Fluorescence And Colorimetric Analysis To Detect Organophosphorus Pesticides Based On Metal Nanomaterials

In this paper,organophosphorus pesticides（OPs）as the research object,combined with the excellent properties of metal nanomaterials and enzyme inhibition method,and the selection of fluorescence method and colorimetric method to methylparathion（PM）as the main representative of organophosphorus pesticides were analyzed and detected.The analytical method introduced in this paper has high sensitivity and selectivity for the detection of organophosphorus pesticides,and the analytical cost is low,without the need of large precision instruments and well-trained researchers,and can be effectively applied to the detection of actual samples.The main contents of this paper are as follows:The first chapter:The general situation of pesticide was mainly expounded.It Includes the classification and use of pesticides.The pesticide residue and its harm were described.Some common methods for detecting organophosphorus pesticides were introduced,and the principle of enzyme inhibition method for detecting organophosphorus pesticides was emphatically introduced.In addition,the general situation of nanomaterials and the selection of nanomaterials in this paper are described.Then the main research content of this paper is introduced.Finally,the development prospect of organophosphorus pesticide residue detection in the field of analysis and detection is prospected.The second chapter:A novel fluorescence assay has been constructed for the determination of parathion-methyl（PM）by using 4-amino-3-hydroxy-1-naphthalenesulfonic acid（AHNSA）as probe.Mn O₂ nanosheets（Mn O₂ NS）could quench the fluorescence of AHNSA,while Mn²⁺,the reduction product of Mn O₂ NS,has no influence on it,resulting in fluorescence recovery.This is because that Mn O₂NS have oxidized characteristic,and they can react with choline（TCh）,which is the product of acetylthiocholine（ATCh）catalyzed by acetylcholinesterase（ACh E）.In the presence of OPs,the activity of ACh E was inhibited,accompanied by the restraint of the redox reaction of Mn O₂ NS,therefore the fluorescence of AHNSA was quenched.Under the optimized experimental conditions,a linear range of PM was determined to be 0.4–40 ng/m L（R²=0.997）by the proposed method with the limit of detection for0.18 ng/m L（S/N=3）.The assay was successfully applied to the determination of PM in lake water,which average recoveries were between 86.5%and 114.4%.The third chapter:A sensitive approach to measure organophosphorus pesticides（OPs）using graphitic-phase C₃N₄ nanosheets（g-C₃N₄）combined with a nanomaterial-based quencher Mn O₂ nanosheets（Mn O₂ NS）.Because Mn O₂ NS could quench the fluorescence of g-C₃N₄ via the inner-filter effect（IFE）,the enzymatic hydrolysate（thiocholine,TCh）can efficiently trigger the decomposition of Mn O₂ nanosheets in the presence of acetylcholinesterase（ACh E）and acetylthiocholine,resulting in the fluorescence recovery of g-C₃N₄.OPs,as inhibitors for ACh E activity,can prevent the generation of TCh and decomposition of Mn O₂ NS,accompanied by fluorescence quenching again.So the ACh E-ATCh-Mn O₂-g-C₃N₄system can be utilized to detect OPs quantitatively based on the g-C₃N₄ fluorescence.Under the optimum conditions,the linear range for the determination of parathion-methyl（PM）and 2,2-dichlorovinyl dimethyl phosphate（DDVP）were found in the range of 0.1-2.1 ng/m L with a limit of detection of 0.069 ng/m L,and0.5-16 ng/m L with a limit of detection of 0.20 ng/m L,respectively.Finally,this method was exploited for the monitoring of PM in real samples.The fourth chapter:A smart phone APP combining gold nanoparticles（Au NPs）and enzyme inhibition method was designed for the first time to visually detect organophosphorus pesticides（OPs）in lake samples.（Au NPs）catalyzed3,3’,5,5’-tetramethylbenzidine（TMB）-H₂O₂ system.Ox TMB is blue and visible to the naked eye.（Choline）TCh,the hydrolyzed products of acetylcholine（ATCh）,can act with gold nanoparticles and can form Au-S,which make the gold nanoparticles aggregated and lose its activity.In the presence of OPs,Acetylcholinesterase（ACh E）is inactivated and cannot hydrolyze ATCh to TCh,engendering the colorimetric signal.The change in the color from colorless to blue was seen with naked eye,indicating the absence or presence of OPs.Color picker APP can convert the color into three primary color digital values of the red（R）,green（G）and blue（B）.The concentration of PM is proportional to the ratio of G/B.In addition,this method was also used to determine the amount of Parathion-methyl in lake samples with recovery of92-118.6%and 90.2-133.3%.These results showed that it was a portable,simple and visible method to detect OPs in water samples analysis and environmental monitoring.The chapter five,several methods of construction are summarized,and the prospect of organophosphorus pesticide analysis sensing is presented.The main innovation points of this paper are as follows:（1）the prepared metal nanomaterials have abundant raw materials and are cheap,the synthesis method is simple and easy to operate,the required detection equipment is easy to obtain,and the detection methods are simple;（2）To realize the detection of organophosphorus pesticides content in actual samples of lake water,and has good sensitivity and selectivity.Combined with smart phone APP,it can realize the determination of OPs without the participation of large analytical instruments,which has practical promotion value and significance.