Research On Super-grain Assembly And Fluorescence Properties Based On Up-conversion Nanoparticles

Upconversion nanoparticles have important applications in biology,medicine,etc.,but most of the preparation methods produce upconverting nanoparticles that are oil-soluble and cannot be dissolved in water,which greatly limits the applications of upconversion nanoparticles.The modification of the upconversion nanoparticles to make them water-soluble has a strong practical significance.We use a simple and easy-to-use microemulsion method to self-assemble upconverting nanoparticles into different forms and water-soluble superparticles under the synergistic induction of surfactants.Based on this microemulsion system,the two-component superparticles were designed and self-assembled with uniform UP nanoparticles and quantum dots.The research content and result are as follows:The NaGdF₄:Yb,Er UP nanoparticles were prepared by solvothermal method,and their crystal structure,morphology and luminescence properties were characterized.It was proved that the prepared upconverting nanoparticles were uniform in size distribution with8 nm.Furthermore,their upconversion luminescence was studied by tuning structure and morphology.In this section,the upconverting nanoparticles were self-assemble into superparticles in different morphology by the microemulsion method.The morphology of superparticles were assembled by selecting two different surfactants.At the same time,the luminescence properties of the superparticles and the original nanoparticles were studied.The effect of nanoparticle concentration on these upconverting superparticles was explored by varying the concentration of UP nanoparticles.In the microemulsion system,both surfactants make the UP nanoparticles to have good solubility in water owe to synergistic induction,which extends the range of applications.In order to improve the luminescence spectrum of the UP nanoparticles,the NaYF₄:Yb,Er/CdSe colloidal spheres were self-assemble by uniform NaYF₄:Yb,Er UP nanoparticles and CdSe quantum dots.The visible light emitted by the UP nanoparticles re-excites the CdSe quantum dots to achieve multiple color luminescence.The UP luminescence of NaYF₄:Yb,Er/CdSe colloidal spheres were weakened at 408 nm and increased at 655 nm,which proves the coupling between the UP nanoparticles and the quantum dots.It offered a method for colloidal spheres with different components.