Colorimetric Detection Of Heavy Metals Mercury And Chromium By Gold Nanoparticles

Heavy metal ions in the environment can accumulate in the food chain of the ecosystem and pose potential hazards to the environment and human health.The rapid and easy detection of heavy metal content in the environmental system is important to protect the environment and prevent human health risks.The colorimetric method is widely used in the field of heavy metal detection because of the simple operation of the equipment and the intuitive detection results.In this thesis,new methods have been developed for the rapid and simple detection of heavy metals such as mercury ions and hexavalent chromium ions based on colorimetric methods using the local surface plasmon resonance effect of gold nanoparticles and efficient simulated enzymatic activity.The established methods,which are sensitive,reliable and cost-effective,can be used for the rapid determination of heavy metals in real samples,with the following main studies.（1）Synthetic amino-modified gold nanoparticles with positively charged surfaces were prepared using mercaptoethylamine as the coating reagent.The positively charged gold nano-particles were used as signal substances,combined with the specific recognition of mercury ions by mercury ion aptamers,and the different interaction forces between nucleic acid ap-tamers of different conformations and gold nanoparticles in the presence or absence of mercury ions led to different spacing of gold nanoparticles,resulting in the change of solution color,and the quantitative detection of mercury ions was achieved by the solution absorbance ratio（A560/A700）.Under the optimal experimental conditions,the linear relationship between the concentration of mercury ions and the absorbance ratio of the reaction solution was good in the range of 8.2×10^-10～6.2×10^-8M.The detection limit was as low as 4.9×10^-11 M,which was one order of magnitude lower than that when the negatively charged gold nanoparticles were used as the signal probe.The detection limit was one order of magnitude lower than that when neg-atively charged gold nanoparticles were used as signal probes.In addition,the strong affinity between T-Hg-T makes the method highly selective.By using the spiked recovery method to detect the mercury ions in tap water and lake water,and also for the Chan River water samples,the detection results were not significantly different from those of cold vapor atomic absorption spectrometry,indicating that the method has good reliability for the detection of mercury ions.（2）Citrate ion-coated gold nanoparticles with a particle size of about 13 nm were prepared by using sodium citrate as the reducing and stabilizing agent with chloroauric acid as the pre-cursor solution,and it was shown that the prepared gold nanoparticles have strong redox-mi-metic enzymatic activity and can effectively promote the reaction of hexavalent chromium ions with the enzyme substrate TMB to form trivalent chromium ions with blue oxidized TMB.The main reason for the efficient redox-mimetic enzymatic activity of gold nanoparticles is the strong pro-cooperation force between the enzyme and the substrate.Under the optimal experi-mental conditions,the concentration of hexavalent chromium ions in the range of 0.008～0.156mg/L showed a good linear relationship with the absorbance value at 652 nm of the reaction solution,and the detection limit was as low as 0.52μg/L.In addition,the method was highly selective and anti-interference for all the other 28 ions,and the spiked recovery for the deter-mination of hexavalent chromium ions in tap water,river water and wastewater was The spiked recoveries ranged from 95.00%to 105.40%,indicating that the method has good reliability in practical applications.（3）The graphene oxide/gold nanocomposites were prepared by hydrothermal synthesis method,and the study showed that the graphene oxide/gold nanocomposites have peroxide-mimetic enzyme activity,which can effectively promote the reaction between hydrogen perox-ide and enzyme substrate TMB to generate blue oxidation products,and use 8-hydroxyquino-line as an inhibitor to inhibit the reaction when hexavalent chromium ions are present,and the relationship between hexavalent chromium ions and 8-hydroxyquinoline When hexavalent chromium ions are present,the strong chelation between hexavalent chromium ions and 8-hy-droxyquinoline leads to the recovery of the solution color,based on which the quantitative de-tection of hexavalent chromium ions is achieved.Under the optimal experimental conditions,the concentration of hexavalent chromium ions was linearly correlated with the absorbance value at 652 nm of the reaction solution in the range of 0.1～15μM,and the detection limit was0.062μM.The experimental results showed that the method has good selectivity and anti-in-terference to other ions.The results showed that the method has good reliability in practical application.