Preparation And Characterization Of DPA Rare Earth Nanosheets Fluorescence Probe

Lanthanides,rare earth elements,have unique luminous properties.Rare earth materials have a wide range of applications in magnetism,catalysis,ceramic materials,hydrogen storage materials,especially optical luminescence and biomedicine.Due to a sheet-like structure with a lateral dimension greater than 100 nm or up to a few microns or larger,two-dimensional nanomaterials have a large specific surface area,excellent electrical and thermal conductivity,and show promise of very important applications.Following a severe outbreak of anthrax in the United States in 2001,Bacillus anthracis has attracted considerable attention in research.Bacillus anthracis is gram-positive and one of the largest pathogenic bacteria.The inhalation of anthrax spores into the respiratory tract can result in the development of a highly infectious disease with a high mortality rate.If the spore intake exceeds 10⁴B/mL,it can be lethal.Dipicolinic acid（DPA）is a chemical component that accounts for 5 to 15%of the dry weight of bacterial spores,and is a unique biomarker of Bacillus anthracis.Accurate and sensitive detection of DPA can facilitate the identification of Bacillus anthracis contamination.Based on the above,this paper mainly conducts the following three aspects of research:（1）The layered material Y_1.94Eu_0.06（OH）₅（C₅H₆COO）·2H₂O doped with 3%Eu（Ⅲ）was synthesized by one-step hydrothermal method,and its layered structure was proved by powder-x-ray diffraction.Then the monolayer nanosheets were obtained by mechanical ultrasonic peeling.The sheet structure and morphology can be observed by transmission electron microscope.From the TEM pictures,we can see that the transverse size was about a few hundred nanometers.The thickness was measured by atomic force microscope（AFM）,and the flake morphology was also found in the AFM image.The thickness of the nanosheet was about 1nm.The Eu（Ⅲ）-doped nanosheet probe was applied to the detection of Bacillus anthracis biomarker DPA.It was found that the fluorescence intensity of Eu at 614nm increased with the increase of DPA concentration,and the detection range was 0.1μmol/L-30μmol/L.The detection limit was calculated to be 78nmol/L.The selective test was carried out and the sensing mechanism is discussed in detail.（2）In order to reduce the detection limit of DPA,the layered material Y_0.99Tb_0.01OC₆H₅COO doped with 1%Tb（Ⅲ）oxide was prepared by high temperature calcination method,and the monolayer nanowires were prepared by mechanical ball milling.The two-dimensional nanostructures of the materials were characterized by XRD,TEM and AFM.When the 1%Tb-doped oxide nanosheets were used for the detection of DPA,it was found that the fluorescence intensity and lifetime of Tb at 544nm was linearly correlated with the increase of DPA concentration,the detection range was 50 nmol/L-30μmol/L,and the detection limit was 44nmol/L.And its sensing mechanism was deeply studied.（3）Eu（Ⅲ）-Tb（Ⅲ）co-doped layered material Y_1.96Eu_0.02Tb_0.02（OH）₅（C₆H₅COO）·2H₂O was synthesized by one-step hydrothermal synthesis,and the monolayer nanosheets were peeled off by mechanical ultrasound,and the structure of the nanosheets was characterized by XRD,TEM,AFM and so on.At the same time,the nanosheet probe was prepared into a proportional fluorescent probe,and the preliminary results were obtained,and the relationship between the sensing principle and structure was explored.