Hirobumi Shibata

Phase-separated structures of mixed langmuir-blodgett films of fatty acid and hybrid carboxylic acid

Phase separation often occurs in mixed Langmuir-Blodgett (LB) films. Usually circular domains at the micrometer length scale form in the LB films. The size and shape of the domains are governed by a compromise between two competing interactions of line tension and dipole-dipole interaction. An attempt was made to control the line tension by varying systematically the hydrophobic moieties of the film-forming molecules. Phase-separated structures of two-component mixed LB films of fatty acid [C(k)H(2k+1)COOH (HkA)] and hybrid carboxylic acid [C(m)F(2m+1)C(n)H(2n)COOH (FmHnA)] were investigated. IR spectra of the mixed LB films of H17A and F8H10A revealed that the alkyl chains were in an all-trans conformation and that the molecular orientation remained unchanged when the two components were mixed. Nanowires formed in the mixed LB films of HkA and F8H10A. The width of the nanowires increased with an increase in k. Domain size and shape in the mixed LB films of H17A and FmHnA depended strongly on the values of m and n. Circular domains at the micrometer length scale formed in the region m + n < 16. In contrast, domains at the nanometer length scale formed in the region m + n > or = 16 except for F6H10A. These results were explained by using a lattice model that considers the effect of the hydrophobic moieties of fatty acid and hybrid carboxylic acid on the line tension.

Micro- and nanopatterned copper structures using directed self-assembly on templates fabricated from phase-separated mixed Langmuir-Blodgett films.

We report a versatile method to confine metal thin films in micro- and nanopatterns using directed self-assembly on the templates fabricated from phase-separated mixed Langmuir-Blodgett (LB) films. The pattern of the mixed LB films can be tuned by adjusting intermolecular interaction between the film-forming molecules in the LB films and by varying the fabrication conditions of the films such as the mixing ratio, subphase temperature, and surface pressure. We use the patterned LB films for templates to confine metal in patterned regions, taking advantage of the difference between the surface free energy of the patterned regions and that of the self-assembled monolayer of the silane coupling agent. Au nanoparticles are confined onto the patterned films as a catalyst for the succeeding Cu electroless deposition. The atomic force microscopic images, Auger electron spectra, and scanning Auger electron maps of a Cu-deposited film show that Cu is selectively deposited on the patterns of phase separation of the original mixed LB films.

Patterning of J-aggregated dyes using directed self-assembly on micro- and nanopatterned templates fabricated from phase-separated mixed Langmuir-Blodgett films

We report a useful technique for the deposition of dyes in the form of J-aggregates using directed self-assembly on the micro- and nanopatterned templates fabricated from the phase-separated mixed Langmuir-Blodgett (LB) films. The patterns of the mixed LB films can be tuned by adjusting the intermolecular interactions between the film-forming molecules. We used the mixed LB films containing silane coupling agent for the fabrication of micro- and nanopatterned templates, taking advantage of the difference between the surface free energy of the patterned regions and that of the self-assembled monolayers of the silane coupling agent. Atomic force microscopy showed that dyes were deposited by casting, spin-coating and the LB technique in accordance with the patterns of the original mixed LB films. Emission spectroscopy revealed that J-aggregates were formed in the patterned films. We succeeded in obtaining nanopatterns of a cyanine dye in the form of J-aggregates on the templates.

Directed self-assembly of gold nanoparticles and gold thin films on micro- and nanopatterned templates fabricated from mixed phase-separated Langmuir-Blodgett films

We report a useful technique to immobilize Au nanoparticles (Au-NPs), double layers of Au-NPs and Au thin films on micro- and nanopatterns using directed self-assembly on templates fabricated from phase-separated mixed Langmuir-Blodgett (LB) films. The patterns of the mixed LB films can be tuned by adjusting the intermolecular interactions between the film-forming molecules and the fabrication conditions of the films. We used mixed LB films containing a silane coupling agent for the fabrication of micro- and nanopatterned templates to immobilize Au-NPs of different sizes in the patterned regions. Atomic force microscopy, Auger electron spectroscopy and scanning Auger electron mapping of the Au-NP-immobilized films showed that Au-NPs were immobilized in accordance with the patterns of the original mixed LB films. A layer of the immobilized Au-NPs was used as a catalyst for the succeeding Au electroless deposition or as a first layer for the stacking of a second layer using the layer-by-layer deposition method. We have also succeeded in controlling the thickness and density of the Au-NPs.

Preparation and photocatalytic activity of titania particulate film with silica as binder

SummariesA thin film of titania (TiO2) with silica (SiO2) as binder was prepared by sintering titania particles dispersed in cyclohexanone with added alkoxysilane (TEOS) and held on a glass substrate. TEOS was partially hydrolysed with hydrochloric acid at pH 4.0 before use to give a uniform titania thin film. X-ray diffraction and IR absorption measurements on the product revealed the formation of a titaniasilica composite thin film. Evaluation by the pencil hardness test of the mechanical strength showed that the composite film had a strength remarkably higher than that of a titania film with no silica binder. Although the addition of a silica binder was found to decrease the photocatalytic activity of the titania film, removal of silica by treatment with NaOH from the surface layer of the composite film gave a high photocatalytic activity to the film.RésuméUn film mince de dioxyde de titane (TiO2) avec silice (SiO2) comme liant a été préparé par frittage de particules de dioxyde de titane dispersées dans de la cyclohexanone avec l’addition de l’alkoxysilane (TEOS) et tenu sur un substrat de verre Le TEOS a été partiellement hydrolysé par le moyen d’acide chlorhydrique à pH 4.0, avant usage, pour donner un mince film uniforme de dioxyde de titane. Des mesures du produit par diffraction rayon x et par absorption IR ont révélé la formation d’un film mince d’un composite de dioxyde de titane-silice. Une évaluation par un essai de dureté crayon de la robustesse méchanique a montré que le film composite avait une robustesse qui était remarquablement plus élevée que celle d’un film de dioxyde de titane sans liant de silice. Bienque l’on a trouvé que l’addition d’un liant de silice a diminué l’activité photocatalytique du film de dioxyde de titane, l’enlèvement de la silice de la couche surfacique du film composite, par le moyen de NaOH, a donné au film une importante activité photocatalytique.ZusammenfassungEin dünner Film aus Titandioxid (TiO2) mit einem Silikat (SiO2) als Bindemittel wurde hergestellt durch das Sintern von Titandioxidpartikeln, die in Cyclohexanon und Alkoxysilan (TEOS) dispergiert waren und auf einem Glassubstrat gehalten wurden. Das Alkoxysilan wurde vor Verwendung mit Salzsäure bei pH4.0 teilweise hydrolysiert, damit wir einen durchgängigen dünnen Film aus Titandioxid erhielten. Die Messung von Röntgen-Diffraktion und IR Absorption zeigten, dab sich in dem Film ein Komposit aus Titandioxid und Silikat gebildet hat. Wir testeten die Härte und mechanische Stärke des Filmes durch den Bleistifttest und fanden dab der Film eine deutlich grössere Stärke hatte als ein Titandioxidfilm ohne das Silikatbindemittel. Während die Hinzufügung des Bindemittels die fotokatalytische Wirkungsweise des Titandioxidfilmes herabsetzte, lies sich dieses durch die Behandlung der Oberflächenschicht mit NaOH rückgängig machen.

Fabrication and Functionalization of Inorganic Materials Using Amphiphilic Molecules

In this review, the synthesis of inorganic materials with various properties using amphiphilic molecules is examined. Amphiphilic molecules are used for the formation of highly ordered mesostructures and the surface modification. Two examples of the mesostructures are crystalline mesoporous titania (TiO2) and the novel visible light responsive mesostuructured titania modified with dye in the pores, which can be fabricated using the molecular self-assemblies of amphiphiles as templates. Surface modification using amphiphilic molecules enables the construction of self-assembled arrays of silica particles and the preparation of a film that can control adsorption/desorption behavior of bovine serum albumin (BSA) by light irradiation.