| Organicphosphorus pesticide, on one hand, can effectively kill the pest and increase the production of crops significanltly, which makes it widely used. On the other hand, the residues in crops do harm to the health of human and animals. Therefore, the detection of organophosphorus pesticide residues becomes very crucial. Nowadays there are several mature methods to detect organicphosphorus pesticide residues, such as immunoassay, liquid phase/gas phase-mass spectrometry(GC/LC-MS) and acetylcholinesterase activity test, etc.. But due to lack of portability and real-time monitoring of GC/LC-MS and the limitation in organic phosphorus pesticide of immunoassay method, the measurement of enzyme activity test becomes the most rapid and extensive pesticide residue detection method. But since the difference of sensitivity of this method for different pesticide detection is large, the precision is low and the enzyme is susceptible to inactivation, it is urgent to find a new method to preserve the enzyme with a strong specificity, high sensitivity and the activity of biosensor. Main research of this thesis is to design a biological detection chip, which intends to detect the organicphosphorus pesticide based on quantum dots(QDs) /enzyme nano-films, to detect the residues of organophosphorus pesticides in real samples rapidly and high sensitively, and to further explore the effects of biological sensor structure on the effect of pesticide detection, finally to realize the real-time detection of fruits, vegetables and water. The main research contents are as follows:Firstly using layer by layer self-assembly technique(LBL), through Bio Dot AD1510 biochip microarrayer, we fabricated the quantum dots and acetylcholinesterase orderly on biological sensors, through the design and optimization of quantum dot/acetylcholinesterase film structure. By using the mechanism that enzyme promoting product can inhibit the fluorescence intensity of quantum dots and organic phosphorus pesticides can inhibit acetylcholinesterase enzymatic activity, we could draw the standard curve of different concentrations of organic phosphorus pesticide on the enzyme inhibition rate, so as to realize the construction of nano-structure detection chip for fast, high sensitivity, high stability and low cost OPs detection. According to the test results of pesticide standard samples, the detection nano-chip performed with very high sensitivity and the limit of detection of organic phosphorus pesticide standard sample can reach 10 ppb, the linear range is from 5 ppb to 250 ppb, significantly better than other known optical biosensor.Secondly, the quantum dots are deposited on the surface of the Au-electrode by dielectrophoresis(DEP) technology, and the acetylcholinesterase is fixed onto modified quantum dots with the covalent cross-linking principle to constitute quantumdots/cholinesterase nano-film structure, due to the enzymatic product, thiolcholine, can have redox reaction under certain external voltage on gold electrode surface, using cyclic voltammetry detection method can detect the concentration of product so as to realize the organic phosphorus pesticide quantitative detection. The detection chip can detect the change of the product by detecting the micro changes of the current, thus the detection sensitivity and the limit of the detection are further reduced compared with the former detector. The detection of the off line is 1 ppb, linear range is between 1 ppb to30 ppb.Finally, the detection chip is used for the rapid detection of organophosphorus pesticides in fruits and tap water. The contents of organophosphorus pesticides in apples and tap water are determined by using standard addition method. The reproduce of experimental results are well with high accuracy, the recovery rate is maintained between 92% and 117%, and detecting the samples does not need tedious pretreatment process to meet the demand for rapid,high sensitive and real-time monitoring analysis. |
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