Dye Sensitization And Temperature Sensing Of Upconversion Luminescence

Upconversion materials have attracted researchers in various fields because of the stable chemical properties,dependence on near infrared excitation and wide range of radiation wavelength.In recent years,upconversion materials have made breakthroughs in anti-counterfeiting,solar cells,display devices,infrared detection and other fields.However,the application of upconversion fluorescence is still limited by its low luminescence efficiency,and the current methods of improving upconversion efficiency still have some drawbacks,such as the cumbersome process,high cost and limited effect.On the other hand,since a large number of phenomena in nature are related to temperature,monitoring the temperature of the target is of great significance for understanding the mechanism of various macro or micro thermal processes and further application.But the performance of temperature sensors based on upconversion fluorescence is still not ideal,which is not conducive to the need for high-precision and high-sensitivity sensing.Therefore,based on Er³⁺ion doped materials,we focus on the improvement of upconversion efficiency and temperature sensing performance.The first part of this paper is about the improvement of upconversion fluorescence intensity.Firstly,water-dispersive core-shell structure particles SiO₂@NaYF₄:Yb/Er with upconversion luminescence ability were synthesized,and further transformed into NaYF₄:Yb/Er capsules by dissolving silica template.In order to improve the upconversion luminescence ability,IR-808 dye was connected to the inner and outer surfaces of the capsules,and a bidirectional energy transfer channel was constructed.The structures of the samples were characterized by SEM and TEM,and the upconversion fluorescence properties of the samples were analyzed by spectroscopic measurements.The experimental results shown that the dye-sensitized capsules have more efficient upconversion fluorescence,and have broad prospects in biological applications such as drug delivery and release.The second research focuses on the improvement of Er³⁺ion temperature sensing performance.Er³⁺ion doped tellurite glass samples were prepared by high temperature melting method to explore its feasibility as a probe of high sensitivity thermometer.The mechanism of upconversion fluorescence was studied by spectroscopic measurements.It was found that the sensitivity of thermometers based on fluorescence intensity ratio technology increased monotonously with the decrease of doping concentration.However,low doping concentration led to weak upconversion luminescence ability,which further reduced the sensing accuracy.It is difficult to obtain both high sensitivity and high accuracy.In order to solve this contradiction,we further studied the influence of excitation light power on sensing,and proposed a method of high power excitation acting on low-doped samples to achieve high temperature measurement accuracy and sensitivity at the same time.