Laser-power-induced multiphonon resonant raman scattering in laser-heated CdS nanocrystal.

The size stability of nanoparticles is crucial from an application point of view. We probe, using Raman spectroscopy, particle size evolution of CdS nanoparticles by varying laser power. Multiphonon resonant Raman scattering has also been demonstrated. With increase in laser power, the intensity ratio of 2-longitudinal optical (LO) to 1-LO is found to increase dramatically, and LO phonon overtones up to fourth order are observed. Resonant Raman scattering has been achieved by suitably matching the band gap with the excitation photon energy, by varying the local temperature. The effect of increase in local temperature on the band gap is also discussed.