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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 21, Number 12
BKCSDE 21(12)
December 20, 2000 

Synthesis of Monodispersed and Spherical SiO2-coated Fe2O3 Nanoparticle
Yang-Su Han, Seon-Mi Yoon, Dong-Kuk Kim
The preparation of nanocrystalline hematite, α-Fe₂O₃, particles and their surface coating with silica layers are described. The hematite particles with the size of 30~60 nm are firstly prepared by thermal decomposition of trinuclear acetato-hydroxo iron (III) nitrate complex, [Fe₃(OCOCH₃)7OH·2H₂O]NO₃, at 400 ℃. Subsequently the hematite surfaces are coated with silica layers by a controlled hydrolysis and condensation reaction of TEOS with varying the TEOS concentration and pH. Monodispersed and spherical SiO₂-coated Fe₂O₃ particles with the average particle diameter of ~90 nm and extremely narrow size distribution can be obtained at the pH of 11 and the TEOS concentration of 0.68 M, which are found to be the optimum conditions in the present study in achieving the homogeneous deposition of silica layers on hematite surfaces. Diffuse reflectance UV-Vis spectra reveal that the characteristic optical reflectance of α-Fe₂O₃ particles is preserved almost constant even after coating the surfaces, suggesting that the SiO₂ layers can be regarded as protecting layers without degrad-ing the optical properties of hematite particles.
1193 - 1198
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