Synthesis, structural and optical properties of water-soluble Mn-doped CdS nanocrystals

Water-soluble Mn-doped CdS nanocrystals were synthesised by an aqueous colloidal synthetic technique. X-ray diffraction identifies that the Mn-doped CdS nanocrystal is a cubic structure without impurity phase. Transmission electron microscopy suggests a narrow size distribution of the nanocrystals with an average particle size of ~3.6~nm. Moreover, UV~vis absorption and photoluminescence (PL) spectra of the nanoparticle were also measured. PL results show that Mn-doped CdS nanocrystals have a distinct Mn²⁺ related emission well-separated from the trap state emission. Reaction variables such as the 3-Mercaptopropionic acid/Cd (MPA/Cd) ratio, reaction temperature and Mn²⁺ doped concentration were systematically investigated to evaluate the impact of these variables on particle size and optical property. The results indicate that the 2 mol Mn-doped CdS nanocrystals synthesised at 70 C and the MPA/Cd ratio of 3.5 have the highest PL intensity.