Assessment of nanoparticle immersion depth at liquid interfaces from chemically equivalent macroscopic surfaces

Area of Science:

• Colloid and surface science
• Materials science

Background:

• Wettability of nanoparticles (NPs) is crucial for applications like emulsion formulation and water remediation.
• Predicting NP wettability from macroscopic measurements is challenging due to surface complexities.

Purpose of the Study:

• To determine if macroscopic contact angles (mCAs) can accurately predict the wettability of nanoparticles (NPs) at liquid interfaces.
• To assess the influence of surface roughness and electrokinetic potential on NP wettability predictions.

Main Methods:

• Compared wettability of pure silica and amino-terminated silica NPs with macroscopic surfaces of varying roughness.
• Utilized electrophoretic light scattering and streaming current analysis to confirm surface chemistry equivalence.
• Measured advancing (ACAs) and receding contact angles (RCAs) and employed X-ray reflectivity (XRR) to determine NP wettability.

Main Results:

• Receding contact angles (RCAs) on smooth surfaces generally correlate well with NP wetting properties.
• Macroscopic contact angles alone are insufficient to predict adsorption barriers that hinder NP adsorption to interfaces.
• Pure silica nanoparticles exhibited adsorption barriers not predicted by mCAs alone.

Conclusions:

• While mCAs provide insights, they cannot fully predict NP interfacial behavior without considering adsorption phenomena.
• The study facilitates NP wettability assessment for diverse applications by highlighting the importance of RCA and adsorption barrier evaluation.