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Title: Fe-doped nanostructured titanates synthesized in a single step route

In this research nanostructured titanates, containing iron in the structure, were obtained through a single-step alkaline hydrothermal route aiming at reduction of band-gap energy. In the process, a Fe–Ti rich Brazilian mineral sand was mixed with 10 M of NaOH and then submitted to isothermal treatments at temperatures ranging from 110 to 190 °C in an autoclave. The as-obtained products were water-washed and then characterized by transmission electron and scanning transmission electron microscopies, X-ray photoelectron, Mössbauer and diffuse reflectance spectroscopies. Transmission electron microscopy analyses showed a morphological dependence of the product as a function of the temperature, i.e., titanate nanosheets were predominantly formed at lower temperatures (110 °C–150 °C), while nanoribbons, with some nanosheets and nanoparticles, were the main products at higher temperatures (> 150 °C). Using energy dispersive X-ray it was determined that iron was incorporated into nanosheets. On the other hand, the as-obtained nanoribbons were Fe-free, while iron was principally associated with nanoparticles attached to the nanoribbons. By means of X-ray photoelectron and Mössbauer spectroscopies, it was elucidated that iron adopted Fe{sup 3} {sup +} form in the as-prepared nanosheets, occupying octahedral sites inside the titanate lepidocrocite-like structure. Diffuse reflectance spectroscopy showed a change of absorption pattern frommore » nanosheets to nanoribbon/nanoparticle assembly: nanosheets exhibited high absorption from ultraviolet up to the visible light range, while the nanoribbon/nanoparticle assembly demonstrated a drop in absorption in the visible light range. These results suggest that Fe{sup 3} {sup +} incorporation inside the titanate structure is responsible for enhancing the visible light absorption, making these nanosheets potentially suitable for applications in photoinduced processes. - Highlights: • Mineral sand has been used as the precursor for the synthesis of nanotitanates. • Fe-doped nanotitanates have been prepared in a single step wet chemistry route. • The morphology of the nanometric titanates is a function of the temperature. • Mössbauer spectroscopy reveals Fe{sup 3} {sup +} in octahedral sites inside nanosheets. • The Fe incorporation in nanosheets improved the visible light absorption.« less
Authors:
 [1] ;  [1] ;  [2] ;  [3] ;  [4] ;  [1]
  1. Departamento de Engenharia de Materiais, Pontifícia Universidade Católica do Rio de Janeiro, 22451-900 Rio de Janeiro, RJ (Brazil)
  2. Centro Brasileiro de Pesquisas Físicas, 22290-180 Rio de Janeiro, RJ (Brazil)
  3. Department of Physics, Arizona State University, Tempe, AZ 85287 (United States)
  4. Departamento de Física, Pontifícia Universidade Católica do Rio de Janeiro, 22451-900 Rio de Janeiro, RJ (Brazil)
Publication Date:
OSTI Identifier:
22476014
Resource Type:
Journal Article
Resource Relation:
Journal Name: Materials Characterization; Journal Volume: 99; Other Information: Copyright (c) 2014 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ABSORPTION; DOPED MATERIALS; HYDROTHERMAL SYNTHESIS; IRON ADDITIONS; MINERALS; NANOMATERIALS; NANOPARTICLES; NANOSTRUCTURES; PRECURSOR; REDUCTION; SAND; SODIUM HYDROXIDES; SPECTROSCOPY; TITANATES; TRANSMISSION; TRANSMISSION ELECTRON MICROSCOPY; ULTRAVIOLET RADIATION; VISIBLE RADIATION; WATER