Tuning the Flight Length of Molecules Diffusing on a Hydrophobic Surface

Area of Science:

• Surface science
• Physical chemistry
• Materials science

Background:

• Transport at solid-liquid interfaces is crucial for self-assembly, biosensing, and catalysis.
• Surface diffusion on heterogeneous surfaces is challenging to characterize and control.
• Adsorption heterogeneity on solid surfaces complicates understanding molecular behavior.

Purpose of the Study:

• To characterize the surface diffusion of a fluorescent long-chain surfactant on a hydrophobic surface.
• To investigate the influence of methanol concentration on molecule-surface interactions and diffusion dynamics.
• To develop a theoretical framework for understanding surface diffusion on heterogeneous substrates.

Main Methods:

• Employed single-molecule tracking to monitor surfactant diffusion.
• Varied methanol concentration to tune hydrophobic interactions.
• Analyzed diffusion patterns, including periods of confinement and bulk-mediated flights.

Main Results:

• Observed surfactant diffusion characterized by alternating confinement and flights.
• Found a nonmonotonic dependence of confinement frequency on methanol concentration, indicating strong adsorption sites.
• Demonstrated that flight lengths increase monotonically with decreasing hydrophobic attraction.

Conclusions:

• Surface heterogeneity can be accounted for to accurately describe bulk-mediated surface diffusion.
• Theoretical models can predict diffusion behavior even in heterogeneous systems.
• Findings can be applied to optimize molecular search and assembly processes on surfaces.