Iron Oxide and Oxide-Hydroxide Nanoparticles in Organic-Inorganic Matrices

Nuno João O. Silva; Angel Millan; Vitor S. Amaral; Fernando Palacio; Lianshe Fu; Luís D. Carlos; Verónica de Zea Bermudez

doi:10.4028/www.scientific.net/MSF.514-516.142

Paper Titles

Preparation of Photoluminescent Materials from a Lanthanide-Doped Microporous Titanosilicate Precursor
p.123

Photoluminescence of Nanocrystalline Bismuth Titanate Thin Films Synthesized by the Sol-Gel Method
p.128

EPR and TEM Characterization of Electroluminescent Alq₃
p.133

Photoinduced Effects in EPR Spectra of Copper Doped Potassium Tantalate
p.138

Iron Oxide and Oxide-Hydroxide Nanoparticles in Organic-Inorganic Matrices
p.142

New Fluorescent Heterocyclic Materials: Synthesis, Solvatochromic and Fluorescence Properties
p.147

EPR and Optical Absorption Investigations of Photochromic Effect in Nearly Stoichiometric LiNbO₃:Fe
p.152

Thermoelectric Properties of Bi₂Te₃/Sb₂Te₃ Thin Films
p.156

High Field Polarization Response in Ferroelectrics: Current Solutions and Challenges
p.161

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Iron Oxide and Oxide-Hydroxide Nanoparticles in Organic-Inorganic Matrices

Abstract:

Nanometric ferrihydrite, maghemite and magnetite particles formed within an organicinorganic hybrid matrix were obtained by the sol-gel process. In contrast to precipitation techniques, sol-gel process appears as suitable way to achieve size-controlled nanoscopic magnetic particles anchored in a hybrid structure. The hybrid matrix here reported, named di-ureasil, is composed of poly(oxyethylene) chains grafted to siloxane groups by means of urea cross-linkages. The formation of ferrihydrite particles was achieved incorporating iron nitrate during the sol-gel process, at low pH. The formation of maghemite takes place after the incorporation of a mixture of Fe3+ and Fe2+ ions and treatment with an ammonia solution, after the sol-gel process. Magnetite nanoparticles are formed after the incorporation of Fe2+ ions and treatment with ammonia at 80°C. The AC magnetic susceptibility shows thermal irreversibility with a blocking temperature TB≈13K and ≈25K depending on frequency for the ferrihydrite and maghemite particles, respectively. The magnetite nanoparticles are blocked at room temperature. Above the irreversibility the magnetization of ferrihydrite and maghemite follows a Langevin function modified with a linear term, as found in antiferromagnetic and ferrimagnetic particles.