Premium
Effects of the agglomeration state on the Raman properties of Co 3 O 4 nanoparticles
Author(s) -
Lorite I.,
Romero J. J.,
Fernández J. F.
Publication year - 2012
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.4098
Subject(s) - raman spectroscopy , nanoparticle , economies of agglomeration , materials science , phonon , laser power scaling , anharmonicity , laser , chemical physics , nanotechnology , analytical chemistry (journal) , chemical engineering , chemistry , optics , condensed matter physics , physics , organic chemistry , engineering
The features of the Raman spectra of Co 3 O 4 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.