Blue shift of Raman peak from coated TiO2 nanoparticles

Nanosized TiO2 particles coated with dodecylbenzenesulfonic acid (DBS) and stearic acid (St) were prepared using the hydrothermal procedure. The average size of the DBS/TiO2 and St/TiO2 particles is very small, about 8 nm. Raman spectra from DBS/TiO2 and St/TiO2 were measured, and scattering signals from both TiO2 and the coating were observed. It was found that in contrast to the red shift of Raman peaks in the nanoparticles with decrease in particle size, a blue shift, namely the Raman peak shift to the higher wavenumber side, in the coated particles was recorded. It was also found that different coatings show different extents of Raman shifts. The possible origin of the blue shift is discussed. Copyright (C) 2001 John Wiley & Sons, Ltd.