Investigation On Temperature Sensitivity And Biotoxicity Of Tm/Yb Doped ZnO Upconversion Nanopaticles

Upconversion nanoparticles?UCNPs?doped with rare-earth have triggered intensive interest because of their high signal-to-noise ratio,high tissue penetration and temperature transcoding properties,gaining a vast application prospect in the fields of cell temperature detecting and fluorescence imaging of biomedicine.The temperature transformed to optical signal by thermally coupled levels of rare-earth,which realized precise temperature detection.However,there were still some key issues to be solved so far,such as improving the sensitivity and accuracy of temperature detection and enhancing intensity of upconversion emission.Zinc oxide?ZnO?was semiconductor,which possessed a low bio-toxicity and high chemical stability.Herein,ZnO as the host materials doped with rare-earth achieved high efficiency upconversion luminescence.The upconversion emission intensity and relative sensitivity of Yb/Tm/ZnO enhanced via Ga³⁺doping and SiO₂ shell coating.In addition,the biological toxicity of upconversion nanoparticles was not clear.The biotoxicity of core-shell rare earth doped ZnO upconversion nanoparticles was investigated.Yb/Tm/ZnO upconversion nanoparticles with hexagonal "pencil stub" nanorod structure were synthesized by hydrothermal method.In this process,host sensitization combines with rare-earth sensitization can simultaneously increased energy transfer efficiency.Multicolor upconversion emission achieved by double rare earth ion doped-ZnO.The changing of the size and morphology of Yb/Tm/ZnO nanoparticles were studied with different Ga³⁺concents.The symmetry of ZnO lattice decreased.The Tm³⁺ions in the luminescent center could occupy multiple sites,which provided intermediate medium for energy transfer,and enhancing the up-conversion fluorescence intensity.Moreover,DFT theory was used to analyze changing of nanomaterials size with different Ga³⁺concentrations.The Stober method has been taken to coat homogeneous and heterogeneous silicon dioxide on doped zinc oxide,the homogeneous shell not only improve biocompatibility,but also increase the upconversion efficiency.The shell structures repair the surface defects of the nuclear nanoparticles and introduce the rare earth ions to the surface of the nuclear particles into the coordination field.By Tm³⁺ ion temperature coupling energy state and non-temperature coupling energy state,the temperature converted into optical signal to determine the relative temperature sensitivity.The relative temperature sensitivity?Sr?of Yb/Tm/GZO@SiO₂ upconversion nanoparticles increased from 2.1%K-1 to 6.9%K-1 compared with that of Yb/Tm/ZnO.The Sr of Yb/Tm/GZO@SiO₂ with non-temperature coupling level increased to 44.37%K-1.The higher temperature sensitivity was obtained at 693 K.Accurate temperature detection can be achieved by using Yb/Tm/GZO@SiO₂ core-shell upconversion nanoparticles.The toxicity of Yb/Tm/GZO@SiO₂ in the vitro was evaluated by the proliferation and apoptosis.The human hepatocellular cell line 7702 and hepatocellular carcinoma cell line HpG2 were used.The results showed that Yb/Tm/GZO@SiO₂ had lower cytotoxicity.The toxicity of Yb/Tm/GZO@SiO₂ in the vivo was investigated by injecting into the tail vein of Kuming mice.Serum biochemical indexes,HE staining of tissue slices,weight changes of organs and oxidative stress reaction of kidneys were measured with different concentrations of samples.The experimental results showed that Yb/Tm/GZO@SiO₂ had no obvious biological toxicity to liver,kidney,lung and heart.The shadows appeared on the right side of mice through X-ray imaging of mice,which indicated that Yb/Tm/GZO@SiO₂ had deep tissue penetration.The confocal fluorescence imaging of heart tissue was studied.The of fluorescence imaging heart tissue were observed,which realized the visualization of nano-flurescence probe.