Thermal -lens study of thermo-optical properties of CdSe/ZnS quantum dots embedded into PMMA matrix

Abstract

ABSTRACT Thermal Lens (TL) and spectroscopic characterizations were performed in CdSe/ZnS core-shell nanoparticles embedded into the underlying polymethyl methacrylate (PMMA) dissolved in chloroform (CHCl 3 ). TL measurements were accomplished in function of the CdSe/ZnS quantum-dot concentration (12-60 mg/ml). The average value obtained for the thermal diffusivity was (0.85 ± 0.02) u 10 -3 cm 2 /s. The absolute nonradiative quantum efficiency M and the fluorescence quantum efficiency K were determined by the TL method. Higher values of M were obtained with the increase of the core-shell nanoparticles concentrations in PMMA-chloroform solutions. These results are in agreement with the behavior of fluorescence spectra that d ecrease with CdSe/ZnS concentration increase. Keyword: CdSe/ZnS core-shell colloidal nanoparticles, Thermal Lens, Spectroscopic properties 1. INTRODUCTION Semiconductor nanoparticles or quantum dots (QD) materials have generated an increased interest in research area mainly due to the continuous development of new nano-materials with better optical properties, versatility and flexibility in form. For example, core-shell (CS) quantum dot structure can be mixed into liquid solution, common matrix materials (as polycarbonate, polystyrene or polymethyl methacrylate) or films. In this way, trying to take advantage of the merits of both materials, these new quantum dots materials are becoming promising for practical applications requiring excellent transparency, resistance to water, as well as material applications requiring thermoforming, casting and brittle properties. Applications in cludes biological markers, military, solar cells, non-linear optical applications, diodes, lasers, optoelectronic and photonic devices