Synthesis Of Rare-Earth Doped W-LED Materials With Color Tunable And Temperature Sensing Properties

Tunable luminescence nano-materials are attracting huge attention as their unique electronic, optical, and chemical properties. It was widely used in the area of composite biomarkers, ray radiation technology and white LED. As we all know,traditional organic dyestuff and the fluorescent substance based on quantum dot still limit its application due to its own drawbacks. While rare-earth doped phosphors with the properties of low phonon vibration energy and experiment costs gain more value in the area of photochemistry, W-LED, biomarkers, fluorescent probe and solar cell.Due to the growing demand for sensors in life, scientists take more time to study the sensing mechanism. Among the studies, rare-earth doped materials are typical representative. The reason why people pay more and more attention to this kind of material is that the rare earth ion with unique optical properties, characteristic of the energy level structure makes inorganic nano-materials in biological fluorescent probes,tags, and other fields has its good application prospect. Up-conversion（ UC）luminescence materials attract more attention due to its good stability and faster reaction efficiency. Improve the sensitivity of the fluorescence thermometer is necessary for better biological fluorescent tags. As it is a better non-contact temperature measuring method, we need to provide more novel ones. Based on these analyses, my research focuses on three aspects: Hydrothermal synthesis and tunable luminescence of W-LED materials; Target on an new inorganic luminescent thermometer Ca5（PO₄）₃F: Tb³⁺/Eu³⁺; Up-conversion luminescent properties and optical thermometry on rare-earth doped La Mg Al11O19: Yb³⁺/Er³⁺ phosphors.In chapter one, firstly, we introduced the fundamental knowledge of sensor, rare earth ions and rare earth doped W-LED. The effect of crystal field on the energy level of rare earth ions, and the process of energy transfer was also detailed described.Additionally the temperature measuring methods and temperature sensor based on luminescence were introduced briefly.In chapter two, all used experimental raw material, experimental and test methods are introduced in this chapter.In chapter three, tunable luminescence Ca Si O3:RE³⁺(RE³⁺=Eu³⁺, Sm³⁺, Tb³⁺,Dy³⁺) nanocrystals were prepared through hydrothermal synthesis. The FE-SEM results show particle sizes of near-spherical nanocrystals are around 100 nm. The spectral results reveal its strong luminescence properties when doped with different trivalent rare-earth ions. By co-doping with Tb³⁺ and Eu³⁺ ions, white-light emitting was obtained where the quality of white light was tuned and optimized by simply adjusting the relative doping concentrations of dopants.In chapter four, a new Eu/Tb-codoped inorganic apatite Ca5（PO₄）₃F as a luminescent thermometer has been targeted. In these inorganic apatite materials, it has an intense broad bluish emission which might originate from the CO2- radical related defect produced by Cit³⁺ groups, as well as the typical green emission band of the Tb³⁺ions, and a red-light emission of Eu³⁺. The temperature-dependent luminescent intensity ratios ITb/IEu can be optimized by the controlled relatively doping of different amounts of Tb³⁺ and Eu³⁺ ions.In chapter five, La Mg Al11O19: Yb³⁺/Er³⁺ phosphors were successfully synthesized by a conventional sol–gel method with a lower temperature. The composition and phase purity of the samples were examined by X-ray diffraction（XRD）. Under 980 nm excitation, the phosphors exhibited efficient visible up-conversion emissions including strong green emission centered at 525, 545 nm, and weak red emission centered at around 657 nm, which were assigned to the2H11/2â†'4I15/2, 4S3/2â†'4I15/2 and 4F9/2â†'4I15/2 transitions of Er³⁺ ions, respectively. The process involved in the UC emission was evaluated in detail by energy level diagram and the pump power dependence. To investigate the sensing application of thesynthesized phosphor materials, temperature-sensing performance was studied in the temperature range of 298–573 K using the fluorescence intensity ratio technique. The maximum sensitivity was found to be approximately 0.00267K-1, indicating its applicability as an optical temperature sensor.