Synthesis Of Gd₂O₃ Nanoparticles Doped With Ions And Their Luminescent And Magnetic Properties

In recent years,rare earth doped Gd₂O₃ nanomaterials with fluorescence and magnetic properties have attracted more and more attention.As one of the most potential functional materials,they have been widely used in biomedical fields,for example,multi-mode imaging,biological detection,tumor treatment,cell separation,etc.In this paper,Gd₂O₃:Tb³⁺nanoparticles doped with K⁺/Co²⁺were successfully synthesized by polyol method.The content of Tb³⁺ion was fixed at 5mol%and the doping concentration of K⁺/Co²⁺was changed from 0 to 5mol%.The effects of K⁺/Co²⁺doping on the fluorescence and magnetic properties of Gd₂O₃:Tb³⁺nanoparticles were investigated and the optimal doping concentrations were determined.Moreover,the structure,morphology and performance of Gd₂O₃:Tb³⁺nanoparticles doped with K⁺at different calcination temperatures were studied.Fe₃O₄ were combined to improve the magnetic responsiveness and magneto-thermal conversion performance of Gd₂O₃:Tb³⁺.Fe₃O₄@Gd₂O₃:Tb³⁺nanoparticles with core-shell structure were obtained by precipitation and polyol method.Due to the unstable surface properties,poor dispersion and low biocompatibility of exposed particles,polysiloxane Si Ox was coated on the surface of the particles.The fluorescence,magnetism and magneto-thermal conversion efficiency of the nanoparticles were studied.The research conclusions are as follows:?1?After doping a small amount of K⁺ions,the crystal structure,morphology,particle size and dispersion of Gd₂O₃:Tb³⁺nanoparticles did not change significantly.The synthesized spherical particles were cubic crystals with a diameter of 7-15 nmand good dispersion.The fluorescence intensity of Gd₂O₃:Tb³⁺nanoparticles increased with the increase of doping K⁺concentration,because the doping K⁺ions replaced the position of Gd³⁺ions to destroy the local symmetry around the activator Tb³⁺,and produced a large number of oxygen vacancies that can be used as sensitizing agents.The optimal doping K⁺ion concentrations were found to be 3 mol%,and the corresponding absolute quantum yields?QYs?was 7.21%.In addition,doping of 3mol%K⁺ions significantly increased the magnetization of Gd₂O₃:Tb³⁺nanoparticles,and effectively enhanced the brightness of T₁-weighted MR imaging.?2?Gd₂O₃:Tb³⁺nanoparticles doped with 3mol%K⁺were calcined at 600,700,800and 900?.It was found that the morphology and particle size of the samples did not change after calcination.However,when the calcination temperature rose from 800 to900?,the Gd₂O₃transformed from cubic to monoclinic structure,and the dispersion of particles also decreased.Before the phase change of Gd₂O₃,the crystallinity of the sample increased and the surface defects of the particles decreased with the increase of temperature,leading to the increase of fluorescence intensity.After the phase change,the fluorescence intensity decreased obviously and the magnetization intensity increased.?3?As the doping concentration of Co²⁺ions increased,the intensity of fluorescence firstly increased until it reached the maximum at 4 mol%and then decreased.The absolute quantum yields of samples were found to be 5.90%at the optimum doping concentration of Co²⁺.The magnetization of Gd₂O₃:Tb³⁺doped with3mol%Co²⁺was the strongest,because the doping of Co²⁺resulted in the lattice distortion of Gd₂O₃ and a large number of oxygen vacancies,so as to enhance the magnetic exchange between Gd³⁺ions.Moreover,the results of in vitro MR imaging revealed that the doping of 3mol%Co²⁺also improved the relaxation rate r₁ of MR imaging,and the T₁-MR image was significantly brighter than that before doping.?4?Fe₃O₄@Gd₂O₃:Tb³⁺@Si Ox multifunctional nanoparticles were composed of the core of cubic phase Fe₃O₄ and the shell of cubic phase Gd₂O₃:Tb³⁺and amorphous Si Ox.The composites exhibited spherical shape with a diameter of 10-15 nm and highly uniform dispersion.The sample has not only good fluorescence but also strong magnetic responsiveness?Ms=24.040emu/g?.In addition,the high longitudinal relaxation rate r1(6.00 m M^-1s^-1)and transverse relaxation rate r₂(63.95 m M^-1s^-1)of the particles enhanced the contrast of MR imaging and can thus be used as positive T₁ and negative T₂ contrast agents.It was found that Fe₃O₄@Gd₂O₃:Tb³⁺@Si Ox attains hyperthermia temperature?43°C?in 90 seconds under the alternating current?AC?magnetic field,and their specific absorption rate?SAR??229.9 w/g?was higher than that of Fe₃O₄?183.92 w/g?,which is conducive to the magnetic hyperthermia of tumor.