Study On Novel Inorganic/organic Nano-composites To Modify Electrode For Determination Of Lead(?)

The worldwide environmental issue of lead pollution has triggered off a considerable number of scientists to explore simple and effective ways to remove lead from wastewater because of lead's high toxicity,carcinogenicity,and biological accumulation,which has a direct and adverse effect on various biological processes even at low levels.In this study,we have fabricated three types of Pb2+ electrochemical sensors based on various nanocomposites with excellent electrical conductivity modified glass carbon electrode and specificity target recognition of specific–receptor,which exhibits sensitivity toward Pb2+ and high selectivity against other heavy metals when being applied in the detection of Pb2+ in the wastewater.In addition,these constructed sensors all shown satisfactory performance such as low detection limits,wide liner range,satisfactory reproducibility and stability,high selectivity,and successfully determination of Pb2+ in real samples.The contents of this work were listed as following:(1)A sensor made of Fe3O4@TiO2@NG@Au@ETBD was developed to specifically detect Pb2+ in a significantly toxic aqueous environment.Nitrogen–doped graphene(NG)was utilized as the substrate material of the sensor by a self–assembly method.The synergistic effect of the Fe3O4@TiO2 as well as the expanded activated surface and good electrical conductivity of the gold nanoparticles enhanced the detection of Pb2+.2,2'–((1E)–((4–((2–mercaptoethyl)thio)–1,2phenylene)bis(azany–lylidene))bis(methanylylide–ne))diphenol(ETBD)was employed as the capture probe for the label–free detection.Compared with conventional detection technologies and electrodes,this sensor enabled a wide LDR from 4 × 10-13 mol/L to 2 × 10-8 mol/L.Lower LOD and LOQ for Pb2+,7.5 × 10-13 and 2.5 × 10-12 mol/L,respectively,were achieved.Furthermore,the Fe3O4@TiO2@NG@Au@ETBD sensor could distinguish Pb2+ from other metal ions despite the interfering metal ions with concentrations 103–fold higher than that of Pb2+.(2)A lead–chelating ligand,ETBD,was immobilized on a nanocomposite Fe3O4@Au/MoS2/GN possessing a large surface area to produce an electrochemical sensor.The ETBD molecules act as specific–receptor binding sites for Pb2+,resulting in the highly selective Pb2+ response by square wave voltammetry(SWV).In order to acquire highly sensitive analysis,MoS2/GN was utilized as a substrate material,which enhances sensing performance and provides sites for Fe3O4@Au,and the core–shell Fe3O4@Au can interconnect and produce conductivity between the recognition element and nanomaterials.Due to the integration of the properties of Fe3O4@Au,MoS2/GN and ETBD,the proposed electrochemical sensor exhibits a wide LDR from 4×10–14 to 2×10–8 mol/L with a low LOD of 3.38×10–14 mol/L.(3)Fe3O4/GN/GE nanocomposite has been synthesized with garlic extracts(GE)surface modification Fe3O4/GN,which has large sueface area and good electrical conductivity,and applied to electrochemical detection of Pb2+ by square wave voltammetry(SWV).Under optimal experimental conditions,Fe3O4/GN/GE modified electrode has a wide LDR from 1×10-12 mol/L to 1×10-6 mol/L with a low LOD(1.23×10-14 mol/L)and LOQ(4.1×10-14 mol/L).The Fe3O4/GN/GE/GCE was not affected by other ions and also showed good stability and reproducibility.Furthermore,it could be preliminarily applied to determination of Pb2+ in real samples.All the results showed that the proposed method is a rapid,sensitive and selective one to detect heavy metal in wastewater,and is hopeful to apply widely in actual detection.