Visual Detection Of Pesticide Residues Based On Fluorescence Internal Filtering Effect And Multilayer Microfluidic Paper Chip

The output of food,fruits and vegetables is getting higher and higher every year.At the same time,the use of pesticides is also increasing.The pesticide residues in fruits and vegetables are betweenμg/kg～mg/kg.The detection effect of general test paper is not good,and there are many kinds of pesticides.Therefore,it is necessary to realize the rapid,low-cost and visual specific detection of pesticide residues.In this paper,a multi-layer array paper chip visual pesticide detection sensor based on dual emission quantum dots gold nano coupling suitable ligand pesticide specific detection and high-performance paper chip mixed channel structure was designed to detect two different pesticides in nine groups of samples.The specific research contents are summarized as follows:1.First of all,based on the red and green CdTe quantum dots,SiO₂ was doped into the rQDs@SiO₂@gQDs.The results show that the two materials are successfully prepared.The UV absorption peak of Au NPs is 520 mm.The emission peaks of rQDs@Si O2@gQDs are at 542nm and 632nm.The absorption spectrum of gold nanoparticles overlaps with the excitation spectra of the green part of the composite quantum dots.The green quantum dots act as fluorescence response signals and have fluorescence internal rate effect with the gold nanoparticles,while the red part in the composite quantum dots is used as the reference signal The results show that the green part in the composite quantum dots is due to the intrinsic fluorescence effect.Finally,acetamiprid with different concentrations（0.2μM,1.2μM,2.8μM,4.4μM,5.8μM,6.4μM,7.6μM,8.4μM）is obtained by the preparation of double emission quantum dots gold nanoparticle coupling suitable ligands The detection limit of acetamiprid was 0.068μM（S/N=3）,and the linear correlation coefficient（R²）was0.9868.2.In this paper,the principle of mixed flow of fluid on paper was analyzed,and the effects of two different injection modes,vertical injection and parallel injection,on the mixing effect were discussed.The results showed that the mixing effect of vertical injection was better.According to the mixing mode of fluid folding and stretching,three staggered channel structures with different shapes were designed:circular arc,triangle and ladder The results show that the best method is to design a rectangle structure on the two sides of the staggered structure,which is divided into two types according to the results The simulation results show that the two structures can not further mix the fluid,so the three-dimensional inner rib structure of"ladder h-0.3,s-2.6"is selected as the structure of mixing zone.After the simulation,the paper mixing experiment was designed to verify the mixing effect of"ladder h-0.3,s-2.6"structure under vertical injection.The trend of experimental results was consistent with the simulation results.The mixing strength was 250%of the blank channel without any structure design.3.A paper chip based on ratio fluorescence detection method was made.A paper chip detection device was designed to simultaneously detect acetamiprid and profenofos in nine groups of samples.Nine detection areas were set up in the device.Each detection area was provided with a specific detection area for acetamiprid and profenofos and a control area for the final fluorescence control.In the detection area,double emission quantum dots were modified in advance and aptamers to achieve the purpose of specific detection of pesticides.The fluorescence color of detection area changes from light red to yellow green to carry out semi quantitative detection of pesticides.The fluorescence photos of different concentrations of pesticides in the detection area on paper were taken.The RGB values in the photos were extracted by MATLAB.The relationship between the b value which can represent the color change rule and the pesticide concentration was found out The detection range of acetamiprid was 4～72μg/kg,the linear equation was B₁=0.69c₁+115,which was lower than the national standard of 0.01mg/kg～0.1mg/kg;the detection range of Profenofos in Chinese cabbage was 3～54μg/kg,the linear equation was B₂=c₂+117,which was lower than the national standard of 0.01mg/kg～0.1mg/kg.In order to verify the reliability of the device,the recovery rate of pesticides on Chinese cabbage was tested.The recoveries of acetamiprid and profenofos were 75%～87%and 80%～90%,respectively,indicating that the detection device was reliable.