Tunable luminescence of spherical CdSe/ZnS and tetrahedron CdSe/Cd1−xZnxS core/shell quantum dots created using same cores

Spherical CdSe cores with tunable photoluminescence (PL) between green and red were fabricated through a novel organic synthesis. The CdSe cores were coated with ZnS or Cd1−xZnxS shells through an environmentally friendly approach using oleic acid as a capping agent. These shells resulted in those core/shell quantum dots (QDs) with different morphologies and PL properties. Namely, CdSe/ZnS core/shell QDs revealed a spherical morphology while CdSe/Cd1−xZnxS core/shell QDs exhibited an irregular tetrahedron shape. This phenomenon indicated that the growth kinetic of these core/shell QDs depended strongly on the shell composition. Two kinds of core/shell QDs exhibited narrow size distributions and tunable PL spectra. Under optimal preparation conditions, the PL quantum yields of CdSe/ZnS and CdSe/Cd1−xZnxS core/shell QDs were up to 48% and 55%, respectively. The absorption and PL spectra have a significant red shift after coating with ZnS and Cd1−xZnxS on CdSe cores. The red shift degree depended on the thickness and composition of those shells. Especially, two kinds of QDs revealed red emission (PL peak wavelength of 648 nm for CdSe/ZnS and 653 nm for CdSe/Cd1−xZnxS) when large CdSe cores with a PL peak wavelength of 624 nm were used. These core/shell QDs will have an important application as biomarkers.