Two types of biomimetic chemical sensing systems are reviewed. One is an electronic nose and tongue which can recognize odor or taste from the output pattern of arrayed chemical sensors with different but overlapped specificities. The other is a chemical plume tracing system which has been developed to mimic the moth behavior in tracing the sexual pheromone from a female. We have created an odor/gas tracing robot and a compass, both of which can detect the direction from which an odor/gas is issuing.

In order to examine the validity of Mott-Schottky model at organic/metal interfaces, the position of the vacuum level of N,N'-bis(3-methylphenyl)-N,N'-diphenyl -[1,1'-biphenyl]-4,4'-diamine (TPD) film formed on various metal substrates (Au, Cu, Ag, Mg and Ca) was measured as a function of the film-thickness by Kelvin probe method in ultrahigh vacuum (UHV). TPD is a typical hole-injecting material for organic electroluminescent devices. At all the interfaces, sharp shifts of the vacuum level were observed within 1 nm thickness. Further deposition of TPD up to 100 nm did not change the position of the vacuum level indicating no band bending at these interfaces. These findings clearly demonstrate the Fermi level alignment between metal and bulk TPD solid is not established within typical thickness of real devices.

In this study, we prepared red organic light- emitting-diode (OLED) with a fluorescent dye(Sq)-doped and inserted 1,3-bis (5-p-t-butylphenyl)-1,3,4-oxadiazol-2-yl) benzene (OXD7) or/and tris (8-hydroxyquinoline) aluminum (Alq3) layers between emission layer and cathode in order to increase electroluminescent (EL) efficiency. This inserting effect has been observed and EL mechanism characteristics have been examined. The hole transport layer was N,N'-diphenyl-N, N'bis-(3-methylphenyl)-1,1'diphenyl-4,4'-diamine (TPD); the host material of emission layer was Alq3; the guest material of emission layer was Sq. When Alq3 was inserted between the emission layer and the cathode, emission efficiency increased. Highly pure red emission, however, was not attaina ble with Alq3. On the other hand, the insertion of OXD7 between the two layers blocked and accumulated holes. Because of its increasing recombination probability of electron and hole, luminance characteristics and emission efficiency were improved with holding highly pure red color.

Optically patternable light-emitting devices based on conducting polymers were fabricated and were characterized. The cathode of the devices is made with a semitransparent-Al film, which enables to photoinduced degradation of the polymers in air. The optically patternable devices were successfully made with poly (2-methoxy-5-dodecyloxy-p-phenylene vinylene) (MDOPPV), as well as with poly (3-dodecylthiophene) (PAT12). However, optical absorption study indicated that the patterning mechanism of the MDOPPV device is considerably different from that of the PAT12 device.

We demonstrate unique dye-doping method to realize organic light emitting diodes (OLED) with high efficiency, high brightness and pure red emission. In this study, we used 5,10,15,20 tetraphenyl -21H,23H-porphine (TPP) as emitting dopant into 8-hydroxyquinoline aluminum (Alq₃) emissive layer. To improve turn-on voltage and emission characteristics, a sufficient amount of 4-(dicyano methylene) -2-methyl -6-(p-dimethyl aminostyryl) -4H-pyran (DCM) was added to the TPP doped Alq₃ emissive layer. The mechanisms and the emission characteristics of the co-doped EL device are discussed using energy band diagram of the materials used in the device.

Luminance and luminous efficiency of EL devices have been improved considerably by inserting double buffer layers composed of two types of Phthalocyanine deposited by the LB technique. This is considered to be caused by hole injection through relatively smooth energy levels.

There are methods used to test the optical purity of enantiomers; however, most of the simple methods are not precise and more complicated methods are better. As a result, these methods cannot be widely used for industrial purposes. The aim of this research is to design a sensor which can discriminate D-amino acids from L-amino acids. The designed sensor has chiral membranes and uses the technique of impedance change of these chiral membranes to discriminate the amino acids. We used a noise-FFT (Fast Fourier Transform) technique to determine the membrane impedance. When an enantiomer membrane resides in a chiral environment, (E^*), diastereomeric interactions (E^*-D) and (E^*-L) are created, which may differ sufficiently in the arrangement of molecules of the membranes so as to permit the discrimination of optical substances due to the change in membrane characteristics. With increasing concentrations of the amino acids, the membrane resistance changes depended on the optical activity of the amino acids. The results suggest that the impedance changes of the chiral membrane with diastereomeric reaction can be used for the high-performance chemical sensor to measure the optical purity of different substances.

A novel chemical sensor for sulfate detection was proposed in this study, utilizing sulfate binding protein (SBP) derived from Escherichia coli as sulfate recognition element. Purified SBP was immobilized on a gold electrode modified with cysteamine and glutaraldehyde. In this study the surface potential change of the SBP modified electrode to sulfate and various ions were investigated. In order to evaluate nonspecific interaction with ionic species, proteins with various isoelectric point were immobilized on the surface of gold electrode and response to ions were measured and compared to sulfate binding protein modified electrode. We made clear that the protein modified electrode shows the potential change to ions and these potential change was effected by the isoelectric point of the protein molecule, and BSA, whose isoelectric point is closest to that of SBP, showed the similar response to ions except sulfate. With use BSA modified electrode as a reference electrode, this sensing system showed selective response to sulfate, probably because of the selective binding sulfate by SBP. This potential change difference between the SBP modified electrode and the BSA modified electrode depended on the concentration of sulfate with in the range of 5 - 150 mM.

Saltiness elicited by salt is one of the basic tastes. However, components of salt on the market differ depending on manufacturing processes and its taste as well. Salt manufactured by ion-exchange membrane process is composed of more than 99% pure sodium chloride, while bay salt contains trace coexisting components. Despite reports on sensory evaluation, the differences in taste are still uncertain because of a small amount of coexisting components. We studied the taste of salt with trace coexisting components; the bittern ("nigari" in Japanese) was evaluated objectively and quantitatively using a multichannel taste sensor with lipid/polymer membranes. A taste sensor is comprised of several types of lipid/polymer membranes for transforming information of taste substances into electric signals. The model samples were composed of sodium chloride and trace coexisting components such as magnesium sulfate, magnesium chloride, calcium chloride and sodium chloride. The taste sensor clearly discriminated each sample according to the response patterns. Based on the sensor outputs, we evaluated the taste by means of the combination of principal component analysis and ionic strength. The results show the taste of salt with nigari has a correlation with ionic strength.

Since odor sensing system is required in many fields, we have developed the system using QCM (Quartz Crystal Microbalance) sensor array and neural-network pattern recognition. In the present study, the mixed sensing films of two kinds of liquid-phase materials were characterized. As a result, it was found that the variety of sensing films were obtained by mixing two kinds of liquid-phase materials. The relative remnant of sensing film after repeated exposures was examined, and mixed films of two kinds of liquid-phase materials were found stable for the sensing materials.

In the food, beverage and cosmetic industry and so on, odor sensing systems instead of human sensory test are demanded. We have developed odor sensing systems using QCM (quartz crystal microbalance) sensor array and pattern recognition method. Since the properties of the sensors depend on the gas sorption characteristics of the sensing films coated on them, the optimum films according to target odors should be selected. In this study, we tried to select sensing films appropriate for discrimination of slightly different apple flavors. The examples of typical apple flavors were prepared blending 9 compounds. The sensing films were extracted from various kinds of materials such as lipid, stationary phase material of GC (gas chromatography) and cellulose. The selection method under the condition of the small number of measurements was studied. We analyzed the data of steady-state sensor responses in terms of the Euclidean distance, and the films appropriate for apple flavor discrimination were successfully selected.

The cationic dye, E-N-alkyl-4-[2-(4-alkyloxynaphthyl) ethenyl] quinolinium bromide has a wide-bodied chromophore with alkyl groups at opposite ends, i. e. C_mH_2m+1-D-π-A⁺-C_nH_2n+1 X^-, where D and A are electron-donor and electron-acceptor groups respectively, π is a conjugated bridge and X^- is the bromide counterion. It forms non-centrosymmetric Langmuir-Blodgett (LB) structures in which the packing is dependent upon the combination and compatibility of the alkyl groups. Films of two isomeric analogues where m + n = 34, have a layer thickness of 4.3 nm when the groups are significantly different (m = 12 and n = 22) which decreases to 2.5 nm when they are similar (m = 18 and n = 16). The latter adopts an interdigitating layer arrangement at both the upper and lower interfaces and it is the first example of a Lego-type structure with non-centrosymmetric alignment of the optically nonlinear chromophores. This is evidenced by the second-harmonic intensity, which increases quadratically with the number of layers, i. e. as .

The author's recent research topics of organic monolayer films have been reviewed. The importance of the study of organic monolayers is discussed from the viewpoints of future electronics and dielectric physics, keeping in mind the difference between monolayers and bulk materials.

We have developed a new type electrical probing system based on an atomic force microscope. This method enables us to measure simultaneously the surface topography and surface potential of thin films containing the crystal grains. The obtained local potential changes give an insight into conduction through the grains and their boundaries.

Carrier mobilities in poly(3-alkylthiphene) cast films have been studied by means of fabricating a field effect transistor (FET) at the field range of (0.4-1.6)10⁴ V/cm. It is found that the regioregurality is markedly effective to the mobilities than the side chain length. The FET mobilility of the regioregular poly(3-hexylthiophene), PHT is approximately 310^-3 cm²/Vs which is larger than that of regiorandom PHT by 3 orders of magnitude. The mobility of regioregular poly(3-dodecylthiophene), PDDT is 810^-4 cm²/Vs and is also 3 orders of magnitude larger than that of regiorandom PDDT. The mobilities of regioregular ones decrease, however, those of regiorandom ones increase at higher fields. The FET mobilities are nearly same to the mobilities estimated by the time of flight method. These results have been discussed taking the regularity of the main chain and the length of side chain into consideration.

We examined the current-voltage (I-V) characteristic of metal/polyimide/rhodamine-dendorimer/polyimide/ metal junctions prepared by the Langmuir-Blodgett (LB) technique. At a temperature of 32.8 K, a step structure was observed in the I-V characteristic, whereas it was not observed for the junctions without rhodamine-dendorimer. The step structure was very similar to that seen in so-called Coulomb staircase. On the basis of the model of Coulomb blockade, the possibility of single electron tunneling via rhodamine-dendrimer (Rh-G2) molecule as a quantum dot was discussed.

Short-circuit photocurrents (I_SC) utilizing surface plasmon polariton (SPP) excitation were investigated for the merocyanine (MC) LB film photoelectric device. The device has a prism/MgF₂/Al/MC LB film/Ag structure. In the attenuated total reflection (ATR) configuration, SPPs were resonantly excited at the interfaces between MgF₂ and Al (MgF₂/Al) and between Ag and air (Ag/air). The thickness and the dielectric constants of the layers were evaluated from the ATR measurements. Short-circuit photocurrents, I_SCs, as a function of the incident angle of the laser beam were observed simultaneously during the ATR measurements. In the I_SC curves, large and small peaks were observed, and the peak angles of the I_SC almost corresponded to the dip angles of the ATR curves due to the SPP excitations. Electric fields and optical absorptions in the cell were calculated using the dielectric constants and the film thickness obtained from the ATR measurements. The calculated absorption in the MC layer as a function of the incident angle corresponded to the I_SC curve. It was thought that the optical absorption in the MC layer affected directly to the profile of the I_SC. Furthermore, the calculated absorption in the cell with the prism and the MgF₂ layer exhibited much larger than that of the cell without them. It was estimated that the photocurrents were enhanced by the excitation of SPPs in the ATR configuration.

Photocarrier transport of regiorandom poly(3-hexylthiophene) P3HT in ITO/P3HT/Al sandwich cell configuration has been investigated by means of Time-of-Flight technique. Characteristics of Schottky diode and the magnitude of hole mobility have been found to be affected by impurities involved during the synthesis. The hole mobility in regiorandom P3HT at room temperature has been estimated to be 2.4 10^-5 and 2.6 10^-4 cm²/V. s before and after the removal of ferric ions, respectively, at a field of 5.010⁵ V/cm. Field dependencies of mobility before and after purification show unique feature and have been discussed in terms of the disorder model.

Layer-by-layer sequential adsorption process of polyelectrolytes had conventionally been used for the fabrication of the ultra-thin organic film formed by various polymers with different polarity of charge. In this study, hydrophobic Ruthenium complex monomer (tris (bilyridyl) ruthenium (II) hexafluorophosphate) was micelle-wrapped with an anionic surfactant, sodium dodecylbenzenesulfonate, and was assembled with PAH (poly (allylamine hydrochloride)) which has the opposite charge on ITO substrates. With this method, we succeed in fabricating ultra-thin organic films even when the adsorption material is not polymer but monomer. Moreover it was found that the bilayer thickness of the self-assembled (Ru micelle/PAH) was systematically changed by adjusting the solution pH of each bath. By using this process, EL device was fabricated by depositing the thin film of micelle-wrapping ruthenium complex monomer on ITO and formed Bi electrode on top of the film. Light emission was observed by applying voltage to this device.

Micropatterning of organosilane self-assembled monolayers (SAMs) was demonstrated on the basis of photolithography using an excimer lamp radiating vacuum ultra-violet (VUV) light of 172 nm in wavelength. This lithography is generally applicable to micropatterning of organic thin films including alkyl and fluoroalkyl SAMs, since its patterning mechanism involves cleavage of C-C bonds in organic molecules and subsequent decomposition of the molecules. In this study, SAMs were prepared on Si substrates covered with native oxide by chemical vapor deposition in which an alkylsilane, that is, octadecyltrimethoxysilane [CH₃(CH₂)₁₇Si(OCH₃)₃, ODS] or a fluoroalkylsilane, that is, 1H, 1H, 2H, 2H-perfluorodecyltrimethoxy-silane [CF₃(CF₂)₇CH₂CH₂Si(OCH₃)₃, FAS] were used as precursors. Each of these SAMs was photoirradiated through a photomask placed on its surface. As confirmed by atomic force microscopy and x-ray photoelectron spectroscopy, the SAMs were decomposed and removed in the photoirradiated area while the masked areas remained undecomposed. A micropattern of 2 µm in width was successfully fabricated. Furthermore, microstructures composed of two different SAMs, that is, ODS and FAS, were fabricated as follows. For example, an ODS-SAM was first micropatterned by the VUV-lithography. Since, the VUV-exposed region on the ODS-SAM showed an affinity to the chemisorption of organosilane molecules, the second SAM, i. e. , FAS, confined to the photolithographically defined pattern was successfully fabricated. Due to the electron negativity of F atoms, the FAS covered region showed a more negative surface potential than that of the ODS surface: its potential difference was ca. 120 mV as observed by Kelvin probe force microscopy.

Layered Multicomposites by Sequential Adsorption (LAMSA) is layer by layer approach for ultrathin film fabrication that has been applied to a variety of organic and inorganic materials. In this paper, we present our objectives and work on the fabrication and modification of display devices and sensors primarily using LAMSA techniques. The term supramolecular layer assembly denotes the selective incorporation of processing techniques, layer configuration and molecular ordering that is achieved within planar devices. The first application involves modifying a polymer light emitting diode (PLED) device fabricated using the ITO/MEH-PPV/Ca protocol with ultrathin polyaniline derivatives. The second example involves photoinduced alignment in a hybrid LC cell configuration using polarized light with azo dye/polyelectrolyte ultrathin films. A supramolecular concept on substrates for opto- bioelectronic sensor configurations is described.

We have fabricated a static induction transistor structure by using copper phthalocyanine (CuPc) films. Its layer-structure is Au(drain)/CuPc/Al(gate)/CuPc/Au(source)/glass. The source-drain current is controlled by the Al gate bias-voltage when the drain voltage is positive but is almost independent of it when the drain voltage is negative. The current-voltage characteristics are governed by the space-charge-limited conduction which depends on shallow traps.

Vanadyl-phthalocyanine (VOPc) single crystals were prepared on KBr substrate by molecular beam epitaxy (MBE). Their maximum size is 1380.16 µm³. The morphology of the VOPc single crystal was investigated from the results of UV/VIS spectra and RHEED. They suggest that the VOPc single crystal may be grown with pseudomorphic layers. The growing process was expained by Volmer-Weber model. The third order nonlinear optical property of VOPc single crystal was measured with Maker fringe method. The value of the third order optical susceptibility (χ⁽³⁾) of VOPc single crystal was estimated to be about 10^-9 esu from the result of Maker fringe.

We have developed a polymer tunable wavelength filter using cross-linked silicone as a waveguide material for wavelength division multiplexing (WDM) systems. The filter operated with a low insertion loss of 3.6-4.1 dB, a low crosstalk of < -30 dB, and a wide tuning range of 10 nm in the 20 to 80C temperature region without any changes in the spectral profile. We investigated the optical characteristics of the 32-ch WDM signals transmitted through the filter. We realized a stable filtering operation by introducing a feedback system. We also applied the filter to a WDM/SCM (subcarrier multiplexing) broadcast-and-select LAN system. We were able to realize a LAN system which operated at 6 Mbit/s and had 3200 channels by using 10-wavelength WDM signal. This suggests that our polymer tunable wavelength filter is suitable for practical use.

Topographical changes induced by optical near-field around photo-irradiated nanoparticles were attained using a pulsed laser with a large peak power as a light source. The arrayed structure of nanoparticles was transcribed on urethane-urea azo copolymer film as dent structure. The experiments by the pulsed laser of different wavelength showed that the topographical change was caused by the light absorption. The dent diameter and the dent depth changed depending on the diameter of nanoparticles.

Polymeric thin films can be prepared by physical vapor deposition in several manners such as direct evaporation of the polymer, co-evaporation of two monomers followed by polyaddition or polycondensation reaction, or evaporation of single monomer followed by chain polymerization. The ionization-assisted deposition (IAD) was proposed as a new method of polymer deposition that has special features such as activation of polymerization reaction and aligning of the dipole orientation. These mechanisms were utilized for the formation of vinyl polymer and polyurea thin films aiming for such applications as organic light emitting diodes and piezoelectric devices.

Thin films of carbon (C)-sulfur (S) compound were formed by plasma CVD (PCVD) at the special chemical condition. The reactor has a parallel plate electrode system and was operated at a discharge frequency of 13.56 MHz with using a mixture gas of argon (Ar), methane (CH₄) and SF₆. The deposition was performed on a substrate placed on the grounded electrode. Atomic composition of the film was observed to depend on the gas mixture ratio. The sulfur atom density was increased up to 30% with using a mixture gas at a pressure of 0.1 Torr and at a flow rate of 20, 20 and 50 SCCM for Ar, CH₄ and SF₆, respectively. It was expected that the C-S compounds were deposited under the condition of F atom elimination by forming HF.

We developed a new water repellent coating consisting of PTFE particles dispersed in PVDF resin. This coating exhibited a contact angle of 150 degrees. By ice accreting test, the intensity of reflected microwave on the water-repellent coated plate did not decrease, whereas that on uncoated one decreased.

Photoacoustic spectroscopy (PAS) has recently received much attention especially for plant photosynthesis research, because this technique is capable of performing non-destructive measurement without any pre-treatment of specimens. So far we have developed a PAS system equipped with an open photoacoustic cell (OPC), which allows in situ and in vivo measurements of plant photosynthesis of intact undetached leaves. In this study, we have measured photosynthesis reaction using OPC and developed a Confocal Scanning Photoacoustic Microscopy (CSPAM) system, in which PAS is combined with confocal scanning laser microscopy. The system allows simultaneous measurement of acoustic signal and another signal such as fluorescence, and also gives two- and three- dimensional intensity distributions of these signals, thereby giving two- and three- dimensional information about photosynthetic activity of plants.

The propagation characteristic of 670 nm laser light on the array of 10 µm diameter polystyrene micro-sphere was studied. For the linearly arranged array of micro-spheres from one to 12, the propagated light intensity was decreased from 700 mV to 45 mV. However, the propagated light intensity in the air was significantly decreased and it became 2 mV at 60 µm from the optical fiber light source. For the micro-sphere array on the curvilinear line, the light intensity at 12th micro-sphere became 35 mV. This fact means the light was propagated almost same as that on the linear line. Whereas it is expected that three dimensionally crossing optical wave-guide is possible to be fabricated by arranging the micro-spheres.

This paper deals with the scattering of a TE plane wave by an apodised sinusoidal surface. The analysis starts with the extended Floquet solution, which is a 'Fourier series' with 'Fourier coefficients' given by band-limited Fourier integrals of amplitude functions. An integral equation for the amplitude functions is derived and solved by the small perturbation method to get single and double scattering amplitudes. Then, it is found that the beam shape generated by the single scattering is proportional to the Fourier spectrum of the apodisation function, but that generated by the double scattering is proportional to the spectrum of the squared apodisation. As a result, the single scattering beam and the double scattering beam may have different sidelobe patterns. It is demonstrated that the sidelobes are much reduced if Hanning window or Hamming window is used as an apodisation function.

The sharpness of the roll-off response of bandpass filters is a major concern for wireless communication systems. Bandpass filters with attenuation poles provide sharp roll-off. This paper investigates the performance of a ceramic comb-line filter with attenuation pole resonators (APRs), and studies the effects of the attenuation pole resonators on the filter response. The presented APRs are improved versions of previous ones and they are modeled here. The obtained results show that the length of APRs can be miniaturized via the loading capacitance. The resultant volume is about 400 mm³, which is very small comparing to coaxial type filters with the same attenuation rate in the stopband. With attenuation pole resonators added, skirt attenuation is greatly improved. Narrow bandwidth bandpass filters with attenuation poles in the stopband are designed and tested. Two designed examples demonstrate the flexibility of the attenuation pole resonator in the filter configuration. Experiments show good agreement with simulation results.

The authors report ultra-high-speed digital IC modules that use 0.1-µm InAlAs/InGaAs/InP HEMTs for broadband optical fiber communication systems. The multiplexer IC module operated at up to 70 Gbit/s, and error-free operation of the decision IC module was confirmed at 50 Gbit/s. The speed of each module is the fastest yet reported for its kind.