Hydrothermal Preparation And Physical Properties Study Of Titanate Nanotube Doped With Ions

Titanate nanotube is a novel nanotube material that is prepared by the nano-powder precursor of TiO₂. This kind of nanotube material will be endowed with novel properties by doped with magnetic ions or luminescience ions. The potential applications will also be putted to it.In this paper, the preparation and physical and chemical properties of titanate nanotube undoped and doped with ions were carried out. Some innovative results were obtained. They are shown as following:(1) Preparation and characters of titanate nanotubeTaking pure anatase TiO₂ nano-particles as precursor, titanate nanotubes were synthesized by hydrothermal method. The microstructure and formation mechanism have been studied by many means of characterization, such as, Scan Electron Microscope, High-Resolution Transmission Electron Micrographs, Powder X-ray Diffraction, BET surface area analyse and so on. The results of research show that titanate nanotubes have muti-layer structure with the open end, inner diameter is about 6nm, outer diameter is 8 to 10 nm and the length is about 500nm. Besides, titanate nanotubes have larger surface area than TiO₂ nano-particle, which is promising as high quality catalyzer or catalyzer carrier.(2) The thermal stability of titanate nanotubeTreatment of high temperature will bring into big changes to structures of titanate nanotubes. When the temperature below 250℃, the nanotube structure could be kept; after calcined at 350℃, the interlayer spacing decreased rapidly, meanwhile partial of the nanotube structure were destroyed markedly and the titanate phase was transformed into anatase-type TiO₂; when the temperature excessed 450℃, the tubular structures were destroyed completely and the structure changed into anatase-typed TiO₂.(3) Study on preparation and magnetic property of titanate nanotube doped with magnetic ionsIn this paper, titanate nanotubes doped with magnetic ions (Fe³⁺,Ni2+,Mn²⁺) were synthesized by hydrothermal treatment of pure anatase TiO₂ powders in concentrated NaOH solution. In this process, preparation of nanotubes is synchronously with doping magnetic ions. Magnetic properties of titanate nanotubes doped with Fe³⁺,Ni²⁺,Mn²⁺ ions were studied using a superconducting quantum interference device (SQUID) magnetometer. The magnetization versus the applied field curves (M versus H) of Fe³⁺,Ni²⁺,Mn²⁺ doped titanate nanotubes at 300 K show that the almost linear curve pass the origin point and the slope is plus. The temperature dependence of magnetization (M versus T) in an applied field of 0.2 Tesla show that the value of M decrease sharply along with the increases of the temperature at low temperature, when the temperature is above 25K, the value of M changes slowly along with the increases of the temperature. Furthermore, the saturated magnetization (Ms) of titanate nanotube is so small. All of these results indicated that titanate nanotubes doped with Fe³⁺, or Ni²⁺, or Mn²⁺ ions demonstrates a paramagnetic behavior at room temperature.(4) Study on preparation and photoluminescence property of titanate nanotube doped with rare earth ionsTitanate nanotubes doped with Eu3+ or Tb3+ were obtained by hydrothermal treatment of pure anatase TiO₂ powders in concentrated NaOH solution. The photoluminescence property of titanate nanotube doped with Eu3+ or Tb3+ were measured on a modular double grating excitation spectrofluorimeter with a TRIAX 320 emission monochromator. The results show that titanate nanotubes doped with Eu3+ or Tb3+ are optically active at room temperature. Both spectras are composed of a series of straight lines ascribed to Tb3+ and Eu3+ intra- transitions. Besides, the abnormal higher value of the fwhm0-0 indicates that the Eu3+ doped titanate nanotube has at least two distinct Eu3+ local coordination sites.