title: Formation of Langmuir Monolayers of Titanium Dioxide Nanoparticles at Air/Aqueous Interfaces by the Addition of Ions to the Subphase: Effect of Ion Concentration and Type.
abstract: A Langmuir monolayer of bare, hydrophilic TiO2 nanoparticles (diameter = 75 nm) was formed at an air/pH 5.8 aqueous interface by adding salt to the subphase. The effect of the concentration and type of salt in the subphase on the surface pressure-area per particle isotherms was determined. Increasing the concentration of NaCl from 0 to 3.8 M increased the maximum surface pressure (Πmax) and shifted the isotherms to a larger area per particle. The ion type also affected the area at which the close packing commenced and the value of Πmax. The presence of salt in the subphase also stabilized SiO2 nanoparticles, suggesting that the ions in the subphase interacted with the dioxide groups on the particles. The combination of structure making or borderline ions with structure breaking ions (LiCl, MgCl2, NaCl, and CaCl2) appeared to stabilize the particulate monolayers more than the combination of structure breaking ions (KBr and KCl). These results suggested that the particles were stabilized by a hydrogen bond network between the particles or the formation of a salt bridge between the particles. Attractions between particles at the air/aqueous interface caused the particles to aggregate, resulting in the particles becoming more stable at the air/aqueous interface.
authors: Department of Chemistry and Materials, Faculty of Textile Science and Technology, Shinshu University , Tokida 3-15-1, Ueda, Nagano 386-8567, Japan.
authors: Yuya
authors: Y
authors: Iwafuji
authors: Department of Chemistry and Materials, Faculty of Textile Science and Technology, Shinshu University , Tokida 3-15-1, Ueda, Nagano 386-8567, Japan.
authors: Cathy E
authors: CE
authors: McNamee
mesh_terms: D006860:Hydrogen Bonding; D007477:Ions; D008567:Membranes, Artificial; D053758:Nanoparticles / Q000737:chemistry*; D014025:Titanium / Q000737:chemistry*; D014867:Water / Q000737:chemistry*
chemical_list: D007477:Ions; D008567:Membranes, Artificial; D014867:Water; C009495:titanium dioxide; D014025:Titanium