Study Of Fluorescent Detection Of Silver,Copper,and Lead Ions In Water

The pollution of heavy metal ions in the water environment is very harmful to the natural environment and human health.Therefore,it is very important to detect heavy metal ions quickly and accurately.Fluorescence detection technology has the advantages of simple operation,high sensitivity,good selectivity and real-time performance,making it more and more prominent in the analysis of metal ions.The paper organically combines new nanoprobes,fluorescence detection technology and microfluidic chip analysis technology to carry out efficient detection of different heavy metal ions in water quality and multi-parameter simultaneous testing research.Related research is in heavy metal ion detection,biochemical sensor analysis,and environmental monitoring,food safety monitoring and other fields have important research significance and potential practical prospects.The paper makes full use of the aggregation-induced luminescence（AIE）properties of fluorescent probes that can overcome the aggregation-caused quenching（ACQ）effect in traditional fluorescent probes,selected and prepared（E）-N’-（pyrene-1-ylmethylene）hydrazine-carbohydrazide fluorescent probe with aggregation-induced luminescence properties,carried out quantitative detection of Cu²⁺in water environment;Utilizing the features of easy functionalization,good water solubility and biocompatibility of fluorescent carbon dots（CDs）,using glucose as the carbon source and doping with different nitrogen sources to synthesize nitrogen-doped carbon dots 1（NCDs-1）and nitrogen-doped carbon dots 2（NCDs-2）respectively.Fluorescent carbon dot probe;Use the self-made fluorescent carbon dot probe NCDs-1to carry out the selective detection research of Co²⁺in the water environment;Using the self-made fluorescent carbon dot probe NCDs-2,it was found that it responds to the three heavy metal ions of Ag⁺,Cu²⁺,and Pb²⁺.Then,a microfluidic chip was designed and developed,combined with the selective identification characteristics of nucleic acid aptamers,and the microfluidic chip was developed.Research on the synchronous fluorescent chip detection of Ag⁺,Cu²⁺,Pb²⁺three heavy metal ions on the flow control chip.The main content and results of the paper are as follows:（1）Cu²⁺detection based on（E）-N’-（pyrene-1-ylmethylene）hydrazine-carbohydr-azide fluorescent probe:In the experiment,1-pyrene formaldehyde and carbohydrazide were used as raw materials,and absolute ethanol was used as the solvent.The reaction was carried out for three hours under reflux conditions to synthesize the ENPMCH probe.ENPMCH probes have typical AIE properties,and they hardly fluoresce in aqueous solutions.When the solvent N,N-dimethylformamide（DMF）is added,there is a significant increase in fluorescence.Adding different metal ions to the mixed solution of ENPMCH probe(V_H2O:V_DMF=1:1),it can be clearly observed that Cu²⁺can induce fluorescence enhancement of ENPMCH probe.Furthermore,the detection of Cu²⁺in the aqueous solution was carried out,and it was found that the copper ion concentration was 0-20.00μmol·L^-1,and the copper ion concentration showed a good linear relationship with the fluorescence intensity of the ENPMCH probe,and the detection limit was as low as 0.10μmol·L^-1.The ENPMCH probe was used for the detection of Cu²⁺ions in tap water,and the recovery of standard addition was 99.37%-103.00%.（2）The synthesis of nitrogen-doped carbon dots 1 and its application in Co²⁺detection:Using glucose as the carbon source and carbohydrazide as the nitrogen source,the one-pot hydrothermal method was used to synthesize NCDs-1 with high fluorescence quantum yield,and the fluorescence quantum yield was 37.80%.NCDs-1has good water solubility and excellent optical stability,has bright blue fluorescence under 365nm ultraviolet light irradiation,and has an obvious emission peak at 423nm.Due to the existence of the amide bond of NCDs-1,it shows selective recognition of Co²⁺.Experiments have found that when the concentration of cobalt ion is in the range of 0.50-100.00μmol·L^-1,it has a good linear relationship with the fluorescence intensity of NCDs-1,and the detection limit of Co²⁺is 0.11μmol·L^-1.When NCDs-1 was used for the detection of Co²⁺in tap water,the recovery rate of standard addition was98.70%-102.10%.（3）The synthesis of nitrogen-doped carbon dots 2 and the simultaneous detection of Ag⁺,Cu²⁺and Pb²⁺ions on the microfluidic chip:Using glucose as the carbon source and urea as the nitrogen source,NCDs-2 with high fluorescence quantum yield was synthesized by a one-pot hydrothermal method.The NCDs-2 prepared has good water solubility and optical stability.It is under 365 nm ultraviolet light.It has bright blue fluorescence under irradiation,with an obvious emission peak around 455 nm,and the fluorescence quantum yield is 34.50%.Because NCDs-2 has abundant nitrogen and oxygen functional groups,it shows obvious fluorescence response to the three heavy metal ions of Ag⁺,Cu²⁺,and Pb²⁺in aqueous environmental solutions.Based on this,a microfluidic chip containing a filter layer,three channels and three detection chambers was designed and prepared,and a nucleic acid aptamer capable of capturing three heavy metal ions of Ag⁺,Cu²⁺,and Pb²⁺was modified in the detection chamber of the chip.When the NCDs-2 aqueous solution is passed into the detection chamber that captures the above three heavy metal ions,the fluorescence of NCDs-2 is quenched,and the fluorescence spectra of the three detection chambers are tested separately to realize the three types of Ag⁺,Cu²⁺,and Pb²⁺on the microfluidic chip Simultaneous detection of heavy metal ions.The detection limits of Ag⁺,Cu²⁺,and Pb²⁺reached 0.21μmol·L^-1,0.20μmol·L^-1,0.31μmol·L^-1,respectively.In the standard addition recovery experiment,the recovery rates of Ag⁺,Cu²⁺,and Pb²⁺were 98.00%-100.70%,98.70%-102.00%,and99.20%-101.00%,respectively.Research shows that the constructed microfluidic chip analysis system based on fluorescence response test has outstanding advantages and broad application prospects in the field of heavy metal ion detection.