Effect of capping and particle size on Raman laser-induced degradation of γ-Fe2O3 nanoparticles

Diol capped gamma-Fe2O3 nanoparticles are prepared from ferric nitrate by refluxing in 1,4-butanediol (9.5 nm) and 1,5-pentanediol (15 nm) and uncapped particles are prepared by refluxing in 1,2-propanediol followed by sintering the alkoxide formed. X-ray diffraction (XRD) shows that all the samples have the spinel phase. Raman spectroscopy shows that the samples prepared in 1,4-butanediol and 1,5-pentanediol and 1,2-propanediol (sintered at 573 and 673 K) are gamma-Fe2O3 and the 773 K-sintered sample is Fe3O4. Raman laser studies carried out at various laser powers show that all the samples undergo laser-induced degradation to alpha-Fe2O3 at higher laser power. The capped samples are however, found more stable to degradation than the uncapped samples. The stability of gamma-Fe2O3 sample with large particle size (15.4 nm) is more than the sample with small particle size (10.2 nm). Fe3O4 having a particle size of 48 nm is however less stable than the smaller gamma-Fe2O3 nanoparticles. (C) 2004 Elsevier Inc. All rights reserved.