Construction And Characteristics Of Rare Earth Ions-doped Polymetallic Oxides One-dimensional Nanostructures

Inorganic luminescent nanomaterials have become the frontier and research hotspots in the luminescence field.Luminescent materials with unidimensional nanostructures have aroused extensive attention due to their unique morphologies.Polymetallic oxides,such as melilite-typed aluminates,have become popular luminescent matrixes owing to their simple synthetic conditions and high physical-chemical stability.So far,many studies on this kind of aluminates matrixes are reported.However,reports on this kind of aluminate-based luminescent unidimensional nanomaterials fabricated via electrospinning are rarely found.Electrospinning has become one of the efficient techniques to fabricate unidimensional nanostructures as a result of the advantages of simple device,low cost,high efficiency and prepared products with multi-shapes.Therefore,it is a topic of significance to prepare melilite-typed polymetallic oxides luminescent unidimensional nanostructures via electrospinning.The main research contents are as follows:1.CaGdAl₃O₇:Eu³⁺down-converting luminescent one-dimensional nanostructures including nanofibers,nanobelts and hollow nanofibers were synthesized successfully by electrospinning technology and subsequent oxidation procedure.The formation mechanisms of the three kinds of one-dimensional nanostructures have been put forward and a new technology of constructing unidimensional nanostructures is innovated.All of pure tetragonal structured CaGdAl₃O₇:Eu³⁺unidimensional nanostructures possess satisfactory fluorescent properties.Under the excitation of 256 nm ultraviolet light,the unidimensional nanostructures mainly exhibit orange-red emissions at 590,619,657 and705 nm attributed to ⁵D₀→⁷F_j（j=1,2,3,4）energy level transitions of Eu³⁺ions,respectively.Further,the luminescence properties of the nanostructures can be adjusted by altering Eu³⁺ion content,calcination temperatures and morphologies of nanostructures.2.CaGdAl₃O₇:Yb³⁺,Ho³⁺up-converting luminescent one-dimensional nanostructures including nanofibers,nanobelts and hollow nanofibers were prepared via combining electrospinning technology with oxidation procedure.All of three unidimensional nanostructures are tetragonal in structure.Under the excitation of 980 nm laser,CaGdAl₃O₇:Yb³⁺,Ho³⁺unidimensional nanostructures show green up-conversion emission at 546 nm and red up-conversion emission at 659 nm resulted from⁵F₄/⁵S₂→⁵I₈and⁵F₅→⁵I₈energy level transitions of Ho³⁺ions,respectively.Further,the tunable upconversion luminescence properties of nanostructures are achieved by altering rare earth ion content,calcination temperatures,pump power and morphologies of nanostructures.3.CaYAl₃O₇:Tb³⁺,Eu³⁺color-tunable luminescent one-dimensional nanostructures including nanofibers,nanobelts and hollow nanofibers were constructed via the method of combining electrospinning technology with high-temperature oxidation process.Under the excitation of 243 and 256 nm ultraviolet light,CaYAl₃O₇:Tb³⁺,Eu³⁺unidimensional nanostructures exhibit blue and green emission of Tb³⁺and orange-red emission of Eu³⁺.When the concentration of Tb³⁺is fixed,multi-color luminescence can be realized from green,yellow and warm white to standard white light by changing the concentration of Eu³⁺ions,which implies CaYAl₃O₇:Tb³⁺,Eu³⁺unidimensional nanostructures are promising luminescent materials in color displaying devices.Besides,when the concentrations of Tb³⁺and Eu³⁺ions are fixed,the emission color of the nanostructures can be adjusted by altering calcination temperatures and morphologies of nanostructures.In this thesis,melilite-typed aluminates doped with rare earth ions unidimensional nanostructures with down-conversion luminescence,up-conversion luminescence and color-tuned luminescence are constructed successfully based on electrospinning technology.Some significant research results are obtained,which will lay a certain foundation for the subsequent research and application of aluminate based unidimensional nanomaterials.