Synthesis And Upconversion Properties Of (Gd_1-x Y_x)₂ O₃:Er³⁺, Yb³⁺ Nanoparticles

Bioluminescence imaging is the only way to obtain biomedical imaging of biological tissues at cellular and molecular level. Compared with organic fluorescent probes, upconversion fluorescent nano-materials have a longer fluorescent display cycle. Compared with quantum dots fluorescent probes, it is infrared light that excites the upconversion fluorescence. As is known, infrared light can penetrate deep into the biological tissues, create a weaker background light and caused less damage to biological tissues. NMR imaging has a merit of good clarity and a large imaging depth, but it can be used in large tissues and organs only. So it is of great significance to combine the two types of imaging technology. In this paper, the preparation and upconversion properties of (Gd_1-xY_x)₂O₃: Er³⁺, Yb³⁺ nanoparticles were studied as a functional Nanomaterial which can be used as both upconversion fluorescence probes and NMR enhancement reagents.(Gd1-xYx)₂O₃: Er³⁺, Yb³⁺ nanoparticles were prepared in three ways in order to control the morphology and dispersion of the product. The TEM images showed that the nanoparticles synthesized by solve-thermal method have congregated into clusters and had an uneven granularity dispersion. The particle size of the samples sintered at 800℃distributes between 20⁶0 nm. Samples prepared by the sol-gel method congregated into blocks and also had an uneven granularity dispersion. The particle szie of the samples sintered at 800℃distributes between 40²00 nm. The particles synthesized by the polyacrylamide method had a better dispersion than that synthesized by the other two methods. The nanoparticles joined into thin pieces and the size of that sintered at 800℃distributed between 25³0nm. The upconversion spectrum showed that in the process of the solve-thermal method left a quantity of rare earth ions in the water phase, which led to that the compounds of the product were hard to control. After calculation, we know the productivity of the solve-thermal method is about 65%, though the other two methods have a productivity of almost 100%.We prepared nanoparticles of different compounds of matrix and doping ions. The XRD spectrum showed that Gd₂O₃ and Y₂O₃ could solve in each other at any rate, and the Er³⁺, Yb³⁺ and Li+ ions could be doped into the matrix's crystal lattice with no change of the phase. The upconversion spectrum showed that the upconversion efficiency rose with the enhancement of the compound Y until the content of compound Y arrived at 80 mol%, and rose with the concentration of the Er³⁺ ions until it went to 0.8 mol%. Doping 6 mol% Li+ ions can enhance the efficiency of upconversion. The red lights can be enhanced by 5 times and the green ones 10 times. The FT-IR spectrum showed that the doping Li+ ions could decrease the OH- and CO₃^2- absorbed on the surface of the particles, so as to raise the upconversion efficiency.Nanoparticles were prepared by being sintered at different temperatures and in different sorts of atmosphere. The XRD spectrum showed that with the enhancement of the sintering temperature, the granularity of the samples magnified, then the rate of the effective activator raised, so the upconversion performance were enhanced. The upconversion spectrum showed that the upconversion efficiency raised with the elevation of the temperature among 600⁹00℃. The oxygen vacancies wouldn't appear in the material until the sintering temperature reached 1000℃. Their appearance could also enhance the upconversion efficiency. The FT-IR spectrum showed that rising the sintering temperature could decreased the OH- and CO₃^2- absorbed on the surface of the particles, so as to enhance the upconversion efficiency.