title: The role of oleic acid: from synthesis to assembly of perovskite nanocuboid two-dimensional arrays.
abstract: Oleic acid, an 18-carbon chain fatty acid, has been widely used as a surfactant to fabricate colloidal nanocrystals. In previous work, we discovered a lamellar microemulsion strategy to fabricate sub-20 nm SrTiO(3) nanocuboids using oleic acid and oleate species. Here, we demonstrate (i) the general synthesis with lamellar microemulsions of a family of compositionally varied BaxSr(1-x)TiO(3) crystalline nanocuboids with uniform size, and (ii) subsequent assembly into two-dimensional arrays by nanoparticle-bound oleate in a nonpolar solvent. The measured interparticle distance (2.4 nm) of adjacent nanoparticles in an array is less than the length of a double oleate layer (∼4 nm). On the basis of calculations of the interfacial free energy, we propose the hydrophobic, hydrocarbon-terminated groups of oleate from adjacent nanocuboids are situated closely but do not overlap. Lower aspect ratio nanocuboids are bordered by four adjacent nanocuboids which results in a uniform direction self-assembly array, whereas higher aspect ratio nanocuboids are bordered by five or six adjacent nanocuboids and can develop an arced local coordination.
authors.affiliation: Department of Chemistry, ‡Department of Materials Science and Engineering, Northwestern University , Evanston, Illinois 60208, United States.
authors.forename: Linhua
authors.initials: L
authors.lastname: Hu
authors.forename: Chuandao
authors.initials: C
authors.lastname: Wang
authors.forename: Robert M
authors.initials: RM
authors.lastname: Kennedy
authors.forename: Laurence D
authors.initials: LD
authors.lastname: Marks
authors.forename: Kenneth R
authors.initials: KR
authors.lastname: Poeppelmeier