thiabendazole were analyzed and the LOD was 5×10-8M.