Up-conversion Luminescent Material NaGdF₄: Preparation Of Yb, Er And Study Of Its Fluorescence Properties

Rare earth upconversion luminescence material is a new material that can transform long wavelength to short wavelength.Because of its unique luminous mechanism,it has broad application prospects in biological imaging,biological probes,infrared diode lasers,solar cells,environmental monitoring and other fields.However,the characteristics of the low luminescence intensity and surface hydrophobicity of rare-earth conversion limit its wide application.Therefore,the enhancement of fluorescence intensity by doping transition metal and surface conversion from hydrophobic to hydrophilic,which provides new opportunities for the upconversion development.In this paper,NaGdF₄:Yb,Er nanocrystals with uniform size and good dispersion were synthesized using a facile hydrothermal method.The best synthesis conditions were found by controlling the reaction conditions.At the same time,in the preparation of NaGdF₄:Yb,Er nanocrystals,different concentration of Fe³⁺was doped to explore the relationship of the appearance,concentration,phase structure and the fluorescence intensity.In addition,NaGdF₄:Yb,Er nanomaterials were coated silica shell on the surface and prepared successfullynanomaterials NaGdF₄:Yb,Er@SiO₂,and to explore the related factors of package thickness and fluorescence intensity.First of all,NaGdF₄:Yb³⁺,Er³⁺nanocrystals of uniform size and good morphology were prepared successfully by hydrothermal method.then explore the influence of appearance?phase and upconversion fluorescence intensity,which concentration different reaction time and different amount of NaOH produced by means of EDS,XRD,TEM,SEM and fluorescence spectra.To get the best preparation conditions for the synthesis of nanoparticles:reaction temperature 180^o C,reaction time was 20 h,and the amount of NaOH reaches 0.03 mol to get the most regular morphology and size of the nanorods.Then,different concentrations of Fe³⁺ions were doped and the effects of doping concentration on the fluorescence intensity of NaGdF₄:Yb³⁺,Er³⁺nanocrystals were studied in detail.As the concentration increases,the fluorescence intensity increases first and then decreases.When the doping concentration of Fe³⁺ions is 20%,the luminescence intensities of green and red light both reach their maximum values,and the mechanism of this change is analyzed.Finally,the prepared NaGdF₄:Yb³⁺,Er³⁺nanocrystals were surface-modified and modified by silica encapsulation and emulsification methods.By controlling the amount of TEOS added,the thickness of silica shell and up-conversion fluorescence intensity were explored.In addition,during the experiment,the surfactant PVP was added to change the surface properties and fluorescence intensity.