Study On The New Methods Of Visual Detection For Pesticides Based On Functionalized Silver Nanoparticles

Nanomaterials,especially precious metals nanomaterials have received much more consideration with the development of nanotechnology.Compared with gold nanomaterials,owing to the intrinsic characteristics such as easy of preparation,good stability,low cost,high extinction coefficient and highly efficient catalysts,silver nanomaterials have been a popular topic for decades.Because of the silver nanoparticles（AgNPs）have attracted extensive attentions,they can be applied in pesticide detection,antibacterial,catalysis,drug carriers,biological probes and visual sensors.Public concern over pesticide residues has been increasing dramatically owing to the high toxicity and bioaccumulation effects of pesticides and the serious risks that they pose to the environment and human health.The development of biosensors for pesticides has been an active research area for recent years.In this paper,the pesticide triazophos,6-benzylaminopurine and carbendazim were used as the research object to explore a new method for visual detection of trace pesticides based on the silver nanoparticles.Combined with the computational chemistry,silver nanoparticles and their composite materials have detection of pesticide residue.Based on the above considerations,the paper is divided into the following chapters:Chapter 1: This part introduced the development of nanotechnology,precious metals nanomaterials,detection methods of pesticide residues and the preparation methods of the silver nanoparticles（AgNPs）and their respective applications.Chapter 2: A simple colorimetric assay has been developed to detect 6-benzylaminopurine（6-BA）in a complex environment by using the novel probe p-aminobenzenethiol functionalized silver nanoparticles（ABT-AgNPs）.When ABT-AgNPs bind with 6-BA,a huge conjugate network can form based on intense electrostatic effects,hydrogen bonding and π-π stacking interactions,resulting in a visible colour change from faint yellow to reddish orange.The interactions between the 6-BA and ABT also were validated by the density functional theory（DFT）approach.The influence of experimental conditions on the analytical performance was investigated systematically.Under optimal conditions,the absorbance ratio(A_510nm/A_397nm)is linearly related to the logarithm of 6-BA concentration from 1μM to20 μM,with a detection limit of 0.1μM.Furthermore,no obvious interference was observed from common inorganic ions and other pesticides.6-BA was also successfully determined in samples with complicated matrices.The recoveries obtained from water and vegetable samples were in the range 81.3–101.2%.Chapter 3: Comparison of three different nanomaterials visual inspection triazophos,a simple colorimetric sensing assay was constructed for quantitative detection of triazophos via citrate capped silver nanoparticles（Cit-AgNPs）with an on-off type color change by comparing the reaction time and detection limit.In the presence of triazophos,the Cit-AgNPs was aggregated,resulting in the obvious color change from yellow to prunosus via hydrogen bonding,π-π interactions and substitution.The theoretical investigations between the triazophos and Cit-AgNPs were also validated by density functional theory（DFT）approach.Meanwhile,the calibration curve was found to be linear over the range of 0.1-280 μM and this proposed colorimetric sensing was demonstrated an excellent sensitivity with a detection limit of 5 n M of triazophos.The recoveries obtained from complex sample matrices were in the range 82%-100.8%.Significantly,the colorimetric probe has been successfully applied for visual detection of triazophos,which validated the excellent potential for real-time and on-site application and possessed considerable advantages of simplicity,rapid detection,portability,cost efficiency and visualization.Chapter 4: We developed a colorimetric assay to detect carbendazim using Rhodamine B modified silver nanoparticles（RhB-AgNPs）.RhB-AgNPs were aggregated in the presence of carbendazim and the color was changed from light yellow to light orange.The UV-visible absorption peak of RhB-AgNPs decreased at 400 nm and appeared a new peak at 510 nm.The results showed that the absorbance（A510 nm/A400 nm）was linear with the logarithm of concentration,the concentration range was 5-400 μM and the detection limit was 88 n M.It is feasible that using this method analyzing carbendazim with excellence sensitivity.The method has been successfully applied to the detection of carbendazim in the water（tap water,Yellow River）and fruit（apple）samples.