Rapid In-situ Detection Of Pesticide Residues In Fruits Using Flexible SERS Substrates

With the further development of China’s industrialization process,more and more companies are entering various fields of agricultural production.Although there are various types of pesticides available,if the amount of pesticide used is not controlled,it may pose a threat to human health.Pesticide residues can lead to damage to organs such as the liver and kidneys,serious health problems such as cancer and fertility disorders,and also have an impact on ecological balance,animal and plant health in soil and water bodies,posing a serious threat to human food safety.Therefore,it is necessary to establish a new method with high resolution,high sensitivity,non-contact and applicable to different types of samples for on-site detection of pesticide residues on fruit surfaces,which is also a key link in preventing,controlling and treating pesticide residues.In this study,a flexible SERS substrate was developed using high-elasticity and microstructure-stable mask fabric（FM）and polyvinyl alcohol（PVA）materials.By adding silver nanoparticles and utilizing the strong plasma scattering signal caused by surface-enhanced Raman scattering（SERS）,the substrate was modified for the rapid detection of commonly used pesticide residues on fruit surfaces.The main research content and conclusions are as follows.In the first part,a FM/PDA/Ag NPs SERS substrate was prepared by utilizing the adhesion and reduction properties of polydopamine（PDA）to reduce Ag ions into silver nanoparticles（Ag NPs）and bond them to FM.The substrate was able to detect Nile blue A（NBA）probe molecules at concentrations as low as 10^-9 mol/L,with a random signal RSD of 14.12%,indicating good sensitivity and uniformity of the substrate.To further investigate the practical application of the substrate,it was used to detect chlorpyrifos on the surface of grapes and pears by wiping the samples with the SERS substrate,achieving detection limits of 0.48 ng/cm² and 0.24 ng/cm²,respectively,at concentrations as low as 10^-7 mol/L.The R² values between SERS peak intensity and chlorpyrifos concentration on grape and pear surfaces were 0.9878 and 0.9100,respectively,providing a theoretical basis for accurate quantification of the research target.Finally,the RSD of chlorpyrifos residues detected on multiple grape surfaces randomly selected was 17.66%,indicating good reproducibility.This simple and low-cost flexible SERS substrate provides a reliable and convenient platform for the rapid detection and on-site monitoring of pesticides.The second part is to add a certain volume of Ag NPs to the transparent PVA solution to form a high-performance SERS film substrate.Under the optimal conditions（the volume of Ag NPs is 10 m L）,the SERS substrate can detect NBA probe molecules down to 10^-8 mol/L,and the signal RSD at the random position of the substrate is14.03%,with good sensitivity and uniformity.In addition,the substrate successfully detected various organic molecules such as malachite green（MG）,crystal violet（CV）,and methyl orange（MO）.In order to further explore the practical application ability of the substrate,the substrate was first used to wipe the surface of apples and pears to detect carbaryl pesticides as low as 5×10^-7 mol/L.The SERS peak intensity of carbaryl pesticides and the corresponding logarithmic concentration R² were 0.9556,0.9593,respectively,providing a theoretical basis to quantify the research objectives.Secondly,the substrate has good stability and still has SERS signal after being stored at room temperature for 4 weeks.Finally,the SERS peaks of carbaryl wiped from the surface of random multiple apples showed small fluctuations,with an RSD of 17.02%,and good reproducibility.The substrate can meet various SERS sensing needs and has great potential in the field of food safety.