title: Optically probing nanoemulsion compositions.
abstract: Many types of colloids, including nanoemulsions, which contain sub-100 nm droplets, are dispersed in molecular and micellar solutions, especially surfactant solutions that confer stability. Since it would be desirable to measure the droplet volume fraction ϕ and surfactant concentration C of a nanoemulsion non-destructively, and since the droplet and surfactant structures are significantly smaller than the shortest wavelengths of visible light, optical refractometry could provide a simple and potentially useful approach. By diluting a silicone oil-in-water nanoemulsion having an unknown ϕ and C with pure water, measuring its refractive index n(ϕ,C) using an Abbé refractometer, and fitting the result using a prediction for n that treats the nanoemulsion as an effective medium, we show that ϕ and C can be deduced accurately over a relatively wide range of compositions. Moreover, we generalize this approach to other types of nanoemulsions in which a molecular constituent partitions in varying degrees between the dispersed and the continuous phases.
authors.affiliation: Department of Chemistry and Biochemistry, University of California-Los Angeles, 607 Charles Young Dr East, Los Angeles, CA 90077, USA.
authors.forename: Xiaoming
authors.initials: X
authors.lastname: Zhu
authors.forename: Michael M
authors.initials: MM
authors.lastname: Fryd
authors.forename: Jung-Ren
authors.initials: JR
authors.lastname: Huang
authors.forename: Thomas G
authors.initials: TG
authors.lastname: Mason
mesh_terms: D004655:Emulsions / Q000737:chemistry*; D036103:Nanotechnology; D012031:Refractometry; D012827:Silicone Oils / Q000737:chemistry; D013501:Surface-Active Agents / Q000737:chemistry; D014867:Water / Q000737:chemistry
chemical_list: D004655:Emulsions; D012827:Silicone Oils; D013501:Surface-Active Agents; D014867:Water