A green and simple synthesis method based on a two-step chemical vapour deposition approach has been developed to synthesis transition metal dichalcogenides flakes. With non-toxic precursor such as transition metal oxides and elemental sulphur, large-area, strong photoluminescent, and uniform MoS 2 nanoflakes was produced at a relatively low growth temperature (650 °C). Controlling layer number and morphology was achieved only by precursor concentration without any oxide impurity revealed by SEM, PL and Raman spectroscopy. This method can be used to make wide range of metal chalcogenides such as ZnS, SnS 2 , PtS 2 and PdS 2 .
In this research, mono-dispersed quantum dots of CdSe were produced using a phosphine-free approach to synthesis of colloidal quantum dots. Selenium precursor was selected as the main precursor. It was found that the initial concentration ratio of monomers critically controlled the size distribution of the nanoparticles through its influence on the growth kinetics of these particles. The best result was obtained using an initial Se/Cd ratio of 5 where CdSe quantum dots of a uniform size were synthesized. This was manifested in the absorption spectra of these particles by occurrence of sharp peaks at a wavelength of about 615 nm.
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