An investigation of the elements of the photodecomposition of Zn_xCd_1-x Se quantum dot

Abstract

High quality Zn_xCd_1-xSe quantum dots useful for medical imaging were synthesised by high temperature or embryonic nuclei-induced alloying technique by incorporating varying amounts of Zn precursor into CdSe nuclei. The prepared Zn_xCd_1-xSe nanoparticles were digested in acid and the amount of metal ions present in the solution were determined by electroanalysis and AAS techniques. It was found that the Cd to Zn ratio in the prepared nanoparticles matched that present in the reaction solution. A UV-vis and HR-TEM analyses of the quantum dots showed that the Zn-Cd-Se nanoparticles were nearly mono dispersed, had well resolved lattice fringes and remained fully crystalline upon zinc incorporation. As the zinc content increased from 0.25 to 0.67, the nanoparticle size increased from 5.8 nm to 7.5 nm, and the colour of the solution varied from brown to blue. Upon tuning the quantum dots by photodecomposition, in order to produce materials suitable for biomedical imaging applications, it was observed that the nanoparticles remained crystalline, the particles sizes were reduced to a uniform size, and its solution remained permanently blue, while the absorption wavelength remained in the low wavelength region.

Keywords: Cadmium zinc selenide, embryonic nuclei induced, photodecomposition, atomic absorption spectroscopy, stripping voltammetry, nanocrystals