A Raman Study of Titanate Nanotubes
The effect of the addition of NaOH or KOH on commercial Degussa Titania P25 was investigated using TEM, Raman and in situ Raman spectroscopy. Treatment of titania with conc. NaOH generated a tubular material corresponding to a sodium titanate. An in situ Raman study on the sodium titanate nanotubes as a function of temperature revealed that the titanate structure was stable up to 700°C.Ramanspectra of the titanate nanotubes after acid treatment, showed that the titanate structure was retained andEDX analysis revealed only trace amounts of sodium (0.3%) left in the material. HRTEM data are also consistent with the synthesis of protonated titanate nanotubes. An in situ Raman study of protonated titanate nanotubes as a function of temperature showed that the material was stable up to 150°C, while anatase appeared at T > 300°C. An in situ Raman study of the protonated titanate nanotubes produced from KOH as a function of temperature showed that the shape and size of the nanotubes prepared from NaOH and KOH are similar although rutile formation at 1000°C was different. A proposal for the formation of tubular titanates (and anatase) is given.
Keywords: Titania nanotubes, titanate nanotubes, in situ Raman spectroscopy, HRTEM.