Effects of the agglomeration state on the Raman properties of Co3O4 nanoparticles
Article first published online: 20 JUL 2012
Copyright © 2012 John Wiley & Sons, Ltd.
Journal of Raman Spectroscopy
Volume 43, Issue 10, pages 1443–1448, October 2012
How to Cite
Lorite, I., Romero, J. J. and Fernández, J. F. (2012), Effects of the agglomeration state on the Raman properties of Co3O4 nanoparticles. J. Raman Spectrosc., 43: 1443–1448. doi: 10.1002/jrs.4098
- Issue published online: 15 OCT 2012
- Article first published online: 20 JUL 2012
- Manuscript Accepted: 4 APR 2012
- Manuscript Revised: 3 APR 2012
- Manuscript Received: 30 JAN 2012
- Raman spectroscopy
The features of the Raman spectra of Co3O4 30-nm nanoparticles depend strongly on their agglomeration state. When measured at low incident laser power, the spectrum of isolated nanoparticles corresponds to that found in bulk materials, whereas the agglomerated nanoparticles present a clear red-shift and broadening of the Raman bands. On the other hand, when measured at even lower power, both agglomerated and isolated nanoparticles show the same spectrum of microscopic particles. These effects have been studied by variations of the 532-nm laser power and the environmental temperature. The thermal dependence of Raman spectra of agglomerated nanoparticles is different to that of isolated nanoparticles but is comparable to the one of bulk material. The different behaviour of the nanoparticles at different agglomeration state is associated to the transmission of phonons among the particles. On the other hand, an increase of the laser power causes a larger number of acoustic phonons, producing a variation of the vibration anharmonicity of the nanoparticles. This increase is more pronounced in the agglomerated nanoparticles, due to the transmission of phonons, causing a much intense modification of the Raman spectrum produced by the laser power. These results clearly indicate that the agglomeration state of the nanoparticles affects their Raman properties. Copyright © 2012 John Wiley & Sons, Ltd.