Research On The Constructure And Performance Of Rare Earth Doped Fluorescent Nanotemperature Probe

With the development of nanotechnology,people put forward higher requirements for temperature measurement.New technologies and materials with higher spatial resolution and temperature sensing sensitivity are urgently needed.Therefore,in this thesis,two types of fluorescent temperature probes with good performance are constructed based on rare earth doped fluoride upconversion nanocrystals.One is the core-shell structure nanopaticles based on the energy migration mechanism,the other is nanopaticles based on size-dependent thermally enhanced fluorescence differences.This thesis inclueds the following content:Firstly,rare-earth-doped fluoride nanocrystals were synthesized by an improved liquid-phase co-precipitation method.Rare-earth-dopedβ-NaGdF₄ nanocrystals with controllable particle size and homogeneous morphology were successfully prepared by adjusting the important synthesis conditions such as reaction temperature,reaction time and precursor ratios.Secondly,two core-shell structures based on the energy migration mechanism were designed,and temperature probes based on fluorescence intensity ratio were constructed by using the reverse fluorescence temperature-sensitive property between the activating ions Tm³⁺and Eu³⁺.The two synthesized core-shell structure nanocrystals all have hexagonal phase structure with uniform size and shape,and the thickness of the shell layer is within the effective energy transfer range between rare earth ions,so the lattice thermal expansion at high temperature promotes the energy transfer at the core-shell interface,and the activating ions Tm³⁺and Eu³⁺show the reverse fluorescence temperature-sensitive property.The fluorescence temperature probes based on the fluorescence emission peaks of Tm³⁺and Eu³⁺were constructed,and the highest absolute temperature sensitivity values obtained were up to1.8 K^-1 and the highest relative temperature sensitivity value was 1.31%K^-1.Finally,the temperature probes based on fluorescence intensity ratio with hybrid nanocrystals were constructed using the thermally enhanced upconversion fluorescence properties of different sizes of rare earth doped nanocrystals.The emission peaks with more significant thermally enhanced fluorescence of small-sized nanocrystals and the emission peaks with smoother thermally enhanced fluorescence of large-sized nanocrystals were selected as the fluorescence reference signals,and the maximum relative temperature sensitivity of the constructed fluorescence intensity ratio temperature probe could reach 1.26%K^-1 in the temperature range of 298 K to 423 K,indicating this probe is a class of upconversion fluorescence nanothermometer probes with great potential for applications.