Structure And Luminescence Properties Of Fluoride Up-conversion Materials

Up-conversion is a nonlinear optical process that the ground electron energylevel of materials which absorbs the long-wavelength low-energy photons jumps tothe excited level, and then back to the ground energy level with emittingshort-wavelength high-energy photons. With recent tremendous progress ofbiomedical and biology, the biomarkers materials face the higher challenge. Thetraditional biomarkers materials,such as organic dyes and QDs, have some inherentflows,including width spectrum band, poor chemical stability,unstable luminescencewavelength and expensive laser equipment, which limiting its application. Thelanthanide doped up-conversion luminescence has good chemical stability likeinorganic materials, which ensures the stability of the emission. Besides thelanthanide has excellent light-emitting monochromatic owing to its special emittingmechanism and inexpensive laser equipment. The most important is that it isnon-toxic and just be excited by low energy light, which will prevent damaging thebiological tissue and ensuring the truth of the test. In addition, the biological tissuehas good permeability to the750¹000nm light. if the up-conversion materials’emitting light and exciting light are at this region, it will greatly enhance markingdepth and imaging clarity. In this case, the study of the infrared up-conversionmaterials is one of the present challenges. Combining the group research base, we dosome work as follows:1. NaYbF4:Ho3+and NaYbF4:Ho3+/Ce3+up-conversion materials were synthesizedusing the hydrothermal method. The introduction of the Ce3+made the sampleemitting tuning from the primary green to the red. And with a series of experimentswe tracked out the optimal experimental ratio （Ho3+:0.25mol%, Ce3+:15mol%） for thebest emitting intensity and red-to-green ratio. Combing the XRD and TEM data, weanalyzed the influence of the introduction of Ce3+to the structure and morphology ofsample. Ensure that the luminescence difference of Ho3+was caused by theintroduction of Ce3+with the exploring the up-conversion performance andmechanism under the excitation of980nm infrared laser.2. NaYbF4:Ho3+/Gd3+and NaYbF4：Ho3+/Ce3+/Gd3+upconversion materials were synthesized using the hydrothermal method. The structure and morphology wereturned owing to the introduction of Gd³⁺to the system. With the analyzingup-conversion spectrum of sample, the main cause of the change of the red-to-greenratio was the cross energy transfer between the Ho³⁺and Ce³⁺.3. The different concentration Gd³⁺doped KYb_mF_3m+1（m=1,2）： Tm³⁺up-conversion materials were synthesized using the hydrothermal method. Thestructure transform from the initial orthorhombic to the cubic phase with theintroduction of Gd³⁺,and the particle size increased first and then decreased to thefinally20nm as the concentration arising. With the increasing of the Gd³⁺concentration, the luminescence intensity increased and then decreased, got themaximum at the10mol%under the excitation of the980nm laser.