Preparation and luminescence study of Eu(III) titanate nanotubes and nanowires using carbon nanotubes as removable templates

Eu(III) titanate nanotubes and nanowires have been successfully synthesized by solvothermal method using carbon nanotubes (CNTs) as removable templates. The products were characterized by X-ray diffraction spectroscopy, transmission electron microscopy, energy-dispersive X-ray spectrometry, thermogravimetric and differential thermal analysis. It is demonstrated that CNTs are fully coated with an amorphous Eu₂(TiO₃)₃ layer, which is about 10 nm thick and almost continuous and uniform. After the Eu₂(TiO₃)₃/CNTs composites have been calcined at various temperatures, Eu₂(TiO₃)₃ nanotubes and nanowires are obtained by removing the CNTs templates. The diameter of the Eu₂(TiO₃)₃ nanotubes is 40–60 nm, which is consistent with that of CNTs. Both nanotubes and nanowires have a narrow distribution of diameters. The fluorescence properties of the Eu₂(TiO₃)₃ nanotubes and nanowires calcined at various temperatures have been investigated. The results indicate that when the Eu₂(TiO₃)₃/CNTs composites were calcined at 700 °C for 5 h, the Eu₂(TiO₃)₃ nanotubes obtained can be effectively excited by 395 nm light, and exhibit strong red emission around 616 nm. It is very interesting to discover that a few residual carbons doped in Eu₂(TiO₃)₃ nanotubes and many oxygen vacancies could promote the intensity of red emission peak of Eu³⁺ ions. In addition, Eu₂(TiO₃)₃ nanowires calcined at 900 °C for 5 h also have a strong red emission peak due to many oxygen vacancies and defects formed on the surface of the nanowires and inside them.