Diffusion coefficients from signal fluctuations: influence of molecular shape and rotational diffusion

Area of Science:

• Physical Chemistry
• Chemical Physics
• Materials Science

Background:

• Analysis of signal fluctuations from diffusing molecules near a probe can determine diffusion coefficients.
• Existing theoretical models are limited to point-like or circle-shaped particles.
• Characterizing diffusion of non-spherical molecules is crucial for understanding complex systems.

Purpose of the Study:

• To extend theoretical treatments of diffusion analysis to molecules with rectangle-like shapes.
• To develop methods for determining both translational and rotational diffusion coefficients for these molecules.
• To explore the utility of peak width distributions, interpeak time intervals, and autocorrelation functions.

Main Methods:

• Theoretical analysis of signal fluctuations for diffusing rectangle-shaped molecules.
• Incorporation of rotational diffusion into the theoretical framework.
• Validation using kinetic Monte Carlo simulations.

Main Results:

• A theoretical framework for analyzing diffusion of rectangle-shaped molecules was established.
• Methods to determine translational and rotational diffusion coefficients from signal peak widths were demonstrated.
• The effectiveness of interpeak time intervals and autocorrelation functions for diffusion coefficient determination was explored.

Conclusions:

• The developed approach enables the characterization of translational and rotational diffusion for rectangle-shaped molecules.
• Signal fluctuation analysis provides a versatile tool for studying molecular diffusion beyond simple shapes.
• The findings are validated by kinetic Monte Carlo simulations, confirming the theoretical predictions.