Preparation Of Up-conversion Luminescent Materials With Core-shell Structure And Research On Luminescent Properties

Lanthanide ions doped upconversion nanoporticles?UCNPs?constitute an emerging research field recognized with wide ramifications and impact in many areas ranging from energy to security and,to healthcare.It is found that the upconversion luminescence intensity is closely related to the crystalline,size and structure of nanomaterials in a large number of studies of the UCNPs.Therefore,the controllable synthesis and structure design of the UCNPs are of great practical significance for expanding the application range.In this paper,by changing the reaction temperature,the UCNPs with different sizes and different crystalline phases were synthesized.And The core-shell UCNPs are synthesized by the design structure.The microstructure,crystal shape and luminescence properties of upconversion nanoscale were investigated.The main research contents are as follows:The influence of reaction temperature on the morphology,crystal phase and UC luminescence intensity of the was investigated.By changing the reaction temperature,the size of 4?13 nm UCNPs were successfully synthesized,and the UCNPs could disperse evenly in organic solvents.With the increase of reaction temperature,the size of the UCNPs becomes larger and its UC luminescence intensity is gradually enhanced.In the case of this experiment,we find that the size of UCNPs obtained at 300 ? and 1.5 hours is 13 nm,and the morphology is homogeneous.The UC luminescence intensity is the highest.The core-shell structure NaGdF₄:Yb³⁺,Er³⁺@SiO₂ nanoparticles were prepared via micro-emulsion preparation techniques.The results show that after encapsulating silica,the shell coating can protect the luminescent center Er³⁺ ions,thereby reducing the fluorescence quenching of nanomaterials,increasing the UC luminescence efficiency and enhancing the luminescence intensity.The luminescence intensity of the UCNPs exhibit a 7-fold increase in green emission at 542 nm and a 12-fold increase in red emission at 660 nm.Moreover,the encapsulation of silica makes the UCNPs become hydrophilic from oleophilic and enhances their application in the biological field.The europium???complexes with downconversion?DC?properties attached to the outer surface of NaGdF₄:Yb³⁺,Er³⁺@SiO₂ nanoparticles.Thus,nanospheres with UC and DC properties were prepared.And,their microstructure,surface functional groups and luminescence properties were s investigated.The modification of the europium???complexes makes the range of the UCNPs excitation light extend from the near infrared to the ultraviolet,and increases the intensity of the UC luminescent intensity.