Stratification during evaporative assembly of multicomponent nanoparticle films

Area of Science:

• Materials Science
• Colloid Science
• Surface Science

Background:

• Multicomponent coatings with distinct functionalities are crucial for advanced applications like electronics, energy storage, and biomaterials.
• Traditional methods for creating such films involve multiple deposition steps, which are time-consuming and complex.
• Recent theoretical models describe particle stratification during film formation, particularly concerning the particle Peclet number (Pe).

Purpose of the Study:

• To explore a single-step method for creating multicomponent stratified films by manipulating particle Peclet numbers (Pe).
• To investigate the influence of varying particle sizes and evaporation rates on film stratification.
• To test theoretical predictions of stratification phenomena in different Pe regimes.

Main Methods:

• Fabrication of films containing poly(styrene) nanoparticles (25-90 nm) and silica nanoparticles (8-14 nm).
• Utilized a controlled range of particle Peclet numbers (Pe ≈ 0.3-4), distinct from previous studies using high Pe values (120-460).
• Atomic Force Microscopy (AFM) was employed to analyze the surface composition and stratification of the films.

Main Results:

• Demonstrated evidence of particle stratification in the single-step fabricated films.
• Observed a qualitative agreement between experimental results and theoretical predictions regarding the effect of the Pe ratio on stratification.
• Validated recent theoretical models that predict distinct stratification regimes (large-on-top vs. small-on-top) based on drying dynamics.

Conclusions:

• A single-step method utilizing controlled particle Peclet numbers is effective for creating stratified multicomponent films.
• The findings support theoretical frameworks for particle stratification during colloidal film formation.
• This approach offers a simplified route to fabricating functional coatings for various technological applications.