title: 2D "soap"-assembly of nanoparticles via colloid-induced condensation of mixed Langmuir monolayers of fatty surfactants.
abstract: We describe a new type of colloidal 2D gels formed in mixed Langmuir monolayers of stearic acid and octadecylamine on a surface of gold hydrosol. The adsorption of gold nanoparticles on the mixed monolayer led to an increase of interactions between oppositely charged surfactants giving a "soap" of mixed fatty salt. The observed effect is equivalent to a virtual "cooling" of floating monolayer, which undergoes rapid condensation on a surface of aqueous colloid. The consequent shrinking and rearrangement of the monolayer resulted in aggregation of nanoparticles into colloidal 2D "soap"-gels, which represented arrested colloidal phases within nonadsorbing organic medium. When sequentially deposited onto solids by Langmuir-Blodgett technique, the 2D "soap"-gels separated into organic and colloidal phases and gave dendrite-like bilateral organic crystallites coated with gold nanoparticles. The reported colloidal "soap"-assembly can offer a new opportunity to design 2D colloidal systems of widely variable chemistry and structures.
authors.affiliation: Frumkin Institute of Physical Chemistry and Electrochemistry RAS, 31 Leninsky prospect, Moscow 119991, Russia.
authors.forename: Denis I
authors.initials: DI
authors.lastname: Babenko
authors.forename: Alexander A
authors.initials: AA
authors.lastname: Ezhov
authors.forename: Dmitry S
authors.initials: DS
authors.lastname: Turygin
authors.forename: Vladimir A
authors.initials: VA
authors.lastname: Ivanov
authors.forename: Vladimir K
authors.initials: VK
authors.lastname: Ivanov
authors.forename: Vladimir V
authors.initials: VV
authors.lastname: Arslanov
authors.forename: Maria A
authors.initials: MA
authors.lastname: Kalinina