Optical limiting and optical properties of water soluble CdTe quantum dots prepared through a colloidal chemical route

Abstract

Luminescent, water soluble, CdTe colloidal QDs were synthesized by simple wet chemical method. The prepared CdTe QD samples were showing wide range of color tunability from green to red when irradiated with UV light. The quantum confinement effect of the synthesized QDs was confirmed using UV–vis absorption and fluorescence spectroscopy. The spherical morphology of the synthesized QDs was confirmed using transmission electron microscopy (TEM). The X-ray diffraction (XRD) analysis indicates that the QDs were having cubic structure. Analysis of the third order nonlinear property using Z-scan technique indicates that the QDs were having two photon absorption properties. Unlike the previous reported results, the variations in the third order nonlinear susceptibility (χ3) was found to be in correlation with emission intensity. The value of imaginary part of nonlinear χ3 and refractive index was found to be of the order of 10−11 and 10-7esu respectively. Imaginary part of χ3 is found to be Gaussian dependent function of reaction time, which provides a possible way of tuning of imaginary part of third order susceptibility. The figure of merit (n2/β) of the synthesized QDs was found to be greater than that for the bulk material. Thus these QDs possess good nonlinear optical characteristics which enable them as a potential candidate for the optical limiting application.