Up-conversion NaGdF₄:Yb³⁺, Er³⁺ Nanorod Preparation, Doping And Modification Research

Rare earth doped upconversion nanoparticles have attracted widespread attention due to their unique properties for converting longer wavelength light into shorter wavelength light.Among them,color display,solid-state laser,bio-imaging and many other applications are quite extensive.In addition,compared with conventional luminescent materials,rare earth doped upconversion nanomaterials have[=\many advantages of weak background fluorescence,long fluorescence lifetime,strong photochemical stability,low radiation damage and photobleaching.However,there have disadvantages that water solubility is poor and the intensity of light emission is low.Therefore,the surface modification of the rare earth upconversion nanoparticles can be used to improve the defects of poor water solubility and low fluorescence intensity,and the transition metal can be doped to increase the fluorescence intensity.Firstly,NaGdF₄:Yb³⁺,Er³⁺upconversion nanorods with uniform morphology and good dispersion were prepared by simple hydrothermal method.The effects of different conditions on the morphology and fluorescence intensity were investigated by changing the temperature,time and amount of sodium fluoride.At 180?and 20h,NaGdF₄:Yb³⁺,Er³⁺upconversion nanoparticles are hexagonal.TEM shows that the prepared nanorods had regular morphology and uniform size.The results show that the fluorescence intensity is strong.Then,Fe³⁺with different concentrations were doped into NaGdF₄:Yb³⁺,Er³⁺upconversion nanorods.XRD diffraction peak movement and EDX mapping show that Fe³⁺was evenly doped into nanorods.The upconversion fluorescence intensity reached the maximum when the Fe³⁺doping concentration was 20%.This provides a preparation method for high concentration transition metal ions doped onto upconversion nanoparticle crystals.Finally,the CTAB was combined with NaGdF₄:Yb³⁺,Er³⁺nanorods.After full emulsification,it is found that the nanorods could be well dispersed in aqueous and the upconversion fluorescence intensity is enhanced.Besides,nanorods were combined with ZIF-8 to obtain composite nano-particles NaGdF₄:Yb³⁺,Er³⁺/ZIF-8.TEM shows NaGdF₄:Yb³⁺,Er³⁺upconversion nanorods on the surface of ZIF-8.Upconversion fluorescence intensity of composite nanoparticles is lower than pure upconversion nanorods.In order to synthesize NaGdF₄:Yb³⁺,Er³⁺/ZIF-8 composite nanoparticles with better binding,it is necessary to find better surfactants and explore the reasons for the decrease of fluorescence intensity.