Diffusion Behavior of Differently Charged Molecules in Self-Assembled Organic Nanotubes Studied Using Imaging...

Area of Science:

• Supramolecular Chemistry
• Nanotechnology
• Physical Chemistry

Background:

• Bolaamphiphile-based organic nanotubes (ONTs) possess unique hollow cylindrical structures.
• Understanding molecular diffusion within ONTs is crucial for applications like drug delivery and contaminant adsorption.
• Previous studies have not fully elucidated the factors governing diffusion within these nanostructures.

Purpose of the Study:

• To systematically investigate the diffusion behavior of fluorescent molecules within bolaamphiphile-based ONTs.
• To determine the influence of solution conditions (pH and ionic strength) on molecular diffusion.
• To assess the uniformity of ONTs for potential applications.

Main Methods:

• Utilized imaging fluorescence correlation spectroscopy (imaging FCS) to study diffusion.
• Employed wide-field fluorescence video microscopy to acquire FCS data.
• Investigated diffusion of anionic, zwitterionic/cationic, and cationic dyes in ONTs across varying pH and ionic strengths.

Main Results:

• Molecular diffusion within ONTs was significantly hindered (D = 10⁻¹ to 10⁻² μm²/s) due to molecule-nanotube interactions.
• Diffusion coefficients (D) were strongly pH-dependent, indicating control by electrostatic interactions with protonated amine groups on the inner surface.
• ONT length did not affect diffusion coefficients, suggesting uniform nanotube properties.

Conclusions:

• Molecular diffusion in ONTs is primarily governed by pH-dependent electrostatic interactions.
• The findings highlight the potential of ONTs as drug vehicles and contaminant adsorbents.
• ONTs exhibit uniform properties suitable for various nanotechnological applications.