Design, Synthesis And Application Of Surface Functionalization Of Up-conversion Nano-phosphor With NaYF₄ As The Substrate

Compared with semiconductor quantum dots and organic dyes,rare-earth-doped upconversion nanoparticals?UCNPs?possess many advantages,such as narrow emission peak,large anti-Stokes shifts,superior photostability,long lifetimes,low fluorescence background,and hey can overcome the inherent limitations of traditional materials.The near-infrared?NIR?for upconversion excitation inhibits light-induced autofluorescence and photodamage to biological tissues for which enables high penetration depth.Recently,UCNPs have attracted much attention because of their performance of bio-labeling,multimodal bioimaging,photodynamic therapy,drug delivery,bio-sensing,molecular detection.For UCNPs,the effect of host materials are of great importance,because it provides a crystal field that make the excited ions produce a suitable emission.Fluorides are hopeful host materials for upconversion aiming at fluorescence light owing to their low phonons energy,high luminous efficiency and high stability.NaYF₄ is one of the more widely used host materials.NaYF₄:Yb,Er and NaYF₄:Yb,Tm are two representative upconversion fluorescence materials which possess high luminous efficiency at present.Low quantum yield of NaYF₄:Yb,Er and NaYF₄:Yb,Tm limits it application in biological imaging and photodynamic therapy.Surface modification is an effective way to solve the above problem.It includes surface passivation,loading precious metal,ect.In our work,we synthesized upconversion nano-fluorescent heterojunction materials by surface absorption in situ reduction method and investigated the application of photodynamic therapy and photodegradation.NaYF₄:Yb,Er nanospheres have been synthesized using hydrothermal method.The XRD confirmed that the NaYF₄:Yb,Er nanospheres have high crystallinity.TEM images showed the diameter of NaYF₄:Yb,Er nanospheres was about 100 nm to 200nm.NaYF₄:Yb,Er@Au was synthesized based on surface adsorption and reduction reaction at room temperature.NaYF₄:Yb,Er@Fe₃O₄ were synthesized based on surface adsorption at room temperature.The photodynamic and magnetodynamic therapy results of NaYF₄:Yb,Er@Au and NaYF₄:Yb,Er@Fe₃O₄ were evaluated by heat test.The solution of NaYF₄:Yb,Er@Au was irradiated with 980 nm laser at the current of 2.5A for 10min,the experimental date showed that temperature rises to37?.Heat test was conducted under the current of 2.08A and the voltage of 5.4V.The temperature of NaYF₄:Yb,Er@Fe₃O₄ rises to 40?after 10min.NaYF₄:Yb,Er@Au and NaYF₄:Yb,Er@Fe₃O₄ material were used for cell experiments.It was found that the cell gradually apoptozed which indicated that effect of photodynamic and magnetodynamic therapy of the heterojunction were enhanced.NaYF₄:Yb,Tm nanocrystalline was synthesized using hydrothermal method.NaYF₄:Yb,Tm@TiO₂ was synthesized by hydrolysis of tetraethyl titanate at room temperature.The XRD confirmed that the NaYF₄:Yb,Tm nanospheres have high crystallinity.TEM images showed the diameters of NaYF₄:Yb,Tm and NaYF₄:Yb,Tm@TiO₂ was about 20 nm to 35 nm and 50-70 nm,respectively.NaYF₄:Yb,Tm@TiO₂@Ag was synthesized by impregnation and surface adsorption in situ reduction reaction at room temperature,respectively.Photocatalytic degradation of methylene blue solution was carried out under Xe lamp?350W?irradiation and 980nm laser,respectively.The data showed that the degradation rate of heterojuntions synthesized by impregnation and surface adsorption in situ reduction reaction were7.1%and 30.9%under the Xe lamp irradiation,respectively.Compared to the above test data,the NaYF₄:Yb,Tm@TiO₂@Ag synthesized by impregnation and surface adsorption in situ reduction reaction have better photocatalytic performance whose degradation rate were 85.1%and 93.9%under 980 nm laser,respectively.To sum up,the upconversion heterojuntion materials were synthesized by surface adsorption in situ reduction reaction method,which possess good performance in bio-imaging,photodynamic therapy,photocatalytic degradation.The synthetic method is simple and easy to popularize.