Infrared and Raman spectroscopic studies on iron oxide magnetic nano-particles and their surface modifications
| Autor: | Andrea L. Woodhead, Ying-Sing Li, Jeffrey S. Church |
|---|---|
| Rok vydání: | 2012 |
| Předmět: |
Thermogravimetric analysis
Materials science Iron oxide Analytical chemistry Infrared spectroscopy Maghemite Hematite engineering.material Condensed Matter Physics Electronic Optical and Magnetic Materials chemistry.chemical_compound symbols.namesake chemistry visual_art symbols visual_art.visual_art_medium engineering Raman spectroscopy Spectroscopy Magnetite |
| Zdroj: | Journal of Magnetism and Magnetic Materials. 324:1543-1550 |
| ISSN: | 0304-8853 |
| DOI: | 10.1016/j.jmmm.2011.11.065 |
| Popis: | Iron oxide magnetic nano-particles (MNPs) have been prepared in aqueous solution by a modified co-precipitation method. Surface modifications have been carried out using tetraethoxysilane (TEOS), triethoxysilane (TES) and 3-aminopropyltrimethoxysilane (APTMS). The uncoated and coated particle products have been characterized with transmission electron microscope (TEM), energy dispersive X-ray (EDX) spectroscopy, infrared (IR) and Raman spectroscopy, and thermal gravimetric analysis (TGA). The particle sizes were determined from TEM images and found to have mean diameters of 13, 16 and 14 nm for Fe 3 O 4 , TES/Fe 3 O 4 and APTMS/Fe 3 O 4 , respectively. IR and Raman spectroscopy has been applied to study the effect of thermal annealing on the uncoated and coated particles. The results have shown that magnetite nano-particles are converted to maghemite at 109 °C and then to hematite by 500 °C. In contrast, the study of the effect of thermal annealing of micro-crystalline magnetite by IR spectroscopy revealed that the conversion to hematite began by 300 °C and that no maghemite could be identified as an intermediate phase. IR spectra and TGA measurements revealed that the Si–H and 3-aminopropyl functional groups in TES and APTMS coated magnetite nano-particles decomposed below 500 °C while the silica layer around the iron oxide core remained unchanged. The molecular ratio of APTMS coating to iron oxide core was determined to be 1:7 from the TGA data. Raman scattering signals have indicated that MNPs could be converted to maghemite and then to hematite using increasing power of laser irradiation in a manner similar to that observed for thermal annealing. |
| Databáze: | OpenAIRE |
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