When human erythrocytes are subjected to high pressures for 30 min at 37 °C, hemolysis and vesiculation begin to occur at a pressure of 140 MPa. Response of the erythrocytes to 140 MPa is expected to provide unique information about the membrane structure. So, we examined the effect of freshness and trypsin treatment of human erythrocytes on the membrane response to 140 MPa. Upon exposure of old erythrocytes to the pressure, the size of erythrocytes reduced gradually due to vesiculation and fragmentation without significant hemolysis, irrespective of trypsin treatment. In trypsin-treated fresh erythrocytes, on the other hand, the suppression of vesiculation and fragmentation under pressure resulted in distinct hemolysis that was characterized by release of large vesicles from mother cells and also by critical hemolysis volume. ESI-MS of lipids demonstrated that the lipid compositions of 140 MPa-induced vesicles were independent of the freshness and trypsin treatment of erythrocytes. Interestingly, the membranes of 140 MPa-induced vesicles contained low cholesterol and high levels of phosphatidylserine and phosphatidylinositol, compared with erythrocyte membranes. Thus, the properties of 140 MPa-induced vesicles reflect partially the initial response of erythrocytes to that pressure.
To investigate the catalytic utility of the imidazo[1,5-a]pyrid-3-ylidene (IPC) ligand, Pd-catalyzed transfer semihydrogenation of alkynes with formic acid as a hydrogen source was conducted. The steric bulkiness of the substituent on N2 affected the configuration of the π-allyl moiety of the precatalyst of IPC-Pd-π-allyl complexes and the robustness of the catalytic process. The catalytic activities of IPC-Pd complexes were clearly higher than those of conventional NHC-Pd complexes.
We herein report a series of sulfonated poly(arylene perfluoroalkylene) terpolymers (SPAF-P) containing sulfophenylene, perfluoroalkylene, and meta- or para-phenylene groups in the main chain. The SPAF-P terpolymers with reasonable molecular weight and various ion exchange capacity (IEC = 1.85–3.18 meq g−1) provided transparent and flexible membranes. Compared with our previous membrane sharing the same perfluoroalkylene groups (SPAF-MM, IEC = 1.59 meq g−1), SPAF-P achieved higher proton conductivity over a wide range of humidity because of their higher IEC values. A fuel cell with SPAF-pP 1.85 membrane exhibited slightly higher performance than that of SPAF-MM at 30% RH with H2/air because of the improved proton conductivity. After the open-circuit voltage (OCV) hold test for 1000 h, the SPAF-pP fuel cell retained high OCV value (>0.94 V), similar polarization curves, ohmic resistance curves, molecular weight and chemical structure, indicating the excellent chemical stability of the SPAF-pP 1.85 membrane.
Zn-ZSM-5 zeolite is a promising catalyst that activates methane at room temperature without the need of a high-temperature pre-oxidation step, which is required for Fe- and Cu-ZSM-5 to form Fe- and Cu-oxo active sites. While two distinct structures of Zn active site, namely [Zn–O–Zn]2+ and Zn2+, were experimentally proposed, the mechanism of how the C–H bond of methane is cleaved is still an intense debate. In addition, the mechanism for moderate-temperature formation of acetic acid by CO2 insertion to the CH4-reacted Zn-ZSM-5 is unclear and the possibility of methanol formation in the presence of an oxidant has never been explored. In the present study, we performed density functional theory (DFT) calculations on the periodic structure of Zn-ZSM-5 zeolite to investigate and clarify these issues. We found that the C–H bond of methane is preferably cleaved on the mononuclear Zn2+ active site through a heterolytic, non-radical mechanism, where the resultant CH3 is bound to the Zn center (Zn–CH3) in the closed-shell singlet state. A good agreement with the reported experimental C–H activation barrier is achieved and plausible mechanisms for the CO2 insertion to and N2O decomposition on the Zn–CH3 bond forming acetic acid and methanol, respectively, are discussed. This study provides a theoretical prediction of an alternative metal-exchanged zeolite catalyst for the low-temperature continuous process of methane selective oxidation to methanol.
Carbon-carbon coupling reactions are one of the most important systems to be studied and the design of palladium based phosphine free catalysts is crucial. In this account, we present a summary of the work carried out by our research group on the design and synthesis of efficient palladium based phosphine free catalysts for the Heck and Suzuki coupling reactions of deactivated and sterically hindered substrates.
One of the most effective ways to solve the dilemma between resources shortages and increasing demand is to develop a cost-effective approach for recovery and reuse of the precious metals (especially Au and Ag) derived from e-wastes (electronic devices and the components thereof), which will most likely be driven by breakthroughs in environmentally friendly methodologies that combine the economy of scale with function. Here a facile and novel approach is described for the recovery of gold from simulated e-wastes by using hollow polyaniline nanospheres (P(VAn-g-PANI)) in which PANI and its derivatives can not only be used to reduce Au3+ to Au0 from the metal salts, but also be used to stabilize the achieved polymer nanosphere-supported Au nanoparticles (Au@P(VAn-g-PANI)). The Au@P(VAn-g-PANI) was directly used to fabricate electronic devices with a configuration of Al/Au@P(VAn-g-PANI) + PVA]/ITO, in which Au@P(VAn-g-PANI) was uniformly integrated into poly(vinyl alcohol) (PVA) as electrically insulating matrix. When the Au/N molar ratio in P(VAn-g-PANI) reached 1:10, the device could be electrically erased and reprogrammed showing typical nonvolatile rewritable memory effect, with an ON/OFF current ratio exceeding 105, a turn-on voltage of −1.85 V and a turn-off voltage of 2.90 V. In the case of Au/N molar ratio of 1:1, the corresponding device exhibited conductor behaviour. This work opens a way that can both recycle gold in situ from e-wastes and fabricate electronic devices by using polymer nanosphere-supported Au nanoparticles.
We have developed two novel approaches for the construction of artificial metalloenzymes showing either unique catalytic activities or substrate specificity. The first example is the use of a hollow cage of apo-ferritin as a reaction vessel for hydrogenation of olefins, Suzuki-Miyaura C-C coupling and phenylacetylene polymerization by employing Pd0 nano-clusters, Pd2+(η3-C3H5) complexes and Rh1+(nbd) (nbd = norbornadiene) complexes introduced in the hollow cage, respectively. The second approach is the use of “decoy molecules” to change substrate specificity of P450s, allowing epoxidation and hydroxylation activities toward nonnative organic substrates in P450SPα, P450BSβ and P450BM3 without the mutation of any amino acid. Finally, the decoy strategy has been applied to an in vivo system of P450, i.e., the use of P450BM3 expressed in the whole cell of E. coli to oxidize benzene to phenol.
The versatility of the synthesis of sulfonated aromatic polymers using NiBr2 was investigated. The copolymerization of sulfo-dichlorobenzene protected with a neopentyl group was carried out with chlorine-terminated oligomer (1) or three different comonomers (2, 3, 4). The copolymerization proceeded well to obtain high molecular weight copolymers (Mn = 4.83–60.1 kDa, Mw = 24.9–133 kDa) and provided flexible membranes, comparable to those obtained with Ni(0) as a polymerization promoter. 1H NMR spectra suggested differences in the comonomer sequence between the copolymers synthesized with Ni(II) and Ni(0). The sequence was quantified as a “randomness of sulfophenylene (SP) unit” and correlated with the membrane properties. The randomness of SP unit in the sulfonated polyphenylene copolymer (SPP-QP) did not affect the phase-separated morphology under the dry-state as suggested by TEM images. SAXS analysis under humidified conditions revealed that the SPP-QP with lower randomness of SP unit formed higher periodicity in the self-assembling structures (i.e., the uniform-sized ionic clusters). The increase of the randomness of SP unit from 19% to 47% in SPP-QP caused decrease of the proton conductivity (at 80 °C and 20% RH) by a factor of 1/1.7 and decrease of the elongation (at 80 °C and 60% RH) by a factor of 1/27. Similar tendency was observed for other series of the sulfonated copolymer membranes.
Shittori feel is defined as a texture that is moderately moisturized and is one of the most favorable textures for many Japanese. In this research, we studied the relationship between the tactile and physical properties of cosmetic powders to determine the specific factors that make up shittori feel. We selected nine cosmetic powders with different sizes, shapes, and touch to conduct physical and tactile evaluations. These evaluations suggested that shittori feel is a complex combination of moist and smooth feels induced by a frictional phenomenon on skin. The moist and smooth feels are perceived when the finger starts to move and when the finger rubs the powders, respectively.
With the increasing knowledge about the diverse roles of RNAs within cells, much attention has been paid to the development of RNA-binding fluorescent probes for the study of RNA functions. Especially, the probes for double-stranded RNA (dsRNA) structures are highly useful given the importance of the secondary and tertiary RNA structures on their biological functions. This account describes our recent efforts to develop synthetic fluorescent probes based on peptide nucleic acids (PNAs) carrying fluorogenic cyanine dyes for targeting the overhang structures of dsRNAs with a view toward the analysis of the intracellular delivery process of small interfering RNAs. We also describe the design of triplex-forming PNA probes carrying cyanine dye base surrogates for the sequence-selective detection of dsRNAs.
Nanoporous carbons with well-defined pore structures are promising for advanced energy applications. Herein, we fabricate nitrogen-doped porous carbons via direct carbonization of a triazine-based covalent organic framework (TACOF1) that acts as both intrinsic template and carbon/nitrogen source. The carbonized TACOF1 forms porous carbon that has a large surface area (1194 m2 g−1) comprised of high volumes of micro- and meso-pores (0.58 cm3 g−1 and 0.44 cm3 g−1, respectively) with a narrow size distribution. In addition, nitrogen doping of the graphitic carbons is uniformly achieved. A thermal analysis along with evolved gas investigation reveals that chemical processes, including N2 gas release and graphitization, vary pore texture formation in the resultant carbons with strong dependence on carbonization temperature. Such structural difference of the carbonized TACOF1 changes electrochemical capacitor behavior. The carbonized TACOF1 synthesized at 800 °C is found to show good capacitive performance due to its nitrogen-doped porous structures.
Among microporous adsorbents, N-doped activated carbon monolith has been developed to achieve functionalized nanoporous carbon via cross-linked polymer precursors, which are used in Friedel-Craft alkylation and pyrolysis. Nitrogen-doping is establish an efficient method for boosting the CO2 adsorption capacity of carbon-based adsorbents, and research in this area is still full of challenges to reach a fit doping level of nitrogen (N) and intrinsic microporosity. Herein is an easy method that enables the preparation of microporous nitrogen-doped porous carbon monolith with proportion of 4.6 wt% N, which employs poly (H-BINAM) as primary material. By virtue of chemical activation, high microporosity is generated and gives a monolithic structured porous nitrogen-doped activated carbon (MPC-700). The resulting material showed a remarkable CO2 adsorption capacity (6.74 mmol g−1 at 273 K and 5.18 mmol g−1 at 298 K under 1 bar), and an excellent CO2 over N2 selectivity (153), which is measured from single-component adsorption isotherms according to Henry’s Law. This value exceeds the CO2 over N2 selectivity of reported carbon-based adsorbents including diverse nitrogen doped examples, the features of which are largely associated with remarkably high N-content and furthermore partial graphitic framework.
Dinuclear complex, [Fe2(H2L1,Me)3](ClO4)4 (1Me, H2L1,Me = N,N′-(1,3-phenylene)bis(1-(5-methyl-1H-imidazol-4-yl)methanimine)), and octanuclear complexes, [Fe8(H2L2,H)12](ClO4)16 (2HClO4: H2L2,H = N,N′-(1,3-phenylenebis(methylene))bis(1-(1H-imidazol-4-yl)methanimine) and [Fe8(H2L2,Me)12](X)16 (2MeX: H2L2,Me = N,N′-(1,3-phenylenebis(methylene))bis(1-(5-methyl-1H-imidazol-4-yl)methanimine), X = ClO4, BF4), were synthesized. It was revealed by X-ray analysis that 1Me has a dinuclear mesocate structure. On the other hand, 2HClO4 and 2MeX have novel octanuclear bicapped trigonal prism structures with six iron(II) sites having the meridional configuration on vertexes and two iron(II) sites having the facial one on the centers of each triangular base. Magnetic susceptibility studies indicated that these dinuclear and octanuclear complexes show gradual spin-crossover (SCO) behavior.
Amorphous alloys are still attracting great attention in the field of catalysis despite the fact that they have been investigated since the 1950s. One of the reasons why amorphous alloys have been in the spotlight until now, are their physical and chemical properties, which would make them suitable materials to be used as catalysts at industrial scale. This review deals with the recent research on applications of amorphous alloys for catalysis. These investigations were addressed to elucidate the relationship between the structural changes (morphology, surface-exposed metal sites, etc.) and the catalytic activity for representative reactions such as hydrogenations, oxidations and hydrogen production from hydrogen carrier molecules. Furthermore, the impact of the combination of an amorphous alloy with another kind of material (MOF and CeO2) and the introduction of a third metal was also discussed.
To date, a wide variety of mesoporous metals has been synthesized using self-assembly of polymeric micelles for catalytic and sensing applications. However, systematic study of trimetallic mesoporous alloys has rarely been performed due to their complex nature. Herein, we demonstrate the synthesis of mesoporous PdPtRh particles by a chemical reduction process with the assistance of a block copolymer, Pluronic® F127. Furthermore, we have also systematically characterized these alloys and evaluated their catalytic performance for methanol oxidation reaction (MOR), in comparison to mesoporous Pt and PdPt particles. Among all the prepared catalysts, the mesoporous PdPtRh sample shows the highest electrocatalytic performance for MOR with high conversion efficiency and tolerance for intermediate generation as well as excellent stability.
Thermal migration of sodium cation in the cavity of Preyssler-type phosphotungstate is reported here. Heating of a Preyssler-type compound, [P5W30O110Na(side)(H2O)]14−, in which a sodium cation occupies one of the two side cavities, at 300 °C forms a new compound, [P5W30O110Na(center)]14−, in which the sodium cation is encapsulated in the central cavity. Characterization by single crystal X-ray structure analysis, NMR spectroscopy, elemental analysis, IR, and ESI-MS confirmed the structure of the compound. The thermal displacement ellipsoid of the central sodium, estimated by the crystallographic study, is elongated along the direction perpendicular to the equatorial plane of the Preyssler molecule. These results confirmed prediction using DFT calculation by López and Poblet (ref. 21, J. Am. Chem. Soc. 2007, 129, 12244.) that the most stable site for sodium is the central cavity with a slight shift from the center of the molecule.