Optical Temperature Sensing Investigation Based On Fluoride Doped With Rare Earth Ions

Temperature monitoring plays an important role in product quality,energy saving,the development of national economy and the field of bio-medical.In some cases,the requirements for temperature control and measurement are becoming higher and higher.For example,fast response,high temperature detection sensitivity,and high spatial resolution and so on.Temperature measurement technology based on fluorescence characteristics of rare earth ions can achieve non-contact temperature measurement,overcome the difficulties faced by traditional temperature detection,and has the characteristics of wide dynamic range,fast response,small thermal inertia,and high sensitivity.So,it has a very widely application prospect.The work involved in this paper is mainly focused on the research of temperature measurement technology based on the fluorescence intensity and fluorescence intensity ratios of rare earth ions,introducing the single-doped and co-doped optical temperature measurement materials,the previous research results are summarized,further research directions have been discussed according to the current research progress.It is hoped that the research in this paper can provide new inspiration for new non-contact temperature detection in the future.The first chapter mainly introduces some basic knowledge of luminescence,several luminescent materials which has special structures or properties,the spectrum of rare earth ions,study on temperature measurement of rare earth doped materials,and it focuses on the principle and research progress of temperature detection technology based on fluorescence characteristics of luminescence materials doped with rare earth ions.The second chapter introduces the synthesis method and characterization method of ?-NaGd4:Eu3+fluorosilicate glass ceramics.And temperature detection was studied based on the ground-state thermal coupling energy level(7F0 and 7F2)of Eu3+.Under the excitation of a certain wavelength,Eullions in the 7F2 energy level can be directly excited to the 5D0 energy level,and the emission of 5D0?7F4 of Eu3+at different temperatures can be monitored.As the temperature rises,the amount of Eu3+ at the 7F2 energy level increases,and under the excitation of light that resonance with the 7F2?5D0 transition,more Eu3+can be pumped onto 5D0,resulting a stronger emission intensity of 5D0?7F4.By calculation,the relative sensitivity of the?-NaGdF4:Eu3+ glass ceramics can reach 3.96%k-1 at 150 K.In the third chapter,we studied the mono-dispersed ?-NaYF4:1%Sm3+nanoparticles synthesized by thermal decomposition.The temperature sensing which is based on the ground state thermal coupling energy level(6H5/2 and of Sm3+was introduced.Under 594 nm pulsed laser excitation,the emission intensity of 4G5/2?6H5/2 enhances monotonously with rising temperature from 300 K to 430 K,including physiological temperature range(300 K-333 K),and don't need to consider decoupling at low temperature.The results show that the ?-NaYF4:1%Sm3+-nanoparticles with high spatial resolution and good sensitivity may have a good application prospect in the field of optical temperature detection.The fourth chapter is based on the second chapter,it mainly introduces the characterization method and temperature detection investigation of Ba2LaF7:Nd3+/Eu3+glass ceramics.The structure and morphology of the samples were investigated by X-ray diffraction,Transmission electron microscopy and High resolution transmission electron microscopy,as well as Selected area electron diffraction.Due to the 5D0 energy level of Eu3+is very close to that of 2G7/2 energy level of Nd3+,under 578.3 nm laser excitation,the emission spectrum was measured at different temperature,and it was found that with the change of temperature,the emission intensity of Nd3+at 800.0 nm(4F5/3?4I9/2)and the emission intensity of Eu3+at 699.0 nm(5D0?7F4)changed in the opposite direction,it is due to the fact that the luminescence initial state 4F5/2 of Nd3+and excitation initial state 7F0 of Eu3+are at the upper and lower levels of their respective thermocouple equilibrium.And the ratios of the emission intensity of these two emissions were used as the temperature measurement scheme.A relatively good temperature sensing performance was obtained with a maximum relative sensitivity of 1.02%K-1 at 420 K.Both the emission peaks for temperature sensing were at the optical window of biological tissue,which is favorable for biomedical applications in the future.In fifth chapter,we studied the high concentration of Er3+ doped ?-NaYF4 up-conversion nanoparticles.Er3+ acts as both sensitizer and activator.The emission spectrum of Er3+were measured under 1532 nm laser excitation in a wide temperature range from 297 to 417 K.We use the ratios of emission intensity at 980 nm(4I11/2?115/2)and the emission intensity at 810 nm(4I9/2?4I15/2)of Er3+as the temperature measurement scheme under two-photon excitation(note that 4I9/2 and the following 4I11/2 are not in thermally coupled equilibrium),The relative temperature sensitivity can reach 1.15%K-1 and 0.93%K-1 at 300 K and 330 K,respectively.In this new scheme,the excitation wavelength and emission wavelength are all in the near infrared biological window.Compared with excitation with ultraviolet and visible light,near-infrared light does not cause damage to organisms,and has better penetration ability in biological tissues,which can be used for temperature detection of tissues deeper in organisms.