Structural and chemical characterization of CdSe-ZnS core-shell quantum dots

• Published in: Applied surface science Vol. 457; pp. 93 - 97
• Main Authors: Fernández-Delgado, N., Herrera, M., Tavabi, A.H., Luysberg, M., Dunin-Borkowski, R.E., Rodriguez-Cantó, P.J., Abargues, R., Martínez-Pastor, J.P., Molina, S.I.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.11.2018
• Subjects: Core-shell nanoparticles; EDX; HAADF-STEM; HRTEM; Quantum dots; Semiconductors; Core-shell nanoparticles; EDX; Semiconductors; HAADF-STEM; Quantum dots; HRTEM
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2018.06.149

[Display omitted] •Photoluminescence and quantum yield of CdSe QDs are greatly improved when covered by ZnS shell.•The synthesis by hot injection and SILAR leads to two crystal structures, Wurtzite and Zinc Blende.•The presence of the shell is directly proved by electron microscopy techniques.•The shell presents thickness variations that make the covering highly irregular. The structural and compositional properties of CdSe-ZnS core-shell quantum dots (QDs) with a sub-nm shell thickness are analyzed at the atomic scale using electron microscopy. QDs with both wurtzite and zinc blende crystal structures, as well as intermixing of the two structures and stacking faults, are observed. High-angle annular dark-field scanning transmission electron microscopy suggests the presence of a lower atomic number epitaxial shell of irregular thickness around a CdSe core. The presence of a shell is confirmed using energy dispersive X-ray spectroscopy. Despite the thickness irregularities, the optical properties of the particles, such as photoluminescence and quantum yield, show clear enhancement after growth of the ZnS shell.