title: How to prepare and stabilize very small nanoemulsions.
abstract: Practical and theoretical considerations that apply when aiming to formulate by ultrasonication very small nanoemulsions (particle diameter up to 150 nm) with very high stability are presented and discussed. The droplet size evolution during sonication can be described by a monoexponential function of the sonication time, the characteristic time scale depending essentially on the applied power. A unique master curve is obtained when plotting the mean diameter size evolution as a function of sonication energy. We then show that Ostwald ripening remains the main destabilization mechanism whereas coalescence can be easily prevented due to the nanometric size of droplets. The incorporation of "trapped species" within the droplet interior is able to counteract Ostwald ripening, and this concept can be extended to the membrane compartment. We finally clarify that nanoemulsions are not thermodynamically stable systems, even in the case where their composition lies very close to the demixing line of a thermodynamically stable microemulsion domain. However, as exemplified in the present work, nanoemulsion systems can present very long-term kinetic stability.
authors.affiliation: CEA-LETI, Campus MINATEC, Département des Technologies pour la Biologie et la Santé, 17 rue des Martyrs, F-38054 Grenoble, France.
authors.forename: Thomas
authors.initials: T
authors.lastname: Delmas
authors.forename: Hélène
authors.initials: H
authors.lastname: Piraux
authors.forename: Anne-Claude
authors.initials: AC
authors.lastname: Couffin
authors.forename: Isabelle
authors.initials: I
authors.lastname: Texier
authors.forename: Françoise
authors.initials: F
authors.lastname: Vinet
authors.forename: Philippe
authors.initials: P
authors.lastname: Poulin
authors.forename: Michael E
authors.initials: ME
authors.lastname: Cates
authors.forename: Jérôme
authors.initials: J
authors.lastname: Bibette
mesh_terms: D004655:Emulsions / Q000737:chemistry*; D008567:Membranes, Artificial; D049329:Nanostructures / Q000737:chemistry*; D013010:Sonication; D013501:Surface-Active Agents / Q000737:chemistry
chemical_list: D004655:Emulsions; D008567:Membranes, Artificial; D013501:Surface-Active Agents