Proceedings of nanoGe Fall Meeting 2018 (NFM18)
DOI: https://doi.org/10.29363/nanoge.nfm.2018.065
Publication date: 6th July 2018
Quantum confinement in semiconductor nanocrystals leads to size-dependent optical properties. Conventionally, the growth of nanocrystal results in a gradual red-shift of the features in absorption spectra. However, in certain cases, the absorption features shift in discrete energetic steps with growth. Such discrete growth is often assigned to nanoplatelets or magic-sized clusters. Although the existence and growth of nanoplatelets is proven1,2, the understanding for the latter remains elusive. This is due in part to complicated synthetic routes that involve multiple ligands and coordinating solvents3,4 or specific complex pathways5 (e.g. templates), which make the investigation of such species difficult. Here, we introduce a simple route to synthesize and isolate stable CdSe nanocrystals showing discrete evolution of absorption features, a subset of which have been previously assigned to magic-sized clusters. We grow them in a template-free regime using only one type of ligand in a non-coordinating solvent up to a size of 2.8 nm. Their isolation is confirmed by absorption, photoluminescence, photoluminescence excitation, and NMR studies. The particles are further analyzed using electron microscopy to evaluate their size and monodispersity. Finally, we provide mechanistic insight into the evolution of different sizes by conducting parametric studies and studying the growth in precursor-free conditions. This synthetic protocol allows us to investigate the early stages of nucleation and growth of nanocrystals in greater detail.
1. Ithurria, S. et al. Colloidal nanoplatelets with two-dimensional electronic structure. Nat. Mater. 10, 936–941 (2011).
2. Riedinger, A. et al. An intrinsic growth instability in isotropic materials leads to quasi-two-dimensional nanoplatelets. Nat. Mater. 16, 743–748 (2017).
3. Kudera, S. et al. Sequential Growth of Magic-Size CdSe Nanocrystals. Adv. Mater. 19, 548–552 (2007).
4. Cossairt, B. M. et al. CdSe Clusters: At the Interface of Small Molecules and Quantum Dots. Chem. Mater. 23, 3114–3119 (2011).
5. Wang, Y. et al. Magic-Size II–VI Nanoclusters as Synthons for Flat Colloidal Nanocrystals. Inorg. Chem. 54, 1165–1177 (2015).
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