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The structure and continuous stoichiometry change of 1DTbBrx@SWCNTs
N A Kiselev1, A S Kumskov1,2,3, V G Zhigalina1,3
1Electron microscopy laboratory, Shubnikov Institute of Crystallography RAS, Moscow, Russia.
Journal of Microscopy
|December 2, 2015
Summary
Structural modifications in terbium bromide (TbBrx) nanocrystals within single-wall carbon nanotubes (SWCNTs) were observed. Stoichiometry changes and bromine loss influence crystal structure and acceptor doping of SWCNTs.
Area of Science:
- Materials Science
- Nanotechnology
- Solid State Chemistry
Background:
- Single-wall carbon nanotubes (SWCNTs) are versatile nanomaterials with tunable electronic properties.
- Intercalation of guest materials into SWCNTs offers a route to create novel meta-nanostructures.
- Understanding the structural and chemical interplay between guest and host is crucial for advanced applications.
Purpose of the Study:
- To investigate the structural modifications of terbium bromide (TbBrx) nanocrystals encapsulated within SWCNT channels.
- To correlate structural changes with stoichiometry variations and their impact on SWCNT electronic properties.
- To explore the formation of different TbBrx crystal unit cells inside SWCNTs of varying diameters.
Main Methods:
- High-resolution transmission electron microscopy (HRTEM) and high-angle annular dark-field scanning transmission electron microscopy (HAADF STEM) for structural analysis.
- Energy-dispersive X-ray spectroscopy (EDX) for elemental analysis and mapping.
- Optical absorption and Raman spectroscopy to probe electronic properties.
Main Results:
- Three distinct structural modifications of 1D TbBrx nanocrystals were identified within SWCNTs.
- SWCNTs with larger diameters (>1.4 nm) host a complete tetragonal unit cell, while smaller ones (<1.4 nm) induce deformation and monoclinic structures.
- Bromine loss, confirmed by chemical analysis, leads to vacancies or peripheral/central atom loss in TbBrx, potentially influenced by electron irradiation.
- Intercalation results in acceptor doping of SWCNTs, with an average Tb:Br atomic ratio of 1:2.8 ± 0.1.
Conclusions:
- The stoichiometry of the guest crystal significantly dictates the structural modifications of TbBrx within SWCNTs.
- The confinement effect of SWCNTs influences the unit cell symmetry and stability of the encapsulated nanocrystals.
- The observed doping and structural changes highlight the potential for creating functionalized SWCNT-based materials with tailored electronic properties.
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