Studies On New Technology For Detection Of Heavy Metal Contaminated Ions In The Environment

Heavy metal ions are one of the most dangerous contaminants present in the environment.And because of its persistence and accumulation in the environment,even exposure to low concentrations of heavy metal ion contaminants can have a series of health effects on humans,including nerve damage,brain damage,reproductive and developmental disorders.Lead ion(Pb²⁺)and mercury ion(Hg²⁺)are two common heavy metal contaminants,and monitoring their contents in the atmosphere,soil and water environment has become an important issue.At present,the detection methods for Pb²⁺and Hg²⁺mainly include atomic absorption spectrophotometry,atomic fluorescence spectrometry,and inductively coupled plasma emission spectrometry.However,these methods require expensive equipment and materials,and the samples to be tested must undergo complex pre-treatment to eliminate other interferers.In addition,they must be analyzed by a technician in a specialized laboratory.Therefore,it is necessary to find a fast and simple method with high sensitivity to detect heavy metals,and real-time monitoring is necessary.Recently,electrochemical sensors have provided new research ideas for the detection of heavy metal ions due to their high sensitivity,good stability,easy operation,low cost,and on-line monitoring in complex environments.This paper mainly studies how to realize the specific recognition of Pb²⁺and Hg²⁺and how to achieve high sensitivity signal response to construct a new electrochemical biosensor.The research content is mainly divided into the following two parts:1.A new technology based on Pb²⁺specific 8-17 DNAzyme combined with iron metal organic framework and bimetallic palladium platinum nanocomposites for Pb²⁺detectionThis study is based on the fact that Pb²⁺can trigger the substrate strand nucleic acid cleavage of 8-17 DNAzyme as a mechanism for specifically recognizing Pb²⁺,combined with palladium-platinum bimetallic?PdPt NPs?modified iron metal organic framework?Fe-MOFs?.The nanocomposites?Fe-MOFs/PdPt NPs?were used as signal tags to construct a novel electrochemical biosensor for the specific detection of Pb²⁺.The streptavidin-modified reduced graphene oxide-tetraethylenepentamine-gold nanoparticles?rGO-TEPA-Au?was first used as a sensor platform for immobilizing more biotin-labeled DNAzymes.In the presence of Pb²⁺,the catalytic activity of the 8-17 DNAzyme is initiated,and the substrate strand is specifically cleaved into two parts at the ribonucleotide site?rA?to generate new single-stranded DNA at the sensor interface.Then,Complementary DNA complementary to the sequence of single-stranded DNA was modified with Fe-MOF/PdPt NPs to form a signal probe,which was immobilized to the sensor interface by a strand hybridization reaction for signal amplification.Fe-MOFs/PdPt NPs catalyze the production of excellent electrochemical signals by hydrogen peroxide?H₂O₂?,which was detected by chronoamperometry.Benefiting from Pb²⁺-dependent DNAzyme,the proposed method can specifically detect Pb²⁺in the presence of other metal ions.The newly designed biosensor exhibits a good linear relationship ranging from 0.005 to 1000nmol L^-1 with a detection limit of Pb²⁺as low as 2 pM.The Pb²⁺-dependent DNAzyme ultra-sensitive biosensor has high sensitivity and high specificity,which provides potential application value for Pb²⁺detection in environmental wastewater.2.A new technique based on T-Hg²⁺-T specific base pair triggered hybridization chain reaction?HCR?combined with gold nanoparticle modified dandelion-like CuO for Hg²⁺detectionIn this study,a novel electrochemical biosensor was prepared based on specific thymine-Hg²⁺-thymidine(T-Hg²⁺-T)base pair for high sensitivity detection of mercury ion Hg²⁺and utilization of toluidine blue?TB?.Used as a redox indicator in combination with HCR for signal amplification.First,Dandelion-like CuO?D-CuO?microspheres modified with Au nanoparticles?D-CuO/Au?was introduced as the sensor interface modification material,which provides more active sites for binding the thiolated probe?P1?.Then,the presence of Hg²⁺induces P1 and other oligonucleotides?P2?to hybridize by Hg²⁺-mediated T-Hg²⁺-T base pairing.Furthermore,a partial sequence of P2 serves as a priming sequence which results in the two hairpin DNA?H1 and H2?chains together forming an extended double-stranded DNA through the HCR process.TB is used to interact with double-stranded DNA and to insert into the DNA duplex to produce an efficient electrochemical signal.The proposed strategy combines the amplification effect of HCR with the intrinsic redox activity of TB,and uses the D-CuO/Au complex as a sensor platform,which has high sensitivity to Hg²⁺determination.Under optimal conditions,the proposed biosensor exhibits a significant electrochemical signal response to Hg²⁺,including a linear range of 1 pM to 100 nM and a detection limit of0.2 pM.In addition,the new biosensor demonstrates its potential application for the determination of trace Hg²⁺in environmental water samples.In summary,this study provides a new technology platform for monitoring lead and mercury ions in the environment.In a part of the study,avidin-modified rGO-TEPA-Au was used as a sensor platform.The utilization of avidin-biotin system,Fe-MOFs/PdPt NPs to achieve efficient signal amplification and high sensitivity and specific detection of Pb²⁺based on 8-17 DNAzyme.In another part of the study,D-CuO/Au was used as the sensor interface modification material.The combination of TB and the HCR as a signal amplification strategy obtained excellent signal response to achieve rapid and accurate detection of Hg²⁺based on T-Hg²⁺-T specific base pairs.The two heavy metal ion sensors constructed this time provide a new idea for early monitoring of heavy metal pollution,and also provide a new direction for the detection and exploration of other heavy metal contaminated ions.