Enzyme-like Activities Of Heteroatom-doped Graphenes And Their Applications In Pesticide Detection

Nanozymes,the nanomaterials with enzyme-like activities,are promising candidates to replace natural enzymes due to their ease of preparation,low cost,stability,and long storage time,which have broad applications in many fields including bioanalysis,imaging,therapy,and environmental protection.Among them,carbon-based nanozymes are rising stars because of their abundant resources,low cost,and good biocompatibility.This thesis focused on the enzyme-like activities of heteroatom-doped graphenes.Among them,N-doping significantly improved the peroxidase-like activity.According to the kinetic analysis,N-doped graphene had a higher affinity to hydrogen peroxide than natural horseradish peroxidase does.Following the success of N-doping,we synthesized dual-doped graphene and tested their enzyme-like activities.It was demonstrated that B-doping slightly increased the peroxidase-like activity of N-doping graphene,while S-doping increased the oxidase-like activity.Pesticides are chemicals used in agriculture to regulate plant growth and control pests and weeds.However,overuse of pesticides will pollute the environment,damage the ecosystem,and do harm to human health.Therefore,it is necessary to detect pesticides.Conventional detection methods including chromatography,enzyme-linked immunosorbent assay(ELISA),and biosensors are sensitive and selective.However,chromatography depends on expensive instruments and requires sample preparation.ELISA and biosensors need expensive enzymes and antibodies with low reuse capability and cannot perform multiplex detection.This thesis constructed sensor arrays by using the as-prepared nanozymes(i.e.,Ndoped graphene,N,S-codoped graphene,and graphene oxide)for pesticide detection.Sensor arrays classify and discriminate various analytes for multiplex detection by generating cross-responsive array data at a time.Since aromatic pesticides can differentiatly inhibit the peroxidase-like activities of graphene-based nanozymes by absorbing on the graphene through ?-? interaction,we used colorimetric sensor arrays for the discrimination of five aromatic pesticides(i.e.,lactofen,fluoroxypyr-meptyl,bensulfuron-methyl,fomesafen,and diafenthiuron).The five pesticides from 5 ?M to 500 ?M were successfully differentiated by the nanozyme sensor arrays.The nanozyme sensor arrays could also discriminate different concentrations(0-1000 ?M)of a pesticide.Moreover,the nanozyme sensor arrays differentiated different proportions of two mixed pesticides.The practical application of sensor arrays was demonstrated by detecting pesticides in soil samples.