| 1. |
玉田 薫, 特集 「女性の翼を折らない組織作りとは」 ポリモルフィアVol.8, P20-33(2023年3月）, ポリモルフィアVol.8, P20-33, 2022.03, 2021-2023年の間に東京大学、北海道大学、千葉大学にて行なったダイバーシティ推進に関わる依頼公演の内容をまとめたもので、九州大学のダイバーシティ推進の過去〜現在〜未来の方向性をまとめて提示してある。. |
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玉田 薫, 無機表面から有機表面へ：ソフトナノテクノロジー分野の進展, 表面と真空 特集「21世紀序盤の表面真空科学技術の進展―e-JSSNT創刊20周年記念特集―」, https://doi.org/10.1380/vss.66.271, 2023.05. |
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Kaoru Tamada, From Inorganic to Organic Surfaces: Progress of Soft Nanotechnology, e-Journal of Surface Science and Nanotechnology, https://doi.org/10.1380/ejssnt.2023-035, 2023.05. |
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玉田 薫, DEI推進のために日本の大学はどう変わっていくべきか, 表面と真空 2023 年 66 巻 1 号 p. 64-65, https://doi.org/10.1380/vss.66.64, 2023.01. |
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玉田 薫, 研究と人間と, 化学と工業, Vol.75-7, 2022.07. |
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玉田 薫, 差別均衡から平等均衡を目指す：これからの理工系学会のあるべき姿とは, 表面と真空 2022 年 65 巻 6 号 p. 290-291, https://doi.org/10.1380/vss.65.290, 2022.06. |
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玉田 薫, 事例分析から考えるーPBL型教育と課題認識, 月刊経団連, 2020.06. |
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玉田 薫, 和賀三和子, 理工系分野女性研究者の活躍促進に向けて：日米の事例から将来を展望する, 表面と真空, doi.org/10.1380/vss.63.314, 2020.06. |
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増田志穂美, 玉田薫, 金属微粒子シートによる細胞接着ナノ界面の可視化, 膜（日本膜学会）, 45,3, 115, 2020.05. |
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増田志穂美, 玉田薫, LSPRシートによる細胞接着ナノ界面の観察法, メディカルサイエンスダイジェスト：医療用AI技術の最前線, Vol.46, 52-55, 2020.03. |
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玉田 薫, ダイバーシティ・キックオフシンポジウム開催報告, 表面と真空 2019 年 62 巻 3 号 p. 170, https://doi.org/10.1380/vss.62.170, 2019.03. |
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玉田薫, プラズモニックナノシートの特性と蛍光増強, 化学と工業, 2014.10. |
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玉田薫, 金属微粒子シートによるフルカラーコーテイング, 色材協会誌, 2014.08. |
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玉田薫, 岡本 晃一, 銀微粒子によるプラズモニックナノシートの作製と応用, 光アライアンス, 2013.06. |
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Koichi Okamoto, Brian Lin, Keisuke Imazu, Akihito Yoshida, Koji Toma, Mana Toma, Kaoru Tamada, Tuning Colors of Silver Nanoparticle Sheets by Multilayered Crystalline Structures on Metal Substrates, Plasmonics, 10.1007/s11468-012-9437-2, Vol.8, No.2, pp.581-590, 2013.06, We report a new concept of tuning plasmonic colors of two-dimensional crystalline silver nanoparticle sheets with layer-by-layer structures. The multilayered crystalline sheets fabricated by the Langmuir-Schaefer method keep the localized surface plasmon resonance bands at the same position (λmax = 465 nm) on quartz, while they change their colors drastically on metal substrates depending on the number of layers (one to five layers). The response of the absorption spectra was absolutely nonlinear, with maximum absorption for two or three layers. The obtained results were well reproduced by the finite difference time domain simulation. The simulation confirmed that these plasmonic colors originate not only from near-field coupling of plasmon resonance but also far-field nano-optics of the multilayered silver nanoparticle sheets. © 2012 Springer Science+Business Media, LLC.. |
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玉田薫, 岡本 晃一, 大岩さゆり, ナノ材料の自己組織化による新しい機能発現, レーザー研究, 2013.03. |
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玉田薫, 金属微粒子を使ったフルカラーコーティング, コンバーテック, 2013.03. |
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玉田 薫, 岡本 晃一, 大岩 さゆり, ナノ材料の自己組織化による新しい機能発現, レーザー研究, Vol.41, No.3, pp.184-190, 2013.03. |
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Kaoru Tamada, Shinobu Yokokawa, Gemini SAMs, Handbook of Biofunctional Surfaces, 10.4032/9789814364188, pp.31-58, 2013.01. |
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Makoto Yamamoto, Toshifumi Terui, Rieko Ueda, Keisuke Imazu, Kaoru Tamada, Takeshi Sakano, Kenji Matsuda, Hisao Ishii, Yutaka Noguchi, Photoinduced conductance switching in a dye-doped gold nanoparticle transistor, Applied Physics Letters, 10.1063/1.4733612, Vol.101, No.2, 2012.07, Photoinduced conductance switching was demonstrated in a copper phthalocyanine (CuPc)-doped gold nanoparticle (GNP) transistor formed in a nanogap electrode with a back gate structure. Two specific states were reversibly induced in conductance of the CuPc-doped devices by light irradiation and applied voltages. The probability of occurrence of conductance switching decreased with a reduction in the number of incident photons. In addition, conductance switching was not observed in the devices before CuPc doping. Conductance switching originates from change in the local potential of GNPs, possibly induced by a charge-state bistability of an individual CuPc molecule worked as a floating gate. © 2012 American Institute of Physics.. |
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玉田薫, 表面プラズモン共鳴によるバイオ計測の現状, 表面科学, 2012.04. |
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玉田薫, 無限の可能性を信じる, 表面科学, 2011.06. |
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Hyo Won Kim, M. Han, H. J. Shin, S. Lim, Y. Oh, K. Tamada, M. Hara, Y. Kim, M. Kawai, Young Kuk, Control of molecular rotors by selection of anchoring sites, Physical Review Letters, 10.1103/PhysRevLett.106.146101, Vol.106, No.14, 2011.04, We demonstrate a new method to switch on and off the rotational motion of a long-chain molecule by controlling the bonding geometry between the molecule and a substrate. An azobenzene derivative molecule adsorbed on a Au(111) surface is immobile only when its three rotation centers, comprised of two phenyl rings and a nitrogen-nitrogen bond, are located at hollow sites of the Au(111) surface, as observed by scanning tunneling microscopy. Rotational motion can be activated by exciting the vibrational modes and inducing hopping motion away from the immobile site with a voltage pulse. © 2011 American Physical Society.. |
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Takeshi Nagahiro, Kenichi Ishibashi, Yasuo Kimura, Michio Niwano, Tomohiro Hayashi, Yasuhiro Ikezoe, Masahiko Hara, Tetsu Tatsuma, Kaoru Tamada, Ag nanoparticle sheet as a marker of lateral remote photocatalytic reactions, Nanoscale, 10.1039/b9nr00240e, Vol.2, No.1, pp.107-113, 2010.01, The lateral remote photocatalytic activity of TiO2 nanotubes fabricated by anodic oxidation, was characterized by use of a ‘silver nanosheet’ as a marker. The silver nanosheet is a two-dimensional crystalline film composed of myristate-capped silver nanoparticles (d = 5 nm), which has a sharp localized plasmon absorption band at λmax = 470 nm. A quartz substrate was coated with TiO2 nanotubes to a coverage of 10% and then covered with a silver nanosheet. Upon UV irradiation a rapid decrease in the intensity of the 470 nm plasmon band and an increase in the long-wavelength absorption (550–1000 nm) band were clearly confirmed, indicating fusion of the nanoparticles due to decomposition of the myristate capping agent. Surface morphology measured by high-resolution scanning electron microscopy (SEM) and atomic force microscopy (AFM) revealed the decomposition and fusion of silver nanoparticles even in regions of the surface a micron away from the TiO2 nanotubes. © 2010 The Royal Society of Chemistry.. |
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Himadri Acharya, Jinwoo Sung, Byeong Hyeok Sohn, Dong Ha Kim, Kaoru Tamada, Cheolmin Park, Tunable surface plasmon band of position selective Ag and Au nanoparticles in thin block copolymer micelle films, Chemistry of Materials, 10.1021/cm901245g, Vol.21, No.18, pp.4248-4255, 2009.09, The manuscript describes a novel method to fabricate a thin composite film based on spin coating in which surface plasmon bands of Au and Ag nanoparticles are effectively coupled with each other because of position-selective deposition of both nanoparticles on a self-assembled block copolymer structure. Simple solution blending and subsequent spin coating of Au nanoparticles (NPs) and a block copolymer micelles containing Ag NPs in the core regions offers a facile route for controlling coupled surface plasmon band (SPB) of the two NPs over 100 nm in wavelength in thin solid films. Effective coupling of two individual SPBs relies upon the self-assembled composite structure where Ag and Au NPs are preferentially located in the core and corona regions of the micelles, respectively, allowing not only a controlled interparticle distance but also homogeneous dispersion of the NPs throughout film. © 2009 American Chemical Society.. |
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Takeshi Nagahiro, Haruhisa Akiyama, Masahiko Hara, Kaoru Tamada, Photoisomerization of azobenzene containing self-assembled monolayers investigated by Kelvin probe work function measurements, Journal of Electron Spectroscopy and Related Phenomena, 10.1016/j.elspec.2009.02.009, Vol.172, No.1-3, pp.128-133, 2009.05, Photoisomerization of asymmetric azobenzene disulfide self-assembled monolayer (SAM) on gold was characterized by the Kelvin probe work function measurements in ambient atmosphere. The reversible changes in work function between trans and cis azobenzene SAMs are reasonably interpreted by the molecular dipole moments normal to the surface based on the molecular conformational models. The different para-substituents of azobenzene with electron donating and electron-withdrawing properties induce opposite responses in work function against UV-vis photoirradiation, which is a direct evidence of functional SAMs being effective for the energy-level alignment at the organic/electrode interface. The Kelvin probe measurements in atmosphere eventually provide the work function value equivalent to that determined by ultraviolet photoelectron spectroscopy (UPS) in ultrahigh vacuum in our previous study. © 2009 Elsevier B.V. All rights reserved.. |
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Xinheng Li, Kaoru Tamada, Baba Iakira, Masahiko Hara, pH-controlled two dimensional gold nanoparticle aggregates for systematic study of local surface plasmon coupling, Journal of Nanoscience and Nanotechnology, 10.1166/jnn.2009.J066, Vol.9, No.1, pp.408-416, 2009.01, We report a way of using citrates, ionic capping molecules on gold nanoparticles, as a 'tuner" to adjust the charge density on the particles by solution pH, in correlation with their association constants (pKa). We have synthesized 10% biotin-capped gold nanoparticles with 90% citrates covering on the remaining surfaces. The controlled electrostatic repulsion force between the particles determines the distance between the particles on substrate, i.e., the surface density of the particles, even for the case of immobilization via biotin-avidin reaction. Thus the density of gold nanoparticles on surface was varied in a wide range systematically, especially to high density, and the optical response of two dimensional particle aggregates was investigated to discuss the effect of local plasmon coupling. The UV-vis-Near-IR reflection absorption spectrum of the particle aggregates at low pH (pH |
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Yasuhiro Ikezoe, Yoshikazu Kumashiro, Kaoru Tamada, Takuro Matsui, Ichiro Yamashita, Kiyotaka Shiba, Masahiko Hara, Growth of giant two-dimensional crystal of protein molecules from a three-phase contact line, Langmuir, 10.1021/la802104f, Vol.24, No.22, pp.12836-12841, 2008.11, A novel method to fabricate a two-dimensional (2D) crystal of protein molecules has been developed. The method enables us to control both the position of nucleation and the direction of the crystal growth. The crystal obtained using a protein molecule, ferritin, was found to be composed of a number of densely packed single crystal domains with an unprecedentedly large size of approximately 100 μm2. This method also reveals characteristic behavior of the spatiotemporal evolution of the crystal; for example, "fusion" of the crystal domains, which is never observed in an ordinary crystal composed of atoms or ions, was demonstrated. Our approach could have potential in fabricating extraordinarily large and highly ordered nanoparticle arrays of organic or inorganic materials. © 2008 American Chemical Society.. |
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Priastuti Wulandari, Takeshi Nagahiro, Kanae Michioka, Kaoru Tamada, Ken ichi Ishibashi, Yasuo Kimura, Michio Niwano, Coordination of carboxylate on metal nanoparticles characterized by Fourier transform infrared spectroscopy, Chemistry Letters, 10.1246/cl.2008.888, Vol.37, No.8, pp.888-889, 2008.08, The coordination of carboxylate capping agents on silver and gold nanoparticles is investigated by Fourier transform infrared spectroscopy (FTIR). The shift of carboxylate stretching frequency confirmed that carboxylate bound on gold nanoparticle forms unidentate coordination, while that on silver nanoparticle shows ionic bonding. The different coordinations on gold and silver NPs are reasonably interpreted by molecular orbital (MO) calculation based on metal carboxylate molecules. Copyright © 2008 The Chemical Society of Japan.. |
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Yoshikazu Kumashiro, Yasuhiro Ikezoe, Kaoru Tamada, Masahiko Hara, Dynamic interfacial properties of polyethylene glycol-modified ferritin at the solid/liquid interface, Journal of Physical Chemistry B, 10.1021/jp7104506, Vol.112, No.28, pp.8291-8297, 2008.07, Poly(ethylene glycol)-modified ferritins (PEG-ferritins) with various molecular weights were synthesized by the grafting method, and their dynamic interfacial properties at the solid/liquid interface were investigated. The number of PEG grafted to ferritins was controlled by the amount of 1,1′-carbonyldiimidazole-modified PEG adding to the reaction solution. The adsorption kinetics and energy dissipation of PEG-ferritins onto bare Si substrate and amino-modified Si substrate were investigated with a quartz crystal microbalance (QCM) in 10 mM bis-Tris/HCl buffer (pH 5.8), while their morphologies were characterized by scanning electron microscopy (SEM). The adsorption dynamics of PEG-ferritins onto amino-modified Si substrate were quite different from those of unmodified ferritin, which can be reasonably interpreted by the desorption capability of PEG-ferritins on the surface attributed to amphiphilicity and the high-chain mobility of PEG chains. © 2008 American Chemical Society.. |
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Chang Dae Keum, Noriyuki Ishii, Kanae Michioka, Priastuti Wulandari, Kaoru Tamada, Masahiko Furusawa, Hitoshi Fukushima, A gram scale synthesis of monodispersed silver nanoparticles capped by carboxylates and their ligand exchange, Journal of Nonlinear Optical Physics and Materials, 10.1142/S0218863508004093, Vol.17, No.2, pp.131-142, 2008.06, In this paper, we report a simple yet powerful synthetic method for obtaining monodispersed silver nanoparticles by direct thermal decomposition of two materials - one is silver acetate as a source of the metal core and the other is myristic acid as a capping agent. The reaction was performed at 250°C, the boiling point of myristic acid, without additional solvent. The nucleation and growth of the particles were monitored by dynamic light scattering in order to optimize the reaction time. By this simple procedure, we could obtain uniformly sized Ag nanoparticles with the average diameter of 4.8 ± 0.1 nm. Although the particles were synthesized at high temperature, the ligand exchange between myristates and alkanethiolates can be achieved at room temperature. Significant characteristics of Ag nanoparticles attributed to localized surface plasmons were investigated. © 2008 World Scientific Publishing Company.. |
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Priastuti Wulandari, Xinheng Li, Kaoru Tamada, Masahiko Hara, Conformational study of citrates adsorbed on gold nanoparticles using fourier transform infrared spectroscopy, Journal of Nonlinear Optical Physics and Materials, 10.1142/S0218863508004032, Vol.17, No.2, pp.185-192, 2008.06, We investigated the structure of citrates adsorbed on Au nanoparticles (AuNPs) synthesized by the Frens method by Fourier transformed infrared spectroscopy (FTIR). We found that physisorbed citrates are stable enough to stay on the surface of AuNPs during purification. The FT-IR spectra of citrates on AuNPs are quite uniquely different from bulk citrates, suggesting the formation of coordination bond between carboxylate group and gold. The shifts of carboxylate vibration modes on AuNPs are larger than that on flat Au substrates, as expected from the stronger dipole field on AuNPs compared with that on flat substrates. © 2008 World Scientific Publishing Company.. |
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Lloyd F.N. Ah Qune, Kaoru Tamada, Masahiko Hara, Self-assembling properties of 11-ferrocenyl-1-undecanethiol on highly oriented pyrolitic graphite characterized by scanning tunneling microscopy, e-Journal of Surface Science and Nanotechnology, 10.1380/ejssnt.2008.119, Vol.6, pp.119-123, 2008.04, Molecular resolution scanning tunneling microscope (STM) images the spontaneous self-assembly of 11-ferrocenyl-1-undecanethiol ((C5H 5)Fe(C5H4)(CH2)11-SH) forming a large striped-phase on highly oriented pyrolitic graphite (HOPG) at a phenyloctane-HOPG interface. In the image, the alkyl chains lying flat on HOPG appear as bundles in groups of five in the moiré pattern due to lattice mismatch with the underlying HOPG. The ferrocene units appearing as either fuzzy or ring-like structures suggest the random rotation of cyclopentadienyl (Cp) rings sandwiching the central iron ion of the ferrocene moieties with their principal axis either oblique or perpendicular to the HOPG. The ferrocene moieties are more clearly resolved in a mixed film with octanethiol, where the fuzzy or ring-like structures of the ferrocene units are asymmetrically distant from the sulfur head-groups forming alternating rows in the phase segregated image. Both molecules can be clearly distinguished by the length of the molecular rows. © 2008 The Surface Science Society of Japan.. |
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Lloyd F.N. Ah Qune, Kenji Makino, Kaoru Tamada, Wei Chen, Andrew T.S. Wee, Selective adsorption of L-tartaric acid on gemini-type self-assembled monolayers, Journal of Physical Chemistry C, 10.1021/jp076785d, Vol.112, No.8, pp.3049-3053, 2008.02, Synchrotron photoelectron spectroscopy and X-ray absorption spectroscopy studies of cationic self-assembled monolayers (SAMs) of quaternary ammonium (QA) sulfur derivates prepared on gold substrates were performed to investigate the adsorption mechanism of L-tartaric acid on a gemini-structured didodecyl dithiol (HS-gQA-SH). Using soft X-rays from a synchrotron light source, the carboxylate (deprotonated carboxylic acid) of L-tartaric acid was found to undergo an exchange reaction with the native bromide counterion of HS-gQA-SH-SAM. We also report the first soft XPS spectra of the bromide counterion of the QA. These results indicate the necessary chemical architecture via distance matching for exchange reactions to occur between complex molecules and point the way to more effective molecular recognition systems. © 2008 American Chemical Society.. |
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Megumi Sadaie, Naoki Nishikawa, Yoshikazu Kumashiro, Yasunori Ikezawa, Yuuki Kumagai, Kenji Marino, Satomi Ohnishi, Kaoru Tamada, Masahiko Hara, Quantitative friction map on surface composed of β-cyclodextrin monolayer, Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers, 10.1143/JJAP.46.7838, Vol.46, No.12, pp.7838-7845, 2007.12, Our developing method "quantitative friction map" enables us to compare the spatial distribution of friction forces on the surface among separately scanned samples sensitively. We applied this technique to evaluate the friction acting between mono-[6-deoxy-6-[(mercaptoethyl)amino]]-β- cyclodextrin (β-CD-EA-SH) and OH-terminated C11 alkanethiol (OH-C11-SH) self-assembled monolayers (SAMs) in terms of symmetric and asymmetric features. The friction acting between symmetric β-CD-EA-SH SAMs is significantly larger than that acting between asymmetric β-CD-EA-SH SAM vs OH-C11-SH SAM and symmetric OH-C11-SH SAMs, although all the surfaces are commonly composed of hydroxyl terminated groups. The different frictional forces on these surfaces are closely correlated with the different adhesion forces, in which symmetric β-CD-EA-SH SAMs exhibited 1.5- and 1.3-fold larger pull-off force than β-CD-EA-SH SAM vs OH-C11-SH SAM and symmetric OH-C11-SH SAM vs OH-C11-SH SAM, respectively. Both force data can be explained by the "specific interactions" between glucose units on cyclodextrin heads rather than the deformation of the SAM by cantilever scanning. © 2007 The Japan Society of Applied Physics.. |
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Kaoru Tamada, Fumio Nakamura, Masateru Ito, Xinheng Li, Akira Baba, SPR-based DNA detection with metal nanoparticles, Plasmonics, 10.1007/s11468-007-9035-x, Vol.2, No.4, pp.185-191, 2007.12, In this short review paper, we summarize some of our ideas to utilize gold nanoparticles for the enhancement of surface plasmon resonance signals on DNA microarray. The hybridization of target-DNA capped gold nanoparticles with probe DNA on surface provides ca. ten times stronger optical contrast compared with that of target-DNA molecules. Our simulation result based on the Maxwell-Garnet theory explains well our experimental data and proves a potential of metallic nanoparticles for the substantial sensitivity enhancements for biosensor application in DNA diagnostics and bio-affinity studies, which leads to the fabrication of high resolution DNA microarrays. © 2007 Springer Science+Business Media, LLC.. |
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Masateru Ito, Fumio Nakamura, Akira Baba, Tamada Kaoru, Hirobumi Ushijima, King Hang Aaron Lau, Abhijit Manna, Wolfgang Knoll, Enhancement of surface plasmon resonance signals by gold nanoparticles on high-density DNA microarrays, Journal of Physical Chemistry C, 10.1021/jp070524m, Vol.111, No.31, pp.11653-11662, 2007.08, We have developed a new methodology to fabricate high-resolution DNA microarrays (2500 dots/cm2) in combination with microcontact printing (μCP) and surface plasmon resonance (SPR) imaging. A novel COOHterminated PEG-disulfide with para-carborane (p-carborane) was synthesized as an initiator chemically bound to a gold substrate for surface coupling reactions with NH 2-terminated DNA. The hybridization between target DNA immobilized on gold nanoparticles and probe DNA arrayed on flat gold substrates was successfully demonstrated by SPR imaging, where nonspecific adsorption was not observed at the array background. The gold nanoparticles on the array give quite high contrast even at low surface coverage with gold nanoparticles (∼10%) by the enhancement effect of optical signals based on nanoscale phenomena. This enhancement effect can be well described by the simulation based on the Maxwell-Garnett theory for the effective dielectric constants and Fresnel's equation. © 2007 American Chemical Society.. |
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Hwei Ling Khor, Yujun Kuan, Hildegard Kukula, Kaoru Tamada, Wolfgang Knoll, Martin Moeller, Dietmar W. Hutmacher, Response of cells on surface-induced nanopatterns: Fibroblasts and mesenchymal progenitor cells, Biomacromolecules, 10.1021/bm0611533, Vol.8, No.5, pp.1530-1540, 2007.05, Ultrathin films of a poly(styrene)-block-poly(2-vinylpyrindine) diblock copolymer (PS-b-P2VP) and poly(styrene)-block-poly(4-vinylpyrindine) diblock copolymer (PS-b-P4VP) were used to form surface-induced nanopattern (SINPAT) on mica. Surface interaction controlled microphase separation led to the formation of chemically heterogeneous surface nanopatterns on dry ultrathin films. Two distinct nanopatterned surfaces, namely, wormlike and dotlike patterns, were used to investigate the influence of topography in the nanometer range on cell adhesion, proliferation, and migration. Atomic force microscopy was used to confirm that SINPAT was stable under cell culture conditions. Fibroblasts and mesenchymal progenitor cells were cultured on the nanopatterned surfaces. Phase contrast and confocal laser microscopy showed that fibroblasts and mesenchymal progenitor cells preferred the densely spaced wormlike patterns. Atomic force microscopy showed that the cells remodelled the extracellular matrix differently as they migrate over the two distinctly different nanopatterns. © 2007 American Chemical Society.. |
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Yasuyuki Yokota, Akira Miyazaki, Ken Ichi Fukui, Toshiaki Enoki, Kaoru Tamada, Masahiko Hara, Dynamic and collective electrochemical responses of tetrathiafulvalene derivative self-assembled monolayers, Journal of Physical Chemistry B, 10.1021/jp062285t, Vol.110, No.41, pp.20401-20408, 2006.10, Electroactive tetrathiafulvalene (TTF)-containing alkanethiol self-assembled monolayers (SAMs) were designed and synthesized to elucidate the relationship between electrochemical responses and film structures. Two TTF derivative molecules having one alkanethiol chain (1) and two alkanethiol chains (2) were utilized to modulate the molecular packing arrangements in the SAMs, and the formation and structure of the SAMs were characterized by surface plasmon resonance spectroscopy (SPR). SPR measurements in various contacting media demonstrated loose packing of SAM 1 and close packing of SAM 2 due to the different space fillings of the molecules. Two successive one-electron redox waves were observed for both SAMs by cyclic voltammetry. The peak widths of the redox waves were strongly dependent on the oxidation states of the TTF moieties, the packing arrangement of the SAMs, and the contacting medium. We found that TTF-based SAMs exhibited collective electrochemical responses induced by dynamic structural changes, depending on the degree of freedom for the component molecules in the SAMs. These results imply that the molecular design, taking into account the electrochemical responses, extends the available range of molecular-based functionalities in TTF-based SAMs. © 2006 American Chemical Society.. |
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Xinheng Li, Kaoru Tamada, Akira Baba, Wolfgang Knoll, Masahiko Hara, Estimation of dielectric function of biotin-capped gold nanoparticles via signal enhancement on surface plasmon resonance, Journal of Physical Chemistry B, 10.1021/jp062004h, Vol.110, No.32, pp.15755-15762, 2006.08, Biotin-capped gold nanoparticles assembled on flat gold with volume fraction/are studied by surface plasmon resonance (SPR) spectroscopy and atomic force microscopy (AFM) in order to estimate the dielectric function of the gold nanoparticles based on the Maxwell-Garnett (MG) theory. The complex dielectric function (∈′, ∈″) of the spherical nanoparticles at three representative wavelengths in the vis-near-IR region, i.e., λ = 543, 632.8, and 1152 nm, is estimated for a surface homogeneously covered with nanoparticles in order to discuss the wavelength dependence of the dielectric function. The SPR response of a surface covered with particles in 2D aggregates is also analyzed. The experimental SPR curve of the particle aggregates deviates from the theoretical predictions, suggesting dipole interactions between particles. © 2006 American Chemical Society.. |
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Megumi Sadaie, Naoki Nishikawa, Satomi Ohnishi, Kaoru Tamada, Kiyoshi Yase, Masahiko Hara, Studies of human hair by friction force microscopy with the hair-model-probe, Colloids and Surfaces B: Biointerfaces, 10.1016/j.colsurfb.2006.06.004, Vol.51, No.2, pp.120-129, 2006.08, We employed a cantilever modified with a self-assembled monolayer (SAM) as a "hair-model-probe" for friction force microscopy (FFM) to measure friction acting between hair and hair-like surfaces. The "hair-model-probe" was prepared by forming a SAM of octadecanethiol on a gold-coated cantilever. We investigated frictional properties of human hair at both root and tip, and the dependency on applied load, influence of scanning direction, and local frictional distribution. The friction coefficient of the hair tip was greater than that of the hair root. Load dependency of friction at the hair tip was clearly observed, while friction at the hair root was less dependent on applied load. At the hair root, an anisotropic frictional property was observed: friction force along the long axis of the hair fiber was about 1.5-2 times larger than that along the short axis. Atomic force microscopy (AFM) images showed striations on the cuticle cells that have about 6 nm depth and their long axis oriented in the direction of the hair fiber. The frictional distribution images revealed that the local areas showing strong shear corresponded to striations. Since such distribution of friction was not observed at the hair tip, it is suggested that the anisotropic frictional property at the hair root was caused mainly by the striations. The frictional distribution in regions that excluded the striations also showed the anisotropic frictional property that friction parallel to the long axis of the hair fiber is greater than that along the short axis. This result suggests that the orientation of fatty acid molecules comprising the fat layer (F-layer) may also contribute to the anisotropic frictional property. We have concluded that loss of the F-layer is a dominant cause of strong friction detected at the hair tip, and at the striations of the hair root. © 2006 Elsevier B.V. All rights reserved.. |
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Shinobu Yokokawa, Kaoru Tamada, Masahiko Hara, Formation of chiral surface with enantiomeric tartaric acid on gemini-structured self-assembled monolayers, Journal of Nanoscience and Nanotechnology, 10.1166/jnn.2006.242, Vol.6, No.6, pp.1772-1778, 2006.06, Chiral surfaces were prepared by L, D, and Meso-tartaric acids (TAs) adsorbed on geministructured self-assembled monolayers (SAMs) composed of ethylenebis [(12-mercaptododecyl) dimethyl ammonium bromide] (HS-gQA-SH). The formation and structure of the chiral surfaces were characterized by surface plasmon resonance spectroscopy (SPR) and Fourier transform infraredreflection adsorption spectroscopy (FTIR-RAS). The thickness of enantiomeric TA layers on the HS-gQA-SH SAM was estimated to be c.a. 5-6 Å regardless of their chirality, in good agreement with the height of TA molecules anchoring on the surface with two COOH groups. All the TAs on the HS-gQA-SH SAM exhibit the same ionization state independent of their chirality in their vibration bands of carboxyiic groups. We attempted a second-layer adsorption of the enantiomeric TAs on L-TA monomolecular layer (L-TA SAM) precomposed on the HS-gQA-SH. A strong affinity between first and second TA layers resulted in the film growth when their chirality is identical (i.e., L-TA on L-TA SAM). We found the structure of second L-TA layer was completely different from that of the first layer, where a crystalline-like L-TA phase was found as a predominant component. Our results imply a preferential crystalline growth of chiral molecules on the same chiral surface, which may lead to a work for optical resolution into two enantiomers at a solid-liquid interface. Copyright © 2006 American Scientific Publishers All rights reserved.. |
| 43. |
Fumio Nakamura, Masateru Ito, Ablihito Manna, Kaoru Tamada, Masahiko Hara, Wolfgang Knoll, Observation of hybridization on a DNA array by surface plasmon resonace imaging using Au nanoparticles, Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers, 10.1143/JJAP.45.1026, Vol.45, No.2 A, pp.1026-1029, 2006.02, To realize the sensitive detection of DNA hybridization, DNA-modified Au nanoparticles (DNA-AuNPs) containing single-and double-stranded portions were prepared. The hybridization of a target DNA using the DNA-AuNPs on a DNA self-assembled monolayer (DNA-SAM) was monitored in situ by surface plasmon resonance (SPR) imaging. A sandwich type hybridization (DNA-SAM/target DNA/DNA-AuNP) experiment was carried out in order to enhance the hybridization signal. SPR imaging results strongly indicate that the hybridization signal is enhanced several times compared to the case of target DNA hybridization. ©2006 The Japan Society of Applied Physics.. |
| 44. |
Nobuko Fukuda, Jun Young Kim, Takashi Fukuda, Hirobumi Ushijima, Kaoru Tamada, Synthesis and optical characterization of novel imidazole-based Azo materials, Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers, 10.1143/JJAP.45.460, Vol.45, No.1 B, pp.460-464, 2006.01, We synthesized novel imidazole-based azo compounds and their optical properties were investigated. In the course of recrystallization, pink-orange and violet products were obtained. The violet one shows poor solubility for most organic solvents except polar aprotic solvents such as dimethylsulfoxide (DMSO) and dimethylfolmamide (DMF). The spectra of NMR in DMSO-d6 and UV-vis absorption spectra in DMSO for both products were found to be identical. However, there were differences in FT-IR absorption spectra. The violet solid compound exhibited broad bands that could be attributed to N-H⋯N hydrogen bonding. These results show that the violet product consists of an aggregation of molecules formed via intermolecular hydrogen bonding. Additionally, imidazole-based azo copolymers containing liquid crystalline side chain groups were also synthesized. The photoinduced birefringence of these copolymers was observed by irradiation of a linearly polarized 532 nm laser beam as a pumping light. It was confirmed that the material exhibited photoisomerization properties and the observed birefringence was attributed to photoinduced molecular reorientation. Moreover, the dipolar effect in photoinduced birefringence was briefly discussed. © 2006 The Japan Society of Applied Physics.. |
| 45. |
F. Fitrilawati, R. Renu, C. Baskar, L. G. Xu, H. S.O. Chan, S. Valiyaveettil, K. Tamada, W. Knoll, Langmuir-blodgett-kuhn and self-assembled films of asymmetrically substituted poly(paraphenylene), Langmuir, 10.1021/la0505667, Vol.21, No.26, pp.12146-12152, 2005.12, Asymmetrically substituted poly(paraphenylene) (PhPPP) with hydrophilic and hydrophobic side chains was investigated. The polymer behavior at the air-water interface was studied on the basis of surface pressure-area (π-A) isotherms and compression/expansion hysteresis measurements. PhPPP can form stable monolayers with an area per repeat unit of A = 0.20 ± 0.02 nm2 and a collapse pressure in the range of π = 25 mN/m. Then, Langmuir-Blodgett-Kuhn (LBK) films of PhPPP were prepared by horizontally and vertically transferring the Langmuir monolayers onto hydrophilic solid substrates at π = 12 mN/m. Cross-section analysis of the AFM tapping-mode topography images of a single transferred monolayer reveals a thickness of d0 = 0.9 ± 0.1 nm. Taking into account the obtained monolayer thickness, curvefitting calculations of angular scan data of LB monolayers measured using surface plasmon resonance (SPR) spectroscopy lead to a value for the refractive index of n = 1.78 ± 0.02 at λ = 632.8 nm. Next, the spontaneous formation of a PhPPP monolayer by adsorption from solution was studied ex situ by atomic force microscopy and UV-vis spectroscopy and in situ by using SPR spectroscopy. Stable self-assembled monolayers of PhPPP can be formed on hydrophilic surfaces with a thickness similar to that of the monolayer obtained using the LB method. The characterization results confirmed the amphiphilic character and the self-assembly properties of PhPPP, as well as the possibility of preparing homogeneous monolayer and multilayer films. © 2005 American Chemical Society.. |
| 46. |
石井 則行, Fitrilawati F, Manna A, 秋山 陽久, 玉田 靖, 玉田 薫, 3P337 金ナノ微粒子をキャリアとする免疫学的応答と効率的な抗体生産(バイオエンジニアリング)), 生物物理, Vol.45, No.1, 2005.10. |
| 47. |
Soichi Otsuki, Koji Ohta, Kaoru Tamada, Shin Ichi Wakida, Thickness measurements on transparent substrates based on reflection ellipsometry. I. Optical effects of high-refractive-index additional layers, Applied Optics, 10.1364/AO.44.005910, Vol.44, No.28, pp.5910-5918, 2005.10, Theoretical studies were conducted for thickness measurements using transparent substrates on the external and internal reflection configurations. For three-phase systems consisting of ambient, film, and substrate, the refractive index of the substrate could be optimized to obtain the high sensitivity of an ellipsometric quantity Δ to the film thickness and the small susceptibility of Δ to errors in the incident angle. It was shown that the combination of an ordinary glass substrate and an additional dielectric layer with an appropriate layer thickness works as a synthetic high-index single substrate (SHIS). The optical effect of the combination was approximately described by use of the effective refractive index of SHIS. A method to select the refractive index of the additional layer was also given. © 2005 Optical Society of America.. |
| 48. |
Soichi Otsuki, Kaoru Tamada, S. Wakida, Wavelength-scanning surface plasmon resonance imaging, Applied Optics, 10.1364/AO.44.003468, Vol.44, No.17, pp.3468-3472, 2005.06, A new surface plasmon resonance (SPR) imaging technique was proposed. After measurements were conducted at varying wavelengths, the wavelength affording the minimum brightness (SPR wavelength) was determined at each pixel of the image. A two-dimensional map of the SPR wavelength could be converted to a thickness profile by use of a nonlinear calibration curve, which was obtained by Fresnel calculation. An array of protein thin layers on a gold film was evaluated in air to present the layers' surface structure in nanometer scale. © 2005 Optical Society of America.. |
| 49. |
M Ito, K Tamada, F Nakamura, KHA Lau, A Manna, W Knoll, A Baba, RC Advincula, Bio-photonics devices with gold nanoparticles., ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, Vol.229, p.U141, 2005.03. |
| 50. |
M Ito, K Tamada, F Nakamura, KHA Lau, A Manna, W Knoll, A Baba, RC Advincula, Bio-photonics devices with gold nanoparticles., ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, Vol.229, p.U141, 2005.03. |
| 51. |
RS Xu, A Baba, J Locklin, K Tamada, RC Advincula, Fabrication, optical properties, and modeling of gold nanoparticle/polyelectrolyte layer-by-layer ultrathin films., ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, Vol.229, p.U962, 2005.03. |
| 52. |
RS Xu, A Baba, J Locklin, K Tamada, RC Advincula, Fabrication, optical properties, and modeling of gold nanoparticle/polyelectrolyte layer-by-layer ultrathin films., ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, Vol.229, p.U962, 2005.03. |
| 53. |
CD Keum, K Tamada, M Furusawa, H Fukushima, Novel synthesis method of silver nanoparticles and surface functionalization., ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, Vol.229, p.U674, 2005.03. |
| 54. |
CD Keum, K Tamada, M Furusawa, H Fukushima, Novel synthesis method of silver nanoparticles and surface functionalization., ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, Vol.229, p.U674, 2005.03. |
| 55. |
Soichi Otsuki, Kaoru Tamada, Shin Ichi Wakida, Two-dimensional thickness measurements based on internal reflection ellipsometry, Applied Optics, 10.1364/AO.44.001410, Vol.44, No.8, pp.1410-1415, 2005.03, An imaging ellipsometer technique on internal reflection geometry that can measure the thickness distribution of a thin film possessing an assumed refractive index is described. Because a prism is used for the internal reflection geometry, it was theoretically predicted that angular derivation from the normal incidence on the prism surface affects only the ^ value by a factor of 0.97 at maximum. Measurements were carried out for an optical system of silica substrate-TiO2 layer-silica layer-protein film-air, with a thin-film array of dried protein as the sample film. Thickness of the protein films was two-dimensionally estimated only from the measured map of the A value by use of the simulated relationship between the thickness and the A value. The thickness map obtained was coincident on the whole with the results according to a mechanical scanning. The detection limit was approximately ±0.2 nm. These findings validate the optical effect of a high-index additional layer to improve the sensitivity and precision of thickness measurements of the sample film on transparent substrates. © 2005 Optical Society of America.. |
| 56. |
Masateru Ito, Tian Xin Wei, Peng Lei Chen, Haruhisa Akiyama, Mutsuyoshi Matsumoto, Kaoru Tamada, Yoshinori Yamamoto, A novel method for creation of free volume in a one-component self-assembled monolayer. Dramatic size effect of para-carborane, Journal of Materials Chemistry, 10.1039/b411121d, Vol.15, No.4, pp.478-483, 2005.01, We fabricated the self-assembled monolayers (SAMs) composed of 4-(12-(10-mercaptodecyl)-1,12-dicarba-closo-dodecaborane)-4′-octyloxy azobenzene and 4-(10-mercaptodecyloxy)-4′-octyloxyazobenzene on a gold surface, and performed photoswitching experiments. The SAM including p-carborane exhibited a much higher and more reversible photochemical response in comparison with the SAM in the absence of the p-carborane. This result suggests that the free volume of the azobenzene moiety to change its conformation is increased due to the size effect of the p-carborane.. |
| 57. |
King Hang Aaron Lau, Le Shon Tan, Kaoru Tamada, Melissa S. Sander, Wolfgang Knoll, Highly sensitive detection of processes occurring inside nanoporous anodic alumina templates: A waveguide optical study, Journal of Physical Chemistry B, 10.1021/jp0498567, Vol.108, No.30, pp.10812-10818, 2004.07, We have applied nanoporous anodic alumina films as planar optical waveguides and studied changes in the effective dielectric constants of these thin films due to various processes occurring in the pores. We demonstrate the potential of the porous anodic alumina waveguide for high sensitivity (bio-) chemical sensing with bovine serum albumin adsorption and desorption at various pH values, with subangstrom sensitivity in the effective thickness of protein adsorbed. We also monitored pore widening (alumina dissolution) with subangstrom sensitivity, which is conceptually the reverse of detecting conformal film deposition on pore surfaces. Furthermore, we monitored the exchange of pore-filling media between phosphate buffer solution and ethanol, which produces qualitatively the same response as complete pore filling with other materials by various deposition techniques. Thus porous anodic alumina films may be employed simultaneously as deposition templates and as highly sensitive detectors of processes within the pores.. |
| 58. |
Wolfgang Knoll, Ming Yong Han, Xinheng Li, Jose Luis Hernandez-Lopez, Abhijit Manna, Klaus Müllen, Fumio Nakamura, Lifang Niu, Rudolf Robelek, Evelyne L. Schmid, Kaoru Tamada, Xinhua Zhong, Nanoscopic building blocks from polymers, metals, and semiconductors for hybrid architectures, Journal of Nonlinear Optical Physics and Materials, 10.1142/S0218863504001815, Vol.13, No.2, pp.229-241, 2004.06, This paper describes some of our efforts in the area of nanostructured thin film architectures. The resulting interfacial hybrid assemblies are built from (1) organic/polymeric objects based on dendrimer systems, from (2) surface-functionalized Au nanoparticles, and (3) from a variety of semiconducting quantum dots. Dendrimers as polymeric building blocks with a strictly monodisperse particle size distribution in the nanometer range can be functionalized in the core, the scaffold, or at the periphery, thus offering interesting hybrid materials for a wide range of applications. The combination with Au clusters and their local surface plasmon resonances suggests new strategies for optoelectronic devices or unconventional bio-sensor platforms. The possibility of tuning the luminescent properties of semiconducting nanoparticles by size or compositional bandgap engineering complements the assembly kit with building blocks for supramolecular thin film nanocomposite materials.. |
| 59. |
Chang Dae Keum, Takashi Fukuda, Him Matsuda, Kaoru Tamada, Facile photofabrication of stable, submicrometer-wide, electrically conductive patterns, Advanced Materials, 10.1002/adma.200306175, Vol.16, No.8, pp.696-699, 2004.04, A fabrication method for submicrometor-wide electric conductive patterns using Ag nanoparticle/polymer composites on furan-functionalized substrates (see Figure) is reported. A 180 nm wide (full width at half maximum) photofabricatcd pattern has been achieved, well below the wavelength of incident light. After anneating at 200°C for 40 min. the pattern worked as an electric wire with a resistivity of -8 × 104 Ω cm.. |
| 60. |
A Baba, K Tamada, W Knoll, Electropolymerization of EDOT at high-pressure studied by electrochemical-surface plasmon resonance spectroscopy., ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, Vol.227, pp.U432-U433, 2004.03. |
| 61. |
K Tamada, A Manna, W Knoll, S Yokokawa, M Hara, Functionalized self-assembled monolayers and metal nanoparticle devices., ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, Vol.227, p.U506, 2004.03. |
| 62. |
W Knoll, K Tamada, K Mullen, MY Han, JP Majoral, Nanoscopic building blocks for supramolecular functional thin film architectures., ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, Vol.227, p.U469, 2004.03. |
| 63. |
W Knoll, K Tamada, K Mullen, MY Han, JP Majoral, Nanoscopic building blocks for supramolecular functional thin film architectures., ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, Vol.227, p.U469, 2004.03. |
| 64. |
Tianxin Wei, Kaoru Tamada, Shinobu Yokokawa, Eisuke Ito, Kiyoshi Yase, Masahiko Hara, Fabrication and characterization of novel mixed-valence pentaamminechlororuthenium(III) hexacyanoruthenate(II) coordination compound self-assembled film, Chemistry Letters, 10.1246/cl.2004.164, Vol.33, No.2, pp.164-165, 2004.02, Functional self-assembled film of a class II mixed-valence coordination compound, pentaamminechlororuthenium(III) hexacyanoruthenate(II) (Na[NH 3]5Ru(III)-CN-Ru(II)(CN)5), was fabricated and characterized by surface plasmon resonance (SPR), X-ray photoelectron spectroscopy (XPS) and phase modulation infrared reflection-absorption spectroscopy (PMIR-RAS).. |
| 65. |
Akira Baba, Jörn Lübben, Kaoru Tamada, Wolfgang Knoll, Optical Properties of Ultrathin Poly(3,4-ethylenedioxythiophene) Films at Several Doping Levels Studied by In Situ Electrochemical Surface Plasmon Resonance Spectroscopy, Langmuir, 10.1021/la034848n, Vol.19, No.21, pp.9058-9064, 2003.10, In this paper, we report on in situ optical/electrochemical investigations using a combination of surface plasmon resonance spectroscopy and electrochemistry in order to determine the complex dielectric constants of poly(3,4-ethylenedioxythiophene) (PEDOT) thin films. The PEDOT films were deposited by in situ electropolymerization. The film thickness was monitored by a quartz crystal microbalance. In the electrochemical surface plasmon resonance (EC-SPR) measurements, three wavelengths corresponding to interband and intraband electronic transition regions were used in order to investigate electrochromic properties. The optical conductivity was also determined by EC-SPR measurement with a near-infrared laser wavelength which corresponds to the region outside the anomalous dispersion.. |
| 66. |
Jianjiang Hu, Chao Yin, Hai Quan Mao, Kaoru Tamada, Wolfgang Knoll, Functionalization of poly(ethylene terephthalate) film by pulsed plasma deposition of maleic anhydride, Advanced Functional Materials, 10.1002/adfm.200304384, Vol.13, No.9, pp.692-697, 2003.09, Poly(ethylene terephthalate) (PET) films have been functionalized with carboxyl groups by pulsed plasma polymerization of maleic anhydride (MA). The preserved anhydride groups of MA were converted to carboxyl groups by subsequent hydrolysis. Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) were used to determine the chemical composition of the deposited MA plasma polymers. Atomic force microscopy (AFM) observations visually confirmed the coverage of the PET surface with plasma polymers after water treatment of the processed PET substrate, and the functionality in the XPS spectra of samples before and after water treatment indicated the persistence of functional groups and the good adhesion of the deposited layers on the PET substrate. In accordance with FTIR and XPS results, the density of carboxyl groups increased with decreasing plasma duty cycle. Compared with the pristine PET substrate, a higher roughness was observed on the modified PET surface by AFM. The roughness decreased sharply with decreasing plasma duty cycle.. |
| 67. |
S Yokokawa, K Tamada, E Ito, M Hara, Cationic self-assembled monolayers composed of gemini-structured dithiol on gold: A new concept for molecular recognition because of the distance between adsorption sites, JOURNAL OF PHYSICAL CHEMISTRY B, 10.1021/jp027375m, Vol.107, No.15, pp.3544-3551, 2003.04, Cationic self-assembled monolayers (SAMs) composed of quaternary ammonium (QA) sulfur derivatives have been synthesized to control the distance between charged headgroups on gold substrates. Two molecules bearing resembling molecular structures, "gemini"-structured didodecyl dithiol (HS-gQA-SH) and didodecyl disulfide (QA-SS-QA), were utilized in this study, and the formation and structure of the SAMs were characterized by surface plasmon resonance spectroscopy (SPR), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared-reflection adsorption spectroscopy (FTIR-RAS). In the HS-gQA-SH SAM, the orientation and distance between QA groups are specified by the covalent bonding with ethylene spacer, while those of the QA-SS-QA SAM are determined by the electric repulsion between charged headgroups, that is, QA groups in the QA-SS-QA SAM are more randomly located, being more distant than with those in the HS-gQA-SH SAM. We found that L-tartaric acid, a probe molecule with two carboxyl groups having the distance of an ethylene unit, exhibits a strong affinity on the HS-gQA-SH SAM. In contrast, no specific binding was observed on the QA-SS-QA SAM. These results imply the possibility to build up a molecular recognition system on surfaces because of the control of the distance between the charged headgroups by using the gemini-structured molecular design.. |
| 68. |
Kaoru Tamada, Haruhisa Akiyama, Tian Xin Wei, Seung Ae Kim, Photoisomerization reaction of unsymmetrical azobenzene disulfide self-assembled monolayers: Modification of azobenzene dyes to improve thermal endurance for photoreaction, Langmuir, 10.1021/la0258493, Vol.19, No.6, pp.2306-2312, 2003.03, Recently we have developed an unsymmetrical azobenzene disulfide with a short alkyl side chain, 4-hexyl-4′-(12-(dodecyldithio)-dodecyloxy)azobenzene (C6AzSSC12), aiming of a high efficiency in photoisomerization in SAMs on planar gold surfaces (Tamada, K.; et al. Langmuir 2002, 18, 5239). In this paper, we introduce an additional modification on the molecule to improve the thermal endurance for the photoreaction by attachment of a methyl group to the azobenzene ring, thus avoiding dye aggregation sterically. A "methyl-derivatized" azobenzenethiol (C6Az(Me)SH) SAM revealed a significant improvement in their photoreactivity compared with an unmodified azobenzenethiol (C6AzSH) SAM due to the steric effect of the methyl group. A "methyl-derivatized" unsymmetrical azobenzene disulfide (C6Az(Me)SSC12) SAM exhibited quite a similar photoresponse to that of C6AzSSC12 SAM before heat treatment owing to the free volume given by the unsymmetrical structure; however, only the C6Az(Me)SSC12 SAM could retain high photoreactivity in phase-segregated domains formed by annealing, unlike the C6AzSSC12 SAM. The C6Az(Me)SH and C6Az(Me)SSC12 SAMs exhibited a reaction kinetics different from that of C6AzSSC12 SAM due to a different quantum yield and the molecular tilt angle of the azobenzene unit. The C6Az(Me)SH SAM exhibited a typical character of "congested surface", where the reaction rate from cis to trans was faster, while that from trans to cis was slower compared with those of C6Az(Me)SSC12 SAM.. |
| 69. |
Abhijit Manna, Peng Lei Chen, Haruhisa Akiyama, Tian Xin Wei, Kaoru Tamada, Wolfgang Knoll, Optimized photoisomerization on gold nanoparticles capped by unsymmetrical azobenzene disulfides, Chemistry of Materials, 10.1021/cm0207696, Vol.15, No.1, pp.20-28, 2003.01, Gold nanoparticles capped by an unsymmetrical azobenzene disulfide, 4-hexyl-4′-(12-(dodecyldithio)dodecyloxy)azobenzene (C6AzSSC12), were synthesized in order to investigate the efficiency of azobenzene photoisomerization on colloidal gold surfaces. The nanoparticles were synthesized by a two-step method to avoid the direct contact of azobenzene units with a reducing agent. The average size of the particles was determined to be ∼5.2 ± 1.3 nm from transmission electron microscope (TEM) images. The CH2 antisymmetric (∼2919 cm-1) and symmetric (∼2850 cm-1) stretching bands in the FTIR spectra of the nanocomposite confirmed the all-trans conformation of alkyl chains in the C6AzSSC12 on the colloidal gold. The photoisomerization reaction of the C6AzSSC12-capped gold nanoparticles was studied by UV-vis absorption spectroscopy in toluene. The reaction kinetics was identical to that of the free C6AzSSC12 molecules dissolved in toluene, with no deviations from a first-order plot for both trans-to-cis and cis-to-trans photoisomerization, suggesting no steric hindrance throughout the whole reaction process. The free volume guaranteed by the 50% dilution of the dye functions due to the unsymmetrical disulfide structures, as well as their noncompact molecular tails owing to the assembly on the curved colloidal gold, must be responsible for such a highly efficient photoreaction. Sedimentation of the nanoparticles arose in toluene subsequent to the photoisomerization of the capping azobenzene molecules from trans to cis isomers. This phenomenon can be interpreted as resulting from differences in the degree of solvation between the azobenzene isomers.. |
| 70. |
H Akiyama, K Tamada, J Nagasawa, K Abe, T Tamaki, Photoreactivity in self-assembled monolayers formed from asymmetric disulfides having para-substituted azobenzenes, JOURNAL OF PHYSICAL CHEMISTRY B, 10.1021/jp026103g, Vol.107, No.1, pp.130-135, 2003.01, Asymmetric dialkyl disulfides with a para-substituted azobenzene (i.e., 4-substituted 4'-(12-(dodecyldithio)dodecyloxy)azobenzenes) produced photoresponsive self-assembled monolayers (SAMs) on gold (111) surfaces. Infrared reflection absorption (IR-RA) spectroscopy and reflection ultraviolet (UV) and visible (vis) light absorption spectroscopy gave information on the molecular orientational order of the adsorbates in the SAMs. The photoreactivity was investigated using dynamic contact-angle measurements with a Wilhelmy-type surface balance. The structure and photoreactivity of the SAMs were dependent on the substituent at the para position of an azobenzene moiety. Relatively ordered structures in the methylene parts and the photoisomerization of azobenzene moieties were observed for the SAMs formed from the hexyl- and the nonsubstituted azobenzene disulfides. However, a less-ordered SAM structure was seen for the cyanoazobenzene disulfide SAM, and the photoresponse is rather unstable.. |
| 71. |
石田 敬雄, 玉田 薫, セルフアセンブリー : 近年の進展と今後の展望, 應用物理, Vol.72, No.1, p.102, 2003.01. |
| 72. |
R Yuge, A Miyazaki, T Enoki, K Tamada, F Nakamura, M Hara, Intercalation effect of 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimetane having strong electron affinity in self-assembled monolayers composed of charge transfer complex prepared by coadsorption and layer-by-layer adsorption methods, JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS, 10.1143/JJAP.41.7462, Vol.41, No.12, pp.7462-7468, 2002.12, Charge transfer (CT) complex self-assembled monolayers (SAMs) on a gold substrate are prepared using layer-by-layer adsorption and coadsorption methods with mercapto-methyl-tetrathiafulvalene (TTF-CH2SH) and strong acceptor 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (TCNQF(4)), in comparison with TTF-CH2SH/TCNQ SAMs consisting of moderate acceptor TCNQ. The layer-by-layer method yields TTF-CH2SH/TCNQF(4) SAMs with the coexistence of neutral TCNQF(4) and anionic TCNQF(4)(-), where the TCNQF(4)(-) anions are laid on the TTF layer with the TTF-CH2SH molecules standing perpendicular to the gold substrate. The neutral TCNQF(4) molecules are stacked above the TCNQF(4)(-) anion layer. This is in contrast to the fact that TCNQ having intermediate strength of acceptor character does not yield any CT SAMs when using the layer-by-layer technique. In the coadsorption method, TTF-CH2SH/TCNQF(4) SAMs are formed, where all the TCNQF(4) molecules are completely reduced as TCNQF4 anions, similar to those in bulk TTF-TCNQF(4) crystals. Taking into account that TTF-CH2SH/TCNQ SAMs have the same fractional value (0.6) of the degree of charge transfer to that of bulk TTF-TCNQ crystal, the coadsorption technique can reproduce the electronic structure of the bulk CT complex in the 2D SAMs. The coadsorbed SAMs have an intercalation structure, where acceptor molecules are intercalated into the interstitials of TTF-CH2SH/Au units with the molecular axes of both acceptor and donor molecules parallel to each other. Such a donor/acceptor molecular arrangement can provide a favorable situation in the charge transfer between the two ingredients, resulting in the similar electronic structure to that of bulk CT crystals.. |
| 73. |
R Yuge, A Miyazaki, T Enoki, K Tamada, F Nakamura, M Hara, Fabrication of TTF-TCNQ charge-transfer complex self-assembled monolayers: Comparison between the coadsorption method and the layer-by-layer adsorption method, JOURNAL OF PHYSICAL CHEMISTRY B, 10.1021/jp0135757, Vol.106, No.27, pp.6894-6901, 2002.07, We propose a novel technique to fabricate self-assembled monolayers (SAMs) of 2D charge-transfer complexes by coadsorption of thiol-functionalized tetrathiafulvalene derivatives (TTF-CH2SH) with 7,7,8,8-tetracyanoquinodimethane (TCNQ) on a gold substrate. For the "coadsorption" method, the gold substrates are immersed into the TTF-CH2SH and TCNQ mixed acetonitrile solution under optimum conditions for TTF-TCNQ bulk crystalline growth. TTF-CH2SH/TCNQ SAMs are also prepared by the conventional "layer-by-layer" adsorption method to compare the film properties with those of the coadsorbed SAMs, where the gold substrates are exposed to TCNQ solution after TTF-CH2SH (single component) SAM formation. For both TTFCH2SH/TCNQ SAMs, the adsorption process and the optical thickness are characterized by surface plasmon resonance (SPR) measurements. The coadsorbed TTF-CH2SH/TCNQ SAMs form slightly thicker films (15.9 Angstrom) than do the SAMs prepared by the layer-by-layer adsorption method (15.1 Angstrom) because they incorporate the TCNQ molecules more efficiently in the film. The FTIR-RAS data reveal that all TCNQ molecules in the coadsorbed SAMs are in the mixed valence state, whereas no intermolecular charge transfer is present in the SAMs prepared by the layer-by-layer adsorption method. From the Cequivalent toN absorption bands in the IR spectra, the degree of charge transfer is estimated to similar or equal to0.6 for the coadsorbed SAMs, which is comparable to the value for the bulk TTF-TCNQ crystals.. |
| 74. |
K Tamada, H Akiyama, TX Wei, Photoisomerization reaction of unsymmetrical azobenzene disulfide self-assembled monolayers studied by surface plasmon spectroscopy: Influences of side chain length and contacting medium, LANGMUIR, 10.1021/la0157667, Vol.18, No.13, pp.5239-5246, 2002.06, We report the characteristics of azobenzene-containing self-assembled monolayers (SAMs) which are designed and synthesized for surface photoisomerization reactions. The photoreactive SAMs were composed of unsymmetrical azobenzene disulfides, in which the free volumes for photoreaction of azobenzene moieties are guaranteed by 50% dilution of dye functions at the molecular level on the surface. The photoswitching reaction was monitored in situ through the change of optical film thickness by means of surface plasmon spectroscopy. The influences of alkyl side chain length and contacting medium on the photoreaction were also investigated. The profile of the trans to cis photoisomerization reaction by UV light irradiation exhibited a clear deviation from first-order kinetics, suggesting a steric hindrance effect on the photoreaction process.. |
| 75. |
T Ederth, K Tamada, PM Claesson, R Valiokas, R Colorado, M Graupe, OE Shmakova, TR Lee, Force measurements between semifluorinated thiolate self-assembled monolayers: Long-range hydrophobic interactions and surface charge, JOURNAL OF COLLOID AND INTERFACE SCIENCE, 10.1006/jcis.2000.7318, Vol.235, No.2, pp.391-397, 2001.03, Long-range interactions between self-assembled monolayers (SAMs) of semifluorinated alkanethiols have been studied by direct force measurements in water and aqueous NaCl solutions. SAMs prepared from three different thiols, with identical fluorinated head groups but varying hydrocarbon spacer lengths, were investigated: CF3(CF2)(9)(CH2)(x)SH, where x = 2, 11, or 17. Force measurements show that the interactions in water and electrolyte solutions are composed of both double-layer interactions emerging from what appears to be charges adsorbed onto the surfaces and long-range "hydrophobic" attractions, in excess of the expected van der Waals forces. The three investigated thiols produce similar results in force measurements, though the contact angles with water are slightly different, The "hydrophobic" attraction has the form of step-like attractive discontinuities in the force profiles at separations ranging from 20 to 40 nm, caused by bridging of microscopic bubbles residing at the surfaces, The shape or range of these discontinuities are not significantly affected by replacement of the water with either 1 mM or 1 M NaCl solutions. The origin of the charges causing the electrostatic double-layer interaction is unclear, but some possible causes are discussed. (C) 2001 Academic Press.. |
| 76. |
K Tamada, T Ishida, W Knoll, H Fukushima, R Colorado, M Graupe, OE Shmakova, TR Lee, Molecular packing of semifluorinated alkanethiol self-assembled monolayers on gold: Influence of alkyl spacer length, LANGMUIR, 10.1021/la001212c, Vol.17, No.6, pp.1913-1921, 2001.03, The structures of semifluorinated alkanethiol self-assembled monolayers (SAMs) generated by the adsorption of CF3(CF2)(9)(CH2)(n)SH (F10HnSH, n = 2, 6, 11, 17, 33) onto gold were investigated with atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and surface plasmon resonance spectroscopy. Images obtained by AFM of the F10H2SH SAM showed a remarkably ordered 2D hexagonal lattice with a lattice constant, alpha = 5.9 +/- 0.1 Angstrom, on Au(111)/mica. As the total number of carbon atoms in the alkyl spacer groups (n) was increased, the fluorocarbon adlayer structure appeared more disordered in the AFM images; however, the thicknesses of the fluorocarbon layers estimated from the C 1s (CF3), C 1s (CF2), and F 1s XPS signal intensities were indistinguishable in all of the SAMs. In contrast, the C ls (CH2) signals revealed that the tilt angles of the alkyl spacer groups depended strongly on n. We utilized a contrast variation SPR technique with various contacting media for an independent determination of the refractive indices and the film thicknesses of the semifluorinated SAMs. The obtained data were consistent with our AFM and XPS results, which show that the longer alkyl chains pack more densely than the shorter ones in these SAMs.. |
| 77. |
H. Fukushima, H. Fukushima, H. Fukushima, S. Seki, T. Nishikawa, H. Takiguchi, K. Tamada, K. Abe, R. Colorado, M. Graupe, O. E. Shmakova, T. R. Lee, Microstructure, wettability, and thermal stability of semifluorinated self-assembled monolayers (SAMs) on gold, Journal of Physical Chemistry B, 10.1021/jp0003499, Vol.104, pp.7417-7423, 2000.08, The microstructure, wettability, and thermal stability of self-assembled monolayers (SAMs) on gold generated from semifluorinated alkanethiols F(CF 2 ) 10 (CH 2 ) n SH, where n = 2, 6, 11, 17, and 33 (F10HnSH), were examined by polarization modulation infrared reflection absoprtion spectroscopy (PM-IRRAS) and dynamic contact angle measurements. Analysis by PM-IRRAS revealed that the length of the methylene spacer (Hn) influenced the tilt angle of the fluorocarbon segments in the semifluorinated SAMs. As the length of the methylene spacer was increased, the tilt angle of the perfluorocarbon moiety increased with respect to the surface normal. The longer methylene spacers (Hn,n = 11, 17, and 33) exhibited well-ordered trans-extended conformations as indicated by the position of the antisymmetric methylene band Shortening the length of the methylene spacer to n = 6, however, led to a decrease in conformational order Dynamic contact angle measurements, using the Wilhelmy plate method showed that the semifluorinated SAMs were poorly wet by both water (average θ a = 120°) and hexadecane (average θ a = 81°). The wettability varied with the length of the methylene spacer; in particular, both the thinnest and the thickest semifluorinated SAMs (derived from F10H2SH and F10H33SH, respectively) exhibited relatively low dynamic contact angle values. In addition, the thermal stability of the semifluorinated SAMs was found to increase as the length of the methylene spacer was increased. Overall, these films exhibited remarkable resistance to thermal degradation (e.g., SAMs derived from F10H33SH sustained a relatively high contact angles after incubation at 150 °C for 1 h in air). © 2000 American Chemical Society.. |
| 78. |
H Fukushima, S Seki, T Nishikawa, H Takiguchi, K Tamada, K Abe, R Colorado, M Graupe, OE Shmakova, TR Lee, Microstructure, wettability, and thermal stability of semifluorinated self-assembled monolayers (SAMs) on gold, JOURNAL OF PHYSICAL CHEMISTRY B, 10.1021/jp0003499, Vol.104, No.31, pp.7417-7423, 2000.08, The microstructure, wettability, and thermal stability of self-assembled monolayers (SAMs) on gold generated from semifluorinated alkanethiols F(CF2)(10)(CH2)(n)SH, where n = 2, 6, 11, 17, and 33 (F10HnSH), were examined by polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS) and dynamic contact angle measurements. Analysis by PM-IRRAS revealed that the length of the methylene spacer (Hn) influenced the tilt angle of the fluorocarbon segments in the semifluorinated SAMs. As the length of the methylene spacer was increased, the tilt angle of the perfluorocarbon moiety increased with respect to the surface nomlal. The longer methylene spacers (HIE, n = 11, 17, and 33) exhibited well-ordered trans-extended conformations as indicated by the position of the antisymmetric methylene band (nu(a)(CH2) = 2919 cm(-1)). Shortening the length of the methylene spacer to It = 6, however, led to a decrease in conformational order (nu(a)(CH2) = 2925 cm(-1)). Dynamic contact angle measurements using the Wilhelmy plate method showed that the semifluorinated SAMs were poorly wet by both water (average theta(a) = 120 degrees) and hexadecane (average theta(a) = 81 degrees). The wettability varied with the length of the methylene spacer; in particular, both the thinnest and the thickest semifluorinated SAMs (derived from F10H2SH and F10H33SH, respectively) exhibited relatively low dynamic contact angle values. In addition, the thermal stability of the semifluorinated SAMs was found to increase as the length of the methylene spacer was increased. Overall, these films exhibited remarkable resistance to thermal degradation (e.g., SAMs derived from F10H33SH sustained a relatively high contact angles after incubation at 150 degrees C for 1 h in air).. |
| 79. |
K Abe, H Takiguchi, K Tamada, Dynamic contact angle measurement of Au(111)-thiol self-assembled monolayers by the Wilhelmy plate method, LANGMUIR, 10.1021/la990624m, Vol.16, No.5, pp.2394-2397, 2000.03, The efficient use of the Wilhelmy plate method to measure dynamic contact angles with asymmetric Au-thiol self-assembled monolayer (SAM) plates is studied. To prepare a Au(111) surface for SAM formation, gold is deposited only on one side of substrates. The sessile drop method is applied to estimate wettability of SAMs, because of this asymmetric feature of Au-thiol SAM samples. A modified Wilhelmy plate method to analyze the wettability of SAMs is proposed. Using mica as substrates, this method provides sufficient precision. This will help future studies of Au-thiol SAM wetting in combination with other surface characterization techniques.. |
| 80. |
H Takiguchi, K Sato, T Ishida, K Abe, K Yase, K Tamada, Delicate surface reaction of dialkyl sulfide self-assembled monolayers on Au(111), LANGMUIR, 10.1021/la981450w, Vol.16, No.4, pp.1703-1710, 2000.02, Self-assembly of n-dioctadecyl sulfide (ODS) on Au(111) has been closely investigated by using X-ray photoelectron spectroscopy (XPS), in which the binding condition of sulfur on Au(111) was determined by the S(2p) XPS peak position, and the surface density and chain conformation of adsorbed molecules were determined by the relative XPS peak intensity, C(1s)/S(Pp). The surface reaction of ODS on Au(111) was unstable unlike ODT SAM, and it was changed drastically by small variation of adsorption condition. When adsorption was carried out in 1 mM CH(2)Cl(2) solution at room temperature, ODS molecules mostly formed fully adsorbed SAMs, intact without C-S cleavage. This was evaluated by the C(1s)/S(2p) intensity, which was twice as strong as ODT SAM, and by the S(2p) peak which appeared as a doublet at the position of "unbound" sulfur [S(2p(3/2)) at similar to 163 eV], suggesting "physisorption" of ODS on Au(111). On the other hand, when a different condition for SAM formation was used (e.g., high temperature, long time immersion, or CHCl(3) as a solvent), the C(1s)/S(2p) intensity decreased to a value smaller than ODT SAM, and the S(2p) peak was shifted to lower binding energies, the "bound" (162 eV) and "free" (161 eV) sulfur positions. In these SAMs, different surface reactions including carbon-sulfur (C-S) bond cleavage seem to occur rather than nondestructive adsorption. High-resolution atomic force microscope images revealed that ODS SAM, prepared by 24-h immersion in 1 mM CH(2)Cl(2) solution at room temperature, formed a hexagonal lattice with the lattice constant, d = 0.46 nm, which is nearly equal to the close-packed distance between alkyl chains and totally incommensurate against gold adlattice. Our data suggest a unique self-assembling process of ODS SAM, in which the chain-chain interaction is expected to be more predominant rather than the molecule-substrate interaction unlike ODT SAM.. |
| 81. |
S Ohnishi, M Hato, K Tamada, HK Christenson, Presence of particles on melt-cut mica sheets, LANGMUIR, 10.1021/la981049+, Vol.15, No.9, pp.3312-3316, 1999.04, We show the presence of numerous particles on mica surfaces melt-cut for use in the surface force apparatus (SFA). The particles, as observed by atomic force microscopy, are typically 20-25 nm in diameter and 2-3 mo high, and cover up to 0.05% of the surface area. They consist of solidified droplets of molten mica, scattered across the surfaces during the cutting of cleaved mica with a white-hot platinum wire. The particles adhere strongly to the mica surfaces in inert atmospheres but become mobile and disappear upon scanning under water and polar liquids. They seem to remain attached to the surfaces in nonpolar liquids. The particles appear to affect to a noticeable extent only experiments involving capillary condensation of water between mica surfaces.. |
| 82. |
M Hato, H Minamikawa, K Tamada, T Baba, Y Tanabe, Self-assembly of synthetic glycolipid/water systems, ADVANCES IN COLLOID AND INTERFACE SCIENCE, 10.1016/S0001-8686(98)00085-2, Vol.80, No.3, pp.233-270, 1999.04, Glycolipids (amphiphiles that bear oligosaccharides as their hydrophilic headgroups) are of importance both scientifically and technically. This review describes recent advances in our understanding of the molecular correlations in phase behavior in aqueous glycolipids over the past several years. In the first part, we discuss how headgroup stereochemistry affects the phase behavior of glycolipids both in two- and three-dimensional systems. In the second part, we discuss the effects of alkyl chain structure and phase behavior of phytanyl-chained glycolipid/water systems. The physical properties of glycolipid/water systems depend strongly on the inter-headgroup interactions that are related to such factors as stereochemistry (conformation) and size of headgroups, type of sugar residues involved, alkyl chain structure, etc. Thus, apart from the conventional concept like 'hydrophilic/lipophilic balance', explicit accounts of headgroup interactions are crucial to control the particular glycolipid/water system concerned. This is in marked contrast to the conventional amphiphile/water systems where the inter-headgroup interactions are in most cases simply repulsive. (C) 1999 Elsevier Science B.V. All rights reserved.. |
| 83. |
K Tamada, K Abe, F Nakanishi, Wetting property of hydrophobic surfaces prepared by Au(111)-thiol self-assembled monolayers., ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, Vol.216, p.U614, 1998.08. |
| 84. |
K Tamada, J Nagasawa, F Nakanishi, K Abe, T Ishida, M Hara, W Knoll, Structure and growth of hexyl azobenzene thiol SAMs on Au(111), LANGMUIR, 10.1021/la971348j, Vol.14, No.12, pp.3264-3271, 1998.06, The structure and growth of functionalized thiol self-assembled monolayers (SAMs) on Au(lll) derived from a new compound, 12-(4-((4-hexylphenyl)azo)phenoxy)dodecane-1-thiol ("hexyl azobenzene thiol"), were examined by atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), dynamic contact angles, Fourier transform infrared-reflection absorption spectroscopy (FTIR-RAS), and reflection UV-vis absorption spectroscopy. The hexyl azobenzene thiol SAM showed adsorption kinetics comparable to that of alkanethiols. At the initial stage of SAM growth, formation of nanosize domains resulting from the rearrangement of molecules on the surface was confirmed in a similar manner as for alkanethiol SAMs with long alkyl chains. The hexyl azobenzene thiol SAM exhibited a unique molecular ordering due to the intermolecular interaction between tail groups. Molecular resolution AFM images revealed an expanded lattice (nearest neighbor spacings, a = 5.3 +/- 0.1 Angstrom, b = 5.6 +/- 0.1 Angstrom; angle between the two axes, phi = 85 +/- 1 degrees) relative to that of simple azobenzene-terminated SAMs, due to the influence of the hexyl-terminal groups attached to the para-position of the azobenzene moieties. Average molecular tilt and twist angles (alpha = 14 degrees, beta = 42 degrees) were determined by quantitative analysis of C-H stretching mode for FTIR-RAS data. The reflection UV-vis absorption spectra implied that the long axes of the trans-azobenzene moieties were aligned normal to the plane of surface in fully covered SAMs, while those were more tilted (aligned more parallel to the surface plane) in the submonolayers.. |
| 85. |
Fusae Nakanishi, Jun'ichi Nagasawa, Kaoru Tamada, Masaru Yoshida, Haruhisa Akiyama, Yong Kuan Gong, Koji Abe, Photoreactive poly(vinyl alcohol) bearing p-phenylenediacrylic acid moiety: Property and photoreaction of Langmuir-Blodgett film, American Chemical Society, Polymer Preprints, Division of Polymer Chemistry, Vol.39, pp.355-356, 1998.03, A novel photoreactive Langmuir-Blodgett film was prepared using poly(vinyl alcohol) with conjugate diolefin moiety as the side chain. The characteristics of LB film were evaluated and its high photoreactivity as a function of molecular arrangement were investigated using spectroscopic analysis. The photoreactivity of these polymers were enhanced due to the presence of excimers. The IR spectrum of irradiated LB film showed the decrease in double bonds absorption intensity. Cycloaddition of double bonds took place in the irradiated LB film forming cyclobutane rings.. |
| 86. |
W Knoll, G Pirwitz, K Tamada, A Offenhausser, M Hara, Supramolecular interfacial architectures for controlled electron transfer, JOURNAL OF ELECTROANALYTICAL CHEMISTRY, 10.1016/S0022-0728(97)00088-0, Vol.438, No.1-2, pp.199-205, 1997.11, We report on the structural principles and requirements for the controlled formation of supramolecular architectures of electron transfer protein layers at electrode surfaces functionalized by organic mediator layers, organized by self-assembly or Langmuir/Blodgett/Kuhn technique. STM and AFM are employed to elucidate at the molecular level details of the monolayer formation, in particular, at early stages of the nucleation and growth process of SAMs. Optical methods, in particular surface plasmon spectroscopy and mica waveguide spectroscopy are used to observe on-line the build-up of these multilayer assemblies. With a combined surface plasmon spectroscopy and cyclovoltammetry set-up it is possible to investigate the interfacial architecture and the electron transfer reactions of the proteins simultaneously. (C) 1997 Elsevier Science S.A.. |
| 87. |
Kaoru Tamada, Masahiko Hara, Hiroyuki Sasabe, Wolfgang Knoll, Surface phase behavior of n-alkanethiol self-assembled monolayers adsorbed on Au(111): An atomic force microscope study, Langmuir, 10.1021/la950630s, Vol.13, No.6, pp.1558-1566, 1997.03, n-Alkanethiol (CnH2n+1SH) self-assembled monolayers (SAMs) adsorbed on Au(111) were studied with an atomic force microscope (AFM) to confirm the influence of the lateral interaction between adsorbed thiols on the film morphology. Two experiments were performed: firstly, a study of the domain formation at the initial stage of SAM growth (single component) and, secondly, investigations of the coadsorption phenomenon in mixed SAMs composed of two alkanethiols having different chain lengths. For the kinetics study, Au(111) was immersed into the 10-2 mM ethanol solutions with the single component alkanethiol (C4H9SH, C12H25SH, or C18H37SH), for varying times (1 s to 10 min). In all cases, the film coverage increased as the immersion time became longer, and finally the surface was totally covered with thiols after an immersion time of 3 min or more. Clear island formations were observed in the partially covered C12H25SH and C18H37SH SAMs, while C4H9SH formed meshlike domains. The mixed SAMs were prepared by immersing Au(111) into 1 mM ethanol solutions with mixed alkanethiols (C4H9SH/C18H37SH) of various compositions, Rsoln = [C4H9SH]/[C18H37SH] = 1/1 to 100/1, for a time of 1 h. Clear phase separation was observed at Rsoln = 20/1 and 40/1. Above or below these compositions, the film surface appeared very flat, covered with a nearly single component, C4H9SH or C18H37SH, respectively. This is the first systematic study of the surface phase behavior of alkanethiol SAMs by AFM imaging. It reveals more direct information about the film morphology than previous studies with conventional surface analytical techniques such as X-ray photoelectron spectroscopy, ellipsometry, contact angles, etc.. |
| 88. |
W Knoll, M Hara, K Tamada, Ordered nucleation and surface phase behavior of self-assembled monolayers on Au(111) studied by scanning tunneling and atomic force microscopies., ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, Vol.212, pp.375-POLY, 1996.08. |
| 89. |
Kaoru Tamada, Hiroyuki Minamikawa, Masakatsu Hato, Kenjiro Miyano, Phase transition in glycolipid monolayers induced by attractions between oligosaccharide head groups, Langmuir, 10.1021/la9503257, Vol.12, No.6, pp.1666-1674, 1996.03, The surface property of two kinds of synthetic glyceroglycolipids was investigated to confirm the stereoeffect of sugar residues on the phase behavior in monolayers: one is the maltooligosaccharide-containing lipids [MalN(C12)2] and the other is cellooligosaccharide-containing lipids [CelN(C12)2]. The two kinds of glycolipids exhibit the opposite dependence of the surface pressure - area (II-A) isotherm on the number of glucose residues (N), in that MalN(C12)2 tends to be more expanded as N increases, while CelN(C12)2 tends to be more condensed. The liquid-expanded/liquid-condensed phase transition in Cel4(C12)2 was evaluated by the Brewster angle microscopy and the latent heat analysis with the Clausius - Clapeyron equation, as a model of film condensation induced by the attraction between oligosaccharide head groups. The film morphology of Cel4(C12)2 was unique in that it exhibits the optically isotropic and flexible fluid type of the LC phase, while Glc(C16)2 forms a two-dimensional tilted crystalline phase in the same way as fatty acids and phospholipids. The heat of transition (ΔH) of Cel4(C12)2 does not converge toward zero even at high temperature. In other words, the main transition of Cel4(C12)2 does not become second order in contrast to the behavior usually encountered in monolayers. The refractive index of the oligosaccharide head groups in water as well as the alkyl chains in air must be properly taken into account to interpret the reflectivity.. |
| 90. |
Kaoru Tamada, Kenjiro Mlyano, Capillary wave propagation on water covered with polyamic acid monolayer films, Japanese Journal of Applied Physics, 10.1143/JJAP.33.5012, Vol.33, No.9 R, pp.5012-5018, 1994.09, Externally generated capillary wave propagation has been studied on water covered with poly(amic acid) alkylammonium salts. In addition, fluorescence microscope observation was performed with a poly(amic acid) containing a fluorophore dye. The octadecylammonium salt of this polymer exhibits condensed liquid/gas coexistence films when the pressure is very low (pressure Π ≃ 0), where the liquid phase is highly viscoelastic. Such domain structures were not found in the hexadecylammonium salts of other polymers. However, all films used here can be compressed homogeneously and isotropically at higher pressures, independent of the chain length of alkyl amines. These observations suggest that the mechanical character in the highly condensed state is determined mainly by the flexibility of polymer chains, while the degree of condensation in the dilute state is more influenced by the alkyl amines. © 1994 IOP Publishing Ltd.. |
| 91. |
K TAMADA, M NAIR, H YU, PROBE DIFFUSION IN A BINARY MONOLAYER SYSTEM - NANOPARTICLE PHOSPHOLIPID MIXTURES ON THE AIR-WATER-INTERFACE, ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, Vol.207, pp.215-POLY, 1994.03. |
| 92. |
K TAMADA, M NAIR, H YU, LATERAL DIFFUSION OF NANO-PARTICLES AT THE AIR-WATER-INTERFACE, ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, Vol.206, pp.23-COLL, 1993.08. |
| 93. |
K. Tamada, S. Kim, H. Yu, Lateral Diffusion of a Probe Lipid in Biphasic Phospholipid Monolayers: Liquid/Gas Coexistence Films, Langmuir, 10.1021/la00030a020, Vol.9, No.6, pp.1545-1550, 1993.01, The method of fluorescence recovery after photobleaching has been used to determine the lateral diffusion coefficient (D) of a fluorescent lipid probe in L-α-dilauroylphosphatidylcholine monolayers. The surface mass density was varied over a wide range from the liquid expanded/gas coexistence phase (LE/G) to the homogeneous liquid phase. The lateral diffusion coefficient reached a maximum value at the “liftoff” point on the surface pressure-area curve (D ≈ 1.2 × 1(10 −10 m 2 /s, A = 1.1−1.3 nm 2 /molecule, T = 22−24 °C), corresponding to the onset of the uniphasic LE state, and decreased from this maximum as the mass density was varied to both higher and lower values of area per molecule (A). The results were analyzed according to the effective-medium theory and the free area model, respectively. The D values in the LE/G biphasic monolayers were evaluated as a function of the area fraction of the LE phase, whereby it was shown that the gas bubbles in the LE/G can be regarded as semipermeable obstacles for the lipid probes, with a relative permeability of the gas bubbles with respect to the LE phase of 0.2–0.3. © 1993, American Chemical Society. All rights reserved.. |
| 94. |
Kenjiro Miyano, Kaoru Tamada, Capillary waves: a new monolayer characterization technique using an old method, Thin Solid Films, 10.1016/0040-6090(92)90178-E, Vol.210-211, No.PART 1, pp.96-97, 1992.04, The capillary wave (surface wave) on water is shown to be a sensitive probe to characterize the monolayers spread on it. The principle of the capillary-wave probe, the unique features of the technique, and its use as an integral part of an LB-deposition trough are briefly described. © 1992.. |
| 95. |
Kenjiro Miyano, Kaoru Tamada, Capillary Wave Propagation on Water Covered with Inhomogeneous Monolayers: Liquid/Gas Coexistence Films, Langmuir, 10.1021/la00037a030, Vol.8, No.1, pp.160-163, 1992.01, Externally generated capillary wave propagation has been studied on water whose surface was covered with a monolayer in the liquid/gas coexistence phase up to 1 kHz. A simultaneous morphology observation with a fluorescence microscope enabled us to make a one-to-one correspondence between the fraction of the liquid film and the propagation characteristics. It was found that the liquid film does not affect the capillary wave significantly until it covers more than 90% of the water surface, which indicates that the dynamic elasticity of the liquid monolayer below 1 kHz is extremely low. It was also noted that the bubbles (the gas phase) were very stable against coalescence, implying that the line tension of the liquid phase is quite low. These findings suggest that the liquid phase in equilibrium with the gas phase is in a very shallow intermolecular potential. It was confirmed that the surface waves do not affect the morphology of the monolayer. © 1992, American Chemical Society. All rights reserved.. |
