Theoretical analysis of structures and electronic spectra in molecular cadmium chalcogenide clusters
Nguyen, Kiet A.
Day, Paul N.
Date of Issue2015
School of Materials Science and Engineering
We present calculated structural and optical properties of molecular cadmium chalcogenide nonstoichiometric clusters with a size range of less than 1 nm to more than 2 nm with well-defined chemical compositions and structures in comparison to experimental characterization and previous theoretical work. A unified treatment of these clusters to obtain a fundamental understanding of the size, ligand, and solvation effects on their optical properties has not been heretofore presented. The clusters belong to three topological classes, specifically supertetrahedral (Tn), penta-supertetrahedral (Pn), and capped supertetrahedral (Cn), where n is the number of metal layers in each cluster. The tetrahedrally shaped Tn clusters examined in this work are Cd(ER)4^2− (T1), Cd4(ER)10^2− (T2), and Cd10E′4(ER)16^4− (T3), where R is an organic group, E and E′ are chalcogen atoms (sulfur or selenium). The first member of the Pn series considered is M8E′(ER)16^2−. For the Cn series, we consider the first three members, M17E′4(ER)28^2− , M32E′14(ER)36L4 , and M54E′32(ER)48L4^4− (L = neutral ligand). Mixed ligand clusters with capping ER groups replaced by halogen or neutral ligands were also considered. Ligands and solvent were found to have a large influence on the color and intensity of the electronic absorption spectra of small clusters. Their effects are generally reduced with increasing cluster sizes. Blueshifts were observed for the first electronic transition with reduced size for both cadmium sulfide and cadmium selenide series. Due to weakly absorbing and forbidden transitions underlying the one-photon spectra, more care is needed in interpreting the quantum confinement from the clusters’ lowest-energy absorption bands.
Materials Science and Engineering
The Journal of Chemical Physics
© 2015 American Institute of Physics. This paper was published in Journal of Chemical Physics and is made available as an electronic reprint (preprint) with permission of American Institute of Physics. The published version is available at: [http://dx.doi.org/10.1063/1.4922320]. One print or electronic copy may be made for personal use only. Systematic or multiple reproduction, distribution to multiple locations via electronic or other means, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper is prohibited and is subject to penalties under law.