title: Low-Vacuum Deposition of Glutamic Acid and Pyroglutamic Acid: A Facile Methodology for Depositing Organic Materials beyond Amino Acids.
abstract: Thin layers of pyroglutamic acid (Pygl) have been deposited by thermal evaporation of the molten L-glutamic acid (L-Glu) through intramolecular lactamization. This deposition was carried out with the versatile handmade low-vacuum coater, which was simply composed of a soldering iron placed in a vacuum degassing resin chamber evacuated by an oil-free diaphragm pump. Molecular structural analyses have revealed that thin solid film evaporated from the molten L-Glu is mainly composed of L-Pygl due to intramolecular lactamization. The major component of the L-Pygl was in β-phase and the minor component was in γ-phase, which would have been generated from partial racemization to DL-Pygl. Electron microscopy revealed that the L-Glu-evaporated film generally consisted of the 20 nm particulates of Pygl, which contained a periodic pattern spacing of 0.2 nm intervals indicating the formation of the single-molecular interval of the crystallized molecular networks. The DL-Pygl-evaporated film was composed of the original DL-Pygl preserving its crystal structures. This methodology is promising for depositing a wide range of the evaporable organic materials beyond amino acids. The quartz crystal resonator coated with the L-Glu-evaporated film exhibited the pressure-sensing capability based on the adsorption-desorption of the surrounding gas at the film surface.
authors.affiliation: School of Computer Science, Tokyo University of Technology, Katakura, Hachioji, Tokyo 192-0982, Japan ; Graduate School of Bionics, Tokyo University of Technology, Katakura, Hachioji, Tokyo 192-0982, Japan.
authors.forename: Iwao
authors.initials: I
authors.lastname: Sugimoto
authors.affiliation: Graduate School of Bionics, Tokyo University of Technology, Katakura, Hachioji, Tokyo 192-0982, Japan ; Shiseido Co., Ltd., Higashi-shimbashi, Minato-ku, Tokyo 105-8310, Japan.
authors.forename: Shunsaku
authors.initials: S
authors.lastname: Maeda
authors.affiliation: School of Computer Science, Tokyo University of Technology, Katakura, Hachioji, Tokyo 192-0982, Japan.
authors.forename: Yoriko
authors.initials: Y
authors.lastname: Suda
authors.affiliation: Bionanotechnology Center, Tokyo University of Technology, Katakura, Hachioji, Tokyo 192-0982, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Makihara
authors.affiliation: Faculty of Science and Engineering, Doshisha University, Kyotanabe, Kyoto 610-0321, Japan.
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Takahashi