Study On Temperature Sensing Based On Novel Nd Sensitized Up-conversion Fluorescence

In recent years,lanthanide-doped upconversion luminescence materials using near infrared（NIR）photons as excitation source have broad application prospects in display devices,solar cells,short-wave all-solid-state lasers,and optical sensors.Especially,Nd³⁺sensitized upconversion materials have the characteristics of weak autofluorescence,low-light bleaching,low-light damage to biological specimens,and deep penetration of tissues,and are widely used in biological imaging and cancer diagnosis and treatment.Recently,Nd³⁺sensitized upconversion materials are usually concentrated on Er³⁺and Tm³⁺emission systems,and complex multilayer core-shell structures are required to suppress harmful cross relaxation processes between Nd³⁺and activators.Therefore,it is necessary to develop a compact upconversion material codoped with Nd³⁺and activators.Its mechanism of luminescence and potential applications are further developed.In this dissertation,Na YF₄ microrods codoped with Nd³⁺and various activator ions were synthesized by hydrothermal method.The sensitization mechanism of Nd³⁺was analyzed and its temperature sensing characteristics were explored.The details are as follows:Firstly,different concentration of Nd³⁺doped Na YF₄ samples were prepared.The near-infrared spectra were measured and the luminescence characteristics were analyzed.Na YF₄:Nd/Yb samples with different concentrations were prepared due to Yb³⁺with simple near-infrared emission as the activator.The energy transfer between Nd³⁺/Yb³⁺was confirmed by analyzing the near-infrared emission intensity changes of Yb³⁺and Nd³⁺through normalized spectrum,and the effect of temperature on the luminescence characteristics of Na YF₄:Yb/Nd was further studied.Secondly,Ho³⁺,as the activator,was doped with Nd in Na YF₄ micrometer rods with different concentration.And the emission spectra of different doped samples were measured.It was found that the Nd³⁺concentration can significantly change the red to green emission intensity ratio of Ho³⁺.The mechanism of Nd³⁺/Ho³⁺was systematically studied.Then,the temperature dependent spectrum of Na YF₄:Nd/Ho was measured.Based on the different behavior of red and green emission as changing the temperature,the Na YF₄:Nd/Ho optical thermometer was developed.Finally,a novel Nd³⁺/Yb³⁺Pr³⁺triple doping system was designed.Compared with the traditional single sensitizer sample the triple doped sample greatly improves the upconversion emission intensity of Pr³⁺.The triple doped system was optimized by adjusting the Nd³⁺doping concentration,and the influence of the Nd³⁺concentration change on Pr³⁺visible emission was analyzed combined with near-infrared spectrum.And the energy transfer mechanism of the double-sensitized system was systematically analyzed.The temperature sensor based on Pr³⁺blue emission was designed by using Na YF₄:Nd/Yb/Pr micrometer rod,and its sensing performance was studied.In this dissertation,a novel Nd sensitized upconversion fluorescence system is constructed,and the optical sensing properties of the above materials are further studied.This dissertation can provide a certain reference for the construction and application of novel Nd³⁺sensitized upconversion materials.