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Published online by Cambridge University Press: 01 February 2011
Size dependence of the low frequency vibrational spectra of ZnO nanocrystals prepared using chemical method has been investigated. Optical transmission spectra of the ZnO colloid solution exhibit a shift in the onset of the absorption band edge from 332 to 350 nm due to particle growth. X-ray diffraction analysis of the prepared ZnO nanocrystals exhibit peaks corresponding to the hexagonal wurtzite structure. Two peaks with unusually very high intensity were observed in the low frequency (∼ 10- 25 cm-1) Raman spectra of these nanocrystals. The peak position of these phonon modes shifted towards lower frequencies as the size of the nanocrystals increases and assigned to the confinement of acoustic phonons in ZnO nanocrystals.