Measuring the three-phase contact angle of nanoparticles at fluid interfaces

Area of Science:

• Materials Science
• Surface Chemistry
• Nanotechnology

Background:

• Understanding nanoparticle wettability is crucial for applications in emulsions, coatings, and drug delivery.
• Directly measuring nanoparticle wettability at liquid interfaces is challenging due to their small size and the dynamic nature of interfaces.

Purpose of the Study:

• To develop and validate a generic technique for imaging and studying the wettability of spherical nanoparticles adsorbed at liquid surfaces.
• To demonstrate the imprinting of nanoparticle monolayers at air-water and oil-water interfaces.
• To determine the three-phase contact angle of nanoparticles at liquid interfaces using atomic force microscopy (AFM).

Main Methods:

• A novel imprinting technique to create stable replicas of nanoparticle monolayers at liquid interfaces.
• Atomic force microscopy (AFM) analysis of the imprinted replica to reconstruct the nanoparticle arrangement and measure the three-phase contact angle.
• Testing the technique with four distinct types of nanoparticles, including those with a radius as small as 37 nm.

Main Results:

• Successful imprinting of nanoparticle monolayers at both air-water and oil-water interfaces.
• Demonstrated ability to accurately determine the three-phase contact angle of nanoparticles from the AFM scan of the replica.
• The technique proved effective for nanoparticles down to 37 nm in radius.

Conclusions:

• The developed generic technique provides a robust method for characterizing nanoparticle wettability at liquid interfaces.
• This approach enables precise measurement of the three-phase contact angle, essential for predicting nanoparticle behavior in complex systems.
• The technique's versatility and scalability make it valuable for advancing nanoparticle science and engineering.