title: Preparation and characterization of silica coated iron oxide magnetic nano-particles.
abstract: Iron oxide magnetic nano-particles have been prepared by precipitation in an aqueous solution of iron(II) and iron(III) chlorides under basic condition. Surface modifications have been carried out by using tetraethoxysilane (TEOS) and mercaptopropyltrimethoxysilane (MPTMS). The uncoated and coated particles have been characterized with transmission electron microscopy (TEM), energy dispersive X-ray (EDX) spectroscopy, thermal gravimetric analysis (TGA), and infrared (IR) and Raman spectroscopy. The particle sizes as measured from TEM images were found to have mean diameters of 13nm for the uncoated and about 19nm for the coated particles. The measured IR spectra of the uncoated and MPTMS coated particles showed the conversion of magnetite to hematite at high temperature. The results obtained from both IR spectroscopy and TGA revealed that the mercaptopropylsilyl group in the MPTMS coated magnetite decomposed at 600 degrees C and the silica layer of the TEOS coated magnetite was rather stable. Raman spectroscopy has shown the laser heating effect through the conversion of magnetite to maghemite and hematite.
authors.affiliation: Department of Chemistry, University of Memphis, 3774 Walker Ave., Memphis, TN 38152, USA. yingli@memphis.edu
authors.forename: Ying-Sing
authors.initials: YS
authors.lastname: Li
authors.forename: Jeffrey S
authors.initials: JS
authors.lastname: Church
authors.forename: Andrea L
authors.initials: AL
authors.lastname: Woodhead
authors.forename: Filsun
authors.initials: F
authors.lastname: Moussa
mesh_terms: D005290:Ferric Compounds / Q000737:chemistry*; D008280:Magnetics; D053768:Metal Nanoparticles / Q000737:chemistry*; D046529:Microscopy, Electron, Transmission; D010316:Particle Size; D012822:Silicon Dioxide / Q000737:chemistry*; D013052:Spectrometry, X-Ray Emission; D013055:Spectrophotometry, Infrared; D013059:Spectrum Analysis, Raman; D013499:Surface Properties; D013818:Thermogravimetry
chemical_list: D005290:Ferric Compounds; C000499:ferric oxide; D012822:Silicon Dioxide