Design And Investigation On Temperature Sensing Properties Of Rare Earth/Transition Metal-doped Inorganic Luminescent Materials

As their excellent optical properties,including tunable luminescence,near-infrared excitation and emission,low toxicity,better photostability,against photobleaching and long luminescence lifetime,compared than traditional organic dyes and quantum dots the research of rare earth（RE）and transition metal（TM）ions doping inorganic luminescence materials has attracted extensive attention.Besides,the near-infrared emission has higher tissue penetration depth,lower autofluorescence and tissue scattering,the applications have made breakthrough,such as anti-counterfeiting,temperature sensing,optical information storage,lighting display,and biomedicine.The ratiometric luminescence thermometry could avoid the limitations of traditional contact thermometers,which realized non-contact temperature measurement.This dissertation has a series of selection and design around luminescence centers and materials,some reasonable applications are presented in RE and TM ions doped inorganic luminescence materials.The detail contents list as follows:（1）Eu³⁺ions doped inorganic luminescence materials can be both used as fluorescent material for light conversion,as well as applied to temperature sensing.LiYGe O₄（LYGO）:Bi³⁺,Eu³⁺fluorescent material was synthesized by high temperature solid state method,red emitting LYGO:Eu³⁺phospor combined with 460nm blue chip and commercial Y₃Al₅O₁₂:Ce³⁺phospor to prepare phospor conversion white light emitting diode.The thermal quenching trend of the Eu-O charge transfer band was opposite to the 4f-4f transition of Eu³⁺ions in LYGO:Eu³⁺,a ratiometric luminescence thermometer was designed.When doping transition metal Bi³⁺ions,in the LYGO:Bi³⁺,Eu³⁺,utilizing luminescence intensity of Bi³⁺（³P₁→¹S₀）and Eu³⁺（⁵D₀→⁷F₂）with temperature variation proposes an approach of ratiometric thermometer,and the Eu-O charge transfer band and the ¹S₀→³P₁(Bi³⁺)transition established the ratiometric thermometer.The temperature measurement performance was improved,relative to LYGO:Eu³⁺,and the optimal sensitivity was increased from0.64%K^-1 to 0.92%K^-1 and 1.76%K^-1.All the experimental results indicate that LYGO:Bi³⁺/Eu³⁺luminescent materials have prospective applications in temperature sensing and solid-state illumination.（2）Ba₂TiGe₂O₈（BTGO）inorganic material was appropriate for RE ions doping,which has low phonon energy and appropriate crystal field,and it can realize cyan self-activated photoluminescence based on own ultraviolet absorption.Introducing RE ions(Eu³⁺,Tb³⁺,Pr³⁺)as the luminescence center,the emission color of material can change with excitation wavelength various,different color points were designed to represent some specific information,and identify the corresponding hidden information with alphabetical code table.In addition,BTGO:Yb³⁺,Ho³⁺,Er³⁺sample realizing downshifting emissions(Ho³⁺and Er³⁺)with near-infrared excitation,a near-infrared optical thermometer was developed using phonon-assisted energy transfer between Ho³⁺and Er³⁺in biological window,which has higher relative sensitivity and accuary.（3）Owing to the superior tissue penetration and high signal-to-noise ratio of Near-infrared（NIR）biological windows（BWs）,real-time temperature reading with nano-spatial resolution can be achieved in vivo,which has attracted much attention in biomedical imaging field.In this work,a Y₃Al₅O₁₂（YAG）:Cr³⁺/RE³⁺（RE=Ho,Er,Yb）phosphors was synthesized,which can achieve simultaneous luminescence in three NIR biological windows,and three modes of ratiometric luminescence temperature measurement methods were designed by utilizing its optical properties.Firstly,a ratiometric luminescence thermometer was designed by using the up-conversion emission of Cr³⁺/RE³⁺in the BWs-I.The luminescence intensity ratio temperature measurement of BWs-III/II mode is constructed with the Er³⁺/Ho³⁺phonon-assisted downshifting.The BWs-III ratiometric luminescence thermometer was designed by the thermal coupling levels between the Er³⁺(⁴I_13/2)Stark levels.The independent thermometry modes show own various thermometry performance in different NIR biological windows and temperature ranges,and the combination of the three modes will contribute to obtain more accurate temperature reading in a wider temperature range.（4）From the perspective of biomedicine and micro/nano electronics,nanomaterials receive extensive attentions in the corresponding temperature measurement field.Hydrothermal method synthesizes successfully Sr₂YF₇:RE³⁺nano materials.The morphology and optical properties of Sr₂YF₇ nanomaterials could be optimized by adjusting the fluorine source and p H without using any surfactant.Selecting the 808 nm laser can avoid thermal damage to biological tissues.Sr₂YF₇:Nd³⁺nanoparticles realized the ⁴F_3/2→⁴I_9/2,⁴I_11/2 and ⁴I_13/2 characteristic emission of Nd³⁺located in the biological window.Based on the Nd³⁺luminescence intensity ratio of ⁴I_9/2/⁴I_11/2,BWs-I/II ratiometric optical thermometer was designed.Doping Yb³⁺ions,the Sr₂YF₇:Nd³⁺/Yb³⁺ratiometric luminescence thermometer performance is optimized with phonon-assisted proces,which improves the temperature uncertainty and repeatability.This work provides not only a feasible strategy for designing efficient near-infrared lanthanide nano luminescent materials,but also an approach to enhance non-contact optical thermometer performance.