Speaker
Description
Colloidal nanocrystals (NCs) offer the opportunity for realising novel solid state materials with tailored functionalities. By chemical synthesis, a large variety of semiconducting and metallic NCs can be realised [1] that can be used as efficient light emitters [1, 2] or in novel batteries designs [3].
Especially the inner structure and the shape of semiconducting core/shell NCs determine the photoluminescence (PL) output. We have revealed a relation between structure and functionality by combining different scattering techniques at lab and synchrotron sources with microscopy techniques [2]. In a study at the synchrotron ESRF, we have investigated CdSe/CdS core/shell NCs with different dimensions by recording ASAXS and WAXS spectra. We revealed an elliptical and strongly faceted NC-shape and could related this shape to specific crystallographic directions. This increased anisotropy is directly connected to a decreased PL.
The NC’s shape can also significantly influence the structure of colloidal supercrystals, where NCs act as building blocks to form 3D nanocrystal solids with designed properties [1]. We have probed such a self-assembly with in-situ synchrotron SAXS at ELETTRA using colloidal solutions of Bi NCs [4]. By combining synchrotron data with simulations, we are able to link the supercrystal structure via the NC-shape to the atomic Bi crystal structure: besides a positional ordering we found a parallel alignment of the large NC surface facets [4]. Such a global alignment of crystallographic directions within the superstructure is important for controlled electronic properties of the whole nanocrystal solid.
[1] M. V. Kovalenko, et al., & W. Heiss, ACS Nano 9, (2015) 1012–1057
[2] L. Ludescher, et al. & R.T. Lechner, Front. Chem. 6, (2019) 672
[3] K.V. Kravchyk, et al., & M. V. Kovalenko, ACS Nano 12, (2018) 8297-8307
[4] M.Burian, C. Karner, et al., & R.T. Lechner, Adv. Mater. 30, (2018) 1802078M
| Speaker Country | Austria |
|---|