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09:05
Supercritical Nitrogen Processing for the Purification of Reactive Porous Materials
Published on: May 15, 2015
Purification of boron nitride multiwalled nanotubes
Sara M C Vieira1, David L Carroll
1Department of Engineering, University of Cambridge, 9 JJ Thomson Avenue, Cambridge CB3 0FA, UK.
Journal of Nanoscience and Nanotechnology
|November 21, 2007
Summary
A simple surfactant-based purification method effectively isolates highly pure multiwalled boron nitride nanotubes (BN MWNTs) grown via arc-discharge. This technique removes contaminants, revealing intrinsic nanotube properties for advanced materials applications.
Area of Science:
- Materials Science
- Nanotechnology
- Condensed Matter Physics
Background:
- Arc-discharge synthesis commonly yields multiwalled boron nitride nanotubes (BN MWNTs) mixed with hexagonal boron nitride and metal catalysts.
- Effective purification is crucial for characterizing the intrinsic properties of BN MWNTs.
Purpose of the Study:
- To develop and demonstrate a simple, effective purification method for arc-discharge grown BN MWNTs.
- To characterize the morphology and electronic properties of the purified BN MWNTs.
Main Methods:
- Arc-discharge synthesis using a packed molybdenum tube with h-BN/Ni/B and a water-cooled copper cathode.
- Purification utilizing surfactants for solubilization followed by solution filtration.
- Characterization via transmission electron microscopy (TEM) and scanning tunneling spectroscopy/microscopy (STS/STM).
Main Results:
- A straightforward solubilization and filtration process successfully purified BN MWNTs.
- Purified samples exhibited characteristic square and triangular tube ends with no residual metal catalysts.
- Scanning tunneling spectroscopy revealed an average band gap of approximately 5 eV, independent of nanotube chirality and diameter.
Conclusions:
- The developed surfactant-based method provides highly purified BN MWNTs suitable for detailed characterization.
- The intrinsic electronic properties of BN MWNTs, including their band gap, are consistently observed post-purification.
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Introduction
One of the convenient methods for the preparation of aldehydes and ketones is via hydration of alkynes. Hydroboration-oxidation of alkynes is an indirect hydration reaction in which an alkyne is treated with borane followed by oxidation with alkaline peroxide to form an enol that rapidly converts into an aldehyde or a ketone. Terminal alkynes form aldehydes, whereas internal alkynes give ketones as the final product.
One of the convenient methods for the preparation of aldehydes and ketones is via hydration of alkynes. Hydroboration-oxidation of alkynes is an indirect hydration reaction in which an alkyne is treated with borane followed by oxidation with alkaline peroxide to form an enol that rapidly converts into an aldehyde or a ketone. Terminal alkynes form aldehydes, whereas internal alkynes give ketones as the final product.