Effects of mercaptopropionic acid as a stabilizing agent and Cd:Te ion ratio on CdTe and CdHgTe quantum dots properties

In the present work, mercaptopropionic acid (MPA) capped CdTe and CdHgTe quantum dots (QDs) are synthesized using a method based on the bottom up approach in aqueous medium. The CdTe QDs were prepared with a two different ratios of Cd:Te (3:1 and 4:1). It was noticed that there was a minimum concentration of MPA for each Cd:Te ratio. The resulting QDs were characterized using optical absorption spectroscopy, energy dispersion X-ray (EDX) and high resolution transmission electron microscopy (HRTEM). It was found that the EDXs of CdTe and CdHgTe QDs showed that the stiochiometric ratios of CdTe obtained with Cd:Te ratio of 3:1 is 50:50 and for CdHgTe is 40:26:34 for 100 % of Hg. The band gap of CdHgTe QDs varies slightly with composition from 2.21 eV for a pure CdTe to 1.4 eV for a CdHgTe with 100 % of Hg. The HRTEM image showed a good dispersed nano-crystalline structure for the CdTe QDs with average size of 3-4 nm. The existence of the lattice planes on the HRTEM images of the QD indicated that the CdTe QDs are highly crystalline. In addition, the CdHgTe QDs size is 12 nm for 100 % of Hg.