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The semiconductor properties of a carbon nanotube film can be changed from p-type to n-type by molecular wrapping of oxyethylene surfactants.

The design and scale-up of carbon nanotube (CNT)-based thermoelectric (TE) modules is limited by the low structural similarity between p-type enhancers and n-dopants. This study was aimed at investigating the organic TE properties of polyazacycloalkane/CNT TE films prepared using the drop casting method and the effect of Cu ion doping that can coordinate with its organic ligands. The Seebeck coefficient of cyclen-doped CNTs was −43.3 μV K−1 at 345 K but reduced to 41.6 μV K−1 after adding Cu ions. Cu ion addition switched the charge carrier type of the composite film from electrons to holes owing to cyclen complexation with Cu ions, resulting in a neutral molecular state with suppressed electron donation of the dopant molecules. Notably, conventional approaches cannot maintain sufficient power characteristics owing to the reduced electrical conduction induced by structural defects in the nanotubes. However, herein, an output power exceeding 200 μW m−1 K−2 was obtained, which was 2–5 times higher than that of existing carrier-switchable CNTs. For a typical TE module consisting of five pairs of p-type (Cu(II)-cyclen/CNT)-n-type (cyclen/CNT) junctions, the generated TE voltage and power, depending on the temperature gradient, were similar to the theoretical values. Under optimized conditions, a maximum output power of 1.36 μW was achieved at a temperature difference of 75 K, which is higher than that of previously reported carrier-switchable CNT-based TE modules that used oil-based dopants, whereas we used optimal water-soluble dopants. The proposed approach can help simplify the path from material preparation to module fabrication.

Selective catalytic reduction using NH3 (NH3-SCR) is a chemical process that is used for the elimination of NOx (NO and NO2). Although current vanadia-based catalysts need a high reaction temperature, which leads to deactivation of the catalysts, bulk vanadium oxide showed the potential for NH3-SCR at a low temperature below 150 °C. We investigated a method for synthesis of vanadium oxide with a large surface area using an organic acid to enhance its NH3-SCR activity. Vanadium oxide catalysts were synthesized from ammonium metavanadate (NH4VO3) and organic acids (oxalic acid, succinic acid, malic acid and citric acid). When carboxylic acids (oxalic acid and succinic acid) were used as the organic acid source, the surface area of the catalysts increased up to 41 cm2 g−1, which was larger than that of vanadium oxide synthesized without an organic acid and with hydroxy acid. SEM and TEM measurements showed that vanadium oxide catalysts synthesized by the calcination of vanadyl oxalate at 300 °C (V2O5-OX_300) formed a pore structure that contributed to the increase in surface area. An increase in the number of acid sites and redox sites, which is important for NH3-SCR to proceed, was confirmed from NH3-TPD and H2-TPR measurements for V2O5-OX_300. The NO conversion of V2O5-OX_300 (47 % at 100 °C) was higher than that of the catalysts synthesized from only NH4VO3 (19 % at 100 °C), indicating that vanadium oxide catalysts synthesized using carboxylic acid have the low-temperature NH3-SCR activity due to the increase in their surface area.

The thermoelectric conversion capabilities and stabilities of carbon nanotubes (CNTs) in n-type organic semiconductors are important properties that urgently need improvement for large-scale and low-grade thermal energy applications. Importantly, conventional methods for preparing n-type CNT sheets are disadvantageous because they are incompatible with printing, which is an inherent advantage of organic materials for large-scale applications. Herein, we report the systematic preparation of CNT sheets containing dopant polymers using a drop-casting method that enhances thermoelectric performance and is adaptable to printing. The CNTs exhibit a large, negative Seebeck (S) value that depends on the level of the highest occupied molecular orbital of the dopant polymer, with the optimal poly(N-vinyl-2-pyrrolidone)-poly(vinyl alcohol) graft copolymer (PVP–PVA) providing a large negative S value and a power factor of 289 μW m−1 K−2. The inclusion of 1,2-diphenylhydrazine as a secondary dopant significantly improved the ZT value of the PVP–PVA/CNT from 5.26 × 10−3 for the undoped system to 1.34 × 10−2. Correspondingly, the power factor was ~20% more atmospherically stable after 31 d at room temperature compared to the undoped system. This excellent performance provides new avenues for the development of drop-cast fabricated n-type CNT films without the need for n-doping processes. For n-type organic semiconductors, low thermoelectric conversion properties are an issue that needs to be resolved, moreover current manufacturing methods are not compatible with printing technology. In this communication, we report the systematic preparation of carbon nanotube (CNT) sheets containing dopant polymers using a drop-casting method that enhances thermoelectric performance. The inclusion of 1,2-diphenylhydrazine as a secondary dopant significantly improved the ZT value of poly(N-vinyl-2-pyrrolidone)-poly(vinyl alcohol) graft copolymer/CNT, from 5.26 × 10−3 for the undoped system to 1.34 × 10−2. The developed approach, which is expected to provide on-demand manufacturing through printed electronics technologies.

Regenerative therapeutic approaches involving the transplantation of stem cells differentiated into insulin‐producing cells are being studied in patients with rapidly progressing severe diabetes. Adipose‐derived mesenchymal stem cells have been reported to have varied cellular characteristics depending on the biological environment of the location from which they were harvested. However, the characteristics of mesenchymal stem cells in type II diabetes have not been clarified. In this study, we observed the organelles of mesenchymal stem cells from patients with type II diabetes under a transmission electron microscope to determine the structure of stem cells in type II diabetes. Transmission electron microscopic observation of mesenchymal stem cells from healthy volunteers (N‐ADSC) and those from patients with type II diabetes (T2DM‐ADSC) revealed enlarged nuclei and degenerated mitochondrial cristae in T2DM‐ADSCs. Moreover, T2DM‐ADSCs were shown to exhibit a lower expression of Emerin, a constituent protein of the nuclear membrane, and a decreased level of mitochondrial enzyme activity. In this study, we successfully demonstrated the altered structure of nuclear membrane and the decreased mitochondrial enzyme activity in adipose‐derived mesenchymal cells from patients with type II diabetes. These findings have contributed to the understanding of type II diabetes‐associated changes in mesenchymal stem cells used for regenerative therapy.

The addition of inorganic materials with high thermoelectric properties is a popular approach to modulate the performance of carbon nanotube (CNT), but, the representative hybridization of CNT and toxic Te or Bi is not practical considering safety. Here, we report a CNT film including charge-transfer complex nanoparticles, which has higher generality and thermoelectric properties. Interestingly, the CNT film containing 30 wt% Tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) nanoparticle exhibited a higher in-plane thermoelectric power factor (44.3 μW m-1 K-2) than the pure CNT (10.1 μW m-1 K-2), which is the first result of a nanostructured charge-transfer complex acting as a carrier promoter.

Two-dimensional (2D) nanomaterials with nanopore display an enhancement effect on electrocatalysis behavior, whereas the nanopore engineering for 2D nanocatalysts remains an insurmountable challenge. We advance the synthesis of multilayer Pd nanoplates (Pd NPs) and two types of meshy nanoplates (Pd LMNPs/MNPs) with escalating nanopores from none and sparse to porous. Specially, an in situ nanopore enrichment on these Pd nanoplates hinges on a joint etching strategy with integrated manipulation of reaction kinetics. The optimized Pd MNPs exhibit exceptional oxygen reduction reaction performance, owing to the enhanced intermediates protonation on Pd site neighboring nanopore, which has been elucidated by density functional theory calculations. In addition, Pd MNPs also deliver excellent performances in fuel cell anodic reactions, including ethanol oxidation reaction and formic acid oxidation reaction. This study highlights a new strategy for in situ nanopores engineering, providing a prospect for designing superior nanocatalysts.

The fabrication of low-temperature waste heat power conversion modules will require the development of thermoelectric materials based on mass-produced nanotubes such as super-growth carbon nanotubes (SGCNTs), rather than high-quality nanotubes generated on the laboratory scale. In this work, SGCNT films co-loaded with colloidal ZnO (which has a high Seebeck coefficient) and Ag (which enhances electrical conductivity) were prepared to optimize both carrier concentration and mobility. The resulting carbon-based hybrid films were found to have a p-type power factor of 100.4 µW m−1 K−2 at 383 K, which represented one of the highest values yet reported for a SGCNT system.

Practical catalysts that work at a low temperature for selective catalytic reduction of NOx using NH3 (NH3–SCR) have been required to treat NOx at the outlet temperature in boiler systems (100–150 ...

NH3-SCR (selective catalytic reduction) is important process for removal of NOx. However, water vapor included in exhaust gases critically inhibits the reaction in a low temperature range. Here, we report bulk W-substituted vanadium oxide catalysts for NH3-SCR at a low temperature (100–150 °C) and in the presence of water (~20 vol%). The 3.5 mol% W-substituted vanadium oxide shows >99% (dry) and ~93% (wet, 5–20 vol% water) NO conversion at 150 °C (250 ppm NO, 250 ppm NH3, 4% O2, SV = 40000 mL h−1 gcat−1). Lewis acid sites of W-substituted vanadium oxide are converted to Brønsted acid sites under a wet condition while the distribution of Brønsted and Lewis acid sites does not change without tungsten. NH4+ species adsorbed on Brønsted acid sites react with NO accompanied by the reduction of V5+ sites at 150 °C. The high redox ability and reactivity of Brønsted acid sites are observed for bulk W-substituted vanadium oxide at a low temperature in the presence of water, and thus the catalytic cycle is less affected by water vapor., NH3 selective catalytic reduction is an important technique for NOx removal but water vapor critically inhibits the reaction at a low temperature. Here the authors show bulk W-substituted VOx exhibits higher NOx removal ability than the TiO2 supported vanadia catalyst in the presence of water.

Ti1−xZrxO2 complex oxide particles with 0.02 ≤ x ≤ 0.1 show superior catalytic performances for the direct power storage into glycolic acid via electroreduction of oxalic acid. The atomic pair distribution function analysis of X-ray total scatterings suggested that structural periodicity is the key factor for the catalytic enhancement.

Electrochemical hydrogenation of a carboxylic acid using water as a hydrogen source is an environmentally friendly synthetic process for upgrading bio-based chemicals. We systematically studied electrochemical hydrogenation of non-aromatic carboxylic acid derivatives on anatase TiO2 by a combination of experimental analyses and density functional theory calculations, which for the first time shed light on mechanistic insights for the electrochemical hydrogenation of carboxylic acids. Development of a substrate permeable TiO2 cathode enabled construction of a flow-type electrolyser, i.e., a so-called polymer electrode alcohol synthesis cell (PEAEC) for the continuous synthesis of an alcoholic compound from a carboxylic acid. We demonstrated the highly efficient and selective conversion of oxalic acid to produce glycolic acid, which can be regarded as direct electric power storage into an easily treatable alcoholic compound.

We demonstrated carbon-neutral (CN) energy circulation using glycolic acid (GC)/oxalic acid (OX) redox couple. Here, we report fundamental studies on both catalyst search for power generation process, i.e. GC oxidation, and elemental steps for fuel generation process, i.e. OX reduction, in CN cycle. The catalytic activity test on various transition metals revealed that Rh, Pd, Ir, and Pt have preferable features as a catalyst for electrochemical oxidation of GC. A carbon-supported Pt catalyst in alkaline conditions exhibited higher activity, durability, and product selectivity for electrooxidation of GC rather than those in acidic media. The kinetic study on OX reduction clearly indicated that OX reduction undergoes successive two-electron reductions to form GC. Furthermore, application of TiO2 catalysts with large specific area for electrochemical reduction of OX facilitates the selective formation of GC.

Low-temperature waste heat to electricity conversion modules cannot exhibit their full potential as of this moment, and the design of n-type organic semiconductors is still insufficient. Normally, ...

Here, we described a novel synthetic method of PVP (poly(N-vinyl-2-pyrrolidone))-coated GeO2 nanoparticles by a simple procedure, and its fabrication into a poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS) film. Interestingly, PEDOT-PSS films containing a small amount of PVP-coated GeO2 nanoparticles exhibited higher electrical conductivity than pure PEDOT-PSS. Finally, we have succeeded in the development of a new organic–inorganic thermoelectric conversion film with high performance.

A room-temperature wet chemical method was developed for preparing a catalyst comprising Pd nanoparticles (NPs) supported on a zeolite imidazolide framework-8 (ZIF-8) surface (Pd/ZIF-8). The Pd/ZIF-8 catalyst exhibited a large surface area and high crystallinity, almost equal to those of pristine ZIF-8. The binding of the Pd NPs deposited on the ZIF-8 surface was shown to occur at the ZIF-8 particle surface rather than throughout the metal–organic framework (MOF) structure. The method was also suitable for complexing ZIF-8 with several other, nano-sized noble metals. The Pd/ZIF-8 heterogeneous catalyst was applied in the NaBH₄-reduction of isomeric nitrophenols in both batch and fixed-bed systems. The catalyst was universally active against the isomeric nitrophenols, with a catalytic conversion of 99.7% after 1 h of cycling in the fixed-bed system. Thus, we have demonstrated the preparation of stable, supported catalysts and their application to the continuous reduction of multi-component nitrophenol mixtures.

The p-type properties of carbon nanotubes (CNTs) in organic thermoelectric devices need urgent improvement for large-scale, low-grade thermal energy applications. Here, we present a suitable approach to significantly enhance the power factor (PF) by increasing the electrical conductivity through the low-temperature calcination-induced pyrolysis of the insulating γ-cyclodextrin polymer (PγCyD), which is used as a solubilizer of film-like CNTs. The low-temperature calcination method, which can be used to realize good electrical contact between CNT bundles, shows enhancement behavior as a universal phenomenon for not only PγCyD but also other commonly used polymers for CNT films. To moderate the calcination temperature, the Pd catalyst was added, and the optimal temperature was reduced from 340 °C to 250 °C. Consequently, the PF value of the CNT film was 570 μW m−1 K−2, which was found to be more than twice that of the original CNT film. In addition, we demonstrated the energy harvesting capability of a thermoelectric generator based on this p-type CNT film; a thermoelectric generator with 10 p-type thermoelectric elements showed a maximum power output of 10.3 μW with a temperature difference of 75 °C, which is comparable to the maximum power output of some of the best single-component organic thermoelectric devices demonstrated to date. This outstanding output power shows that easy-to-handle CNT films with low-temperature heat treatment can open new avenues for the development of thermoelectric generators.

We demonstrate the production of glycolic acid, an industrially important alcoholic compound, via the electrochemical reduction of oxalic acid, which is procurable from biomass, and electro-oxidation of water with the help of renewable light energy for the first time. In principle, this new synthesis system is achievable while minimizing the consumption of fossil resources. We built a precious-metal free electrosynthesis system by employing a TiO2 cathode for oxalic acid reduction and a WO3 photoanode for water oxidation. The alcohol production proceeds during the application of electric power above 2.1 V in the dark. Notably, UV-visible light irradiation of the WO3 photoanode enables glycolic acid electrosynthesis above 0.5 V, which is lower (by 0.6 V) than the theoretical bias, i.e., 1.1 V. Glycolic acid electrosynthesis with an 80% high Faradaic efficiency was achieved on applying a bias of 1.5 V under UV-visible irradiation (λ > 300 nm).

A liquid flow-type electrolyser that continuously produces an alcohol from a carboxylic acid was constructed by employing a polymer electrolyte, named a polymer electrolyte alcohol electrosynthesis cell (PEAEC). Glycolic acid (GC, an alcoholic compound) is generated on anatase TiO2 catalysts via four-electron reduction of oxalic acid (OX, a divalent carboxylic acid), accompanied with water oxidation, which achieves continuous electric power storage in easily stored GC. Porous anatase TiO2 directly grown on Ti mesh (TiO2/Ti-M) or Ti felt (TiO2/Ti-F) was newly fabricated as a cathode having favourable substrate diffusivity. A membrane-electrode assembly composed of the TiO2/Ti-M, Nafion 117, and an IrO2 supported on a gas-diffusion carbon electrode (IrO2/C) was applied to the PEAEC. We achieved a maximum energy conversion efficiency of 49.6% and a continuous 99.8% conversion of 1 M OX, which is an almost saturated aqueous solution at room temperature.

Here, we report unusual behaviour of the viscoelasticity of surfactant aqueous solutions consisting of cationic cetyltrimethylammonium bromide (CTAB) and an anionic photoresponsive amphiphile, sodium [4-(4-butylphenylazo)phenoxy]acetate (C4AzoNa). When C4AzoNa molecules are trans-isomers, spheroidal micelles are formed in the surfactant solution, the viscosity of which is low. Irradiation of this solution by ultraviolet (UV) light yields an aqueous solution of CTAB/cis-C4AzoNa (cis-isomers of C4AzoNa), which is a highly viscous gel consisting of wormlike micelles. The drastic change in the surfactant solution viscosity is attributed to the formation and disruption of wormlike micelles. The geometrical structural transformation of the azobenzene groups in the C4AzoNa molecules of the CTAB/C4AzoNa mixture would lead to a change in the critical packing parameter of the mixture, thereby inducing the morphological transformation of the aggregates (spheroidal micelles to wormlike micelles). To our knowledge, this is the first report of a drastic increase in surfactant solution viscosity by UV light irradiation.

This paper reports a method to control the formation and disruption of vesicles from a novel single-tailed surfactant (11-ferrocenylundecylammonium bromide, 11-FAB), which contains two stimuli-responsive groups corresponding to pH variation and redox reaction conditions, by external stimuli. Although 11-FAB is a single-tailed surfactant, pure 11-FAB spontaneously forms vesicles in water. Microscopic observations of 2.5 mM aqueous solutions of pure 11-FAB (pH = 5.2) show that a number of 11-FAB vesicles are giant, with diameters of 10-30 μm. The disruption of vesicles is observed in aqueous 11-FAB solutions under basic conditions. The vesicles are then reformed under acidic conditions. Reduced 11-FAB also forms large vesicles in electrolyte solutions. These vesicles are disrupted by electrochemical oxidation and reformed by subsequent chemical reduction. This reversible disruption and reformation of vesicles is attributed to the drastic change in the molecular structure of 11-FAB. To our knowledge, this is the first report of control over the formation and disruption of vesicles using two stimuli responses.

The major impact of increasing CO2 concentration on climate change has been recognised. Thus, efficient utilisation of renewable electricity is of increasing significant importance and development of various manner of its operation is required for our energetic and environmental sustainability. Recently, electric power storage in high-energy chemicals, called “energy carriers”, has received much attention for the efficient storage and on-demand supply of renewable electricity. Here, we demonstrate direct power charge using an alcohol/carboxylic acid redox couple. Highly transportable glycolic acid, an alcoholic compound, was successfully produced by electroreduction of oxalic acid, a dicarboxylic acid, on ubiquitous TiO2 catalysts with high efficiency and selectivity (70-95% Faradaic efficiency and >98% selectivity) under mild conditions in the potential region of -0.5 to -0.7 V vs. the RHE at 50 ºC. The most desirable characteristic of this electroreduction is the suppression of hydrogen evolution even in acidic aqueous media (Faradaic efficiency of 70–95%, pH 2.1). The detailed observation of TiO2 catalysts using scanning TEM and eels techniques provided a mechanistic insight into the highly selective catalysis. Recently, we coud demonstrate glycolic acid synthesis using an electrochemical cell consisting of the TiO2catalyst and a polymer electrolyte, i.e., a polymer electrolyte alcohol synthesis cell. Furthermore, we succeeded in electric power generation via the selective electrooxidation of glycolic acid to oxalic acid without CO2emission—specifically, carbon-neutral power generation. These results are the first experimental proof of concept for a carbon-neutral energy circulation system based on charging/discharging electric power using an alcohol/carboxylic acid redox couple[1, 2] as shown in Fig. 1. Reference [1] R. Watanabe, M. Yamauchi, M. Sadakiyo, R. Abe, T. Takeguchi, “CO2-free electric power circulation via direct charge and discharge using the glycolic acid/oxalic acid redox couple", Energy Environ. Sci. , 8, 1456-1462 (2015). [2] T. Matsumoto, M. Sadakiyo, M.L.Ooi, S.Kitano, T.Yamamoto, S.Matsumura, K. Kato, T. Takeguchi, and M. Yamauchi, “CO2-Free Power Generation on an Iron Group Nanoalloy Catalyst via Selective Oxidation of Ethylene Glycol to Oxalic Acid in Alkaline Media” , Sci. Rep. , 4,5620(2014). Figure 1

The level of cell transfection mediated by lipoplexes formed using the ferrocenyl lipid bis(11-ferrocenylundecyl)dimethylammonium bromide (BFDMA) depends strongly on the oxidation state of the two ferrocenyl groups of the lipid (reduced BFDMA generally mediates high levels of transfection, but oxidized BFDMA mediates very low levels of transfection). Here, we report that it is possible to chemically transform inactive lipoplexes (formed using oxidized BFMDA) to “active” lipoplexes that mediate high levels of transfection by treatment with the small-molecule reducing agent ascorbic acid (vitamin C). Our results demonstrate that this transformation can be conducted in cell culture media and in the presence of cells by addition of ascorbic acid to lipoplex-containing media in which cells are growing. Treatment of lipoplexes of oxidized BFDMA with ascorbic acid resulted in lipoplexes composed of reduced BFDMA, as characterized by UV/vis spectrophotometry, and lead to activated lipoplexes that mediated high levels of transgene expression in the COS-7, HEK 293T/17, HeLa, and NIH 3T3 cell lines. Characterization of internalization of DNA by confocal microscopy and measurements of the zeta potentials of lipoplexes suggested that these large differences in cell transfection result from (i) differences in the extents to which these lipoplexes are internalized by cells and (ii) changes in the oxidation state of BFDMA that occur in the extracellular environment (i.e., prior to internalization of lipoplexes by cells). Characterization of lipoplexes by small-angle neutron scattering (SANS) and by cryogenic transmission electron microscopy (cryo-TEM) revealed changes in the nanostructures of lipoplexes upon the addition of ascorbic acid, from aggregates that were generally amorphous, to aggregates with a more extensive multilamellar nanostructure. The results of this study provide guidance for the design of redox-active lipids that could lead to methods that enable spatial and/or temporal control of cell transfection.

2013