Preparation And Application Of Rare Earth Upconversion Nanomaterials With High Luminescence Efficiency

In this thesis,?-NaYF₄:Yb,Er nanoparticles with morphology and size-controlled were prepared by hydrothermal method and thermal decomposition method,respectively,and the upconversion luminescence properties were characterized.The samples were characterized by powder X-ray diffractometer?XRD?,Transmission electron microscope?TEM?,Scanning electron microscope?SEM?,Infrared spectrometer?IR?,and Pluorescence spectrophotometer?PL?.Then,nanoparticles were surface modified under the optimal preparation conditions and applied to HeLa cell imaging.The research work is as follows:?1?NaYF₄:Yb,Er particles are prepared by a simple hydrothermal method using rare earth nitrates as precursors.The effects of reaction time,reaction temperature,and the dosage of NaF on the morphology,crystal structure,and luminous properties of the sample were investigated.The results showed that?-NaYF₄:Yb,Er hexagonal prisms with a size of 5×2?m were synthesized when the reaction time was 24 h,the reaction temperature was 200?,and the NaF was 6 mmoL.It was also found that the lower the aspect ratio of the sample,the higher the light intensity,that is,the larger the upper and lower bottom surfaces of the hexagonal prism,the higher the luminous intensity.Therefore,in order to reduce the aspect ratio and improve the luminous intensity of the samples,we also studied the effects of Gd³⁺doping on the properties of the samples at low NaF dosage?4 mmoL?.The results show that Gd³⁺doping not only realizes the material transition from hexagonal prism to hexagonal disk,but also reduces the aspect ratio of the sample.When the Gd³⁺doping dosage is 60 mmoL,?-NaYF₄:Yb,Er?200×200 nm?hexagonal prisms with high luminous intensity can be prepared.In the experiment,the best rare earth ion mole ratio:Y³⁺:Gd³⁺:Yb³⁺:Er³⁺=18:60:20:2.?2?Size-tunable?-NaYF₄:Yb,Er?50-400 nm?UCNPs with strong green emission was successfully prepared by thermal decomposition using rare earth trifluoroacetate RE?CF₃COO?₃ and sodium trifluoroacetate as precursors,oleic acid?OA?and octadecene?ODE?as solvents.The effects of reaction temperature,reaction time,Na⁺dosage,dosage of oleic acid and Gd³⁺doping dosage on the morphology,crystal structure and luminous properties of the sample were explored.The optimal synthesis conditions(reaction temperature was 300?,reaction time was 15 min,the dosage of OA was 15 mL,Na⁺dosage was 2.1 mmoL,Gd³⁺doping dosage was 20mmoL)and the luminescence mechanism of the sample were revealed.?3?Synthesis of NaYF₄:Yb,Er nanoparticles?UCNPs?modified by heterogeneous shell and homogeneous shell by thermal decomposition.The results show that the luminous intensity of UCNPs with core-shell structure is much higher than that of core UCNPs.Among them,the core-shell structure NaYF₄:Yb,Er@NaLuF4:Yb has the highest luminous intensity.Next,different hydrophilic polymers?PAA,PEI?were selected for ligand modification of NaYF₄:Yb,Er@NaLu F₄:Yb nanoparticles,the infrared spectra indicated that the hydrophilic groups were successfully coated on the surface of the sample.?4?HeLa cellular labeling of ligand-modified samples.The effect of coated ligand type and labeled time on the imaging effect was investigated.The results showed that the sample coated with PAA polymers?UCNPs-PAA?after 2 h of co-culture with cells had strong luminescence signal.Hence,UCNPs-PAA nanoparticles have great potential in biomedical applications.