| In the past decade,great progress has been achieved in rare earth(RE)ions doped inorganic micro-/nanoparticles due to their unique luminescence features.With abundant f-orbital configurations,RE ions can exhibit sharp fluorescent emissions via intra-4f or 4f-5d transitions.And the luminescence emissions covers from ultraviolet(UV),passing through the whole visible,to mid-infrared light region upon excitation.Besides,compared with quantum dots(QDs)and organic dye molecules,the RE ions doped materials also possess the advantages of large Stokes-shift,long lifetime,high chemical/photochemical stability,low toxicity,et al.Therefore,they are attributed to be a promising material for a wealth of applications in the fields of lasers,displays,sensors,solar cells,electroluminescent devices,biomedical research,et al.Based on the above statement,this thesis mainly focused on the design and synthesis of multiple RE ions doped inorganic micro-/nano-materials,the analysis of their structures through XRD,TEM,HRTEM,XPS,and FT-IR,and the manipulation of their luminescent properties by PL and UC spectra.The hydro/solvothermal method,molten salt process,and micro-wave assisted process were used for the synthesis of crystals.Through analysis the size,phase,structure,and morphology of the crystals obtained in different conditions,the growth mechanisms were also investigated.Most importantly,the luminescent properties were tuned and analyzed through changing the doping ions,doping concentrations,and the host materials properties.The drug loading and release properties were also tested in two luminescent systems.Specifically,this thesis is mainly focus on the following aspects.Novel three-dimensional(3D)flower-like NaY(WO4)2:Ln3+(Ln = Eu,Yb/Er,Yb/Tm and Yb/Ho)microstructures with uniform shape and dimension have been prepared using Y(OH)CO3 nanospheres as sacrificial template through a hydrothermal process and followed by a subsequent heat treatment process.The whole process was carried out in aqueous condition without using any organic solvents,surfactant,or catalyst.The phase,morphology,size,and photoluminescence(PL)properties were well characterized by means of X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),and high-resolution transmission electron microscopy(HRTEM),photoluminescence(PL)spectra,and kinetic decays,respectively.The results reveal that the as-prepared precursor of NaY(WO4)2:Eu3+ exhibits interesting white light emission under UV excitation.After annealing,the as-obtained 3D flowerlike NaY(WO4)2:Eu3+ microstructures show exclusively red(Eu3+,5D0?7F2)luminescence.Furthermore,the up-conversion(UC)luminescent properties and the emission mechanisms of NaY(WO4)2:Yb3+/Ln3+(Ln = Er,Tm,Ho)microstructures have been systematically studied,which show respective green(Er3+,453/2,2H11/2?4I15/2),blue(Tm3+,1G4?3H6)and yellow-green(Ho3+,5S2?5I8)luminescence under 980 nm NIR excitation.Yttrium tungstate precursors with novel 3D hierarchical architectures assembled from nanosheet building blocks were successfully synthesized by a hydrothermal method with the assistance of sodium dodecyl benzenesulfonate(SDBS).After calcination,the precursors were easily converted to Y2(WO4)3 without an obvious change in morphology.The as-prepared precursors and Y2(WO4)3 were characterized by means of X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),and high-resolution transmission electron microscopy(HRTEM),and photoluminescence(PL)spectra,respectively.The results reveal that the morphology and dimensions of the as-prepared precursors can be effectively tuned by altering the amounts of organic SDBS and the reaction time,and the possible formation mechanism was also proposed.Upon ultraviolet(UV)excitation,the emission of Y2(WO4)3:x mol%Eu3+ microcrystals can be tuned from white to red,and the doping concentration of Er,u has been optimized.Furthermore,the up-conversion(UC)luminescence properties as well as the emission mechanisms of Y2(WO4)3:Yb3+/Ln3+(Ln = Er,Tm,Ho)microcrystals were systematically investigated,which show green(Er3+,4S3/2,2HI1/2? 4I5/2)blue(Tm3+,1G4 ? 3H6)and yellow(Ho3+,5S2 ? 5I8)luminescence under 980 nm NIR excitation.Moreover,the doping concentration of the Yb3+has been optimized under a fixed concentration of Er3+ for the UC emission of Y2(W04)3:Yb3+/Er3+.Gd2O3:Ln@mSiO2 hollow nanospheres(Gd2O3:Ln hollow spheres coated by mesoporous silica layer)were successfully synthesized through a self-template method using Gd(OH)CO3 as template,which involved the incorporation of rare earth compound into the internal of the hydrophilic carbon shell to form a kind of hollow precursors(named HPs),followed by the coating a mesoporous silica shell,and the subsequent calination in air.X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),Fourier transformed infrared(FT-IR),thermogravimetric and differential thermal analysis(TG-DTA),photoluminescence spectroscopy,kinetic decays as well as N2 adsorption/desorption were employed to characterize the composites.The result indicates that the uniform Gd2O3:Ln@/mSiO2 composite with the particle size around 300 nm maintains the spherical morphology and good dispersibility of the precursor.Interestingly,the composite has double-shell structure including an inner shell of Gd2O3 and an outer shell of mesoporous silica.Moreover,they also exhibit respective bright red(Eu3+,5D0? 7F2)down-conversion(DC)emission and characteristic up-conversion(UC)emissions of Yb3+/Er3+.Under beams excitation,the hollow structured sample emerges emissions which should have potential application in biomedicine and other fields. |
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