We report here a review of particle-laden interfaces. We discuss the importance of the particle’s wettability, accounted for by the definition of a contact angle, on the attachment of particles to the fluid interface and how the contact angle is strongly affected by several physicochemical parameters. The different mechanisms of interfacial assembly are also addressed, being the adsorption and spreading the most widely used processes leading to the well-known adsorbed and spread layers, respectively. The different steps involved in the adsorption of the particles and the particle-surfactant mixtures from bulk to the interface are also discussed. We also include here the different equations of state provided so far to explain the interfacial behavior of the nanoparticles. Finally, we discuss the mechanical properties of the interfacial particle layers via dilatational and shear rheology. We emphasize along that section the importance of the shear rheology to know the intrinsic morphology of such particulate system and to understand how the flow-field-dependent evolution of the interfacial morphology might eventually affect some properties of materials such as foams and emulsions. We dedicated the last section to explaining the importance of the particulate interfacial systems in the stabilization of foams and emulsions.

The interaction of carbon black particles (CB) with 1,2-dipalmitoyl-sn-glycerol-3-phosphocholine (DPPC) at the water/air interface has been investigated by means of a pool of surface sensitive techniques, in order to analyze the thermodynamic and rheological aspects of these mixed systems. The incorporation of carbonaceous particles to the lipid monolayers induces changes on the surface pressure–area isotherm, as revealed by the shifting to higher surface area of the maximum packing degree of the monolayer, and the decrease of the collapse pressure. These changes are strongly dependent on the DPPC:CB weight ratio at the interface and can be explained by the disruption of the monolayer structure due to the particle incorporation that provokes the modification of the cohesive interactions along the monolayer. Measurements of dilational viscoelasticity against frequency, at different degrees of monolayer compression, have been performed by means of the Oscillatory Barrier method. The rheological response of the monolayer is only slightly affected by the presence of CB, even if a modification of the quasi–equilibrium dilational elasticity, as well as of the frequency dependence of the viscoelastic modulus, is appreciable increasing the particle concentration. Being DPPC the major component of many systems with biological interest (cell membranes, lung surfactant), the results obtained here are expected to contribute to the understanding of the carbon particle interaction with biological relevant systems.

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An experimental study is here presented on the properties of aqueous dispersions containing carbon nanoparticles and different ionic surfactants which can modify the degree of hydrophobicity/philicity of particles favoring their transfer from the dispersion bulk to the interfacial layer. Aim of this work is to understand the particle-surfactant and particle-fluid interface interactions and their effect on those macroscopic surface properties of the mixed systems which are expected related to the stability and structure of the respective particle stabilized foams. To this purpose a systematic characterization of dispersions have been carried out, based on surface tension measurement against the surfactant concentration, using a drop Profile Analysis Tensiometer (PAT). These results have been crossed with the characterization of the bulk dispersion by Dynamic Light Scattering (DLS) and ζ-potential measurements to check the effects of surfactant on the particle aggregation and on the particle surface charge, respectively. The stability of the foams obtained with the same compositions has been also investigated and correlated to the other surface and bulk properties.

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