| The widespread use of organophosphorus pesticides(OPs)in conventional farming practices and modern civilization has led to the increased occurrence of pesticide residues in air,soil,agricultural products and drinking water supplies.Long-term exposure to OPs residuals would result in a series of health problems,such as dizzy,vomiting,diarrhea,muscle tremors,and even death.Due to the acute toxicity of OPs and their great threats to human health,it is necessary to restrict the recommend level of OPs and at the same time develop sensitive and portable screening device for quantitative monitor of OPs infields.Gold nanomaterials possess unique surface plasmon resonance property and extremely high molar extinction coefficients.In this thesis,gold nanoparticles(AuNPs)and gold nanorods(AuNRs)were selected to integrated with the acetylcholinesterase(AChE)based hydrolysis and inhibition reaction,and used for the development of colorimetric methods for OPs analysis.Detailed works are described as follows:1.AuNPs dissolution based colorimetric method for highly sensitive detection of OPsA simple and sensitive colorimetric method is developed for OPs analysis based on the enzymatic hydrolysis reaction of AChE and the dissolution of AuNPs in Au3+-CTAB solution.In the absence of OPs,the enzymatic hydrolysis product,thiocholine,would reduce Au3+ and protect the AuNPs from dissolution by the Au3+-CTAB.In the presence of OPs,however,the activity of AChE is inhibited,which could not or could only produce a small amount of thiocholine to consume the Au3+.In this case,the large amount of residual Au3+ dissolves the AuNPs and decreases both the concentration and size of the AuNPs,thus leading to obvious red-to-light pink or red-to-colorless color change.Under optimal conditions,the colorimetric method could indicate the presence of OPs,with a concentration down to 0.7 ppb.After loading AuNPs on a cellulose paper,an AuNPs-coated dipstick is developed for the detection of OPs,which is highly sensitive with an observable limit of detection of 35 ppb.Practical sample analyses in tap water and sea water indicate the colorimetric method has acceptable accuracy and good stability,even in the system containing 5 M of NaCl.Regarding these merits,the as-proposed method could be applied for the point-of-care analysis of OPs in complex systems.2.Controllable etching of AuNRs by Au3+-CTAB complex and its applications for semi-quantitative visual detection of OPs by naked eyesA naked eye based semi-quantitative colorimetric method was developed for the highly sensitive and on-site visual detection of OPs.This method is based on the unique aspect ratio dependent localized surface Plasmon resonance properties(LSPR)of AuNRs,which could be tailored by the Au3+-CTAB complex and influenced by the AChE based hydrolysis and inhibition reactions.In the absence of OPs,the enzymatic hydrolysis product,thiocholine,consumes almost all of the Au3+ species.In this case,the amount of residual Au3+-CTAB complexes is too small to etch the AuNRs with an observable color change.In the presence of OPs,however,the activity of AChE is inhibited,which could not or could only produce a small amount of thiocholine to consume the Au3+.Correspondingly,the large amount of residual Au3+ etches the AuNRs and significantly decreases their aspect ratios,thus leading to vivid color changes easily distinguished by naked eyes.After assembly AuNRs on a cellulose paper,an AuNRs-coated paper device is developed for the detection of OPs.Under optimal conditions,both AuNRs in aqueous solutions and on the paper device well demonstrate the presence of OPs with variable concentrations and different toxicities.Practical sample analyses in cabbage washing solutions indicate the colorimetric method has acceptable accuracy and good resolution,which may have great application prospective for point-of-care detection of OPs in agricultural products and food supplies. |
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