Study On Pesticides In Functional Silver Nanoparticles For Colorimetric Detection

Many scientists have paid more and more attention to the precious metal nanomaterials（Au,Ag,Pt）due to the development of science and technology.Gold and silver nanomaterials have some intrinsic characteristics including good biocompatibility,excellent catalytic performance,simple preparation method and good stability compared to other precious metal materials.Silver has higher molar extinction coefficient,lower price and better application prospect than gold.Up to now,silver nanomaterials are widely used in bio-probes,magnetocaloric therapy,photothermal therapy,catalysis,drug delivery,antibacterial and so on.At the same time,with the continuous development of society,the material needs of mankind continue to improve,and the health of human beings is particularly important for the living environment and food safety.Pesticide residue detection has become the focus of the public.Therefore,based on the functionalized silver nanomaterials,this dissertation studied 6-benzyladenine adenine,thiophanate-methyl and phoxim,respectively,to achieve a new visualization method for trace pesticide residues.The paper can be divided into four chapters,briefly as follows:Chapter 1:Briefly introduce the properties,preparation,detection of trace substances of silver nanomaterials in the environment and the current status of Pesticide residues and detection methods.Chapter 2:This report has demonstrated a novel,simple and reliable colorimetric method for the detection of 6-benzylaminopurine（6-BA）using melamine functionalized silver nanoparticles（MA-AgNPs）as a visual probe.The MA-AgNPs were bound up with 6-BA through hydrogen bonding andπ-πbonding,resulting in the color change from yellow to reddish orange.The interactions between the 6-BA and MA were also calculated by density functional theory（DFT）method.Under optimum conditions,the absorbance ratio at A_{510 nm}/A_{397 nm} was related linearly to the concentration of 6-BA in the range of 1-30μM,with a detection limit of 0.06μM.The nanoprobe was utilized to sensing 6-BA in real samples with the recoveries ranges from 83.9%to 108.2%.Chapter 3:A simple and selective colorimetric sensor based on citrate capped silver nanoparticles（Cit-AgNPs）is proposed for the detection of Thiophanate-methyl（TM）has been demonstrated.The method based on the color change of Cit-AgNPs from yellow to cherry red with the addition of TM to Cit-AgNPs that caused a red-shift on the surface plasmon resonance（SPR）band from 394 nm to 525 nm due to the hydrogen-bonding and substitution.The density functional theory（DFT）method was also calculated the interactions between the TM and citrate ions.Under the optimized conditions,a linear relationship between the absorption ratio(A_{525 nm}/A_{394 nm})and TM concentration was found in the range of 2-100μM,with detection limit of TM was0.12μM by UV-vis spectrometer.Moreover,the applicability of colorimetric sensor is successfully verified by the detection of TM in environmental samples with good recoveries.Chapter 4:In this work,a novel and simple colorimetric sensor for the determination of phoxim in water and fruit samples has been demonstrated by using carbon dots functionalized silver nanoparticles（CDs-AgNPs）.The dispersed CDs-AgNPs had strong absorption peak at 400nm,in addition of phoxim,the color change from yellow to red due to the absorption peak with red shift from 400nm to525nm.Under optimized conditions,the absorbance ratio at A_{525 nm}/A_{400 nm} was related linearly to the concentrations of phoxim in the range of 0.1-100μM,with a detection limit of 0.04μM.The colorimetric sensor was successfully utilized to monitoring phoxim in environmental and fruit samples with good recoveries ranges from 87%to 110.0%.