title: Pickering emulsions prepared by layered niobate K₄Nb₆O₁₇ intercalated with organic cations and photocatalytic dye decomposition in the emulsions.
abstract: We investigated emulsions stabilized with particles of layered hexaniobate, known as a semiconductor photocatalyst, and photocatalytic degradation of dyes in the emulsions. Hydrophobicity of the niobate particles was adjusted with the intercalation of alkylammonium ions into the interlayer spaces to enable emulsification in a toluene-water system. After the modification of interlayer space with hexylammonium ions, the niobate stabilized water-in-oil (w/o) emulsions in a broad composition range. Optical microscopy showed that the niobate particles covered the surfaces of emulsion droplets and played a role of emulsifying agents. The niobate particles also enabled the generation of oil-in-water (o/w) emulsions in a limited composition range. Modification with dodecylammonium ions, which turned the niobate particles more hydrophobic, only gave w/o emulsions, and the particles were located not only at the toluene-water interface but also inside the toluene continuous phase. On the other hand, interlayer modification with butylammonium ions led to the formation of o/w emulsions. When porphyrin dyes were added to the system, the cationic dye was adsorbed on niobate particles at the emulsion droplets whereas the lipophilic dye was dissolved in toluene. Upon UV irradiation, both of the dyes were degraded photocatalytically. When the cationic and lipophilic porphyrin molecules were simultaneously added to the emulsions, both of the dyes were photodecomposed nonselectively.
authors: Department of Applied Chemistry, Kyushu Institute of Technology, 1-1 Sensui-cho, Tobata-ku, Kitakyushu-shi, Fukuoka 804-8550, Japan. nakato@che.kyutech.ac.jp
authors: Teruyuki
authors: T
authors: Nakato
authors: Hiroaki
authors: H
authors: Ueda
authors: Sachika
authors: S
authors: Hashimoto
authors: Ryosuke
authors: R
authors: Terao
authors: Miyuki
authors: M
authors: Kameyama
authors: Emiko
authors: E
authors: Mouri
mesh_terms: D000327:Adsorption; D002384:Catalysis; D002412:Cations; D004396:Coloring Agents / Q000737:chemistry*; D004655:Emulsions; D007477:Ions; D008853:Microscopy / Q000379:methods; D008856:Microscopy, Fluorescence / Q000379:methods; D008968:Molecular Conformation; D009556:Niobium / Q000737:chemistry*; D009821:Oils; D009930:Organic Chemicals / Q000737:chemistry*; D010087:Oxides / Q000737:chemistry*; D010777:Photochemistry / Q000379:methods*; D011166:Porphyrins / Q000737:chemistry; D011188:Potassium / Q000737:chemistry*; D000644:Quaternary Ammonium Compounds / Q000737:chemistry; D014466:Ultraviolet Rays; D014867:Water / Q000737:chemistry
chemical_list: D002412:Cations; D004396:Coloring Agents; D004655:Emulsions; D007477:Ions; D009821:Oils; D009930:Organic Chemicals; D010087:Oxides; D011166:Porphyrins; D000644:Quaternary Ammonium Compounds; D009556:Niobium; D014867:Water; C477466:potassium niobate; D011188:Potassium