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Hollow collagen gels are promising materials for drug/cell delivery systems to promote tissue regeneration because they may be able to function as carriers for these types of loads. Controlling the cavity size and swelling suppression is essential to expand the applications and improve the usability of such gel-like systems. We investigated the effects of UV-treated collagen solutions as a pre-gel aqueous mixture on the formation and properties of the hollow collagen gels in terms of their preparation range limits, morphology, and swelling ratio. The UV treatment thickened the pre-gel solutions, which allowed hollowing at lower collagen concentrations. This treatment also prevents the over-swelling of the hollow collagen rods in PBS buffer solutions. The UV-treated collagen solutions provided a large lumen space in the prepared collagen hollow fiber rods with a limited swelling ratio, allowing vascular endothelial cells and ectodermal cells to be cultured separately in the outer and inner lumen.

The morphology involving the height difference and the surface roughness of the binary monolayers of saturated fatty acids were evaluated using atomic force microscopy (AFM) to investigate the mixing behavior of their monolayers. AFM observations revealed that the mixed monolayers of (palmitic acid/arachidic acid) and (arachidic acid/lignoceric acid), which had four methylene group differences between fatty acids, were in a molecularly mixed state. Further, the mixed monolayer of (stearic acid/lignoceric acid), which had six methylene group differences, was in a phase-separated state. From the results of the present and previous studies, it became clear that the difference in the cohesive energy between fatty acids, which corresponds to the enthalpy difference, was an important factor in determining whether the molecular aggregation state of a fatty acid mixed monolayer was in a molecularly mixed or phase-separated state. Moreover, the boundary value of cohesive energy difference was approximately 2.5 kJ mol

Light-driven self-oscillators without electronic circuits or conventional heat engines are carbon-emission-free systems and hold promise for developing autonomous transmission pumps and self-swimming micromotors. Thermosensitive hydrogels as self-oscillators can be used in the exploitation of low-temperature heat sources and in medical applications since the driving temperature is close to body temperature. Here, the autonomous swinging of the hydrogel was achieved by irradiating a constant light beam onto a head laminated with two thermosensitive hydrogels with different transition temperatures. Hysteresis resulting from the transition point difference between the two hydrogels allowed the light-driven self-oscillation without self-shadowing from the irradiation. The proposed theoretical model and numerical simulations explain this light-driven continuous swing, and the results agree qualitatively well with the experiments.

We investigated the morphology of binary monolayers of palmitic acid and behenic acid using atomic force microscopic observations. The monolayers exhibited a phase-separated morphology composed of ...

This paper presents a novel approach for fabricating lead-based layered perovskite films. The perovskite structure was formed during the transfer of a perovskite-unform monolayer onto a substrate. ...

One-pot gelation in capillary glass tubes with carbonate-based buffer solution allows the formation of hollow collagen gels (collagen tubes) with an outer diameter of 1 mm or less. The preparation conditions of collagen concentration, buffer concentration, and capillary diameter impacted the ratio and size of the hollow gel and allowed for morphological control of the cavity. The morphology of the hollows suggests that their vacancies are the result of macroscopic phase separation and pinning due to gelation. Mechanical strength measurements of the dried collagen gel tubes demonstrated that the collagen concentration determines their Young's modulus and maximum stress and that the material is strong enough for practical use. In vitro seeding studies of vascular endothelial cells demonstrated the possible formation of endothelial cells in layers in the gel lumen.

The effect of solvent species and quantity of solvent used for spreading on the morphology of Langmuir monolayer composed of palmitic and lignoceric acids was investigated based on atomic force microscopy observations. The variation in domain size depending on the evaporation time of the spreading solution indicated that the mixed monolayer was in a non-equilibrium phase-separated state.

Ho3+/Yb3+ co-doped ZnO-TiO2 composite system were synthesized by powder-solution mixing method and their upconversion (UC) luminescence characteristics were investigated under the 980 nm laser excitation. The effect of various ZnO/TiO2 mixing ratios, and Ho3+ and Yb3+ concentrations were also studied. The XRD patterns showed that the product fired at 1300 °C consisted of Zn2TiO4, TiO2, RE2Ti2O7, and RE2TiO5 (RE = Ho3+ and/or Yb3+) phases. The green emission centered at 538 nm wavelength was detected as the strongest emission intensity which it was in accordance with the 5F4,5S2 → 5I8 transition of Ho3+ ion. The emission intensity of the product changed by varying ZnO/TiO2 mixing ratios, and Ho3+ and Yb3+ concentrations. Brightest UC emission was observed in the sample of 1ZnO:1TiO2 (in mole) doped with 0.03 mol% Ho3+, 9 mol% Yb3+ fired at 1300 °C for 1 h. Besides, the dependence of the UC emission intensity on the excitation power indicated that the two-photon process was responsible for this UC system.

Tm3+ and Yb3+ co-doped ZnO-TiO2 composite system were successfully synthesized via powder-solution mixing method and their upconversion (UC) luminescence characteristics were studied as a function of various ZnO/TiO2 mixing ratios and dopant concentrations under 980 nm laser excitation. The XRD patterns showed that the product fired at 1300 °C consisted of four phases, Zn2TiO4, TiO2, RE2Ti2O7, and RE2TiO5 (RE = Tm3+ and/or Yb3+). The NIR emission centered at 795 nm wavelength was detected as the strongest emission intensity which it was in accordance with the 3H4 → 3H6 transition of Tm3+ ion. The NIR emission intensity of the products was varied by changing ZnO-TiO2 mixing ratios, and Tm3+ and Yb3+ concentrations. The simple chemical formula equations, for interpreting the site preference of Tm3+ and Yb3+ ions in the host crystal matrix, were originated by considering the host crystal structure, its crystal arrangement, and the effect of Tm3+ and Yb3+ ions to the changes in lattice parameters of host crystal. The 1ZnO:1TiO2 (in mole) doped with 0.125 mol% Tm3+, 15 mol% Yb3+ fired at 1300 °C for 1 h was the best condition that displayed highest NIR emission intensity. The possible UC mechanism was suggested and discussed in detail.

ZnO-TiO2 composites co-doped with Er3+ and Yb3+ ions were successfully synthesized by powder-solution mixing method and their upconversion (UC) luminescence was evaluated. The effect of firing temperature, ZnO/TiO2 mixing ratio, and dopant concentration ranges on structural and UC luminescence properties was investigated. The crystal structure of the product was studied and calculated in detail by means of X-ray diffraction (XRD). Also, the site preference of Er3+ and Yb3+ ions in the host material was considered and analyzed based on XRD results and UC luminescence characteristics. Brightest UC luminescence was observed in the ZnO-TiO2:Er3+,Yb3+ phosphor fired at 1300 °C in which the system consisted of mixed phases; Zn2TiO4, TiO2, RE2Ti2O7 and RE2TiO5 (RE = Er3+ and/or Yb3+). Under the excitation of a 980 nm laser, the two emission bands were detected in the UC emission spectrum, weak green band centered at 544 and 559 nm, and strong red band centered at 657 and 675 nm wavelengths in accordance with 2H11/2, 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2 transitions of Er3+ ion, respectively. The simple chemical formula equations, for explaining the site preference of Er3+ and Yb3+ ions in host crystal matrix, were generated by considering the Zn2TiO4 crystal structure, its crystal properties, and the effect of Er3+ and Yb3+ ions to the host crystal matrix. The UC emission intensity of the products was changed by varying ZnO/TiO2 mixing ratios, and Er3+ and Yb3+ concentrations. The best suitable condition for emitting the brightest UC emission was 1ZnO:1TiO2 doped with 3 mol% Er3+, 9 mol% Yb3+ fired at 1300 °C for 1 h.

Photoresponsive behaviors of thermosensitive hydrogels containing carbon black (CB) were investigated by comparing experimental and simulation results. Poly( N -isopropylacrylamide-acrylamide) (PNIPAm) and poly( N -n-propyl-acrylamide) (PNNPAm) gels were employed as the matrix of photoresponsive hydrogels exhibiting a lower critical solution temperature (LCST) behavior without hysteresis and with hysteresis, respectively; CB-PNIPAm and CB-PNNPAm were used as photoresponsive hydrogels. The size and surface temperature behaviors of the photoresponsive hydrogels were measured under laser irradiation. The surface temperatures of irradiated both gels increased rapidly after the irradiation to a peak and then decreased exponentially. The CB-PNIPAm gel shrank and its size synchronized with the surface temperature rise and reached a constant between the shrunken and swelling states. The CB-PNNPAm gel first shrank, then re-swelled after going through a minimum value. The main different behaviors of the two gels could be explained by the hysteresis effect based on numerical simulation results. The numerical simulation results also demonstrated that photosensitive gels with hysteresis can be self-oscillator driven by stationary light sources.

Molecules aggregate to form a structure through various interactions involving dispersion force, electrostatic force, and so on. In two-dimensional systems, a surface energetic effect is further important for the molecular aggregation structure. We show that the domain size and its morphology in the mixed monomolecular film composed of hydrocarbon and fluorocarbon skeletons with different surface free energies extremely change depending on pH and NaCl concentration in the subphase. Such morphological changes can be interpreted by the balance of dipole density and line tension, which help in the development of an understanding of phase separation phenomena and provide a novel technique for structural control in two dimensions.

Hydrogels formed by low-molecular hydrogelators have been used as anti-microbial agents and cell-attachment materials. However the biomedical application of low-molecular gelators is slowly progressing compared to the hydrogels formed by polymer hydrogelator that is applied to biomedical application such as tissue engineering and biomedical regions. To obtain a simple molecular model for potent and prospective usage of low-molecular hydrogelators, we designed a Lys-based hydrogelator which was mimic to the poly cationic poly- l -lysine that promotes cells to attach to a plastic plate nonspecifically. The gel-coating led to cause 10-fold cell attachment compared to no-coating well. Also five-time cells were attached to the well compared to the poly- l -lysine coating. From the competitive assay, these hydrogels could interact with cells through electrostatic interaction between positive charge from –NH3+ in the hydrogelator and negative charge from substances on the cell surface such as glycosaminoglycans. This strong adhesive ability can be useful for the tissue engineering and molecular glue regions using low-molecular hydrogels in the future.

Through the use of the Langmuir method, a delicate and variable color-controlled perovskite thin film was successfully constructed on a subphase containing halogen salts.

We have successfully prepared thin films of PbBr-based layered perovskite having hole-transporting carbazole chromophore-linked ammonium molecules as an organic layer by a simple spin-coating from the N,N-dimethylformamide solution in which the stoichiometric amount of lead bromide and carbazole-linked ammonium bromides was dissolved. Their X-ray diffraction profiles exhibited that their layer structure formed (0 0 n)-orientation, where c-axis is perpendicular to the substrate plane. Their layer structure depended on the alkyl chain length of ammonium molecules. When methylene length of C5H10 was employed in the carbazole-linked ammonium molecules, highest orderliness of the layer structure was attained; higher-order X-ray diffraction peaks were observed in the layered perovskite films. In the layered pervskite film, in-plane conduction, namely conduction in the direction of the stacking of carbazole chromophore, was measured. For comparison, conductivity of poly(N-vinylcarbazole) (PVCBz) thin film was also measured. The conductivity of the layered perovskite thin film (1.8 × 10−10 Scm−1 at 303 K) was about three order of magnitude larger than that of the PVCBz thin film (5.3 × 10−14 Scm−1 at 303 K). Despite the much higher conductivity of the layered peroskite thin film, the activation energy of the conductivity of the layered perovskite thin film (1.44 eV) was about 2.4 times larger than that of the PVCBz thin film (0.61 eV). This phenomenon is probably due to difference in film morphology through considering the results of AFM observation.

The penetration behavior of Vibrio cholerae hemolysin (VCH) into a mixed monolayer, consisting of dimyristoyl phosphatidylcholine (DMPC) and cholesterol, was investigated by area–time measurements and atomic force microscope (AFM) observations. Time-dependence studies of the surface area at a constant surface pressure revealed that VCH caused a two-step expansion of the monolayer. On the second step, small dots (diameter ∼10 nm) assigned to VCH subunits were observed at the monolayer surface 1.1 × 10 4 s after injection of VCH solution into the subphase, indicating VCH penetration into the monolayer. Compression at a higher surface pressure prevented VCH penetration into the monolayer.

We proposed a novel method for the preparation of W/O/W type microcapsules containing enzymes. In this method, a gas phase was used in place of alcohol that has been conventionally used in solvent change processes for the preparation of W/O/W type microcapsules. As a model system for this study, we prepared glucose-oxidase encapsulated poly( l -lysine-alt-terephthalic acid) microcapsules whose volume can be decreased in the presence of glucose and evaluate the effect of glucose on the shrinking process. To estimate the relative concentration of enzyme in microcapsule, a simple model was proposed on assumption of linear dependence of the rate of change in the size and in the charge density of the microcapsule membrane. The diameters of the shrunk microcapsule observed were consistent with the theoretical value. By a fitting of the observed time course of the microcapsule size to the theoretical equations, two time constants were obtained, both related inversely to the relative enzyme concentration in the microcapsules. From the comparison of their constants for microcapsules prepared by the novel and conventional method, it became apparent that the glucose-oxidase containing microcapsule prepared by the novel method exhibited about 1.5 times higher enzyme activity of the case for the conventional method using ethanol in the solvent change processes.

The action of Vibrio cholerae hemolysin (VCH) on cholesterol monolayer was investigated on the basis of area strain measurements and atomic force microscopic observations of the monolayer. The area strain-time behavior of the monolayer by addition of VCH was mainly classified into the two processes in shorter and longer time ranges with respect to around 2.0 × 103 s. The area strain in a long time range decreased remarkably, that is, the monolayer expanded owing to the penetration of VCH subunits into the monolayer and the gathering growth of them.

A macroscopic pattern consisting of liquid crystal layers in hydorgel is self-organized. The pattern forms when potassium ion diffuses into a κ-carrageenan solution from one end of the glass capillary that contains the κ-carrageenan solution. Both the distance between two adjacent liquid crystalline layers (spacing, xn+1 − xn,) and thickness of liquid crystalline layers (width, w n ) depend linearly on the distance from the diffusing end of the potassium ion xn. The time prior to the formation of the nth liquid crystalline layer tn depends linearly on x n 2 . In addition, the spacing coefficient p is inversely proportional to the concentration of potassium ions. These results are in good agreement with the Liesegang phenomenon. In this system the κ-carrageenan solution behaves as a supporting medium for the spatial pattern, as well as the pattern forming substance. The lower values of p, rather than the common Liesegang pattern, in this system could be attributed to the large molecular weight of the κ-carrageenan–potassium complex. The pattern consisted of discrete liquid crystal phases must be formed due to the much larger diffusion constant of potassium ion (diffusant) than that of κ-carrageenan (product).

Atomic force microscopy observations of a (hydrocarbon guanidinium/fluorocarbon carboxylic acid) mixed monolayer revealed that a nanoscopic phase-separated structure was formed by a combination of attractive interaction between the oppositely charged head groups and repulsive phase separation of the hydrocarbon and fluorocarbon chains.

The aggregation structure of monolayer, consisting of phospholipid and cholesterol, on a pure water and an aqueous solution of Vibrio cholerae hemolysin (VCH) was investigated on the basis of surface pressure–area ( π – A ) isotherm measurements and atomic force microscopic observations. The behavior of π – A isotherm by addition of VCH revealed changes in the monolayer state due to interaction with VCH. Small dots with a diameter of about 10 nm, assigned to VCH subunits, were observed in the matrix region of the mixed monolayer but not in the domain. This result implies that VCH penetrates into the mixed monolayer, suggesting that a stronger aggregation between cholesterols prevents to its penetration into cholesterol-rich phase (domain region).

PbBr-based layered perovskite film was successfully prepared by successive deposition of amphiphilic ammonium bromide monolayer which was formed on a subphase of saturated aqueous PbBr 2 solution. In this work, we studied the formation process of layered perovskite structure on the subphase while evaluating reflection spectra of amphiphilic ammonium monolayers and observing topographs of the monolayer using a scanning probe micrograph. The reflection spectra demonstrated that the layered perovskite structure was formed on the subphase of saturated aqueous PbBr 2 solution. From the reflection spectra and the AFM image, the reasonable formation process of the layered perovskite structure on the subphase was proposed.

Nanoaggregate formation of poly(ethylene oxide)-b-polymethacrylate (PEO-b PMA) is induced by chitosan (Ch) or methylglycolchitosan (MGC). The nanoaggregates are basically obtained by electrical charge neutralization of the anionic PMA block of the PEO-b-PMA polymer with cationic Ch or MGC, which results in insolubilization of the PMA block to form the core of the aggregates. Formation of the nanoaggregates was confirmed by dynamic light scattering, fluorescence spectroscopy, atomic force microscopy and zeta-potential measurements. The properties of the nanoaggregates depend upon the concentration of the polymer as well as the concentration of Ch or MGC. The significance of these aggregates is their ability to incorporate ionic species, leading them to potential applications as drug carriers and nanoreactors.

New organic–inorganic nano-complexes were produced from a micelle of tri-block polymers; poly(styrene)-b-poly(2-vinylpyridine)- b-poly (ethylene oxide) (PS-PVP-PEO) and tungsten compounds such as tungstate (W 1 2− ), undecatungstophospate (PW 11 7− ) and undecatungstosilicate (SiW 11 8− ) in acidic aqueous solutions. The size and morphology of the complexes were characterized by measurements of dynamic light scattering, atomic force microscopy, and scanning electron microscopy. This complex is assembled mainly by the charge interaction between the inorganic polyanions and the positively charged PVP block in the PS-PVP-PEO molecule, which was confirmed by zeta-potential and fluorescence spectroscopic studies. In the absence of the inorganic anions, the zeta-potential of the micelle was +11 mV at pH 3 due to the positive charge of the PVP block. When the inorganic anion was mixed with the PS-PVP-PEO micelle, decrease in the zeta-potential due to charge neutralization occurred with incorporation of inorganic anions into the PS-PVP-PEO micelle. The minimum zeta-potential was 0, −33, and −35 mV for W 1 2− /PS-PVP-PEO, PW 11 7− /PS-PVP-PEO, and SiW 11 8− /PS-PVP-PEO complexes, respectively. Excess negative charge which occurred in the latter two complexes indicates that PS-PVP-PEO molecules bound PW 11 7− and SiW 11 8− by forces other than charge interaction. In addition, the incorporation of an inorganic polyanion into the micelle gave a new morphology to the micelle. In the absence of the polyanion, the PS-PVP-PEO micelles showed an extended conformation due to repulsive forces working among the positively charged PVP blocks. Addition of the polyanion caused the formation of shrunken forms of the micelles, since the charge repulsion was cancelled by the polyanion. This feature may be useful in developing a new type of functioning micelle.

Micelles of poly(styrene-b-2-vinylpyridine-b-ethylene oxide) (PS-b-P2VP-b-PEO) triblock copolymer were prepared in aqueous solutions. The physicochemical properties of the micelles were investigate...

Morphological change of a micelle of poly(styrene)-b-poly(2-vinylpyridine)-b-poly(ethylene oxide) (PS-PVP-PEO) polymer was induced by binding sodium dodecyl sulfate (SDS) to the PVP block in acidic aqueous solutions. The change in the size of SDS/PS-PVP-PEO complexes was detected by dynamic light scattering measurements and atomic force microscopy, and the binding of SDS was confirmed by zeta-potential measurements. When the micelle was free from SDS in acidic aqueous solutions, the hydrodynamic diameter of the micelle was 216 nm, reflecting the extended conformation of the PVP block due to the repulsion between protonated pyridine units. As the cationic PVP block was electrically neutralized with anionic SDS, the diameter was gradually reduced concomitant with the decrease in zeta-potential and finally reached 175 nm when the PVP block was completely neutralized. The decrease in the diameter shows the morphological change of the PVP block from extended to shrunken forms. Further addition of SDS did not cause the changes of the diameter nor zeta-potential. This indicates that SDS was not bound to the PS-PVP-PEO polymer after the PVP block was fully neutralized and that the hydrophobic binding of SDS to the polymer was negligible due to the low concentration of SDS.

The aggregation state of a mixed monolayer of cyanine dye and fatty acid during compression was investigated on the basis of surface pressure–area isotherm measurements, atomic force microscopic observations and spectroscopic measurements. The mixed monolayer was in a miscible state at all surface pressure values. The domains were formed in a matrix region by compression, which is probably due to ordering of molecular conformation. Compression at a surface pressure higher than the plateau pressure causes regularization of stacking of cyanine rings, resulting in the formation of J-aggregates.

Glucose-sensitive microcapsules, whose volume changed in response to glucose, were successfully prepared by encapsulating glucose oxidase (GOx) into poly(L-lysine-alt-terephthalic acid) (PPL) micro...

The tribological properties of behenic acid monolayers in CS and L 2 phases were investigated on the basis of scanning probe microscopic observations. The lateral (friction) force of the monolayers in CS and L 2 phases increased consistently with applied force. The increment in CS phase comes from an increase in contact area between a probe and the monolayer owing to elastic deformation, while that in L 2 phase does from not only increase in contact area owing to plastic deformation but wear of the monolayer. The lateral force of the monolayer in CS phase was independent of the scan velocity. On the other hand, the monolayer in L 2 phase exhibited the scan velocity dependence of the lateral force. The difference in tribological properties of the monolayer is attributable to the static mechanical properties of elasticity and plasticity which are governed by the molecular packing in monolayer.

The effect of molecular structure of anionic (2CnPOH (n=12, 16)) amphiphiles with dialkyl chains that bind with the hydrophilic group only through ether bond and cationic (2CnN+2C (n=18, 22)) amphiphiles with dialkyl chains that directly bind with the hydrophilic group without a spacer on aggregation structure of amphiphile monolayers was investigated on the basis of π-A isotherm measurement and electron diffraction (ED) analysis. π-A Isotherms of the 2C12POH and 2C18N+2C monolayers exhibited a plateau region, whereas those of the 2C16POH and 2C22N+2C monolayers did a sharp rise in surface pressure with decreasing surface area. ED analysis revealed that 2C12POH, 2C18N+2C and 2C22N+2C monolayers were in an amorphous state even at higher surface pressures. On the other hand, the 2C16POH monolayer was in a crystalline hexagonal state in which the degree of molecular aggregation is low. Noncrystallization of the 2C12POH, 2C18N+2C and 2C22N+2C monolayers and the low degree of molecular aggregation of the 2C16POH monolayer may be attributed to the molecular aggregation by distantness between dialkyl chains in their parallel alignment due to binding between the hydrophilic and hydrophobic portions without or through only one spacer.

We investigated the aggregation state of a mixed monolayer of 1,2-dimyristoyl-sn-glycero-3-phospholine and cholesterol at different surface pressures by AFM. AFM images revealed a nanoscopically se...

We have synthesized novel heptaalkyl amphiphiles, Heptopus(12,12), Heptopus(12,14), and Heptopus(12,14), that have six identical outer alkyl chains (C12, C14, or C16) and a single inner alkyl chain (C12). Their monolayer properties were investigated by π−A isotherm measurement and atomic force microscopy (AFM). Limiting areas in their isotherms are 1.54, 1.38, and 1.40 nm2 for Heptopus(12,12), Heptopus(12,14), and Heptopus(12,16), respectively, suggesting formation of close-packed condensed phases. An AFM observation of a monolayer of Heptopus(12,12) transferred onto a mica showed hexagonal packing of its alkyl chains. However, the outer and inner chains were not distinguishable. These results indicate that further elaboration on the molecular design of Heptopus is required to create novel two-dimensional molecular organization.

The structure concerning the molecular aggregation in Langmuir-Blodgett (LB) films of pheophytine a (Phe- a ) has been studied by ultraviolet–visible (UV–Vis) and infrared (IR) spectroscopies and their morphology has been delineated by atomic force microscopy (AFM). UV–Vis spectra were measured for a chloroform (CHCl 3 ) solution of Phe- a , cast film from the CHCl 3 solution and six-layer LB films of Phe- a prepared in air and argon (Ar) atmospheres. A comparison of these UV–Vis spectra indicates the existence of two kinds of aggregates of Phe- a in the cast and LB films. One has a Qy band at 683 nm and another has a corresponding band at 700 nm. Soret bands of the cast and LB films also show a marked broadening. It is suggested from the UV–Vis measurements that the LB film prepared in the Ar atmosphere includes the aggregate with the 700 nm band at the highest ratio among the three kinds of films. On the other hand, the IR spectra of the solution, and cast and LB films resemble each other, suggesting that Phe- a exists in a monomer in them. Therefore, it seems that the aggregates are composed of stacked Phe- a monomers with a π – π interaction. AFM images for the LB films of Phe- a prepared in the air and Ar atmosphere reveal that they have very smooth and flat surface.

A novel preparation method to obtain a defect-diminished fatty acid crystalline monolayer, that is, a multistep creep method, was proposed on the basis of area-creep mechanisms of the monolayer on the water surface. The fatty acid monolayer prepared by the multistep creep method was morphologically homogeneous and mechanically stable even at a high surface pressure, while the monolayer prepared by a conventional continuous compression method without an area-creep process was easily collapsed. The crystallographical regularity of the crystalline monolayer prepared by the multistep creep method was remarkably progressed compared with that of the monolayer prepared by the continuous compression method. Therefore, the multistep creep method is applicable for the construction of the defect-diminished monolayer.

Attenuated total reflection (ATR)/Fourier-transform infrared (FT-IR) spectra were measured for one-monolayer Langmuir−Blodgett (LB) films of chlorophyll a (Chl-a) fabricated in an argon (Ar) atmosphere. The frequencies of CO stretching bands and marker bands for the coordination number of the central Mg atom suggest that Chl-a takes a five-coordinated dimer in the films prepared in the Ar atmosphere. Ultraviolet−visible (UV−vis) as well as IR spectra were obtained for multilayer LB films of Chl-a prepared in air, Ar, nitrogen (N2), and oxygen (O2) atmospheres. In the cases of the multilayer LB films, spectral features in the CO stretching band region suggest that Chl-a exists as a monomer in the film prepared in air while it assumes a dimer in the films prepared in the Ar, N2, and O2 atmospheres. The marker bands for the coordination number of the Mg atom in the IR spectra indicate that Chl-a is in a five-coordinated state. These results imply that one can control the molecular arrangement in the LB films...

The effect of ionic repulsion among hydrophilic groups of arachidic acid molecules on the aggregation structure of the arachidic acid monolayer on the water surface was investigated on the basis of surface pressure−surface area (π−A) isotherm measurements, Fourier transform infrared spectroscopic (FT-IR) measurements, and transmission electron microscopic (TEM) observations. π−A isotherm and FT-IR measurements revealed that the degree of ionic dissociation of hydrophilic groups in the monolayer drastically changed in a pH range of 10−12. The arachidic acid monolayer in a slightly dissociated state of hydrophilic groups (pH = 5.8) did not exhibit the phase transition from an amorphous state to a crystalline one during compression. On the other hand, the monolayer in a highly dissociated state (pH = 12.6) showed the phase transition from an amorphous state to a crystalline one by surface compression at the subphase temperature, Tsp, below the melting temperature, Tm, of the monolayer, and also, the monolaye...

Flavin adenine dinucleotide (FAD) undergoes multisite molecular recognition at the air-water interface with mixed monolayers that are capable of complementary hydrogen bonding. Molecular images wer...

Atomic force microscopy (AFM), scanning electron microscopy (SEM) and UV–VIS absorption and IR spectroscopies have been used to investigate the morphological and molecular structure of Langmuir–Blodgett (LB) films of the title compound (Chl-a). The AFM and SEM measurements reveal that the surface of the LB films are very smooth and consist of rigid and condensed monolayers. The tilt angle of the chlorin plane in a six-monolayer LB film of Chl-a has been calculated to be 35° between the normal of the chlorin plane and the substrate normal and 44° between the dipping direction and projection of the normal of the chlorin plane, from measurements of its polarized UV–VIS spectra. Band frequencies in the 1750–1400 cm −1 region of the IR spectra of one-, six- and ten-monolayer (ML) LB films of Chl-a suggest that Chl-a exists in a five-coordinated monomer in the films, irrespective of the number of monolayers. Comparison of IR transmission and reflection–absorption spectra of 6 ML LB films of Chl-a indicates that the chlorin plane and the ester and keto CO groups are tilted considerably with respect to the surface normal. LB films of pheophytine a (Phe-a) have also been studied for comparison. Comparison of the UV–VIS and IR spectra of the LB films of Chl-a and Phe-a show that pheophytinization occurs little in the LB films of Chl-a. High-performance liquid chromatography (HPLC) examination has supported this conclusion. All the experiments carried out in the present study suggest that Chl-a molecules in the LB films are oriented in an orderly manner with face-to-face packing of the chlorin rings.

The morphology and layered structure of an alkyl ammonium bromide ultrathin film prepared on an aqueous solution of lead bromide were investigated on the basis of surface pressure-area curve measurements, reflection spectrum measurements, X-ray reflectivity measurements and atomic force microscopic observations. It became apparent that the layered structure sandwiched a two-dimensional inorganic layer between two organic monolayers was formed by folding the monolayer by compression on an aqueous PbBr2 solution.