Interfacial Properties Of Nanoparticles Research Articles

Effects of chain length of surfactants and their adsorption on nanoparticles on stability of CO2-in-water emulsions

Hydrophilic silica nanoparticles (NPs) were employed to stabilize CO2-in-water (C/W) emulsions with three cationic homolog surfactants. In order to explore the effect of surfactant adsorption different alkyl chain lengths and concentrations on the NP surface on NPs’ potential and agglomeration size, zeta potential, particle size analysis and adsorption isotherms were quantitatively characterized by experiments. The distribution of interfacial active substances at the interface affected the emulsion stability. Therefore, the influence of surfactant adsorption on the interfacial properties of NPs was determined by surface tension and contact angle characterization. The results demonstrated that surfactant adsorption on NPs would form vertically oriented bilayer adsorption owing to an increase in surfactant concentration. Surfactants adsorbed onto negatively charged NPs as a monolayer due to electrostatic attraction of hydrophilic head groups, leading to the increase of NPs’ hydrophobicity. Sufficient surfactant bilayer adsorption on the NP surface by virtue of tail chain interactions also altered particles’ wettability. The equilibrium adsorption values of the homologous surfactants on the NP surface were almost identical. However, for the synergistic emulsification of single surfactant and NPs, the surfactant with the longer alkyl chain would achieve its optimum performance with NPs at the lower concentration.

Influences of nano-effect on the thermodynamic properties of solid–liquid interfaces: theoretical and experimental researches

Nano-effect has a significant influence on the interfacial properties of nanoparticles. When r < 10 nm, the relationships between the interfacial thermodynamic properties and the reciprocal of radius deviate from linear behavior.

THE EFFECT OF RESIDUAL POLY(VINYL ALCOHOL) ON BIOPHYSICAL INTERACTION OF NANOPARTICLES WITH ENDOTHELIAL CELL MODEL MEMBRANE

Poly(vinyl alcohol) (PVA) is commonly used as an emulsifier in the formulation of nanoparticles (NPs) comprising poly DL-lactide co-glycolide and polylactide-based biodegradable polymers for drug and gene delivery applications. A fraction of PVA remains associated with the NPs at the interface despite their repeated washing (residual PVA). We hypothesize that this residual PVA influences the interfacial properties of NPs and hence their biophysical interactions with membrane lipids. In this study, we formulated NPs using PVA of different molecular weights to determine the effects of the residual PVA on biophysical interactions of the formulated NPs with the endothelial cell model membrane using a Langmuir balance. Despite similar physical properties (particle size and zeta potential), NPs formulated with different PVA demonstrated significant variations in their intrinsic surface properties and biophysical interactions with the model membrane. This was evident from the difference in the surface pressure–area (π–A) isotherms prepared in the presence of different formulations of NPs and the change in surface pressure of the model membrane following interaction with NPs. The variation in the biophysical properties was observed even with the NPs formulated using the same molecular weight PVA but obtained from different lots. Since the interfacial properties of NPs can significantly influence NP interactions with cells and tissue, their biophysical characterization could prove to be an important parameter not only to obtain consistent results with NPs but also to optimize their properties for drug/gene delivery applications.

From dispersed nano-objects to solutions—A thermodynamic approach

Nanotechnologies take now a wide interest both in the applied and fundamental concerns. The interfacial properties of nano-particles at the fluid–fluid interfaces question the physicist on the extension of the Gibbs surface thermodynamics to interfaces in which nano-particles are entrapped as dispersion stabilizers [K.D. Danov, P.A. Kralchevsky, J. Colloid Interface Sci. 298 (2006) 213] (foams or emulsions). An attempt is proposed to give the physical meaning of the measured surface properties of nano-particles attached to fluid–fluid interfaces like the so-called dynamic surface tension and surface dilational elasticity of suspensions in terms of wetting of the particles at the interface. The Hill [T.L. Hill, Thermodynamics of Small Systems, W.A. Benjamin, New York, 1963] theory for small systems linked to the dissipation fluctuation theorem should give a deeper insight in the statistical mechanics understanding of the interfacial region in which nano-particles are imbedded.