Design And Research Of Pesticide Sensor Based On Silver Ion Regulated Fluorescence Switch

Agriculture is the basic industry to support the construction and development of national economy.Pesticides play an important role in controlling and preventing agricultural biological diseases and pests and protecting crop yield,which can minimize the loss of agricultural production.Although most pesticides show low environmental sustainability,the direct or indirect toxicity of pesticide residues to beneficial insects,fish,bees and birds will destroy the ecological balance and seriously threaten human health.Therefore,pesticide residue analysis is an important technical support for food or environmental safety risk assessment and pesticide poisoning early warning.Although there are many detection methods,most of them are limited by the precise instruments and equipment and the fine operation in the laboratory.So it is of great significance to develop the method of rapid and real-time detection of pesticide residues.In this paper,based on the advantages of fluorescent nano materials,two new portable pesticide detection and sensing platforms based on silver ion?Ag⁺?regulated fluorescent switches are constructed according to the needs of fluorescent sensors for pesticides.The main research contents are as follows:Firstly,a fluorescent sensor for detecting thiram was designed by using the aggregation-induced emission enhancement effect of gold nanoclusters?GSH-AuNCs?.Ag⁺agglomerated gold nanoclusters by electrostatic action,triggering the aggregation-induced emission enhancement effect of gold nanoclusters,effectively improving the fluorescence emission intensity of the system.The fluorescence enhancement was weakened by the strong coordination between Ag⁺and thiram.By monitoring the change of signal,quantitative analysis was carried out for the residue of thiram,and the detection limit was 0.05?g ml^-1.Using a self-made electronic eye system consisting of a test strip and a smartphone,the fluorescence signal changes can be captured within10 minutes.The image information was converted into hue intensity by ImageJ software,and the thiram was quantitatively analyzed,which provides a practical tool for the field analysis of pesticides.The electronic eye system has the advantages of easy operation and portability,which is expected to meet the needs of quantitative detection of pesticides in the field.Next,we designed a portable hydrogel kit for the detection of organophosphorus pesticides?OPs?by using the ratio fluorescent effect of o-phenylenediamine?OPD?and silicon quantum dots?SiQDs?as indicators and Ag⁺as fluorescence control switches.In this sensor,OPs acted as inhibitors of acetylcholinesterase?AChE?,blocking the production of thiocholine?TCh?,thus blocking the formation of Ag⁺-metal polymers.A large number of Ag⁺further triggered the oxidation of OPs,resulting in the production of diaminophenazine?DAP?with yellow fluorescence(?_em=557 nm).The fluorescence intensity at 444 nm of silicon quantum dots was quenched by DAP,forming a ratio fluorescence response.The change of ratio signal of kit was recorded by smartphone,and ImageJ software was further applied to convert picture information into hue intensity to realize the on-site real-time detection of pesticides.In this paper,two portable sensors designed with Ag⁺regulation strategy have realized rapid and sensitive detection of pesticides,which provides technical support for the development of practical pesticide sensors in the future.