Conversion of the Aggregation State of Merocyanine Dye, Modification of the Subcell Packing of Arachidic Acid, and Removal of the Majority of <i>n</i>-Octadecane by Hydrothermal Treatment in the Liquid Phase in a Mixed Langmuir−Blodgett Film of the Ternary System

We have investigated the influence of heat treatment in an air atmosphere (HT) and hydrothermal treatment in the liquid phase (HTTL) on the H-aggregate in a mixed Langmuir−Blodgett (LB) film of merocyanine dye with an octadecyl group (MS18)−arachidic acid (C20)−n-octadecane (AL18) ternary system by means of polarized visible and IR absorption spectroscopy. HT causes the variation from the H-aggregate to the monomer, the increment in the number of gauche conformers in the MS18 hydrocarbon chain, the slight orientation change in the C20 hydrocarbon chain, and the complete evaporation of AL18. The dissociation of MS18 is probably ascribed to the complete evaporation of AL18 from the mixed LB film and the increase in thermal mobility of the long axis of the MS18 hydrocarbon chain during HT. However, HTTL can easily and rapidly induce the conversion of the MS18 aggregation state from H- to J-aggregates, the modification of the C20 subcell packing from hexagonal to orthorhombic, and the removal of most of the AL18 molecules. The conversion of the MS18 aggregation state can be interpreted to consist of two processes from the H-aggregate to the monomer and from the monomer to the J-aggregate. In the initial stage of HTTL, the MS18 aggregation state changes from the H-aggregate to the monomer, which is caused by the removal of almost all of the AL18 molecules from the mixed LB film to warm water via the thermal energy of warm water. Then, the large relative permittivity of warm water is expected to relate strongly to the subsequent variation from the monomer to the J-aggregate. This transformation results in the decrease in the total value of the electrostatic energy based on the MS18 permanent dipole interaction. Moreover, the modification of the C20 subcell packing is possibly due to the hydrophobic effect, where the C20 hydrocarbon chains cohere again in the warm water during HTTL. Consequently, it has been found that HTTL is quite effective to reorganize the chromophore alignment of MS18, to modify the subcell packing of C20 and to erase the majority of AL18 molecules in the mixed LB film of the MS18−C20−AL18 ternary system in a short time

Arg-Glu-Asp-Val Peptide Immobilized on an Acellular Graft Surface Inhibits Platelet Adhesion and Fibrin Clot Deposition in a Peptide Density-Dependent Manner

Acellular blood vessels possess high potential to be used as tissue-engineered vascular scaffolds. Previously, a high patency was achieved for an Arg-Glu-Asp-Val (REDV) peptide-immobilized small-diameter acellular graft in a minipig model. Results revealed the potential of the peptide to capture a circulating cell and also to suppress fibrin clot deposition. Here, the effect of REDV peptide density on the blood response under ex vivo blood perfusion conditions was investigated. When endothelial cells or platelets were seeded under static conditions, the number of adherent endothelial cells increased with the increase in peptide density. Platelets scarcely adhered on the surface where the peptide density was above 18.9 × 10–4 molecules per nm3. Fibrin clot deposition and circulating cell capture were evaluated in a minipig extracorporeal circulatory system. The fibrin clot did not form on the peptide-immobilized surface, in the range of peptide modification density that was evaluated, whereas the unmodified surface was covered with microthrombi. REDV-specific blood circulating cells were captured on the peptide-immobilized surface with a density above 18.9 × 10–4 molecules per nm3. These results illustrated, under ex vivo blood perfusion conditions, that the REDV-immobilized acellular surface was able to capture cells and also suppress platelet adhesion and fibrin clot deposition in a peptide density-dependent manner

Stochastic Resonance in a Molecular Redox Circuit

Beyond single molecule electronics, exploration of device architecture is a central issue in molecular-scale electronics. We have demonstrated that the cytochrome <i>c</i> (Cyt <i>c</i>) network array acts as an electronic circuit that consists of a redox element. The current–voltage characteristics of the Cyt <i>c</i> network array reveal nonlinear curves with a threshold voltage (<i>V</i>_th) that corresponds well with the Coulomb blockade (CB) model over a wide range of temperature. As an indication of the threshold behavior, a weak periodic input signal is optimized by the presence of a particular level of noise that enhances signal detection. This result indicates that stochastic resonance (SR) emerges in the Cyt <i>c</i> redox network array

Thermal Behavior of J-Aggregates in a Langmuir−Blodgett Film of Pure Merocyanine Dye Investigated by UV−visible and IR Absorption Spectroscopy

We have characterized the structure of J-aggregate in a Langmuir−Blodgett film of pure merocyanine dye (MS18) fabricated under an aqueous subphase containing a cadmium ion (Cd2+) and have investigated its thermal behavior by UV−visible and IR absorption spectroscopy in the range from 25 to 250 °C with a continuous scan. The results of both UV−visible and IR absorption spectra indicate that temperature-dependent changes in the MS18 aggregation state in the pure MS18 system are closely and mildly linked with the MS18 intramolecular charge transfer and the behavior of the packing, orientation, conformation, and thermal mobility of MS18 hydrocarbon chain, respectively. The J-aggregate in the pure MS18 system dissociates from 25 to 150 °C, and the dissociation temperature at 150 °C is higher by 50 °C than that in the previous MS18-arachidic acid (C20) binary system. The lower dissociation temperature in the binary system originates from the fact that temperature-dependent structural disorder of cadmium arachidate (CdC20), being phase-separated from MS18, has an influence on the dissociation of J-aggregate. From 160 to 180 °C, thermally induced blue-shifted bands, caused by the oligomeric MS18 aggregation, appear at around 520 nm in the pure MS18 system by contraries, regardless of the lack of driving force by the melting phenomenon of CdC20. The temperature at which the 520 nm bands occur is in good agreement with the melting point (160 °C) of hydrocarbon chain in MS18 with Cd2+, whereas its chromophore part is clearly observed to melt near 205 °C by UV−visible spectra. Therefore, it is suggested that the driving force that induces the 520 nm band in the pure MS18 system arises from the partial melting of hydrocarbon chain in MS18 with Cd2+

Structural Characterization of a Mixed Langmuir−Blodgett Film of a Merocyanine Dye Derivative−Deuterated Arachidic Acid Binary System and the Influence of Successive Hydrothermal Treatment in the Liquid Phase on the Film as Investigated by Polarized UV−Visible and IR Absorption Spectroscopy

We have investigated the structure of the mixed Langmuir−Blodgett (LB) film of a merocyanine dye derivative (MO18)−deuterated arachidic acid (C20-d) binary system and the influence of successive hydrothermal treatment in the liquid phase (HTTL) on the mixed LB film by means of polarized UV−visible and IR absorption spectroscopy. The visible absorption band with in-plane anisotropy at 503 nm before HTTL transforms into an absorption band with in-plane isotropy at 557 nm after HTTL for 16−18 min through a peak maximum near 520 nm after HTTL for 2−12 min. The degree of total MO18 intramolecular charge transfer for the 503 nm band is the largest among those for all of the bands. Therefore, the 503 nm band is ascribed to the MO18 H-like aggregation, based on its shape, peak height, and in-plane anisotropy, the subsequent change to two kinds of visible peaks by successive HTTL, and the most degree of MO18 intramolecular charge transfer among all of the aggregation states. While the MO18 hydrocarbon chain takes the all-trans conformation before HTTL, its conformation and orientation are most disarranged after HTTL for 2 min. Subsequently, the original conformation and orientation are recovered by degrees with successive HTTL, except after final HTTL for 18 min, when the orientation is again changed. On the other hand, the C20-d hydrocarbon chain maintains the all-trans conformation before and after HTTL. The orientation of the C20-d hydrocarbon chain after HTTL for 2 min is more ordered than that before HTTL, with the nature of the C20-d subcell packing changing from hexagonal to orthorhombic. During successive HTTL from 2 to 18 min, the C20-d orientation is gradually disorganized but with the orthorhombic nature remaining constant. Thus, the variations in the conformation and orientation of the MS18 hydrocarbon chain and in the orientation of the C20-d hydrocarbon chain tend to change from ordered and disordered structures and turn to more disordered and ordered ones, respectively, where the former is mainly caused by the priority action of thermal energy and the latter by hydrophobic effect due to the presence of warm water. Consequently, it is suggested that there is a correlation between the degree of structural order for both hydrocarbon chains and the preferential action that takes place during HTTL

Mn₁₂ Molecular Redox Array Exhibiting One-Dimensional Coulomb Blockade Behavior

We have found that nonlinear current–voltage characteristics (<i>I</i>–<i>V</i> curves) are observed in the Mn₁₂ {[Mn₁₂O₁₂(O₂CC₆H₅)₁₂(O₂CC₆H₄NH₂)₄(H₂O)₄]·2­(CH₂Cl₂)} molecular redox array in the temperature range from 10 to 300 K. Among them, <i>I</i>–<i>V</i> characteristics with threshold voltages (<i>V</i>_th) are clearly observed from 10 to 80 K. The <i>I</i>–<i>V</i> curves with <i>V</i>_th can be well fitted by applying the one-dimensional (1D) Coulomb blockade (CB) model. The <i>V</i>_th value is 280 mV at 10 K and decreases linearly with increasing temperature. These results indicate that each Mn₁₂ acts as a CB element in the 1D array at 80 K or below. Thus, it is suggested that the Mn₁₂ molecular redox system can be described by the CB behavior

Fe-Assisted Hydrothermal Liquefaction of Lignocellulosic Biomass for Producing High-Grade Bio-Oil

Although bio-oils produced by pyrolysis and hydrothermal synthesis demonstrate potential toward building a sustainable society, large amounts of char generated as a byproduct and their thermal instability owing to high oxygen content hinder their applications. Hence, a novel approach for the production of high-grade bio-oil was proposed herein. In this approach, zerovalent Fe was used as an agent for generating hydrogen in situ in the hydrothermal liquefaction of oil palm empty fruit bunch (EFB), a lignocellulosic biomass source, affording bio-oil containing water-soluble (WS) and water-insoluble (WI) fractions in high yields. Hydrogen generated by the reaction between Fe and H2O efficiently converted unstable intermediates obtained from the degradation of EFB into stable compounds, resulting in reduced char formation. Hydroxyketones were detected as components characteristic of the WS fraction in the H2O/EFB/Fe system, which were stable under hydrothermal condition. WS fractions were treated with the HZSM-5 zeolite, affording light olefins (C2–C4), as well as benzene, toluene, and xylene. This conversion was more efficient with the WS fraction obtained in the presence of Fe. The liquefaction of EFB and the conversion of WS fractions into olefins via catalytic cracking were also achieved using recycled Fe

Investigation into pH-Responsive Self-Assembled Monolayers of Acylated Anthranilate-Terminated Alkanethiol on a Gold Surface

This article describes the preparation of pH-responsive self-assembled monolayers (SAMs) of acylated anthranilate-terminated alkanethiol. These monolayers are formed by chemisorption of the alkanethiol molecules onto a gold surface, resulting in different wetting properties of the surfaces depending upon the pH. By using various characterization techniques (e.g., infrared spectroscopy, cyclic voltammetry, contact angle measurements, and surface energy analysis), we have found that the changes in the wetting properties originate from the different surface structures of the monolayers in different pH environments. From surface energy analysis, we found that the disperse components of the surface energy on such SAMs predominate after treatment with pH 1 water, whereas the polar components of the surface energy on such SAMs predominate after treatment with pH 13 water. It is greatly anticipated that this line of research will provide new insight into the mechanism behind pH-responsive properties, facilitating the design and synthesis of new surface-active molecules for the fabrication of pH-responsive functional surfaces

Investigation into pH-Responsive Self-Assembled Monolayers of Acylated Anthranilate-Terminated Alkanethiol on a Gold Surface

This article describes the preparation of pH-responsive self-assembled monolayers (SAMs) of acylated anthranilate-terminated alkanethiol. These monolayers are formed by chemisorption of the alkanethiol molecules onto a gold surface, resulting in different wetting properties of the surfaces depending upon the pH. By using various characterization techniques (e.g., infrared spectroscopy, cyclic voltammetry, contact angle measurements, and surface energy analysis), we have found that the changes in the wetting properties originate from the different surface structures of the monolayers in different pH environments. From surface energy analysis, we found that the disperse components of the surface energy on such SAMs predominate after treatment with pH 1 water, whereas the polar components of the surface energy on such SAMs predominate after treatment with pH 13 water. It is greatly anticipated that this line of research will provide new insight into the mechanism behind pH-responsive properties, facilitating the design and synthesis of new surface-active molecules for the fabrication of pH-responsive functional surfaces