Study On The New Colormetric And Fluorescent Methods For The Determination Of Micro Amount Of Hg²⁺ And TNP

In recent years,more and more attention has been paid to the problem of environmental pollution and protection.Heavy metals in environment can enter the body through skin contact,diet,or breathing.The interaction between heavy metals and protein and enzyme will damage the normal function of human body,causing health problems and even disease.Excessive mercury in body will inhibit the activity of enzyme and cause damage to kidney and nervous system.Therefore,the detection of micro amount Hg²⁺in environmental samples and biological samples has been highly concerned.2,4,6-trinitrophenol?TNP?is a substance that is harmful to wild animals and humans and it is one of the important environmental pollutants.In the process of industrial production and application,TNP will enter the environment,leading to soil and aquatic system pollution.Through mammalian metabolism,TNP is converted to 2-amino-4,6-dinitrophenol,which causes a genetic mutation and its toxicity is 10 times higher than that of TNP.Therefore,the detection of micro amount of TNP in environmental samples and biological samples is also one of the most important problems need to be solved for analytical chemistry.One of the most important problems in environmental pollution control is to determine the type and content of pollutants.However,there is still lack of analytical methods with high sensitivity,selectivity,accuracy,as well as high speed for the detection of micro amount of Hg²⁺and TNP.The colorimetric method based on gold nanoparticles?AuNPs?has been widely used due to its advantages,such as simple operation,no need for expensive equipment,short analysis time,determination of the presence or absence of the test object by the naked eye,etc.However,in order to realize the specific identification or detection of analytes,it is often required to be modified with DNA or other functional unit.However,the modification process is complex,time-consuming and costly,which limits the application of colorimetric method.Because of their unique optical properties,the preparation of carbon nanomaterials such as carbon quantum dots?CQDS?and their application in the determination of micro amount analytes incomplex samples have become one of the hot topics in analytical chemistry and other related fields.In addition,design and synthesis of novel organic fluorescent probes is one of the most active research fields in analytical chemistry.Therefore,based on the previous works,the following major innovative researches were carried out in order to develop new method for preparation of AuNPs,CQDs and new imidazole organic fluorescent probes with excellent performance,as well as expand their practical application in the determination of micro amount of Hg²⁺and TNP in real samples.This dissertation consists of seven chapters.Chapter 1: The research progress of AuNPs,CQDs and imidazole type fluorescent probes in recent years was summarized.The application of AuNPs and CQDs in the determination of micro amount of Hg²⁺,TNP and the synthesis of organic fluorescent probes and their application in the detection of Hg²⁺ and TNP were reviewed.Chapter 2: Rhodanine modified gold nanoparticles AuNPs@R were synthesized and the size and pattern were characterized by DLS and TEM.Based on the coordination of Hg²⁺with AuNPs@R resulting in color change of the solution by the AuNPs agglomeration,a new colometric method for the determination of micro amount of Hg²⁺was established.Under optimized conditions,the liner range was0.02-0.5 ?M,the regression equation was650 5202 HgA A2.043c??M?0.036?10??28??10?,R2 =0.997,the limit of detection?S/N=3?was 6 nM.The method can also be used to visualize Hg²⁺.In addition,the detection mechanism was also studied.Chapter 3: A new microwave-aided one pot method was established for the preparation of nitrogen doped carbon quantum dots?N-CQDs?with citric acid as carbon source and ammonioformaldehyde as nitrogen source.Comparison of carbon quantum dots prepared by refluxing using nitric acid as medium,the N-CQDs has strong fluorescence intensity,high quantum yield and long fluorescence lifetime.A new fluorescent method for the determination of TNP was established by using the prepared N-CQDs as probe.Under optimized conditions,the liner range was 1.25-25?M,the regression equation was0 TNPF-F?28?26.92c??M?-29.57,R2 = 0.9902,the limit of detection?S/N=3?was 0.4 ?M.The method has been successfully applied to the determination of TNP in water samples.Chapter 4: A new method was developed for the preparation of nitrogen doped fluorescent carbon quantum dots?N-CQDs?with citric acid as carbon source ando-diaminobenzene as nitrogen source.The method was simple and the prepared nitrogen doped carbon quantum dots does not need to be modifed.A new fluorescent method for the determination of TNP was established by using the N-CQDs as a probe.Under optimized conditions,the liner range was 1.5-50 ?M,the regression equation was0 TNPF-F?28?84.48?10?17.45c??M?,R2 = 0.9892,the limit of detection?S/N=3?was0.5 ?M.The method has the advantages of simple operation,low cost,high sensitivity,high selectivity and good reproducibility,and has been successfully applied to the detection of TNP in real samples.The mechanism for the fluorescence quenching of N-CQDs by TNP was also determined.Chapter 5: Based on the characteristics of imidazole,the N atom in the molecule has strong coordination ability and connects with the aromatic ring and a large ?conjugation system can be formed,a novel fluorescent probe4-?4,5-diphenyl-1H-imidazol-2-yl?benzoic acid was synthesized for the determination of TNP.A new method was established for the determination of micro amount of TNP in real samples with simple operation,low cost,high sensitivity and good selectivity.Under optimized conditions,the liner range was 1.25-55 ?M,the regression equation was0 TNPF-F?28?12.19c??M?+10.30,the limit of detection?S/N=3?was 0.3 ?M.In addition,based on the color change of the probe solution with the concentration of TNP increasing,a new method for visual detection of TNP was developed.And the recognition mechanism of the probe for TNP was studied.Chapter 6: A highly sensitive and selective fluorescent probe for mercury ion was synthesized using iminazole as luminophore,and a new fluorescence method for the determination of trace Hg²⁺ was established.Under optimized conditions,the liner range was 0.9-10 ?M,the regression equation was2+HgF?28?58.4c?10?40,the limit of detection?S/N=3?was 0.3 ?M.The method has been successfully applied to the determination of micro amount Hg²⁺ in real samples.Based on the phenomenon that the color of the probe solution changed with the increase of the concentration of Hg²⁺,a method of visual detection of Hg²⁺was developed.Chapter 7: Conclusions and prospects...