Takeshi Koyano

Second harmonic generation from mixed Langmuir-Blodgett films of N-acyl-p-nitroaniline and its homologous amphiphile

Abstract Mixed Langmuir-Blodgett multilayers of N -acyl- p -nitroaniline and its homologous amphiphile, p -alkylaminophenylacetic acid, show second harmonic generation in Y-type films. The second harmonic output was anisotropic to the dipping direction, and depended on the molecular-chain lengths of the mixture. As a model of noncentrosymmetric structure in the Y-type film, the “herringbone”-like arrangement of interlayer molecules was considered. This arrangement of molecules was confirmed by measurements of second harmonic fringing patterns from heterostructural films with different combination of active and inactive layers.

Development of a Technique for Microimmobilization of Proteins on Silicon Wafers by a Streptavidin−Biotin Reaction

In order to enable the future construction of molecular devices made of functional proteins, we have developed a technique for microimmobilization of proteins into organized patterns on a silicon wafer. A specific binding reaction between streptavidin and biotin forms the basis of our method. Active and inactive biotin regions were created on a silicon wafer using a photolithographic technique. Circuit‐type patterns and 0.75/1.5 μm line‐and‐space patterns of a model fluorescent protein, B‐phycoerythrin, were successfully created on a silicon wafer.

Second-Harmonic Generation from Y-Type Deposition of N-Acyl-p-Nitroaniline Langmuir-Blodgett Films

The second-order nonlinear optical properties of Y-type-deposited N-acyl-p-nitroaniline Langmuir-Blodgett films are studied. The second-harmonic intensity from the film shows a large anisotropy in the dipping direction and is dependent on the acyl-chain length. The same kind of anisotropy and dependence is observed in UV absorbance. It is indicated that the orientation of the p-nitroaniline group in the molecule is changed by the chain length by means of X-ray diffraction and IR spectroscopy.

Molecular rearrangement in heat-treated Langmuir-Blodgett films of mixtures of N-acyl-p-nitroaniline and fatty acid monitored by second-harmonic generation

Abstract A molecular rearrangement was monitored as an induction of second-harmonic generation (SHG). Mixed Langmuir-Blodgett films of N-acyl-p-nitroaniline and fatty acid showed SHG after heat treatment below the melting point. Studies on interference patterns of second harmonics, UV-visible absorption spectra, electron micrographs and X-ray diffraction patterns revealed that molecular rearrangement resulting from molecular movement occurred in heat-treated films. The effect of alkyl chain length of the mixing molecules was measured as an example of this monitoring method.

Electric Responses of Odor Sensor Using Vapor-Deposited Copper-Phthalocyanine Film

We investigated electric responses of a sensor using a copper-phthalocyanine film to various odorants. The film was deposited on a substrate with a pair of interdigital gold electrodes by vacuum evaporation. This sensor could detect with specificity odorants classified under the amine group and benzaldehyde by monitoring changes in electric resistance.

Changes of Chaotic Oscillation Patterns of Artificial Lipid Membrane Induced by Light

We have examined chaotic oscillation patterns of a Millipore membrane infiltrated with dioleyl phosphate and an azobenzene derivative under visible or UV irradiation. As a result, the amplitude of the oscillation was larger and the correlation dimension was smaller under UV irradiation. This result suggests that some of many nonlinear oscillators of the membrane could oscillate coherently under UV irradiation. We believe that it is the first experimental result which can be explained by the globally coupled map model.