ISSN 1995-0780, Nanotechnologies in Russia, 2010, Vol. 5, Nos. 3–4, pp. 223–226. © Pleiades Publishing, Ltd., 2010. Original Russian Text © I.P. Suzdalev, V.E. Prusakov, Yu.V. Maksimov, V.K. Imshennik, S.V. Novochikhin, E.A. Gudilin, A.V. Grigor’eva, K.L. Dubova, S.S. Abramchuk, Yu.D. Tret’yakov, I.S. Lyubutin, K.D. Frolov, 2010, published in Rossiiskie nanotekhnologii, 2010, Vol. 5, Nos. 3–4. 223 INTRODUCTION There is increasing interest in the structure and properties of titania-based nanotubes, which show promise for some electrochemical, catalytic, photo- voltaic, and sensor applications. The unique charac- teristics of these nanotubulenes are largely due to the presence of defects and local distortions in the metal– oxygen layers, as well as the possibility of changing the degree of oxidation of the central atom in the metal– oxygen polyhedrons comprising the nanotubulene lay- ers. As a result, the electronic structure and the physi- cochemical characteristics of nanotubulenes are altered. The TNT structure is extensively discussed in the literature. Some investigations [1–3] point to an ana- tase structure of TNTs, whereas others [4–6] suggest that TNTs are isostructural to metatitanium acid H 2 Ti 3 O 7 . Regarding their microstructure, TNTs are scroll-like particles corresponding in shape to multi- wall nanotubes with open ends. The tubular structure is generally formed in hydrothermal conditions in an alkaline medium. A model was proposed [4] describ- ing the formation of tubular structures through the separation of upper Ti–O layers under the action of stresses arising in the surface layer due to the interac- tion of hydroxyanions with the surface of the material. The purpose of this study was to determine the local environment of iron ionic probes in TNTs and choose an appropriate model for the structure of mul- tiwall nanotubes, as well as to modify the electronic and magnetic properties of TNTs. EXPERIMENTAL TiO 2 nanotubes were produced by hydrothermally treating the initial powder of titanium oxide mixed with 10 M NaOH at 180°C, partially and completely washing NaOH to pH = 9–10 and pH = 6, and drying. The test samples (with a partial retention and the absence of sodium ions in the structure, respectively) were held in a 10 –3 M solution of iron nitrate (93.3% 57 Fe isotope) for several days, washed, and dried at 70°C. The TNT microstructure was examined using transmission electron microscopy in a LEO 912 AB Omega microscope with a LaB 6 cathode at an acceler- ating voltage of 100 kV. The electronic states of titanium and oxygen in the TNTs were analyzed by the XPS method in a Riber LAS-300 instrument (France) equipped with an OPX- 150 potential-delayed hemispherical analyzer. Photo- electrons were excited by the X-ray radiation of an alu- minum anode (Al K α = 1486.6 eV) at a tube voltage of 12 kV and an emission current of 20 mA. The elec- tronic peaks were calibrated against the carbon line C 1s at a binding energy of 285 eV. The analytical spectra were processed using Unifit 2003 and ORIGIN pro- grams. A NIST database was used to identify the valence state of elements. The samples with the iron isotope were prepared for two reasons, namely, to improve the MS sensitivity and the initial TNT structure considering the low con- centration (~10 –2 %) of intercalated iron ions. The Mössbauer spectra were measured using a Wissel elec- trodynamic spectrometer (Germany) at temperatures of 16–300 K provided by a CCS-850 helium cryostat The Local Structure of TiO 2 -Based Nanotubes Intercalated with Iron (III) I. P. Suzdalev a , V. E. Prusakov a , Yu. V. Maksimov a , V. K. Imshennik a , S. V. Novochikhin a , E. A. Gudilin b , A. V. Grigor’eva b , K. L. Dubova b , S. S. Abramchuk b , Yu. D. Tret’yakov b , I. S. Lyubutin c , and K. D. Frolov c a Semenov Institute of Chemical Physics, Russian Academy of Sciences, ul. Kosygina 4, Moscow, 119334 Russia b Faculty of Chemistry, Moscow State University, Moscow, 119991 Russia c Shubnikov Institute of Crystallography, Russian Academy of Sciences, Leninskii pr. 59, Moscow, 117333 Russia e-mail: suzdalev@chph,RAS.ru Received October 19, 2009 Abstract—Transmission electron microscopy, X-ray photoelectron spectroscopy, and 57 Fe Mössbauer spec- troscopy have been used to study TiO 2 -based nanotubes (TNTs) intercalated with 57 Fe. A structural model of doped TNTs has been proposed that includes TNTs in the form of a “scroll” with nonmagnetic Fe–O–Fe layers spaced at ~0.7-nm intervals in the interlayer spacing and ~20-nm iron oxide clusters on the outer sur- face of the TNTs. DOI: 10.1134/S1995078010030109 ARTICLES