Synthesis And Characterization Of Upconversion Luminescent Nanocrystal

There is a growing interest in application of nano-sized upconversion phosphors (UCPs) as fluorescent labels for sensitive biological detection. For bioprobes, the sizes of the targeted molecules (such as proteins, oligonucleotides, and other biomolecules in cells and tissues) range from several nanometers to tens of nanometers.Luminescent nanoparticles are usually excited by visible or ultraviolet light. The disadvantage of using visible or ultraviolet light is that autofluorescence is often created by the biological molecules in the samples. Upconversion nano-crystal excited by 980nm infrared light creates a unique advantage for biological detection.First, the upconversion luminescent nano-crystal of NaYF₄: Er³⁺ and NaYF₄: Yb³⁺ ,Er³⁺ was synthesized at room temperature .Several parameters such as density of Er³⁺ , density of Yb³⁺ ,annealing temperature and so on, impacted on the result. Relatede experiments have been done and mechanisms that affect the performance were discussed.Besides, NaYF4:Yb³⁺,Er³⁺/NaYF₄ Core/Shell nanocrystal was attempted to prepared at room temperature twice. The difference is the sequence of coating layer reactant addition.Lastly, Upconversion luminescence of ZBLAN:Yb³⁺,Tm³⁺ co-excited by double-frequency was discussed. The emission intensity co-excited by both 980nm and 808nm is much stronger than the 980nm or 808nm. This phenomenon can be explained by luminescence mechanism. Under the excitation of 980nm or 808nm, the emission is three photon or two photon process, respectively, while in the 980nm and 808nm system, the emission is due to one photon process.