| Upconversion nanomaterials are a new type of luminescent materials that can continuously absorb two or more photons and convert low-energy excitation light into highenergy emission light.Compared with traditional quantum dots and fluorescent dyes,upconversion nanomaterials have excellent properties,such as narrow emission peak,no autofluorescence,strong tissue permeability,low toxicity,and small damage to organisms,which makes it useful in cell imaging,diagnosis and treatment,molecular detection and other biological fields have a wide range of applications.Although upconversion nanomaterials have many excellent properties,controlling the synthesis of upconversion nanoparticles with high dispersion,uniform size and high upconversion luminescence efficiency is still a hot spot and difficulty.In addition,the surface of upconversion nanoparticles synthesized in oil phase is usually wrapped by hydrophobic OA or OM ligands,which makes them unable to disperse directly in aqueous solution.Although many surface modification strategies such as ligand exchange,ligand oxidation and ligand removal have been proposed,the water-soluble nanoparticles prepared by the above methods are easy to agglomerate,have low luminescent intensity and are generally not biocompatible The application of upconversion nanoparticles in the biological field is greatly limited,so the design of efficient and high-quality surface functionalization methods is still a serious challenge.In order to solve the above problems,this paper mainly studies from the following three aspects:(1)Rod-like upconversion nanoparticles(NaYF4:40%Yb3+/1%Tm3+@NaYF4:10%Yb3+)with high dispersion,high fluorescence intensity and uniform particle size were synthesized by adjusting Yb3+ ions doping concentration and controlling the shell thickness;(2)A simple and efficient method for surface modification of upconversion nanoparticles was proposed.The upconversion nanoparticles(6×His-UCNPs)with high dispersion and high stability were obtained by phase transfer of 6×His.The best phase transfer condition with the highest fluorescence intensity was obtained by adjusting the concentration of 6×His,pH of solution and concentration of UCNPs-OA;(3)Through electrostatic adsorption,DNA-FAM as energy receptor and 6×His-UCNPs as energy donor,a simple upconversion nanoprobe(UCNP-FAM)based on fluorescence resonance energy transfer(FRET)was constructed to quantitatively detect the concentration of Dam methylase. |
