Synthesis, characterization and luminescence properties of thiol-capped CdSe quantum dots at different processing conditions

This work investigated the effect of different processing conditions and surface passivation on the growth and luminescence of CdSe quantum dots (QDs). The synthesis of CdSe QDs by pyrolysis of thiol reagents was performed by using the wet chemical route. In order to modify the size and quality of CdSe QDs, the growth temperature was controlled at 70 °C while the relative amount of 2-mercaptoethanol, pH value and synthesis atmosphere were altered for getting an effective surface passivation of mono-disperse CdSe QDs with highly luminescence. The prepared nanocrystals are characterized by X-ray diffraction, transmission electron microscopy (TEM) and photoluminescence (PL) spectroscopy. The XRD pattern showed that the prepared CdSe has a cubic phase with zinc blend structure. The particle size was estimated from broadening of XRD peak using Scherrer’s formula and also from TEM images. The results showed that the synthesis of CdSe nanocrystals in N2 atmosphere has lower particle size compared with synthesis in open air. It is also found that the size of CdSe nanoparticle increases, as the CdSe/2-mercaptoethanol molar ratio is increased. The photoluminescence emission intensity for as-synthesized CdSe nanocrystals at different reaction conditions depicted that, the emission peak intensity strongly affected by the synthesis atmosphere, pH value and CdSe/2-mercaptoethanol molar ratio.

► Thiol capped CdSe QDs are prepared at different processing conditions.
► The synthesized QDs in N2 atmosphere have the smallest particle size.
► The photoluminescence is strongly affected by the pH and thiol molar ratio.