Preparation Of Lanthanide-doped Down-Conversion Nanoparticles For Detection Of Aflatoxin B₁

Rare-earth doped down-conversion nanomaterials(DCNPs),as a kind of novel nano-fluorescent probes,have more advantages than traditional fluorescent dyes and fluorescent proteins,such as greater stokes shift,stronger photo-beaching resistance,lower biological toxicity,long-term stable light emission,better chemical stability,bio-crosslinking,greater flexibility and lower cost.These advantages make DCNPs have good prospects in the fields of biological detection,molecular diagnostics,and tumor-targeted therapy.In this thesis,we focus on the preparation of rare-earth doped down-conversion nanomaterials,water-soluble modifications,dissolved fluorescence enhancement and construction of down-conversion fluorescent nano-probe for detection of aflatoxin B1.Firstly,rare earth chlorides are used as reactants to react with sodium oleic to generate rare earth oleic(Ln-OA).The uniform DCNPs with tunable size are prepared using Ln-OA as precursor and oleic acid/1-octadecene(OA/ODE)as solvents.The effect of different reaction time and rare earth doping ratio on nanoparticles is studied in the same way.Then,in order to realize the application of the NaYF4:Eu down-conversion nanoparticles in biological detection,the ligand exchange method is used to modify the water solubility of NaYF4:Eu nanoparticles.The polyacrylic acid(PAA)is exchanged with nanoparticles surface oleic acid(OA)ligand,after that,NaYF4:Eu nanoparticles with carboxyl groups(-COOH)on the surface are obtained to achieve water-solubility modification.However,the transitions in the 4F6 configuration are forbidden transitions for lanthanide ions(Ln3+),As a result,photon absorption rate is too low to generate strong fluorescence.In view of the fact that the fluorescence intensity of the nanoparticles is not enough,we add the weakly acidic enhancement solution on the basis of the dissociation-enhanced lanthanide fluorescence analysis method to the modified nanoparticles solution to achieve fluorescence enhancement.Meanwhile,the process of the dissolved fluorescence enhancement of nanoparticles solution is further studied.Finally,a down-conversion nanoparticles-labeled probe is developed on the basis of the third chapter,using the aflatoxin B1 aptamer as a marker for the preparation of down-conversion immunochromatography stripes.In addition,the effect of the experimental condition and the effect of the sample solvent on the test strips are explored to create a new method for the quantitative detection of AFB1 based on down-conversion nanoparticles immunochromatography test strips.After compared with colloidal gold immunochromatographic test strips,it was found that AFB1 quantitative detection method based on down-convertsion fluorescent nanoparticle probes has high sensitivity and can be used for rapid detection of aflatoxin B1 in actual samples.The study provides new research ideas for food safety testing...