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Association in Like-Charged Surfactant-Nanoparticle Systems: Interfacial and Bulk Effects
Manaswini Gowtham V1, Swaraj Deodhar1, Sumesh P Thampi1
1Polymer Engineering and Colloid Science Laboratory, Department of Chemical Engineering, Indian Institute of Technology Madras, Chennai, Tamil Nadu 600036, India.
Langmuir : the ACS Journal of Surfaces and Colloids
|August 20, 2024
Summary
Surfactant molecules surprisingly adsorb onto similarly charged nanoparticles, altering particle and interface properties. This phenomenon, driven by electrostatic interactions, impacts dispersion characteristics but not bulk properties like critical micelle concentration.
Area of Science:
- Colloid and Surface Science
- Materials Chemistry
- Physical Chemistry
Background:
- The interaction between similarly charged surfactants and nanoparticles in aqueous solutions is poorly understood, with conflicting literature findings.
- Investigating these interactions is crucial for applications involving nanoparticle dispersions and interfacial phenomena.
Purpose of the Study:
- To fundamentally investigate bulk and interfacial phenomena in binary mixtures of similarly charged nanoparticles and surfactants.
- To elucidate the role of electrostatic interactions in surfactant-particle complexation.
Main Methods:
- Studied binary mixtures of positively charged nanoparticles with cationic surfactants and negatively charged nanoparticles with anionic surfactants.
- Analyzed bulk and interfacial properties, including particle size, zeta potential, surface tension, and surface excess concentration.
- Varied pH to explore the influence of electrostatic interactions on surfactant-particle complexation.
Main Results:
- Surfactant molecules adsorb onto nanoparticle surfaces despite like charges, leading to particle supercharging.
- Significant changes observed in dispersed species properties (size, zeta potential) and interfacial properties (surface tension, surface excess concentration).
- Effect is more pronounced at low surfactant concentrations and independent of nanoparticle size or surfactant-particle combination; critical micelle concentration remains largely unchanged.
Conclusions:
- Electrostatic interactions play a key role in surfactant-particle complexation, driving adsorption and interfacial changes.
- The adsorption of surfactants onto similarly charged nanoparticles is a significant phenomenon affecting dispersion and interfacial behavior.
- While bulk properties like critical micelle concentration are unaffected, interfacial and dispersion properties are significantly altered by these interactions.
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