Preparation Of Noble Metal Nanocomposites And Their Detection Of Mercury Ions And Dipicolinic Acid

As people pay more and more attention to environmental quality and public safety,trace detection of toxic substances has become a hot research topic.The research of precious metal nanomaterials and the development of functionalized composite materials for the detection of toxic substances in the environment is becoming a new research trend.The main research work of this thesis is to design and synthesize nanocomposites based on the diversity of structures and properties of noble metal materials for visual detection of heavy metal mercury ions,Bacillus anthracis and actual biological samples.The introduction part of this paper mainly introduces the research background related to the subject,and focuses on the main recognition mechanism of fluorescent probes,the research status of heavy metal mercury ions,Bacillus anthracis and the development and application of precious metal materials related to this paper.Introduces our research work:（1）Based on the aggregation state of gold/silver alloy nanocomposites（Au/Ag NCs）,a simple and rapid UV-colorimetric two-channel method was developed for the determination of Hg²⁺in aqueous solution.Monodisperse Au/Ag NCs are orange-yellow.After adding lysine,the strong covalent bond between the amino group of lysine and Au formed uniformly dispersed lysine-modified Au/Ag NCs,the solution was orange-yellow,and the characteristic UV absorption peak was located at 447 nm.Lysine has two amino groups,one binds to the surface of Au/Ag NCs and the other binds to Hg²⁺.Hg²⁺acts as a bridge to connect the lysine-modified Au/Ag NCs.When Hg²⁺is added,the lysine-modified Au/Ag NCs aggregate immediately,and the solution color changes from orange-yellow to yellow-green or gray immediately.The aggregation degree of Au/Ag NCs can be measured not only by the color change from orange-yellow to yellow-green,but also by the change in the UV absorption spectrum.After the aggregation of lysine-modified Au/Ag NCs,a new absorption peak appeared at 650 nm.In this experiment,conditions such as p H value,lysine concentration,and reaction time were optimized.The change in absorbance ratio(A₆₅₀/A₄₄₇)was proportional to Hg²⁺concentration in the range of 0.01-10.0μM,with a limit of detection（LOD）of 4.8 n M.The detection method has high sensitivity and strong selectivity for Hg²⁺detection.（2）The redox reaction of tetramethylbenzidine（TMB）is catalyzed by gold-platinum core-shell nanocomposites（Au@Pt NCs）to generate a blue oxidized tetramethylbenzidine（ox-TMB）solution with UV characteristics The absorption peak is at 650 nm.A simple and rapid determination of Hg²⁺in aqueous solution by UV absorption spectroscopy-colorimetric two-channel method was developed.After adding Hg²⁺,Hg²⁺undergoes amalgam reaction with Au@Pt NCs,occupying the catalytic site of tetramethylbenzidine.With the increase of Hg²⁺concentration,the A₆₅₀absorbance of the UV absorption spectrum gradually decreased,and the solution was accompanied by a color change from blue to colorless.In this experiment,conditions such as p H value,catalyst dosage,and reaction time were optimized.The absorbance of A₆₅₀was inversely proportional to the Hg²⁺concentration in the concentration range of0.005-0.05μM,and the limit of detection（LOD）was 3.2 n M.The detection method has high sensitivity and strong selectivity for the detection of Hg²⁺,and the method is also suitable for the detection of Hg²⁺in actual samples in the environment.（3）In this study,ratiometric fluorescent nanoprobes of BSA-Tb³⁺-Au NCs were designed and synthesized for the detection of DPA.The probe itself has red fluorescence under 254 nm UV light and is not affected by the concentration of DPA,and can be used as a stable fluorescent internal standard for ratiometric fluorescence nanosensing detection.In the linear range of 0-12.5μM,with the increase of DPA concentration,the green fluorescence gradually increases,and the overall reaction solution system exhibits a color change from red fluorescence to green fluorescence,realizing fast and highly sensitive DPA multicolor sensing.The detection limit is as low as 3.4 n M.The detection method has high sensitivity,strong selectivity and wide applicability,and can be applied to the detection of DPA in actual samples.The developed BSA-Tb³⁺-Au NCs paper-based detection probe realized rapid qualitative and semi-quantitative detection of DPA.