| Exogenous hazardous substance was something that did not belong to food at the beginning,which was got in to the food or their raw materials by several approaches like planting,transporting,storing,and so on.Exogenous hazardous substance mainly including heavy metal ions,pesticide residues,and so on.Among them,heavy metal ions accumulated in the human body would cause diseases such as lung cancer,encephalitis,anemia,heart disease easily;pesticide residues can cause acute or chronic toxicity to the human body,and also had risks to teratogenic,carcinogenic and affect the reproductive system;long-term intake of veterinary drugs residues can easily cause kidney damage,allergic reactions and allergic reactions.As people pay more and more attention to food safety issues,it was of great significance to establish a rapid and reliable detection method for detecting exogenous hazardous substance in food or drinking water.In this thesis,quantum dots were used as sensor for rapid detection of exogenous hazardous substance such as heavy metal ions and pesticide residues in food or water rapidly,and the research content mainly includes the following three parts:?1?Ascorbic acid enhanced carbon quantum dots??AA?-enhanced CQDs?were synthesized by Maojian green tea and ascorbic acid as carbon sources,and applied for Hg2+ions specific detection;?2?Visual sensor array was established by using metal quantum dots as matrix and filter paper as carrier,the sensor array was applied for visual qualitative and semi-quantitative detection of various metal ions;?3?Similar to the second part,metal quantum dots were used as sensor to form a matrix on filter paper to establish visual sensor array for visual detection of various pesticide qualitatively and quantitatively.The following results were obtained:Part?:Ascorbic acid enhanced carbon quantum dots??AA?-enhanced CQDs?were synthesized by Maojian green tea and ascorbic acid as carbon sources by hydrothermal method,and as prepared?AA?-enhanced CQDs had specific response to Hg2+ions.The detection limit can be obtained as low as 6.32×10-9 mol/L while the detection linear range was 2.00×10-7-6.00×10-5 mol/L.Besides,interferences from the other 10 metal ions or the 16 amino acids to the CQDs was ignorable,and in three complex matrices?waste water,tea,rice?,the quantum dots can still achieve accurate and fast detecting for Hg2+ions.In addition,great antioxidant property was found in the?AA?-enhanced CQDs,which enabling them to absorb free radicals quickly,and had excellent biocompatibility.Therefore,?AA?-enhanced CQDs have enormous potential applications,and were expected to be extend to the detection of other analytes like bisphenol A and the intracellular detection.Part?:Three kinds of metal quantum dots?QDs?including CdTe?red,Cd:Te=1:0.2?,ZnCdSe?green,Zn:Cd:Se=1:0.03:0.1?and ZnCdSe?blue,Zn:Cd:Se=1:0.04:0.1?,were synthesized by hydrothermal method.These three quantum dots were used as sensors to establish visual sensor array on a filter paper.By addition of different concentrations or kinds of metal ions to the established sensor array,each sensor undergone different degrees of color change.By comparing the color change of the sensing array before and after the addition of different concentrations or kinds of metal ions,combined with the chemometric method?partial least squares discriminant analysis,PLSDA?,seven kinds of metal ions(Ag+,Cu2+,Fe3+,Hg2+,Pb2+,Co2+,Ni2+)can be simultaneously realized qualitatively and semi-quantitatively.Among them,the qualitative detection accuracy of training set and prediction set of qualitative detection can reach 100%and 98.46%respectively;the detection limit of semi-quantitative detection was 5.00×10-11 mol/L,while the semi-quantitative detecting range was5.00×10-11-1.00×10-4 mol/L(Ag+,Cu2+,Fe3+,Pb2+,Co2+,Ni2+)and 5.00×10-11-5.00×10-5 mol/L(Hg2+),the training set and prediction set accuracy for semi-quantitative detection by PLSAD mode can reach 100%.Compared to traditional fluorescence spectroscopy,the sensing array had a lower detection limit?down two orders of magnitude or so?and a wider detection range?three orders of magnitude wider?.Part?:Three kinds of quantum dots including CdTe?red,Cd:Te=1:0.2?,CdSe?green,Cd:Se=1:0.05?and ZnCdSe?blue,Zn:Cd:Se=1:0.04:0.1?,were synthesized by hydrothermal method and used as sensors materials to establish visual sensor array on a filter paper.By addition of different concentrations or kinds of pesticides to the established sensor array,each sensor undergone different degrees of color change.By comparing the color change of the sensing array before and after the addition of different concentrations or kinds of metal ions,combined with the chemometric method?partial least squares discriminant analysis,PLSDA;partial least squares regression,PLSR?,three kinds of pesticides including?paraquat dichloride,hereinafter referred to as paraquat;glyphosate;trichlorfon?can be simultaneously realized qualitatively and semi-quantitatively.Among them,the accuracy of the training set and prediction set of the three quantum dots visual array sensing arrays for qualitative detection of three pesticides can reach 100%;the training set and prediction set accuracy of semi-quantitative detection using the PLSDA calculation mode can also reach 100%(detection limit was 1.00×10-9 mol/L,detection range was 1.00×10-9-5.00×10-4 mol/L).Subsequently,in complex or real samples,combined with the PLSDA calculation method,the three-quantum dot visual sensor array can achieve qualitative and semi-quantitative identification of three pesticides.Among them,the accuracy of training set and prediction set for the classification of three pesticides can reach 100%;the accuracy of paraquat can reach training set 100%,the prediction set was 100%;the accuracy of glyphosate can reach 100%of the training set,96.30%of the prediction set;the accuracy of trichlorfon can reach 100%of the training set,and 100%of the prediction set.The qualitative and semi-quantitative analysis of the three pesticides was achieved in a complex system,provides new research ideas for rapid analysis and real-time monitoring of different pesticides. |
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