Super-resolution microscopy on single particles at fluid interfaces reveals their wetting properties and interfacial...

Area of Science:

• Colloid and interface science
• Super-resolution microscopy
• Nanoparticle characterization

Background:

• Solid particles at fluid interfaces stabilize Pickering emulsions.
• Particle contact angle (θ) is key to colloid properties.
• Existing methods lack simultaneous particle and interface visualization.

Purpose of the Study:

• To develop and apply a novel super-resolution microscopy technique for in situ measurement of nanoparticle contact angles.
• To investigate the influence of particle properties on interfacial behavior.

Main Methods:

• Utilized iPAINT (in situ photo-activatable localization microscopy) with fluorescent probes.
• Achieved nanometer accuracy in localizing nanoparticles and fluid interfaces.
• Applied to spherical and elliptical particles at liquid-liquid interfaces.

Main Results:

• Successfully determined single particle contact angles for hydrophobic and hydrophilic colloids.
• Observed a significant dependence of contact angle on particle size, inferring effective line tension.
• Captured interfacial deformations induced by elliptical particles.

Conclusions:

• iPAINT microscopy provides unprecedented simultaneous visualization of nanoparticles and fluid interfaces.
• Particle size influences contact angle, impacting interfacial behavior.
• The method is effective for characterizing particle-interface interactions and interfacial deformations.