Atsushi Aoki

Photopatterning of a fluorescent polymer Langmuir–Blodgett film by crosslinking reaction

A fluorescent two-dimensional network patterning was fabricated with polymer LB films. An amphiphilic polymer consisting of N-dodecylacrylamide, N-11-acryloylundecyl-4-vinylpyridinium salt and 1-pyrenylacrylamide forms a stable monolayer, which is transferred onto solid substrates yielding LB films. The absorption and emission spectra of the LB films indicate that pyrene chromophore exists in the LB film. On irradiation, photo-crosslinking reaction of the acryloyl group, which is aligned on each interlayer hydrophobic tail surface of LB films occurs efficiently. Consequently, the irradiated polymer LB film becomes insoluble in organic solvents due to the formation of the two-dimensional polymer network in the LB film. The patterned fluorescent polymer LB film was confirmed by the fluorescence microscopy.

Photocurrent amplification by an energy/electron transfer cascade in polymer Langmuir–Blodgett films

Effective photocurrent generation by visible light irradiation on hetero-deposited polymer Langmuir-Blodgett (LB) films containing tris(bipyridine) ruthenium(II) (Ru(bpy)3(2+)) and anthracene derivatives was observed. The photocurrent amplification was found to be assisted by the photoinduced energy/electron transfer cascade, which consists of the interlayer triplet-triplet energy transfer process from photoexcited Ru(bpy)3(2+) to anthracene, and then electron transfer processes from the triplet anthracene to a viologen acceptor, from Ru(bpy)3(2+) to the oxidized anthracene and from the electrode to Ru(bpy)3(3+).

A structural effect on electrochemical behavior of hetero-deposited redox polymer Langmuir–Blodgett films containing ferrocene and tris(bipyridine)ruthenium derivatives

Abstract A structural effect on the electrochemical behavior of hetero-deposited redox polymer Langmuir–Blodgett (LB) films containing ferrocene (Fc copolymer) and tris(bipyridine)ruthenium derivatives (Ru copolymer) on electrodes was investigated by cyclic voltammetry. The hetero-deposited LB film structure consists of Ru copolymer LB film (three layers) as an inner layer and Fc copolymer LB film (two layers) as an outer layer on ITO electrodes. The hetero-deposited redox polymer LB films which are prepared by the deposition at a surface pressure higher than 28 mN m−1 show that the redox behavior of the ferrocene moiety in the outer Fc copolymer LB film is controlled by the redox condition of the ruthenium complex in the inner Ru copolymer LB film and not directly influenced by the electrode potential. On the other hand, in the LB films prepared at a pressure less than 25 mN m−1, such behavior was not observed because the inner Ru copolymer LB films cannot work as an insulator between the outer Fc copolymer LB films and the ITO electrode. The voltammetric shapes of the Ru copolymer LB films were distorted with increasing deposition surface pressure. These results indicate that the insulating property of the inner layer is improved whereas the electron transfer rate in the interlayer becomes slower with increasing deposition surface pressure because of the formation of the high packing density of alkyl side chains of the LB films.

Impedance analysis of the electron transfer process in redox polymer Langmuir–Blodgett films

Abstract The electron transfer process in redox polymer Langmuir–Blodgett films containing tris(bipyridine)ruthenium complex has been investigated as a function of the number of monolayers by an impedance spectroscopy. The complex impedance and capacitance data show that the equivalent circuit model consists of the parallel circuit with the membrane capacitance of the LB films as a fast charging process and the faradaic capacitance controlled by the charge transfer resistance as a slow charging process. The charge transfer resistance and the faradaic capacitance increases with the number of the monolayers whereas the membrane capacitance decreases with increasing number of the monolayers.

Molecular photopatterning with a two-dimensional network of polymer LB films

Abstract The preparation of preformed polymer Langmuir–Blodgett (LB) film which has a cross-linkable group and the formation of a two-dimensional network polymer LB film by the efficient cross-linking reaction in the LB film were described. N-Dodecylacrylamide copolymer containing a cross-linkable group, N-ω-acryloylundecyl-4-vinylpyridinium salt, forms a stable condensed monolayer and can be transferred onto a silicon wafer. On UV irradiation on the polymer LB film through a photomask in which fine patterns are figured, the fine patterns can be drawn clearly as the result of the formation of a two-dimensional network by efficient cross-linking of the linear polymer chain in LB film. The characterization of the LB film as a candidate of high-resolution resists was also investigated from the sensitivity measurement.

Molecular patterning with a two-dimensional network polymer LB film 2: Drawing patterns by an electron beam

Abstract Electron beam lithography was investigated using a cross-linkable polymer Langmuir–Blodgett (LB) film. Cross-linking reaction occurs in the LB film with electron beam irradiation as well as UV light irradiation and the irradiated LB film becomes insoluble in the organic solvents to form a two-dimensional network in the LB film. The sensitivity and contrast of the cross-linkable polymer LB film are 3xa0μCxa0cm-2 and 0.64, respectively. The limiting resolution of patterning is 0.2xa0μm line-and-space. The electron beam lithography using the cross-linkable polymer LB film is applicable to the future nanotechnology.

Fabrication of Photoresponsive Nano-Organized Polymer Assemblies

Abstract We describe here fabrication of organized polymer assemblies where the vectrial photoinduced electron transfer can be controlled by the spatial molecular arrangement by LB technique. The hetero-deposited redox polymer Langmuir-Blodgett (LB) films consisting of poly(N-dodecylacrylamide-co-ferrocenylmethylacrylate)(Fc copolymer) and poly(N-dodecy-lacrylamide-co-(4-(acryloylmethyl)-4′-methyl-2,2′-bipyridine)-bis(2,2′-bipyridine) ruthenium diperchlorate)) (Ru copolymer) were investigated by cyclic voltammetry and the steady state photocurrent measurement. Two kinds of the hetero-deposited structures are constructed by varying with the deposition order of these redox polymer monolayers using the LB technique. The cyclic voltammograms of the hetero-deposited redox polymer LB films show current rectifying and charge storage properties. On light irradiation, the anodic photocurrent is observed at the hetero-deposited redox polymer LB films consisting of Ru copolymer LB film as an inner layer and Fc copol...

Magnetic Properties of Polymer Lb Films Containing Ferrocene Derivatives

Abstract Langmuir-Blodgett (LB) films of copolymer with ferrocenyl-methyl- acrylate(FcMA) and N-dodecyl-acrylamide(DDA) were fabricated. The FcMA moiety is supposed to enter into the alkyl chains of DDA and be arranged two- dimensionally form the X-ray diffraction analysis. The magnetization curve showed a steep rise up to several kOe and a gentle increase with the magnetic field up to 55 kOe. This behavior seems to be ferromagnetic. Even more than room temperature, the half of the magnetic moment at 4.5K remained, and the magnetization curve showed ferromagnetic. Furthermore, this LB film had a magnetic anisotropy depending on the dipping direction. On the other hand, the magnetization curves for the powder and the cast film of the copolymer were paramagnetic. The magnetic moment of the LB film is about 30 times larger than those of the powder and the cast film. These results indicate that a configurational interaction is important to explain the enhancement of magnetic moment of this copolymer.

Determination of Cationic Drugs on a Nafion-Coated Electrode

There has been considerable interest in electrochemical determinations in both static and flow systems because of their high sensitivity. Among extensive studies, some efforts1–3 have recently been focused on treatment of electrode surfaces to improve reproducibility or analyte selectivity in high performance liquid chromatography (HPLC) and flow injection analysis (FIA). We report here the electrochemical determination of several cationic drugs on Nafion-coated electrodes both in static and flow systems.