Isolated NAnoparticle Raman Spectroscopy

Coupling of confocal Raman microscopy and atomic force microscopy provides an experimental tool to perform isolated nanoparticle Raman spectroscopy on Co₃O₄ nanoparticles dispersed on Al₂O₃ microparticles, avoiding the use of solvents or polymeric additives. Single Co₃O₄ nanoparticles showed similar Raman spectrum to that of single crystal or bulk systems. Surprisingly, redshift and broadening of Raman vibrational modes were observed for agglomerated nanoparticles. Nonlinear relationships of Raman shift and full width at half maximum on the agglomeration of the Co₃O₄ nanoparticles have been experimentally determined. These results clearly indicate that proximity effects between nanoparticles in the agglomerate modify optical properties and Raman response. Nanoparticle agglomeration must then be taken into account for the understanding of nanoscale response in oxidic materials. Copyright © 2012 John Wiley & Sons, Ltd.