Patch-distribution effect on diffusion-limited process in dilute suspension of partially active spheres

Area of Science:

• Colloidal science
• Chemical kinetics
• Computational physics

Background:

• Diffusion-limited reactions are crucial in many chemical and biological processes.
• Understanding how particle surface properties, like active patch distribution, influence reaction rates is essential.

Purpose of the Study:

• To investigate the relationship between active patch distribution on spheres and their overall reaction rate constants.
• To quantify the impact of patch distribution and coverage on diffusion-limited reaction dynamics.

Main Methods:

• Utilized sped-up Brownian dynamic simulations to model diffusion-limited processes.
• Introduced a dimensionless separation index (Is) to characterize patch distribution states (0 for compact, 1 for loose).
• Analyzed the normalized overall rate constant (kp/kf) as a function of the separation index.

Main Results:

• A strong, positive, linear correlation was observed between the normalized rate constant (kp/kf) and the separation index (Is) at fixed patch coverage.
• The sensitivity of kp/kf to patch separation depends on patch coverage and size.
• Maximum sensitivity occurs at a specific patch coverage that increases with patch size; larger patches reduce maximum sensitivity.

Conclusions:

• The spatial distribution of active patches on spherical particles significantly impacts overall reaction rates in diffusion-limited systems.
• The developed separation index provides a quantitative measure for predicting reaction kinetics based on particle surface heterogeneity.
• Findings offer a framework for designing colloidal systems with tunable reactivity by controlling patch distribution and size.