Studies on Fe-modified nanostructured trititanates

• Published in: Materials chemistry and physics 2011-03, Vol.126 (1), p.118-127
• Main Authors: Morgado, Edisson, Marinkovic, Bojan A., Jardim, Paula M., de Abreu, Marco A.S., Rocha, Maria da Graça C., Bargiela, Pascal
• Format: Article
• Language: English
• Subjects: 1D nanomaterials; Anatase; Interlayers; Iron; Nanomaterials; Nanostructure; Rutile; Shrinkage; Sodium; Thermal transformation; TiO 2; Titanate; Titanium dioxide
• ISSN: 0254-0584; 1879-3312
• DOI: 10.1016/j.matchemphys.2010.11.054

▶ 1D nanostructured titanate easily exchanged with Fe 3+ following the Langmuir adsorption model. ▶ Iron caused interlayer shrinkage and reduced bandgap energy. ▶ Iron also found in a lower oxidation state Fe 2+. ▶ Fe-modified trititanate nanostructure (Fe/TTNS) is stable up to 400 °C and eventually transforms into rutile and pseudobrookite. 1D nanostructured sodium trititanate was synthesized by alkali hydrothermal treatment of TiO 2 anatase, coexisting with incompletely converted precursors like nanosheets and poorly crystalline aggregates. This product easily exchanged with Fe 3+ at room temperature to saturation at approximately 8 wt% Fe, following the Langmuir adsorption model. Iron exchange caused changes on the structural (interlayer shrinkage) and optical properties of the nanomaterial without affecting significantly its original morphology and mesoporous structure. According to consistent XRD and TEM/EDS data, iron was saturated within the interlayers of the 1D nanostructured particles at a lower content as compared to the coexisting poorly crystalline aggregates. Based on XPS results iron was found to be also in a lower oxidation state Fe 2+, likely on the layered surface of the 1D nanostructured particles, through a mechanism tentatively explained by formation of structural iron defects promoted by the acidic medium. The iron modified trititanate nanostructure (Fe/TTNS) is stable up to 400 °C and at high temperatures it is eventually transformed into rutile (TiO 2) and pseudobrookite (Fe 2TiO 5), whereas some freudenbergite phase (Na 2Fe 2Ti 6O 16) is generated due to residual sodium.