Simple And Sensitive Methods For Detection Of Heavy-metal Ions

Heavy metal pollution has become an important environmental problem in human health.It is highly necessary to develop rapid,simple and sensitive methods to detect trace metal ions.On the issue of metal ions detection in biochemical analysis and biological sensing technology?such as the operating process is tedious,requirement for expensive instruments,ect.?,we developed new methods to detect heavy metal ions,which includes the following three parts of experiments:?1?In Chapter 2,we reports a new gold nanoparticle?GNP?-based colorimentric sensor for the simple,sensitive,specific detection of Hg²⁺,Ag⁺and Cu²⁺via analyte autocatalysis amplification.The nanosensor initially uses the o-phenylenediamine?OPDA?as an efficient promoter for aggregation of as-prepared citrate-coated GNPs that leads to a red-to-blue change in color of the GNP solution.In the presence of these ion analytes,they can specifically oxidate free OPDA molecules to create poly-OPDA or oxide OPDA?OPDAox?.More importantly,mercury,copper or silver nanoclusters could be formed during the above reactions and could further act as auto-nanocatalysts for cyclical oxidation of OPDA.As no GNPs'aggregation takes place due to dramatically reduced free OPDA molecules,the corresponding GNP solution keeps its original red color.With such analyte autocatalysis amplification,this colorimetric sensor enabled the naked-eye,selective,qualitative detection of ca.19.5 nM Hg²⁺,ca.19.5 nM Ag⁺and ca.19.5 nM Cu²⁺with the aid of appropriate masking agents.Accurate quantification of the three ion analytes was also realized by using UV-Vis spectrometry.The obainted linear concentration ranges for the Hg²⁺,Ag⁺and Cu²⁺were 19.5 nM⁵?M,9.7 nM¹0?M and 9.7 nM⁵?M,respectively.The UV-Vis limits of detection of Hg²⁺,Ag⁺and Cu²⁺were estimated to be ca.2.7,1.1 and 1.2 nM?3??,respectively.In addition,the satisfactory recovery results of assaying several complex pond water samples demonstrated the reliablity and practicability of the colorimetric nanosensor proposed herein.?2?In Chapter 3,we initially established a instruments-free visual inspection method for the detection of copper ion based on the MES can reduce chloroauric acid to GNP and the copper can catalyzed this process.In this scheme,the time of the copper ion to catalyzed MES to reduction chloroauric acid to form red GNP was in inverse proportion with the concentration of copper ions,which could be quantitative analysis of copper ion.The new method only requires the operator to have the basic skill of solution mixing,color discrimination and timing capabilities.Compared with the reported methods of quantitative detection of copper ions,the new method has many advantage,such as fewer kinds of reagents required,simple to operation,low cost,instrument-free in the whole testing process,can be applied to field analysis,higher detection sensitivity,linear range wider and so on.The quantitative colorimetric analysis could allow for the determination of Cu²⁺in the dynamic concentration range of 6.4 nM?100?M,with the limit of detection of about 3.5 nM?S/N=3?.?3?In Chapter 4,as we find that the MES can reduce chloroauric acid to GNP that containing the size of uniform of red solution?the color change process is colorless-blue-red?at a certain concentration,and Hg²⁺can inhibit this process so that the MES-chloroauric acid system eventually results in a colorless or blue solution at the same reaction time,we propose a new method for detection of Hg²⁺.Under optimized experimental conditions,the as-prepared sensor exhibited high sensitivity and fast response to Hg²⁺with the linear range from 2.048 nM to 100 mM and a low detection limit of 0.25 nM.In addition,this new method also shows good selectivity,recovery and stability.