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The morphological change of vapor-deposited TPD (N,N′-diphenyl-N,N′-bis-(3-methylphenyl)-[1,1′-biphenyl]-4,4′-diamine) films, used as the hole transport layer of organic electroluminescent (EL) devices, on a glass plate was observed by atomic force microscopy (AFM) and friction force microscopy (FFM) in an ambient atmosphere. The TPD film was flat and amorphous as deposited, but was crystallized partially about a week later. By friction force loop measurement, we found that the bare glass surface was revealed between the crystals and between the amorphous film and the crystal due to mass transport for crystallization of TPD from the amorphous film.

Ion-complexation between a cationic amphiphile and pyrene-1-carboxylate (PyCOO−) dispersed the PyCOO− anions homogeneously in a Langmuir-Blodgett monolayer film. By bringing the film into contact with HCl gas, formation of fluorescent spots in the monolayer was observed by fluorescence microscopy. With an atomic force microscope, the spots were found to be topographically much higher than the monolayer level, and concluded to be aggregates formed by lateral diffusion of neutralized pyrene-1-carboxylic acid (PyCOOH) molecules in the monolayer.

The resolution of scanning near-field optical microscopy (SNOM) is determined by the dimensions of the microscopic light source (or detector) and the probe-to-sample separation rather than the diffraction limit. In the present microscope, we took advantage of scanning force microscopy (SFM) with a vibrating cantilever holding an optical fiber tip not only to give a simultaneous SFM topographic image but also to control the separation for SNOM without mechanical damages of the sample. By the precise control of the separation of the tip within 100 nm from the sample surface, we demonstrate here that this combined non-contact SFM and SNOM method can be used as fluorescence microscopy and nanoscopic fluorescence spectroscopy with a resolution of ∼100 nm.

In order to estimate the potential difference of the electrical double layer formed in heterogeneous Sensitizer (S)/Electron Donor (D) Langmuir–Blodgett (LB) films, the surface potentials of the constituent monolayers were measured simultaneously with the π–A isotherms. The S monolayer was a mixed [Ru(bpy)3]2+ complex monolayer with a long alkyl fatty acid, while the D monolayer was one of three kinds of ferrocene monolayers with different signs of the hydrophilic head groups and with the same redox potential. The formation of the potential difference between the charged head group of the amphiphile and its counterion at the water-air interface was confirmed; those values were consistent with the electrical double-layer effect on the luminescent lifetime of [Ru(bpy)3]2+ in the S monolayer in contact with the D monolayer.

The luminescence decay curves of Ru(bpy)32+ in Langmuir-Blodgett (LB) films were often fitted by multiexponential functions whereas those in homogeneous solutions by a single exponential one. Responsible conditions in the LB film preparation for the luminescence decay kinetics were examined. The single exponential decay was observed when the film was prepared in a clean atmosphere and photooxidation of the LB films was avoided.

In order to build up stable Langmuir-Blodgett (LB) film of the photosynthetic reaction centers (RC) from Rhodopseudomonas viridis, effect of the formation of polyion complex between charged residues of RC and water soluble polyions was examined. Cationic polymer, poly-L-lysine (PLL), enhanced the stability of RC LB films during the film preparing process whereas anionic polymer, poly-L-glutamate, induced complete denaturation of RCs. LB films of RCs prepared with PLL show reproducible surface pressure area isotherm and high transfer ratio of RC monolayer to solid substrate.

A Scanning Surface Potential Microscopic (SSPM) instrument was built by modifying a commercial atomic force microscope (AFM), Seiko SFA 300 with a SPI 3600 probe station. Distribution of surface potentials on test samples microlithographically prepared and on mixed Langmuir-Blodgett (LB) films coated on a vapor-deposited gold film could be imaged in a x-y spatial resolution less than 1 μm and compared with AFM images observed on the same samples.

The products of electrochemical reduction of CO2 on gold were analyzed in-situ by new DEMS with a stationary gas-permeable gold electrode sputtered on a porous water-repellent membrane in a rotational flow produced by a rotating rod.

The rate constants of intramolecular photoinduced electron-transfer reactions of a linked pyrene–viologen molecule A and a linked pyrene–ferrocene molecule B solubilized in micellar solutions of a hexadecyltrimethylammonium chloride were determined to be 9×108 and 4×108 s−1 respectively, from the stationary fluorescence intensity. However, the observed fluorescence decay curve of A suggests that a large fraction of the molecules have conformations for which the distances between two functional moieties are sufficiently small to permit direct electron transfer. The quasi-first-order rate constants of the intermolecular photoinduced electron-transfer reactions between 1-hexylpyrene (HPy) and dodecylviologen (DDV), and between HPy and butylferrocene (BFc) solubilized in a micellar solution, were also determined to be 9×106 and 2×107 s−1 respectively, from the fluorescence decay curves. It is shown that the rate constants of the intermolecular photoinduced electron-transfer reaction in micelles are determined...

We studied stability of indium–tin–oxide (ITO) surfaces chemically modified with –SO2Cl and –PO2Cl2 binding groups of para substituted benzene derivatives as well as those oxidized with UV ozone by...

To understand the origin of the open-circuit voltage of heterojunction photovoltaic (HJ-PV) cells with small-molecular-weight organic thin films, HJ-PV cells with ITO/donor (20 nm)/fullerene (40 nm...

To produce micrometer scale chemical patterns, a new method is developed. In this method, silica beads are used as a mask of an underneath substrate. We produced the patterns with CH3- and COOH-ter...

Alignment behavior of a discotic liquid crystalline triphenylene (C8OBT) on substrates coated with self-assembled monolayers (SAMs) of alkanethiol and asymmetrical disulfide was investigated by polarized microscopy. Discotic nematic (ND) and rectangular columnar (Colr) phases of C8OBT shows a different alignment behavior depending on the element of SAMs. C8OBT exhibits a fan-shaped texture on an alkanethiol SAM in Colr phase, while it shows a planar alignment on a SAM of asymmetrical disulfide.

Doping of N,N′-diphenyl-N,N′-bis(3-methylphenyl)-1,1′-biphenyl-4,4′-diamine (TPD) with antimony pentachloride (SbCl5) as a method to form its p-type organic semiconductor material is described. UV–visible absorption and X-ray photoelectron spectroscopic (XPS) data indicated formation of radial cations and dications in TPD films doped with SbCl5. This doping played important roles in hole conduction and in hole injection from an indium-tin oxide (ITO) electrode to the doped TPD layer in typical electroluminescent (EL) organic thin film devices.

In Langmuir-Blodgett (LB) films consisting of viologen (V2+)-pyrene (Py) dyads, the accumulation of viologen cation radical (V+·) was observed during UV irradiation under N2. The additional quenching due to energy transfer by the colored V+· resulted in an error in determination of photoinduced electron transfer rates between the V2+ and Py moieties in the LB films. This type of error can be generally expected in LB films and self-assembled monolayers.

The effect of capillary force due to surface water on friction force microscopy (FFM) was examined by comparing FFM images on oxidized Si surfaces partially covered with chemically bound hydrocarbon (HC) monolayers in vacuo and in an ambient atmosphere. It was found also from force-distance curves and FFM under various relative humidities that adhesive and friction forces observed on the hydrophobic HC covered surface were almost independent of the humidity, while those on the hydrophilic bare oxidized Si surface increased with an increase in the humidity. The higher friction observed on the oxidized Si in the higher humidity was interpreted by the higher effective normal load due to the higher capillary force which originated from a surface water film formed by adsorption of water vapor in the humid air. The results suggest a novel scanning hydrophilicity microscope under a controlled humidity which can be used to map local hydrophilicities of a sample surface in a x-y plane.

The interfacial change of a vapor-deposited TPD (N,N′-diphenyl-N,N′-bis-(3-methylphenyl)-[1,1′-biphenyl]-4,4′-diamine) and Alq3 (Tris-(8-hydroxyquinoline) aluminum) bilayer film was characterized by photoluminescence (PL) in the temperature range from room temperature to 80 °C under an ambient atmosphere. The TPD and the Alq3 film are widely used as a hole transport and an emitter layer, respectively, in organic electroluminescent (EL) devices (ITO/TPD/Alq3/metal). As the substrate plate, a slide glass was used in this work. In an Alq3/TPD bilayered structure, two PL bands from Alq3 and TPD were observed and the relative PL intensity of Alq3 to that of TPD was increased with time. The change was accelerated with increasing temperature. In case of a co-deposited single layer of TPD and Alq3, an Alq3 PL band predominated and, in addition, the PL intensity was not changed remarkably with increasing temperature. These results support that the PL change observed for the Alq3/TPD bilayered structure is ascribed...

The comparison of the dependence of the electron transfer quenching rate on the signs in head group charge indicates that the inner potential difference of the electrical double layer (EDL) created between the sensitizer and the ferrocene monolayer, Δφ, has to be taken into account for estimation of the effective standard free energy of the electron transfer quenching reaction, ΔG°.

In order to study the electrochemical behavior of a redox species in the Langmuir–Blodgett (LB) film on a glassy carbon (GC) electrode, three kinds of amphiphilic redox compounds, each carrying an anthraquinone, a viologen, and a ferrocene moiety, were confined on the electrode surfaces. Prior to the deposition of the film on the electrode, surface pressure–area isotherms for a number of mixed films of the redox-active amphiphiles and arachidic acid were recorded and the stability of the monolayers was discussed. Finally, the cyclic voltammetric behavior of the LB film-modified electrodes was discussed in terms of the changes in the structure and the nature of the LB film caused by the redox reactions.

Heterogeneous photocatalytic oxidation of aromatic compounds by H2O2 formed from dissolved O2 in the presence of illuminated TiO2 powders was investigated with reference to the Fenton reaction. All the products expected from the Fenton reaction were obtained. The effect of other semiconductor materials and Fe2+ on the reaction was also investigated.

The reduction of molecular oxygen (O2) at glassy carbon surfaces modified with iron porphyrins was studied by cyclic voltammetry and differential pulse polarography in 0.05 mol dm−3 aqueous H2SO4 solution. O2 was reduced more effectively at the electrode modified with iron porphyrin lying in parallel to the electrode surface than at the one with iron porphyrin protruding vertically from the surface.

The defects of the polyimide LB films deposited on glassy carbon electrodes were examined by means of cyclic voltammetry of the redox couple of potassium ferri- and ferrocyanide in aqueous solution. The degree of defects of the polypyromellitimide LB films was apparently less than that of the cadmium arachidate LB film. The polyimide derived from aliphatic tetracarboxylic acid afforded the ten-layer LB films possessing no detectable defects.

The anodic chlorination of anisole on an α-cyclodextrin (α-CD) chemically modified electrode via ether linkage (α-CD-CME) and a naked graphite electrode with α-CD or β-CD in solution was studied. In the presence of CD, the p- to o-chloroanisole ratio, formed in the reaction, was higher than that in the absence of CD since o-positions of anisole included in CD are blocked by the inner wall of CD. Especially, α-CD had a profound effect on the p-isomer formation. Increasing the concentration of NaCl added as a supporting electrolyte in the presence of α-CD resulted in a decrease in the ratio because of the inhibition effect of chloride ion on the inclusion of anisole in α-CD, whereas such effect was small in the presence of β-CD. The ratio on α-CD-CME was slightly higher than that on the naked electrode. This indicates that α-CD was introduced on the graphite surface but the surface coverage of α-CD was low, which was in accord with the ESCA results of α-CD-CME.

The peak-to-peak potential of cyclic voltammogram of (2-anthraquinonylmethyl)trimethylammonium bromide was linear in Kosower’s Z value over a wide range of DMF-water mixtures. Using this relationship, the anthraquinone moiety of (2-anthraquinonylmethyl)dodecyldimethylammonium bromide solubilized in cationic micelles was found to reside at the Stern layer.

Photoelectrochemical control of the ion-blocking ability of the Langmuir–Blodgett (LB) film as an ion gate was demonstrated on a gold optically semi-transparent electrode (Au OTE) coated with multilayers containing photoresponsive amphiphilic compounds. When UV light was irradiated upon the modified Au OTE, this LB film became more compact to block permeation of ions into and out of the LB film and therefore inhibited electrochemical reactions of the redox active species in solution. On the other hand, when visible light was irradiated, this layer became more loose and redox species could penetrate the LB film.

The preparation and properties of a water soluble porphyrin having functional groups, α,β,γ,δ-tetrakis[1-(2-hydroxyethyl)pyridinium-4-yl]porphine, are described. This porphyrin is water soluble from below pH 0 to above pH 14. Acid-base titration revealed the diprotonated diacid-monocation equilibrium (pK4=1.0) and the monocation-free base equilibrium (pK3=1.9) in the acidic range and the free base-monoanion equilibrium (pK2=13.0±0.2) in the basic region. The zinc, iron, and cobalt derivatives of the porphyrin were also synthesized and purified. Catalytic properties of the iron and cobalt complexes for reduction of molecular oxygen in water are reported in terms of cyclic voltammetry. The electrochemical reduction utilizing these complexes was interpreted to proceed via electrochemical catalytic regeneration mechanism as had been observed for tetrakis(1-methylpyridinium-4-yl)orphinatoiron(III). The apparent rate constants for electron transfer from the iron and cobalt porphyrins to oxygen were estimated to...

Fluorescence microscopic observation of clusters of pyrene moieties in the mixed monolayer assembly of pyrene(Py)-substituted fatty acid (Py(CH2)nCOOH; n = 9, 15) and normal fatty acid (CH3(CH2)nCOOH; n = 18, 14) deposited from a water surface on a quartz plate was carried out. The cluster size was changed drastically depending upon difference between chain lengths of the constituent fatty acids.

The oxidation of o-, m-, and p-nitrotoluenes with electro-generated superoxide ion in dimethylformamide was studied using cyclic voltammetry and controlled potential macro-electrolysis. The electrochemical reduction of oxygen in the presence of o- and p-nitrotoluenes yielded the corresponding carboxylic acids because the methyl groups in these derivatives are activated by the nitro group. An intermediate in these oxidations should be the corresponding nitrobenzaldehyde. The reaction mechanism is discussed.

The redox reaction of the polyimide LB films themselves was examined by means of cyclic voltammetry. Both their cathodic and anodic current peaks decreased with potential cycling, and no peaks were observed after a few tens of sweeps, whereas the redox reaction was reversible in the case of polyimide cast films.

The reaction of halogenonitrobenzenes (XNBs) with electrogenerated superoxide ion in N,N-dimethylformamide was studied electrochemically using cyclic voltammetry (CV) and controlled potential macro-electrolysis. It was shown in the CV that electro-generated superoxide ion reacts with all of the o- and p-isomers of iodo-, bromo-, and chloronitrobenzene in the dissolved oxygen medium. However the superoxide ion did not react with the other XNBs during CV. Controlled potential macro-electrolysis of oxygen in the presence of o- and p-bromonitrobenzene yielded the corresponding nitrophenols as the main products. The reaction mechanism via nucleophilic attack of the superoxide ion on the XNB, in the preference to an electron-transfer mechanism, is proposed.

The cyclic voltammetric studies of H2O2 and O2 in aqueous alkaline solutions were carried out on stationary gold electrodes unmodified and modified chemically with dodecyltriethoxysilane. Although two cathodic waves were observed for both H2O2 and O2 on the unmodified electrode, only the second wave was observed for H2O2 on the modified electrode. Since the first cathodic wave of H2O2 overlaps that of O2 on the unmodified electrode, the disappearance of the first wave of H2O2 makes it possible to distinguish O2 from H2O2 on the modified electrode. The effect of alkylsilanization on the diminution and evolution of H2O2 or O2 on gold electrodes was also confirmed by employing rotating ring-disk gold electrodes unmodified and modified similarly with dodecyltriethoxysilane. Furthermore, the reduction mechanism of H2O2 and the application of the independent electrochemical detection of H2O2 and O2 are discussed.

The electrochemical characteristics of chemically modified glassy carbon electrodes via amide bonds have been correlated with the results of surface analysis by X-ray photoelectron spectroscopy (ESCA). The double layer capacitance measurements were proved to be useful to determine the extent of surface modification as well as ESCA analysis.

THe oxidation of nitroalkylbenzene with electro-generated superoxide ion was studied by cyclic voltammetry and controlled potential macro-electrolysis. The electrochemical reduction of oxygen in the presence of nitrotoluenes (o- and p-) and p-nitroethylbenzene yielded under mild conditions the corresponding nitrobenzoic acids from the former and p-nitroacetophenone plus 1-(p-nitrophenyl)ethanol from the latter.

The electric conductivities of frozen nitrobenzene containing various amount of tetrabutylammonium perchlorate and nitrobenzene anion radical were measured. The conductivity increased markedly with the concentration of the nitrobenzene anion radical. The mechanism of the electric conduction of the nitrobenzene is discussed and it is concluded that at low concentration of anion radical the increase of the electric conductivity is due to electronic conduction by a hopping mechanism. The rate constant of electron transfer (hopping) between any nearest neighbored sites is about 105 s−1 at −15 °C, which is smaller by 2 orders than that in hypothetical liquid nitrobenzene at the same temperature.

The ESR spectra of the LB films of N-docosyl- and N-octadecylpyridinium-(TCNQ)n (n=1,2) deposited on glass capillaries or glass slides were measured. The intensity of the ESR spectrum increased markedly with the number of layers. From this and other results, it was suggested that the ordering of the LB film was enhanced by cumulation of monolayers. The ESR spectrum of the LB film deposited on a glass slide showed marked dependence on the orientation of the film in the static magnetic field.

ESR spectra of duroquinone anion radical (DQ−), methyl viologen cation radical (MV+), and 5,10-dimethyl-5,10-dihydrophenazine cation radical (DMPZ+) were measured in various aqueous surfactant solutions. The line width of each peak of the ESR spectra for DQ− in cationic and anionic surfactant solutions showed a quadratic dependence on the total nuclear quantum number, M=Σmi (i=1 to 12), of methyl protons of DQ−. The rotational correlation times, τc, of DQ− determined from these dependences, were 10−9–10−8 s in cationic surfactant (dodecyl-, tetradecyl-, and hexadecyltrimethylammonium bromide) solutions, and 10−10–10−9 s in nonionic surfactant (Triton X-100) solution. ESR spectra of MV+ and DMPZ+ in anionic surfactant (sodium dodecyl sulfate; SDS) solution showed anomalous patterns as not exhibiting the hyperfine splittings due to the nitrogen nucleus. These anomalies were explained by the more significant broadening of the outer peaks due to nitrogen splitting compared with the broadening of the central p...

By using polyallylamine (PAA) for the aqueous subphase, the pure LB films of an azobenzene derivative with a long alkyl-chain showed reversible cis–trans photoisomerization due to the relatively large cross section of the molecule determined by the surface density of the ammonium cations of protonated PAA.

The protonation mechanism of the aromatic hydrocarbon radical anions, such as biphenyl, naphthalene, phenanthrene, anthracene, 1,2-benzanthracene, and pyrene, in dimethylformamide (DMF) and water mixtures was studied. Three methods of measuring the concentration of the radical anions, i.e. polarography and ESR and UV absorption spectroscopy, were compared with each other by making simultaneous measurements of the same anthraquinone radical anion solution. A good linear relation of the polarographic anodic diffusion current to the UV absorbance was found, while the ESR signal intensity had linear relations with neither of the others in the system which contained an excessive number of parent molecules, 2×10−3M. The change in the visible absorption spectra of the aromatic hydrocarbon radical anions as a function of the time suggested that all the aromatic hydrocarbon radical anions decay by a first-order reaction. As a result, the radical anions were considered to decay through the following sequence:R\ewdo...

The rates of the protonation of aromatic hydrocarbon radical anions with water in dimethylformamide (DMF)-water mixtures were measured by means of the decay of the visible absorption maxima of radical anions with time. The rates were found to be greatly accelerated by the increasing water content in DMF-water mixtures. This behavior suggests that the negative charge is much more localized in the transition state than in the original radical anion. The rate constants in DMF could be obtained by extrapolation. The correlation of these rate constants to the molecular structure of radical anions was discussed on the basis of the results of HMO calculations. This correlation and the solvent effect could be interpreted by means of the charge-transfer mechanism.

From the viewpoint of the interaction between the oxidized or the reduced form of a depolarizer and solvents, the solvent effect on the half-wave potentials was studied. Another factor affecting the E1⁄2, i.e., pH or ion-pair formation, was also examined. The correction for the liquid junction potential was carried out by the use of the ferrocene standard. The reduction products, radical anions or dianions, were found to be stabilized by the hydrogen-bonding with water where the hydrogen-bond interaction of the dianion was stronger than that of the monoanion. Aromatic hydrocarbon radical anions, whose charges are dispersed over the molecule, were less susceptible to this solvent transfer than were the anthraquinone radical anion and the dianion, whose charges are strongly localized.

各種フッ素化界面活性剤水溶液の25℃ における表面張力の濃度変化を測定した。炭素数が8～9以上のフッ素化界面活性剤は一般にクラフト点が高く,室温ではミセルを形成せず水和固体がより低濃度で析出してくるため表面張力が十分に低下しないものがあるが,室温でミセルを形成するものは,表面張力が15～20dyne/cmまで低下する。n-C7F15COOMeとその異性体i-C7F15COOMeについて表面張力を測定し炭化フッ素鎖の末端の枝わかれの影響を調べた。ナトリウム塩については枝わかれ構造の方がCMC以下では1～2dyne/cmCMC以上では4.4dyne/cm低い表面張力を示した。酸については低濃度では枝わかれのある方がよく低下するが高濃度では直鎖の方が低くなった。適度の枝わかれをもった方がクラフト点は低下するので,枝わかれ構造の炭化フッ素鎖をもったものの方が使用に便利な場合が多いであろうどフツ素化界面活性剤とドデシル硫酸ナトリウムとの混合物の表面張力の濃度変化の測定によれば,25dyne/cm程度の表面張力の水溶液を得るにはフッ素化界面活性剤を炭化水素型界面活性剤で20～50%程度までうすめても可能であることが示された。通常の炭化水素型界面活性剤と混合すると,気一液界面の表面張力の最低値は少々高くなるものの,油0水溶液間の界面張力を低下させ得るのでγW/A+γO/W

Enthalpy and entropy of solution of non-polar solutes in water diverge strikingly from the normal behavior established for regular solutions. This abnormality has been considered mostly due to the iceberg formation around solute molecules in water. The abnormal solubility and enthalpy and entropy of solution of non-polar solutes in water have been explained coherently by the extension of the regular solution theory, taking into account the iceberg formation of water molecules. Unlike currently accepted views on the hydrophobic bonding, it is concluded that the enthalpy of mixing (interchange) of non-polar solute with water is large, but the enthalpy decrease due to the iceberg formation of water largely cancels the enthalpy increase of mixing (interchange). Thus, the apparent enthalpy of solution is small or negative at low temperature. It is concluded that 1) the small solubility of non-polar solutes in, water is not an entropy effect, and 2) the solubility of non-polar solutes is promoted by the iceberg...

The effect of α-cyclodextrin (α-CD) on the electroreduction of benzaldehyde was investigated. The reduction in aqueous system produces benzyl alcohol and 1,2-diphenyl-1,2-ethanediol (hydrobenzoin, dimerization product). The addition of α-CD caused the decrease in the yield of hydrobenzoin. This suppression effect was observed both in the controlled potential and controlled current electrolyses. This is accounted for by the retardation of the dimerization rate between the neutral radicals, since inclusion of substrate provides severe steric hindrance around the reaction site. The addition had only a small influence on the stereochemistry of hydrobenzoin formed by the dimerization.

The amount of Pt deposited on a glassy carbon (GC) electrode can be controlled precisely by electrochemical reduction of PtCl62− incorporated as a counter ion in the Langmuir–Blodgett (LB) film coated on the electrode surface. Electrocatalysis of the resulting modified electrode for molecular oxygen reduction is also described.

The H2O2 molecules deliberately adsorbed on the surfaces of TiO2 fine particles suspended in an alkaline solution can be oxidized electrochemically on a rotating gold disk electrode.

Electronic absorption spectra for saturated solutions of Na in HMPA–THF mixtures with HMPA mole fractions 0.39–0.061 exhibit only a band for Na−. A log–log plot of maximum absorbance vs. HMPA concentration has led to a numerical value 3 for the number of HMPA molecules solvating a Na− ion.

An in situ cyclic voltammetric measurement of anthraquinone (AQ) moieties in the monolayer assembly spread on water was carried out by horizontal touching with a glassy carbon disk electrode (GC) under various surface pressures. Some unexpected findings on the reactivity of the AQ film in a low surface pressure, which cannot be transferred to the electrode surface as it is on water by other methods than the horizontal touching method, are described.