Upconversion Luminescence Enhancement And Spectra Designation Of NaYF₄:Er³⁺/Yb ³⁺

Lanthanide-doped luminescent nanocrystals have great potentials in the field of solar cells, biological labels, optical devices, and anticounterfeiting applications. Low upconversion efficiency, however, still constitutes the main limit for its practical application. To meet the requirement, developing new technologies to enhance upconversion luminescence is very important both to fundamental research and practical application. NaYF4:Er³⁺/Yb³⁺ nanocrystals have attracted more attention due to the high efficiency and rich spectrum. This dissertation presents a systematic research surrounding the issue of luminescence enhancement and designation of NaYF4:Er³⁺/Yb³⁺ nanocrystals.Cubic and hexagonal phase NaYF4:Er³⁺/Yb³⁺ nanorods were prepared based on the solvo-thermal method. By prolonging the reaction time, raising the reaction temperature, and increasing the ratio of NH₄F/NaF to lanthanide, a facile method was successfully developed, which can prepare hexagonal phase NaYF4 with proper luminescence easily. Assisted by testing the spectra and Infra-red absorption spectrum, we discussed the physical mechanism of luminescence enhancement.Taking advantage of the method mentioned above, we fabricated a serial of NaYF4:Er³⁺/Yb³⁺ nanorods. By changing concentration of Yb³⁺, a method for enhancing and manipulating luminescence simultaneously was developed, without influencing structure as well as the size of nanorods. It's also a great potential model for single-red light. Moreover, we proved energy back transfer process from Er³⁺ to Yb³⁺ ions in fluoride materials.In NaYF4:Er³⁺/Yb³⁺ nanomaterials, Ce³⁺ was tri-doped into the system as a new ion. By using the proper match between Er³⁺ and Ce³⁺ ions, with the help of cross relaxation in the system, upconversion luminescence of Er³⁺ was modulated. In addition, it also paves a way for obtaining single-green luminescence.