Radiolytic synthesis and spectroscopic investigations of Cadmium Selenide quantum dots grown in cationic surfactant based quaternary water-in-oil microemulsions

Abstract

Cadmium selenide (CdSe) quantum dots (QDs) were grown in cationic surfactant cetyltrimethylammonium bromide (CTAB) based water-in-oil microemulsions using high-energy electron beam irradiation. The sizes of the primary QDs were determined from the absorption spectra as well as from high-resolution transmission electron microscope images and were found to be within 3nm. Effects of experimental parameters, such as w0 (molar ratio of water to surfactant in a microemulsion) values and precursor concentrations on the optical properties of these QDs were investigated in detail. The QDs exhibited broad photoluminescence (PL) in the wavelength region extending from 450 to 750nm at room temperature. The time-resolved PL showed multiexponential decay and the average lifetime was estimated to be 4.1ns and the PL decay curve analysis indicated the presence of predominating trap state emission from the as obtained CdSe QDs. The quantum yield exhibited by as-grown QDs was determined to be 2.4%, without involving any postprocessing techniques. However, these QDs possessing ultra small size (⩽5nm) were found to exhibit CIE (Commission Internationale d’Eclairage) chromaticity x, y co-ordinates close to (0.36,0.36), which confirms their potential as white light emitters. Besides, their light emitting color tunability can be conveniently achieved just by varying the experimental parameters. Therefore, the present method employing electron beam irradiation, accompanied by various advantages of CTAB based water-in-oil microemulsion as the host matrix, offers a simple and one step method to obtain CdSe QDs possessing potential applications in white light emitting devices.