Synthesis And Optical Property Studies Of Oxide Coaxial Nanocables

Nowadays, nanomaterials are widely used in our daily life. As a special nanomaterials, coaxial nanocables combine special features of nanomaterials and the hetero structure of core-shell. The energy gap of ZnO is 3.37 e V, while the exciton binding energy of ZnO attains as high as 60 me V. As cheap oxide ZnO can absorb light ranging from ultraviolet to visible light, it is one of the excellent matrix fluorescence materials. Furthermore, it can emit blue and green light when beening stimulated at room temperature. Y₂O₃ is a material equipped with some special features such as heat-resistance, decay resistance, high temperature stability and high dielectric constant. Doped with Eu³⁺, it can emit red fluorescence. Combining structural characteristics of coaxial nanocables and fluorescence properties, fluorescence property of luminescent materials can be adjusted and the white light is realized.In this paper, oxide coaxial nanocable arrays are synthezed by two-step template assemble method. Composition and microstructure characterized by modern research methods including XRD、SEM and TEM. Their fluorescence properties are studied by PL and lase-excitated luminescence spectrum. The framework of our paper can be illustrated as follows:1. Eu₂O₃/ZnO coaxial nanocable arrays are assembled via a electric field deposition and subsequent sol-gel tamplate approach.The shell of nanocable is made up of 15 nm hexagonal wurtzite ZnO while the core is 30 nm body-centered cubic Eu₂O₃. When stimulated at wavelength from 200 nm to 500 nm, Eu₂O₃/ZnO coaxial nanocable presents a ZnO band gap emission（380 nm） and a green luminescnce platform（400 nm⁵00 nm）. The green platform is originated from the interval Zn. Besides, the intensity of both ban gap and green platform emssion decreases with increase of the excitation wavelength from 200 nm to 500 nm. When the excitation wavelength ranging from 200 nm to 245 nm, a major broad ⁵D₀→⁷F₁ transition of Eu³⁺ appeares which can prove energy transfer process from ZnO host lattice to Eu³⁺ ions. When the excitation wavelength increases from 250 nm to 295 nm, the major transition ⁵D₀→⁷F₂ of Eu³⁺ strengthened. In this way, we can adjust the intensity and position of the emission peak by changing the excitation wavelength. Especially, Eu₂O₃/ZnO coaxial nanocable emit a white light when the excitation wavelength is 280 nm.2. ZnO:Tb³⁺/Y₂O₃:Eu³⁺ coaxial nanocable arrays are assembled via an electric field deposition and subsequent sol-gel tamplate approach. The thickness of the shell is 20 nm and the diameterof the core is 30 nm. When stimulating at the wavelength of 250 nm, a strong ZnO green emission is obseved, which indicates that there are a lot of defects in the nanocable. When monitor at 554 nm and 612 nm, respectively, excitation peaks associated with O vacancy is observed. It confirms the energy chansfer between the O vacancy and RE ion. The ⁵D₀→⁷F₂ transition appeares when the excitation wavelength is 250 nm, which confirms that Eu³⁺ mostly entered into asymmetric inversion positions. When stimulating at 250 nm, the red emission increases with increase of Eu³⁺ concentration from 1% to 5%. The samples when the molar ratio of Tb and Eu is 4:2 and 5:2 emit white light when excitation wavelength is adjusted at 250 nm. In this way, we adjust the intensity of the emission peak by changing content of rare earth.