Fabrication And Applications Of Novel Nanosensor In Pestiside Detection

With the rapid development of agriculture,scientists have been pursuing the quantity and quality of agricultural products.Pesticides have been widely used to prevent or control of various pathogens,pests,weeds on the rice,corn and vegetables.However,due to the improper use of pesticide,they have seriously caused environmental problems,even jeopardized the food safety and human health.Thus,the pesticide residues and pollutions have been aroused public concern.In the past decade,great effort has been made to develop various methods to determine pesticide,including chromatography and enzyme-linked immunosorbent assays.Many of them required laborious synthetic procedures,tedious preparation and purification of samples,time-consume immobilizing processes,sophisticated instrumentation etc.,which limit their point-of-care applications.In order to circumvent these problems,practical methods with high sensitivity and selectivity for simple and rapid detection of pesticide residues are crucial for human health and environment pollution monitoring.Owing to its remarkable optical performance and excellent sensitivity,nanosensor have attracted considerable attention in the detection of pesticide.Enlightened by the aforementioned facts,we have designed and constructed a series of novel sensing platforms with excellent sensitivity and high selectivity for the detection of pesticide.In addition,the established nanosensor provide new platforms and idea for the analysis of pesticide,which lay a good foundation for the protection of human safety.Our research is briefly summarized as follows:(1)A convenient and label-free fluorescence sensing platform was established for sensitive detection of organophosphorus pesticides(OPs).The selectivity fluorescent strategy was based on fluorescence enhancement mode of cysteamine-capped Cd Te quantum dots(QDs).Upon addition of adenosine triphosphate(ATP),the amino groups on the surface of Cd Te QDs can form both electrostatic and hydrogen bonding with ATP,leading to obvious fluorescence enhancement of QDs.Acid phosphatase(ACP)can easily catalyze the hydrolysis of ATP into adenosine and phosphate fragments under an acidic environment,causing dramatically decrease of the fluorescence intensity of QDs.Then,the fluorescence could be recovered again by the addition of OPs which could inhibit the activity of ACP.Quantitative detection of parathion-methyl(PM)in a broad range from 0.001 to 10 ?g m L-1 with the detection limit of 0.5 ng m L-1 can be achieved.(2)A novel and sensitive optical near-infrared Cu In S2 QDs fluorescence probe for the detection of PM was developed.The fluorescence of Cu In S2 QDs is quenched in the presence of Pb2+ due to the competitive binding of mercaptopropionic acid between QDs cores and Pb2+.Subsequently,the addition of di-methylthiophosphoricacid(DMPA,the hydrolysate of PM)moiety with a P=S bond would capture Pb2+ on the surface of the Cu In S2 QDs due to its stronger coordinative interaction with metal ions,leading the fluorescence of the Cu In S2 QDs-Pb2+ system recovery.The fluorescence enhancement is related to the amount of PM added to the Cu In S2 QDs-Pb2+ system,which can be used for the quantification of PM.Under the optimized conditions,the fluorescence intensity of the Cu In S2 QD-Pb2+ system was proportional to the concentration of PM in the concentration range of 0.1-38.0 ?mol L-1,with a detection limit of 0.06 ?mol L-1.The proposed method was simple and convenient,and had been used for the detection of PM residues in environmental and agricultural samples with satisfactory results.(3)We develop a novel and sensitive sensor for the detection of OPs based on the inner-filter effect(IFE)between gold nanoparticles(Au NPs)and ratiometric fluorescent quantum dots(RF-QDs).The RF-QDs has been designed by hybridizing two differently colored Cd Te QDs,in which the red emissive QDs entrapped in the silica sphere acting as the reference signal,and the green emissive QDs covalently attached on the silica surface serving as the response signal.The fluorescence of RF-QDs could be quenched by Au NPs based on IFE.Protamine could effectively turn on the fluorescence due to the electrostatic attraction between protamine and Au NPs.Trypsin can easily hydrolyze protamine,leading to the quench of the fluorescence.Then,the fluorescence could be recovered again by the addition of PM which could inhibit the activity of trypsin.By measuring the fluorescence of RF-QDs,the inhibition efficiency of PM to trypsin activity was evaluated.Furthermore,the simple and convenient method had been used for PM detection in environmental and agricultural samples with satisfactory results.Quantitative determination of PM in a broad range from 0.04 to 400 ng m L-1 with the detection limit of 0.018 ng m L-1 can be achieved.(4)A novel fluorimetric sensing platform was constructed for quantitative detection of OPs via tyrosinase(TYR)enzyme-controlled quenching of gold nanoclusters(Au NCs).Initially,TYR can catalyze the oxidation of dopamine to dopaminechrome,which can efficiently quench the fluorescence intensity of Au NCs based on dynamic quenching process.However,with the presence of OPs,the activity of TYR was inhibited,resulting in the fluorescence recovery of Au NCs.This proposed fluorescence platform was demonstrated to enable rapid detection for OPs(paraoxon as model)and to provide excellent sensitivity with a detection limit of 0.45 ng m L-1.Significantly,the fluorescence probe was used to prepare paper-based test strips for visual detection of OPs,which validated the excellent potential for real-time and on-site application.(5)A novel colorimetric sensing platform was constructed for quantitative detection of OPs based on manganese dioxide(Mn O2)nanosheets.Mn O2 nanosheets as an oxidase-mimicking nanomaterial could directly oxidize 3,3',5,5'-tetramethylbenzidine(TMB)into ox TMB without the need of horseradish peroxidase and H2O2.When acetylcholinesterase was introduced,acetylthiocholine can be catalytically hydrolyzed to produce thiocholine which easily trigger the decomposition of Mn O2 nanosheets,causing the decrease of solution absorbance.Due to the inhibition effect of OPs,the enzymatic activity is suppressed,preventing the decomposition of Mn O2 and resulting in the increase of absorbance.Furthermore,the Mn O2-TMB platform has been used to fabricate test strips for rapid and convenient visual detection of paraoxon with highly promising.In conclusion,we designed and constructed a series of nanosensors for the sensitive detection of OPs based on the excellent optical properties of nanomaterials.