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08:39
Liquid-cell Transmission Electron Microscopy for Tracking Self-assembly of Nanoparticles
Published on: October 16, 2017
Structure/processing relationships of highly ordered lead salt nanocrystal superlattices
Tobias Hanrath1, Joshua J Choi, Detlef-M Smilgies
1School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York 14853, USA. th358@cornell.edu
ACS Nano
|September 5, 2009
Summary
Processing conditions critically affect nanocrystal film ordering. Solvent vapor annealing improves supracrystal formation, while ligand displacement degrades order, crucial for advanced materials.
Area of Science:
- Materials Science
- Nanotechnology
- Solid State Physics
Background:
- Controlling the self-assembly of nanocrystals into ordered thin films is essential for developing advanced electronic and optoelectronic devices.
- Understanding the interplay between processing parameters, substrate properties, and solvent dynamics is key to achieving desired nanostructure architectures.
Purpose of the Study:
- To investigate how processing conditions influence the ordering of strongly interacting nanocrystal films.
- To explore the role of nanocrystal/substrate interactions and solvent evaporation rate on supracrystal formation.
- To evaluate solvent vapor annealing as a post-deposition technique for enhancing nanocrystal film order.
Main Methods:
- Synergistic combination of electron microscopy and synchrotron-based small-angle X-ray scattering (SAXS) analysis.
- Fabrication and characterization of lead selenide (PbSe) and lead salt nanocrystal films using spin-casting and drop-casting techniques.
- Controlled manipulation of solvent evaporation dynamics and post-deposition solvent vapor annealing.
Main Results:
- Spin-cast PbSe nanocrystal films formed face-centered cubic (FCC) supracrystals with specific substrate alignment.
- Drop-cast film ordering was highly sensitive to substrate topography and solvent evaporation rate.
- Highly ordered FCC supracrystals formed on flat Si substrates, while rough ITO substrates yielded polycrystalline films.
- Solvent vapor annealing, particularly with octane, significantly improved long-range order and orientation.
- Exposure to 1,2-ethanedithiol vapor degraded order by displacing surface ligands.
Conclusions:
- Processing conditions, substrate characteristics, and solvent evaporation dynamics are critical determinants of nanocrystal film ordering.
- Solvent vapor annealing is an effective post-deposition strategy to enhance the quality of nanocrystal thin films.
- Ligand management is crucial for maintaining or improving nanocrystal assembly order.
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