Optical control of the spindle-liked ZnSe quantum dots with precursor solvent and Mn doping

Spindle-liked ZnSe and Mn:ZnSe quantum dots (QDs) were formed via an optimized greener approach, which may be attributed to the amine ligands adhering asymmetrically to the crystal facets. Powder X-ray diffraction (XRD) patterns revealed that the ZnSe and Mn:ZnSe QDs have a zinc blende cubic crystal structure. The crystallite size of ZnSe was calculated to be about 4 nm from the (1 1 1) peak width using the Scherrer equation, which was in agreement with the HRTEM findings. The fluorescence emission peak of as-prepared ZnSe and Mn:ZnSe QDs was 431 nm and 580 nm respectively. We investigated the effect of the reaction temperature, reflux time, precursor solvent, size of MnSe core and overcoating temperature of ZnSe layer on the optical properties of ZnSe and Mn:ZnSe QDs. It is shown that the precursor solvent plays a key role in the formation of the magic-sized QDs (MSQDs). And as a result, doped quantum dots (d-dots) showed a large Stokes shift and enhanced photoluminescence, and smaller size of the MnSe core and suitable overcoating temperature of ZnSe shell were identified as two key parameters for obtaining the high quality d-dots.