Search

While the architype room temperature ionic liquid (RTIL) based on aliphatic-primary-ammonium was discovered in 1914, it has been undeveloped until 1990s. In this three decades, RTIL composition (i.e., cations and anions) have been developed aiming at electrochemical application and green chemistry. Accordingly, bulky quaternary-ammonium, pyridine, and imidazole have nowadays been the major cations of RTILs. Currently, novel applications using the matured series of RTILs are being highly explored, and one of the promising targets is an additive for hole transport material (HTM) in perovskite solar cells (PSCs). However, although design of RTIL should be modified along each application, RTILs for the PSCs application so far has remained conventional, which limits the function. Herein, a novel RTIL comprising the architype aliphatic-primary-ammonium (i.e., n-octyl-ammonium: OA) cation and a modern Bis(Trifluoromethylsulfonyl)Imide (TFSI) anion, which are designed as an additive for hole transport layer in PSCs, was successfully synthesized for the first time. The OA cation spontaneously and densely passivated perovskite layer taking advantage of the accessibility to its cationic moiety, and simultaneously TFSI anion most likely effectively stabilized cationic radical of HTM owing to the absence of the counter cation in HTM core regime, leading to effective hole correction and thereby power conversion efficiency of 22.9% in the best cell. This work sheds light on importance of RTIL design along each application, even out of the current trend, and will help further development of various material science fields including PSCs.

Efficiency of photon upconversion (UC) from near infrared (NIR) to visible emission by the triplet-triplet annihilation (TTA) mechanism in solid has been limited to be low in spite of its...

An anthracene-terminated self-assembled monolayer (SAM) material, ANT-PA, was synthesized, which contains an anchor unit corresponding to octadecylphosphonic acid, C18-PA itself. Thanks to the comm...

We have synthesized a new compound of a benzothiadiazole central core coupled to terminal thienoimide (TI) via vinyl linker, namely, C8-TI-BT. We investigated physical properties of vacuum-...

Polymerase chain reaction (PCR)-based genetic testing has become a routine part of clinical diagnoses and food testing. In these fields, rapid, easy-to-use, and cost-efficient PCR chips are expected to be appeared for providing such testing on-site. In this study, a new autonomous disposable plastic microfluidic PCR chip was created, and was utilized for quantitative detection of pathogenic microorganisms. To control the capillary flow of the following solution in the PCR microchannel, a driving microchannel was newly designed behind the PCR microchannel. This allowed the effective PCR by simply dropping the PCR solution onto the inlet without any external pumps. In order to achieve disposability, injection-molded cyclo-olefin polymer (COP) of a cost-competitive plastic was used for the PCR chip. We discovered that coating the microchannel walls with non-ionic surfactant produced a suitable hydrophilic surface for driving the capillary flow through the 1250-mm long microchannel. As a result, quantitative real-time PCR with the lowest initial concentration of human, Escherichia coli (E. coli), and pathogenic E. coli O157 genomic DNA of 4, 0.0019, 0.031 pg/μl, respectively, was successfully achieved in less than 18 min. Our results indicate that the platform presented in this study provided a rapid, easy-to-use, and low-cost real-time PCR system that could be potentially used for on-site gene testing.

Continuous-flow polymerase chain reaction (CF-PCR) in microfluidic devices has a great potential for on-site detection of various pathogens and food species because of their high speed deoxyribo nucleic acid (DNA) amplification. However, flow-controlled pumps such as syringe pumps are absolutely necessary, which cause complex and difficult operations. Here, we present a self-propelled CF-PCR (SP-CF-PCR) in a microfluidic device which requires no external pumps to control the flow. The PCR solution is simply dropped onto the inlet and is autonomously transported by capillary forces. One of the difficulties in addressing the capillary flow in PCR microfluidic device is that the temperature of the PCR solution is periodically switched. Differing from previous theoretical approaches which deal with single steady-state temperature zone, for the first time, the displacement of capillary flow during temperature switching was mathematically formulated and was simulated by using experimental values of viscosities and capillary pressures at each temperature as parameters for simulation. Basing on the excellent matching between simulated and experimental data of the capillary flow, we were able to reveal the optimized design of 150-μm-wide and 150-μm-deep microchannel that successfully transported over 1600 mm for carrying out PCR within less than 14 min solely by capillary forces. We also demonstrated the SP-CF-PCR for verifying our concept. The specific amplifications of 295 bp of β -actin from human genome, 232 bp of AH1pdm influenza virus and 95 bp of 16S rDNA of Escherichia coli genomic DNA were successfully achieved, proving the application potentials of our device.

We fabricated perovskite solar cells (PSCs) employing high and low molecular weight dithiophene-benzene (DTB) copolymers as hole-transporting materials (HTMs) under nitrogen atmosphere. We then measured current density–voltage (J–V) characteristics of PSC devices in ambient air. After exposure to air for 5 h, device performance was poor and power conversion efficiency (PCE) was 3.05%. However, device performance gradually improved when the device was kept in dry air, and PCE was 16.20% after 173 h. This result indicates that the carrier density of DTB increased due to oxygen-doping. After oxygen-doping reached saturation, the superior molecular order of the high molecular weight DTB-based device yielded a higher PCE than the low molecular weight DTB-based device. When tris(pentafluorophenyl)borane (BCF) was added to DTB, the initial characteristics improved (PCE = 12.12%) further (PCE = 16.89%) by oxygen-doping, yielding the maximum PCE in this study.

We report structural changes of spin-coated network silicon bearing anthryl groups, poly(9-anthrylsilylene) (PAS), by intense pulsed light (IPL) irradiation. The structural changes are achieved in a few hundred microseconds resulting in the formation of graphite films with sheet resistance up to 50 Ω/sq. The conditions of IPL were optimized in order to tune the formation of graphite films as a function of exposure energy and film thickness. The effect of IPL conditions on the morphology and the electrical properties of PAS films were investigated by UV–visible, X-ray photoelectron (XPS), and Raman spectroscopies, as well as atomic force microscopy and sheet resistance measurements. The elimination of network silicon is evidenced in the changes of XPS. The correlation between Raman spectroscopy analysis and sheet resistance exhibit the formation of graphite films.

We have fabricated dispersions of ethyl-intercalated germanane (GeEt) by a liquid exfoliation approach in chlorobenzene, with sufficient concentration for thin-film fabrication. Monolayers and a few layers of GeEt with lateral dimensions of a few micrometers were deposited from its dispersion onto a solid substrate and characterized with a scanning electron microscope. The physical properties and structures of the GeEt dispersions were investigated by UV–visible, FT-IR and Raman spectroscopies. The sonication power for the dispersion process affected the interlayer distance between germanium sheets, as well as the photoluminescence of GeEt dispersions. Electroluminescence was observed with a peak at 835 nm from a device with a cast film from the chlorobenzene dispersion of GeEt.

The Langmuir layers of amphiphilic bis(tetrathiafulvalene) [bis(TTF)] annelated macrocycle (1) and those of the (1)[2,3,5,6-tetrafluoro-7,7,8,8-tetracyano-p-quinodimethane (F4-TCNQ)]2 charge-transf...

The research on ferroelectric materials-mostly inorganic compounds or organic polymers-is increasingly motivated by both basic scientific concerns and the potential for practical applications in electronics and optics. Ferroelectricity in organic solids would be important for the development of all-organic electronic and photonic devices. The conventional approach to making organic ferroelectrics is based on the use of polar molecules. Here we report that through supramolecular assembly of nonpolar conjugated molecules, a remarkable ferroelectric response can be obtained in co-crystals of low-molecular-weight organic compounds. Co-crystals of phenazine and chloranilic acid reveal large spontaneous polarization and sizable room-temperature dielectric constants exceeding 100. The present findings provide an approach to making potentially useful organic ferroelectric materials.

The effect of subphase temperature on behaviors and morphologies of an amphiphilic spiropyran, 1′,3′-dihydro-3′,3′-dimethyl-6-nitro-1′-octadecyl-8-docosanoyloxymethylspiro[2H-1-benzopyran-2,2′[2H]indol] onto pure water was investigated by measurements of surface pressure–area isotherms and Brewster angle microscopy, respectively. Both depend strongly on the subphase temperature. The isotherms at 30 °C show a distinct phase transition at 7.5 mN m −1 , while no such phase transition is observed at 7 °C. The morphology changes drastically accompanying the phase transition at 7.5 mN m −1 , at which many large circular domains are formed. Furthermore, we have demonstrated that the morphology changes reversibly accompanying appreciable hysteresis in the isotherms upon continuous compression and expansion cycles.

The structures and photoreactions of the Langmuir and LB films of an amphiphilic spiropyran, 1',3'-dihydro-3',3'-dimethyl-6-nitro-1'-octadecyl-8-(docosanoyloxymethyl)spiro[2H-1-benzopyran-2,2'-(2H)-indole] (SP) are investigated. A chloroform solution of SP at a concentration of 0.1 mM is spread on the water surface. When the Langmuir film of SP is compressed on a subphase at 30 °C and a phase transition takes place, the monolayer changes into a mosaic structure where bilayer domains are buried in the monolayer. When the Langmuir films are illuminated with UV light, SP is isomerized to merocyanine (MC). J-aggregates of MC are formed at high temperatures and at high surface pressures where the bilayer domains are formed. The Langmuir films of SP are transferred as LB films onto solid substrates at 30 °C. The LB films consist of the bilayer domains with a diameter of 10 to 20 μm and a height of 4 to 5 nm. Three-dimensional structures are present in almost all the bilayer domains. Room-temperature illumination of the LB films with UV light produces the J-aggregation of MC with the development of dendritic structures starting from the three-dimensional structures in the domains. These dendrites consist of the J-aggregates. Molecules are aligned radially in the dendrites. When the LB film is illuminated at 7 °C, the J-aggregation of MC does not proceed. All these results indicate that the criteria of the J-aggregation of MC in the Langmuir and LB films are the presence of the bilayer domains and the nucleation sites with the mobility of the molecules large enough for the morphological change necessary for the J-aggregation.

Langmuir monolayers of an amphiphilic spiropyran, 1′,3′-dihydro-3′,3′-dimethyl-6-nitro-1′-octadecyl-8-docosanoyloxymethylspiro[1-benzopyran-2,2′-indole] (SP1822) on pure water at 30 °C was investigated by measurements of surface pressure–area (π–A) isotherms and Brewster angle microscopy (BAM). The π–A isotherm shows a phase transition at 7.5 mN m−1. The BAM image reveals drastic morphological changes accompanying the phase transition. Many circular domains appear on uniform monolayers. Atomic force microscopy (AFM) images of as-deposited Langmuir–Blodgett (LB) films suggest that the circular domains consist of bilayers. In addition, monolayers are transformed into bilayers during deposition, which result in the formation of further larger circular domains. Furthermore, the relationship between photochemical property and morphology in the SP1822 LB films was characterized by UV-visible spectroscopy and AFM. We have demonstrated that whether J-aggregates are formed upon irradiation with UV light at room temperature is strongly dependent on the morphology of the SP1822 LB films before irradiation.

The area per molecule of 10,12-pentacosadiynoic acid (DA) was smaller on a pure water subphase than on an aqueous subphase containing a water-soluble polymer, polyallylamine (PAA), at a concentration of the monomer unit of PAA of 0.01 mM. The transmission IR spectra of the LB films of DA transferred from a PAA-containing subphase showed the presence of two species of DA in the LB films, the one in a deprotonated form and the other in the free acid form. The XPS spectra showed that a half of DA molecules formed salt with PAA and that the other half was in the free acid form in the LB films. When the films were irradiated with UV light, two absorption bands appeared at 540 nm (red phase) and 630 nm (blue phase) simultaneously. Upon prolonged irradiation, only the intensities of the two bands increased gradually without noticeable changes in the band positions and the intensity ratio of the two bands. Before irradiation, the films were two-dimensional except for some three-dimensional crystalline structures on the surface. On irradiation of UV light, these three-dimensional structures developed and new three-dimensional crystalline structures also appeared, resulting in three-dimensional structures with several tens of μm in length, a few μm in width and 6 nm in height. Fluorescence microscopy indicated that the red phase was confined within the three-dimensional structures.

Thermochromic behaviors were investigated by measurements of reflectance spectra for urethane-substituted polydiacetylene crystal having side groups of R=(CH)2)6OCONHC2H5 (PDA-6UEt). The PDA-6UEt crystal shows an irreversible thermochromic A-to-B (blue-to-red) phase transition: the absorption band at 1.88 eV due to the lowest exciton shifts to higher energy (2.15 eV) in the heating run, but the reflectance spectra remain in the B phase even when cooled down to room temperature. We have demonstrated that photoinduced phase transition (PIPT) is observed by utilizing the irreversible A-to-B phase transition. The conversion shows the presence of a threshold of the light intensity and depends on photon energy, suggesting that the PIPT is mediated by the photogenerated electron-hole pairs.

The effect of temperature on photochromic reaction of amphiphilic spiropyran, 1’,3’-dihydro-3’,3’-dimethyl-6-nitro-1’-octadecyl-8-(docosanoyloxyme thyl)spiro[2H-1-benzopyran-2,2’-(2H)-indole] (SP1822), was investigated in single-component LB films. The morphological changes accompanying the photochromic reaction of SP1822 in the LB films were measured by atomic force microscopy (AFM) and scanning near-field optical microscopy (SNOM). Many circular domains with a width of 10−20 μm and a height of 4−5 nm were observed in as-deposited LB films before irradiation. Surface structures on circular domain did not change accompanying isomerization of SP1822 to open-colored photomerocyanine (PMC) on irradiation with UV light at room temperature, but the SNOM image reveals that the isomerization to PMC occurs into the circular domains. After reaching the photostationary state of PMC, further addition of heat at 50 °C during UV irradiation induces J-aggregate of PMC. The AFM shows that many cone-shaped structures wit...

A series of urethane-substituted polydiacetylenes (PDA– m UEt) with different alkyl chain lengths ( m =4, 5, and 6) in side chain substituents of (CH 2 ) m OCONHC 2 H 5 were synthesized. The effect of the alkyl chain length on the thermochromic phase transition was investigated by measurements of reflectance spectra for the PDA– m UEt crystals. The thermochromic phase transition shows an even–odd effect for the alkyl chain length. The PDA–5UEt crystal undergoes a reversible thermochromic phase transition between A (blue) and B (red) phases, while the even-numbered PDA– m UEt crystal turns to the B phase on heating but does not revert completely to the initial A phase even when cooled down to room temperature. The difference in the thermochromic phase transitions of PDA– m UEt crystals with varying alkyl chain length was also studied by the differential scanning calorimetry (DSC).

Langmuir–Blodgett (LB) films of an amphiphilic diacetylene (DA) were fabricated from the aqueous subphase where a water-soluble polymer, polyallylamine (PAA), was added by varying the concentrations. The effect of the PAA concentration on the structure, the morphology, and the polymerization in the DA/PAA LB film was investigated by measurements of XPS and IR spectra, atomic force microscopy (AFM), and the UV-visible absorption spectral changes on irradiation with UV light, respectively. The component ratio between DA and PAA and the ionic states of the components changed with the concentrations. The morphology and the polymerization behaviors depend strongly on the component ratio. At PAA concentration of 0.1 mM, nanofibers with a width of 30 nm and a height of 2 nm were observed in the DA/PAA LB films. We have demonstrated that globular structures form the nanofiber structures.

We have synthesized regioregular poly(3-alkylthiophene) (P3T-HT) with different lengths of alkyl chains (CnH2n+1; n = 4, 8, 14, 20) attached to the polymer backbones. The chain-length-dependent thermochromic behavior was investigated by measurements of visible exciton absorption, photoluminescence, and IR vibrational absorption spectra. Optical spectra in ordered P3T-HT thin films show the nearly identical one-dimensional exciton state irrespective of the alkyl chain length, while the hysteretic thermochromic transition temperature decreases with the increase in the length. Upon the thermochromic phase transition, the order−disorder conformational change of alkyl chains occurs in a manner correlated with the conjugation length change of polythiophene backbone structures.

Monolayers of 10,12-pentacosadiynoic acid (DA) were formed on aqueous subphases containing water-soluble polyamines such as polyallylamine (PAA), polyacrylamide and poly( N -vinyl acetoamide). DA was deprotonated in the Langmuir–Blodgett (LB) films transferred from the subphase containing PAA. However, DA remained protonated when the other two polymers were used. X-Ray photoelectron spectroscopy (XPS) revealed that PAA was incorporated in the DA LB films whereas the other two polymers were absent in the LB films. The ratio of DA molecule to the monomer unit of PAA was 1:2. Half of the monomer units of PAA were protonated. The atomic force microscopy (AFM) images of DA/PAA LB films showed a fingerprint-like pattern due to nanofibers with a width of 30 nm and a height of 2 nm. DA polymerized in the DA/PAA LB films on the irradiation of UV light. An absorption band at approximately 530 nm developed, followed by a small blue-shift of the band with the polymerization. Void regions appeared in the AFM images of the DA/PAA LB films accompanied by the polymerization. The band positions and the spectral profiles of CH 2 symmetric and antisymmetric stretching modes did not change significantly during the polymerization.

Thin films of a helical polysilane with chiral substituents were fabricated using a Langmuir−Blodgett (LB) method. The polarized absorption and photoluminescence spectra show the high anisotropy fo...

A thermal dissociation method was employed to fabricate the Langmuir−Blodgett (LB) films of C60. A C60 adduct with an amphiphilic anthracene bearing a carboxylic group (C60−AN) was synthesized as the precursor molecule. C60−AN formed a monolayer at the air−water interface. The monolayers were transferred on solid substrates to form LB films using a horizontal lifting method. The LB films were subjected to heat treatments and their structural change was investigated by using UV−visible and IR spectroscopies. Most of the C60−AN molecules were dissociated to C60 and amphiphilic anthracenes at 100 °C, followed by the exclusion of the anthracene moiety from the LB films. The thermal dissociation proceeded more at higher temperatures. At 200 °C, the dissociation proceeded completely, although a certain form of hydrocarbon remained in the LB films. All the materials disappeared when the films were heated above 350 °C.

A series of urethane-substituted diacetylene monomers (DA-mUPh) with different alkyl chain length (m = 4, 5, and 6) in side-chain substituents of (CH 2 ) m OCONHC 6 H 5 was synthesized. X-ray structural analyses for the DA-mUPh single crystals show that the monomers are packed by hydrogen bonding between the urethane groups, but the arrangement of the diacetylene moieties depends on the alkyl chain length. The reactivity of the DA-mUPh crystals upon γ-irradiation is different depending whether the alkyl chain length (m) is odd or even. The difference can be explained by the distance between the neighboring carbon atoms of the diacetylene groups. The temperature dependence of reflectance spectra for the polydiacetylene crystals has also been investigated. The thermochromic behavior is argued in comparison with the analysis of the differential scanning calorimetry.

Structural changes of the Langmuir-Blodgett (LB) films of azobenzene accompanied by photoisomerization are described. First, photoisomerization is explained in terms of 'free volume'. In the polyion complex monolayers of amphiphiles having two azobenzene units at the air-water interface, the area per molecule depends on the polycation species. The fraction of cis-azobenzene in the LB films at the photostationary state under the illumination with UV light increased with increasing area per molecule, which is consistent with the concept of free volume. Second, a counter example of the concept of free volume is presented. Three-dimensional cone-shaped structures developed with trans-to-cis photoisomerization in the polyion complex LB film of a water-soluble amphiphilic azobenzene. These structures appeared and disappeared reversibly by alternate illumination with UV and visible light. The results indicate that the two-dimensional LB film structure exerts significant modification by photoisomerization. This is against the concept of free volume because this concept does not consider the possibility that the two-dimensional LB film structures may change into three-dimensional ones. Finally, photo-induced J-aggregate formation of non-photochromic and photochromic dyes is described. Two cyanine dyes were each mixed with an amphiphilic azobenzene in the LB films. These cyanine dyes are known to form J-aggregates in single-component LB films. In the mixed LB films, the J-aggregate formation was suppressed to some extent. The alternate illumination of the films with UV and visible light caused the photoisomerization of azobenzene in the mixed LB films, which triggered the J-aggregate formation of the cyanine dyes. The J-aggregate formation was accompanied by the development of three-dimensional cone-shaped structures from the film surface. When an amphiphilic merocyanine was mixed with the azobenzene in the LB films, J-aggregate formation was also induced by the alternate illumination with UV and visible light. This J-aggregate formation was also accompanied by a large morphological change: circular domains changed into fractal-like ones. The J-aggregate formation of the dyes and the concomitant morphological change were irreversible. In these cases, the photoisomerization of azobenzene served as a trigger to induce self-organization of the dye molecules.

Langmuir-Blodgett (LB) films of an amphiphilic diacetylene (DA) complexed with polyallyamine (PAA) were fabricated. Textural structures were observed in the AFM images, while the surface was covered with small grains after the heat treatment at temperatures higher than 100°C. The polymerization of DA proceeded by the irradiation with UV light before the heat treatment whereas only a small fraction of DA polymerized after the heat treatment. The LB films of polymerized DA complexed with PAA showed better stability against heat treatment than the ones without PAA.

Hybrid alternate layered films of transition metal dichalcogenides and amphiphilic compounds were prepared by Langmuir-Blodgett (LB) technique. The conductivity at room temperature depended on the ...

We synthesized a series of amphiphilic diacetylenes with the same total length of the alkyl chains but with the butadiyne moiety at different positions in the molecules. These molecules formed mono...

The thermally restorable photoswitching between the spectroscopically distinct two phases has been observed for thin films of poly(3-alkylthiophene) with regioregular alkyl sidegroups. The primary process of the photoinduced phase transition is completed within a duration of the exciting laser pulse (5 ns), in which photogenerated electron-hole pairs on the polymer backbone with the density above a critical value appear to trigger a self-activated process for the phase conversion. Such a fast photoswitching of the electronic and/or structural state may be applied as well to many other conjugated polymers with optoelectronic functionality.

A series of donors and acceptors are synthesized and, by combing these molecules, Langmuir-Blodgett (LB) films of the charge transfer (CT) complexes are prepared. Ionic CT complexes with partial CT...

Inorganic/organic hybrid ultrathin films of MoS2 and a cationic amphiphile, dihexadecyldimethylammonium bromide (DHA+Br-), were prepared using the Langmuir−Blodgett (LB) technique. The surface pressure−area isotherms of DHA+Br- changed by introducing exfoliated MoS2 particles into the subphase. On the other hand, the isotherms of icosanoic acid in the presence and absence of MoS2 particles in the subphase were essentially the same. The UV/vis reflection spectra of DHA+(Br-) monolayers on MoS2 suspension showed a broad absorption band assignable to MoS2, whereas that of icosanoic acid did not show any appreciable band. These results suggest the formation of hybrid monolayers consisting of DHA+ and MoS2. The hybrid monolayers were transferred successfully onto substrates using a horizontal lifting method to form LB films. That was confirmed by the infrared and UV/vis absorption spectroscopies and AFM, although the transfer ratios were not determined. The X-ray diffraction patterns of the LB films showed the...

Charge-transfer (CT) interactions of tetrathiafulvalene (TTF)-based Langmuir–Blodgett (LB) films with non-centrosymmetrical structure were examined from the viewpoint of nonlinear optics. Five kinds of LB films of CT complexes were prepared using TTF-based electron donors and acceptors of 7,7,8,8-tetracyanoquinodimethane and p -benzoquinone derivatives. The difference of the dipole moments between ground and excited states of these LB films was evaluated from the measurements of electroabsorption spectra.

The macroscopic and the nanoscopic DC electrical current through Langmuir–Blodgett (LB) multilayers, and even through a monolayer of γ -( n -hexadecyl)quinolinium tricyanoquinodimethanide, C 16 H 33 Q-3CNQ ( 1 ) is asymmetric with voltage, and has a large component due to a transition from the ground-state zwitterion to a probably neutral excited-state conformer: the molecule is indubitably a rectifier of electrical current.

The structural and electrical properties of the mixed monolayers and Langmuir–Blodgett (LB) films of BEDOTTF-C 10 TCNQ/arachidic acid were examined. The domain structure of the monolayer at the air–water interface was investigated by Brewster angle microscope. The results were in good agreement with the monolayer dc conductivity behaviour. The conductivity of the LB films on the solid substrate was investigated as functions of the molar fraction of the complex and the layer number. LB films of more than five layers showed a percolation behaviour which is consistent with results reported previously K. Ogasawara, T. Ishiguro, S. Horiuchi, H. Yamochi, G. Saito, Y. Nogami, J. Phys. Chem. Solid 58 (1996) 39. The single- and bi-layer films were highly conducting when the molar fraction of the complex was high. The stability of these films with time was also examined.

An amphiphilic anionic azobenzene derivative, soluble in water, formed a monolayer on an aqueous subphase containing a water-soluble polycation. The monolayers were transferred onto solid substrate by the Langmuir−Blodgett (LB) technique. XPS measurements showed that ion exchange reaction proceeded almost completely at the air−water interface and that the ratio of the monomer unit of the polycation to the azobenzene was almost unity. UV/vis absorption and IR measurements indicated that the azobenzene photoisomerized reversibly in the LB films on alternate illumination with UV and vis light. Furthermore, a reversible morphological change induced by light was observed in the LB films with AFM. Before illumination, the surface of the single-layer LB film was very smooth with a surface undulation of less than 1 nm. On illumination with UV light, however, a number of hills, with the height of ca. 5 nm and the diameter of the base of ca. 100 nm, appeared on the film surface. These structures almost disappeared ...

The clearly resolved ${}^{1}{B}_{u}$ $(\ensuremath{\nu}=1)$ exciton and its vibronic structures show up in ordinary absorption and photoluminescence spectra of films of highly ordered poly(3-octylthiophene). The electroabsorption and the two-photon absorption spectra have unraveled the charge-transfer type ${}^{1}{A}_{g}$ $(\ensuremath{\nu}=2)$ exciton state lying 0.5 eV above the ${}^{1}{B}_{u}$ $(\ensuremath{\nu}=1)$ exciton state, while the electroluminescence spectrum shows the emission from the triplet exciton ${(}^{3}{B}_{u})$ lying 0.45 eV below the corresponding ${}^{1}{B}_{u}$ exciton. On the basis of the excitonic level diagram as well as the FeCl${}_{4}^{\ensuremath{-}}$-doping induced spectral change, the distinct photoinduced band observed at 1.0 eV is assigned to the internal transition between the triplet-exciton levels, ${}^{3}{B}_{u}$ $(\ensuremath{\nu}=1)$ $\ensuremath{\rightarrow}$ ${}^{3}{A}_{g}$ $(\ensuremath{\nu}=2)$.

The structures and functions of LB films were controlled using supramolecular architecture. The orientation control method using hexatriacontane as a trigger molecule in the LB films was applied to nonamphiphilic porphyrin derivatives with substituents at peripheral positions. This method was effective for all the porphyrins examined except for two derivatives: one with a strong hydrophilic substituent at the β -position of one of the pyrrole rings and the other with less bulky substituents. In the mixed LB films of azobenzene and a dye, photoisomerization of azobenzene was used as a trigger to control the aggregation structure of the coexisting dye.

One-dimensional (1D) exciton states have been studied by nonlinear optical spectroscopy on organosilicon polymer polysilanes (PS's). From systematic variation of the linear and nonlinear optical spectra upon changing the backbone conformation, the following two characteristic exciton parameters have been evaluated; the ratio |${\mathrm{\ensuremath{\chi}}}^{(3)}$|/\ensuremath{\alpha} of the modulus of third-order nonlinear optical susceptibility |${\mathrm{\ensuremath{\chi}}}^{(3)}$| to the absorption coefficient \ensuremath{\alpha}; and the energy difference \ensuremath{\Delta}${\mathit{E}}_{12}$ between the lowest and second lowest exciton energies ${\mathit{E}}_{1}$ and ${\mathit{E}}_{2}$, which are theoretically related, respectively, to the Bohr radius and to the binding energy of excitons. It was found that |${\mathrm{\ensuremath{\chi}}}^{(3)}$|/\ensuremath{\alpha} increases, whereas \ensuremath{\Delta}${\mathit{E}}_{12}$ remains almost unchanged, with increasing valence and conduction-band widths. These features cannot be accounted for either by the Wannier- or Frenkel-type exciton model. From analysis by a unified 1D exciton model, it has been concluded that the 1D excitons in PS's represent a unique system having an intermediate character in between the Frenkel- and Wannier-exciton regimes, where the on-site Coulomb (or exchange) interactions play a crucial role in determining the characteristic exciton structures as observed. \textcopyright{} 1996 The American Physical Society.

The conductivity of floating monolayers of a charge transfer complex between bisethylenedioxytetrathiafulvalene (BEDO-TTF) and decyltetracyanoquinodimethane (C10TCNQ) mixed with icosanoic acid (C20) was examined at the air-water interface as a function of the mixing ratio. The conductivity of the film in the region in which the surface pressure increased rapidly showed different behaviour in a.c. and d.c. measurements. This was related to the domain structure of the monolayer. The relationship between the surface pressure and the conductivity is discussed in terms of the surface structure of the monolayer.

The crystal structure of bis(2-methyl-4-nitroanilinium) tetrachlorocadmate, (C 7 H 9 N 2 O 2 ) 2 [CdCl 4 ], has been determined by X-ray diffraction at room temperature. The crystal has a layered structure in which the organic bilayer is sandwiched between the inorganic sheets. The Cd ion and Cl anions form distorted four-coordinate tetrahedra.

The self-development characteristics of Si containing polymers were investigated with the objective of applying these polymers to the surface-imaging process in x-ray lithography. Polymers containing Si atoms in their backbones or substitutents were studied in detail ; UV and Fourier transform infared spectra were used to study their reaction to soft x-rays. The polymers exhibited postive-tone characteristics when exposed to x-rays. Their self-development sensitivity and oxygen reactive ion etching (O 2 -RSB) resistance were measured to estimate the feasibility of their use in lithography. Polysilanes and polystyrene showed low self-development sensitivity while polymethacrylates showed high sensitivity. All of these polymers have O 2 -RIE resistance high enough for application as surface-imaging resists. The films remaining after self-development were characterized by estimating their durability against solvents, their thermal desorption spectra, and their x-ray photoelectron spectra. A polymethacrylate derivative was found to be the most promising of the polymers; it was applied to pattern replication using dry development. The results show that Si containing polymers are fundamentally feasible for the postive-tone dry processes.

Langmuir-Blodgett films of several 1:2 charge-transfer complexes of azobenzene-containing alkylpyridinium and tetracyanoquinodimethane (TCNQ), which exhibit various conductivity-change phenomena upon UV and visible light irradiation, have been investigated by using the ESR technique. The in-situ illumination measurements of these films and the quantitative analyses of the obtained spectrum show the changes in the exchange couplings between the spins and suggest the structural change in the TCNQ columns. By adopting the one-dimensional Hubbard model with dimerization effect, we propose a conductivity-change mechanism in the system.