Single-file nanochannel persistence lengths from NMR.

Area of Science:

• Materials Science
• Nanotechnology
• Analytical Chemistry

Background:

• Crystalline solids with sub-nanometer one-dimensional channels are promising for various applications.
• A critical parameter for these materials is the average open channel persistence length, indicating the distance to the first obstruction.

Purpose of the Study:

• To introduce and validate a novel Nuclear Magnetic Resonance (NMR)-based methodology for measuring average open channel persistence length.
• To apply this method to dipeptide nanotubes (l-Ala-l-Val and l-Val-l-Ala) and assess their structural integrity.

Main Methods:

• Development of an NMR-based protocol to quantify average open channel persistence length.
• Application of the NMR method to polycrystalline samples of l-Ala-l-Val (AV) and l-Val-l-Ala (VA) nanotubes.
• Comparison of NMR-derived persistence lengths with crystallite dimensions obtained from Scanning Electron Microscopy (SEM).

Main Results:

• NMR measurements revealed persistence lengths comparable to crystallite sizes in pristine AV and VA samples, suggesting hollow structures with minimal blockages.
• Pulverization of an AV sample significantly reduced the average open channel persistence length from 50 μm to 6.6 μm.
• SEM analysis corroborated the reduction in crystallite size after mechanical stress, consistent with the observed decrease in channel persistence.

Conclusions:

• The developed NMR methodology effectively measures average open channel persistence length in nanomaterials.
• Dipeptide nanotubes exhibit excellent open channel structures, but are susceptible to blockage upon mechanical processing.
• This technique provides valuable insights into the structural integrity and processability of nanomaterials with one-dimensional channels.