title: Analysis of Gibbs monolayer adsorbed at the toluene/water interface by UV-visible partial internal reflection spectrometry.
abstract: Gibbs monolayers of lipophilic tetraphenylporphyrinatomanganese(III) and hydrophilic diacid of meso-tetrakis(4-sulfonatopheny)porphyrin adsorbed at the liquid-liquid interface have been analyzed by UV-visible external reflection (ER) and partial internal reflection (PIR) spectra measured at different angles of incidence. The angle-dependent ER and PIR spectra over the Brewster angles (thetaERB and thetaIRB) have readily been measured at the toluene/water interface. As preliminarily expected in our previous study, the present study has first proved that the reflection-absorbance of UV-visible PIR spectra quantitatively agrees with the theoretical calculations for the Gibbs monolayer over thetaIRB. In addition, it has also been proved that the absorbance of the PIR spectra is greatly enhanced in comparison to that of the ATR spectra. The enhancement is caused by an optical effect in the monolayer sandwiched between two phases of toluene and water that have different but refractive indices close to each other. This optical enhancement requires an optically perfect contact between the phases, which is difficult to prepare for a solid-solid contact. At the liquid/liquid interface, however, an ideal optical contact is easily realized, which makes the enhancement as much as the theoretical expectation. The PIR spectrometry will be recognized to be a new high-sensitive analytical tool to study Gibbs monolayer at the liquid/liquid interface.
authors.affiliation: Department of Materials-process Engineering and Applied Chemistry for Environments, Faculty of Engineering and Resource Science, Akita University, 1-1 Tegata Gakuen-machi, Akita 010-8502, Japan.
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Moriya
authors.forename: Takeshi
authors.initials: T
authors.lastname: Hasegawa
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Okada
authors.forename: Nobuaki
authors.initials: N
authors.lastname: Ogawa
authors.forename: Erika
authors.initials: E
authors.lastname: Kawai
authors.forename: Kosuke
authors.initials: K
authors.lastname: Abe
authors.forename: Masataka
authors.initials: M
authors.lastname: Ogasawara
authors.forename: Sumio
authors.initials: S
authors.lastname: Kato
authors.forename: Shinichi
authors.initials: S
authors.lastname: Nakata
mesh_terms: D000143:Acids / Q000737:chemistry; D000327:Adsorption; D002412:Cations; D057927:Hydrophobic and Hydrophilic Interactions; D008345:Manganese / Q000737:chemistry*; D008567:Membranes, Artificial; D008962:Models, Theoretical; D009942:Organometallic Compounds / Q000737:chemistry*; D011166:Porphyrins / Q000737:chemistry*; D013057:Spectrum Analysis / Q000379:methods; D013499:Surface Properties; D013997:Time Factors; D014050:Toluene / Q000737:chemistry*; D014867:Water / Q000737:chemistry*
chemical_list: D000143:Acids; D002412:Cations; D008567:Membranes, Artificial; D009942:Organometallic Compounds; D011166:Porphyrins; C092400:meso-tetrakis(4-sulfonatophenyl)porphyrin; C409084:tetraphenylporphyrin; D014867:Water; D014050:Toluene; D008345:Manganese