Wide and Intense Emission Band in the Visible area in CdSe Nanocrystals Dispersed in PMMA
Ch. Abderrahmane, A. Migalska-Zalas, A. K. Arof, Z. Sofiani and B. Sahraoui
The present study focuses on the optical properties of thin films based on CdSe/PMMA nanocomposites deposited on glass substrate using a colloidal solution and the spin-coating technique. Optical study reveals that the CdSe particles in amorphous PMMA host matrix exhibit few bands in the UV-Visible area at: 1.85, 2.31, 2.48, 2.67 and 3.26 eV with a shift to high energies of the absorption edge because of quantum confinement induced by the very small size of CdSe crystallites which was estimated to 2.92 nm. Photoluminescence spectrum at low temperature 77°K with λexc = 355 nm shows a wide and intense emission band in the visible area (400 – 700 nm). Emission is due to excitons, trapped imperfection sites and surface electrons. CdSe/ PMMA nanocomposites show high third order nonlinear optical susceptibilities (comparing to the value of the effective third-order susceptibility of silica). These nonlinear parameters are exalted by Third Harmonic Genration (THG) technique.
Keywords: CdSe nanocomposites, blue shift, THG, exciton, quantum confinement