Surfactant and hydrocarbon aggregates on defective graphite surface: structure and dynamics

Area of Science:

• Surface Science
• Materials Chemistry
• Computational Chemistry

Background:

• Understanding molecular self-assembly on surfaces is crucial for designing advanced materials.
• Graphite surfaces with defects present unique environments for studying adsorption and aggregation phenomena.
• Sodium dodecyl sulfate (SDS) and dodecane (C12) are model amphiphilic molecules relevant to surfactant behavior.

Purpose of the Study:

• To investigate the impact of point (vacancies) and line (steps) defects on graphite surfaces on the aggregation kinetics and structure of sodium dodecyl sulfate (SDS) and dodecane (C12).
• To explore the potential of surface defects for controlling the localization and orientation of molecular aggregates.

Main Methods:

• Molecular dynamics simulations were employed to model the behavior of SDS and C12 molecules on graphite surfaces.
• Simulations considered surfaces with varying types and arrangements of defects, including vacancies and step edges.
• Analysis focused on aggregate formation, molecular orientation, and the influence of defect geometry.

Main Results:

• Vacancies on the graphite surface were found to hinder the formation of extended aggregates without significantly altering molecular orientational bias.
• Line defects, specifically surface steps, effectively localized SDS and C12 aggregates near the step edges.
• A tunable orientational bias of the aggregates along the step edges was observed, dependent on terrace widths.

Conclusions:

• Surface defects, particularly line defects like steps, can act as templates to control the spatial arrangement and orientation of surfactant aggregates on graphite.
• The findings suggest a strategy for fabricating patterned molecular domains by exploiting surface topography.
• This research provides insights into defect-mediated self-assembly for potential applications in nanotechnology and surface patterning.