How to prepare and stabilize very small nanoemulsions

Area of Science:

• Colloid and Surface Science
• Materials Science
• Chemical Engineering

Background:

• Nanoemulsions are crucial in various applications, but achieving long-term stability, especially for very small particle sizes, remains a challenge.
• Understanding the destabilization mechanisms like Ostwald ripening and coalescence is key to formulating stable nanoemulsions.

Purpose of the Study:

• To present practical and theoretical considerations for formulating highly stable nanoemulsions (particle diameter ≤ 150 nm) using ultrasonication.
• To investigate droplet size evolution, destabilization mechanisms, and strategies for enhancing nanoemulsion stability.

Main Methods:

• Utilizing ultrasonication to formulate nanoemulsions and analyzing droplet size evolution over time.
• Investigating the impact of sonication power and energy on droplet size.
• Examining the role of trapped species in counteracting Ostwald ripening.

Main Results:

• Droplet size evolution during sonication follows a monoexponential function dependent on applied power, forming a master curve with sonication energy.
• Ostwald ripening is identified as the primary destabilization mechanism, while coalescence is minimized due to small droplet size.
• Incorporating trapped species effectively inhibits Ostwald ripening, extending the kinetic stability of nanoemulsions.

Conclusions:

• Ultrasonication is an effective method for producing highly stable, small nanoemulsions.
• While nanoemulsions are not thermodynamically stable, strategies like incorporating trapped species can achieve significant long-term kinetic stability.
• The findings provide valuable insights for the rational design and formulation of stable nanoemulsion systems.