Signal Control And Application Of Upconversion Optical Sensors

As a new generation of luminescent materials,upconversion luminescent materials have a series of outstanding advantages over traditional sensing materials in recent years:good light stability,strong penetration ability,low toxicity,good chemical stability,long fluorescence lifetime and high sensitivity.Therefore,as a new type of sensor,up-conversion optical sensor based on the above conversion luminescent materials is widely used in biosensor,temperature sensor and chemical reagent detection.Up-conversion optical sensor is a new type of sensor which can be measured qualitatively and quantitatively by means of optical principle.It has the advantages of non-contact and non-destructive.The measurement is very accurate.It has good optical stability,strong anti-interference ability,high sensitivity.Therefore,it has very important practical significance and broad research prospects to study up-conversion optical sensor in depth.In this paper,rare earth upconversion luminescent crystals as the core material are mainly studied.High-precision upconversion optical sensors are fabricated.Two different experimental schemes were used to study the change of luminescent properties of rare earth upconversion luminescent crystals.Signal regulation of upconversion optical sensor was realized.High precision detection of basic fuchsin was realized based on Upconversion optical sensor.The main contents of this paper are as follows:（1）Rare earth upconversion luminescent crystals have been fabricated.Rare earth upconversion luminescent crystals are the core materials to construct upconversion optical sensors.Upconversion microcrystals with good morphology and size and high luminescent intensity have been fabricated by simple hydrothermal method.The microcrystals can emit bright visible light under the excitation of 980 nm near infrared light.（2）The structure,morphology and optical properties of upconversion luminescent crystals doped with Tm³⁺,Er³⁺and Yb³⁺ions[Na REF₄,RE=Y,Lu,Gd,La]were studied.The samples were characterized by X-ray diffraction（XRD）,scanning electron microscopy（SEM）and photoluminescence（PL）spectra.It is found that upconversion crystal luminescence is closely related to matrix material,particle size,dopant concentration and internal structure.Importantly,the intensity ratio of green to red emission and the intensity ratio of blue to red emission are closely related to the properties of matrix materials.In addition,the upconversion mechanism of four matrix materials is discussed.（3）Based on the previous research,the NaLuF₄:Yb³⁺/Er³⁺upconversion luminescent materials were selected to prepare the microcrystals,considering the morphology,size and luminescent properties of the microcrystals.The luminescence and magnetic properties of NaLuF₄:Yb³⁺/Er³⁺crystals were controlled by doping Na Mn F₃.Because of the energy level matching between Mn²⁺ions and lanthanide ions,the multicolor emission of the crystals could be easily controlled.Paramagnetism and ferromagnetism of these crystals were also found in the study.The intensity of these crystals changed inversely with the content of Na Mn F₃.Finally,the upconversion optical sensor based on Mn²⁺doping is used to detect the basic fuchsin qualitatively and quantitatively.It is found that the integral intensity of red and green light is more sensitive to the concentration of basic fuchsin（BF）.The integral intensity ratio of red and green light increases with the increase of fuchsin concentration.The fuchsin concentration can be easily obtained according to the integral intensity ratio of red and green light and the detection limit,and it can reach 0.0015 mg/ml.