Plasmon-enhanced quasi-solid-state dye-sensitized solar cells with metal@Dendron nanoparticles

We have investigated the effects of localized surface plasmons (LSPs) on the performance of quasi-solid-state dye-sensitized solar cells (DSSCs). Ag and Au nanoparticles (NPs) were prepared by photoreduction in the presence of generation 5 polyester hydroxyl acetylene bis(hydroxymethyl)propanoic acid dendrons (Dendron) as a stabilizer. The plasmon-enhanced DSSCs were achieved by incorporating metal@Dendron NPs into TiO₂ photoanodes. The presence of dendrons prevents the photoelectrons from recombining on the surface of TiO₂ semiconductor and improves the stability of metal NPs. With the addition of Ag@Dendron NPs, the photocurrent and the power conversion efficiency of quasi-solid-state DSSCs increased due to the LSP effect of metal NPs and the barrier effect of dendron, which were confirmed by the increased incident photon-to-photocurrent efficiency and by electrochemical impedance spectroscopy analysis.     

Synthesis and characterization of poly(ether sulfone) grafted poly(styrene sulfonic acid) for proton conducting membranes

Two-step synthesis of proton-conducting poly(ether sulfone) (PES) graft copolymer electrolyte membrane is proposed. Fridel Craft alkylation reaction was used to introduce chloromethyl pendant group onto the PES polymer backbone. Later on, atom transfer radical polymerization (ATRP) was applied to synthesize a series of poly(ether sulfone) grafted poly(styrene sulfonic acid) (PES-g-PSSA). Successful chloromethyl substitution and grafting of the pendant group was characterized by the ¹H-NMR and elemental analysis. Electrochemical properties such as ion exchange capacity (IEC), water uptake and proton conductivity increased with increasing PSSA contents. Thermal gravimetric analysis (TGA) showed the thermal stability of membranes up to 270 °C. Proton conductivity for maximum amount of grafting was 0.00297 S/cm.     

Synthesis and structural properties of lithium titanium oxide powder as-synthesized by two step calcination process

A two-step calcination synthesis, considering the potential for mass production, of lithium titanium oxide powder was carried out to fabricate a single Li₄Ti₅O₁₂ phase, which is useful for anode electrode material of Li-based rechargeable battery as well as an electrode for supercapacitor. The final composition is controlled by adding more TiO₂ powder into powder gained at one calcination process during the two calcination process. We investigated the influence of excess TiO₂ on the structural characteristics of lithium titanium oxide synthesized by the two-step calcination method. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) measurements showed that the as-synthesized powder had a spinel crystal structure as well as A composition of 4: 5: 12. In addition, a high resolution transmission electron microscopy (HRTEM) analysis revealed that the fabricated powder exhibited a single crystalline phase formation. These results indicated that the powder synthesized in the one-step calcination process showed coexistence crystalline phases, which are the Li₄Ti₅O₁₂ and Li_2.39Ti_3.4O₈ phase. However, in the two-step calcination process, the powder synthesized showed the single crystalline Li₄Ti₅O₁₂ phase. A very uniform grain size of the as-synthesized powder was shown in a field emission scanning electron microscopy (FESEM). These results suggested that the two-step calcination process can be used for synthesis of single crystalline Li₄Ti₅O₁₂ powder with uniform grain shape and provide motivation to pursue mass production of lithium titanium based oxide powder for bulk type batteries.     

Formation and Microwave Dielectric Properties of the Mg2V2O7 Ceramics

The formation process and microwave dielectric properties of the Mg₂V₂O₇ ceramics were investigated. The MgV₂O₆ phase that was formed at around 450°C interacted with remnant MgO above 590°C to form a homogeneous monoclinic Mg₂V₂O₇ phase. Finally, this monoclinic Mg₂V₂O₇ phase was changed to a triclinic Mg₂V₂O₇ phase for the specimen fired at 800°C. Sintering at 950°C for more than 5 h produced high-density triclinic Mg₂V₂O₇ ceramics. In particular, the Mg₂V₂O₇ ceramics sintered at 950°C for 10 h exhibited the good microwave dielectric properties of ɛ_r=10.5, Q × f =58 275 GHz, and τ_f=−26.9 ppm/°C.     

Mullite whiskers derived from kaolin

Short mullite whiskers prepared by firing compacts of kaolin and NH₄Al(SO₄)₂·12H₂O powders, with a small addition (0.8, 1.5 wt%) of NaH₂PO₄·2H₂O, in air 1300 and 1400 °C for 15 h have been characterized in terms of whisker morphology, composition and structure. Relatively uniform whisker shaped crystals grew within the silicate glass matrix. After chemically leaching the glass matrix with HF solution using a microwave heating source, the resulting whiskers were exposed as isolated crystals and exhibited an aspect ratio of >17 (～0.5 μm in diameter). The mullite whiskers had a composition of 51.06 mol% Al₂O₃ and 48.94 mol% SiO₂, with an orthorhombic crystallographic structure.     

Promising zeolite-type hydrocarbon trap catalyst by a knowledge-based combinatorial approach

Libraries consisting of more than 100 zeolite samples were prepared and examined for developing a promising HC trap catalyst. Parallel adsorptions of toluene onto the catalyst samples were conducted over a 10 × 10 array reactor under dry and wet conditions with or without a heating process three knowledge-based conditions for developing an automotive catalyst during the cold-start period. FAU and BEA type zeolites revealed a high performance of toluene adsorption under the dry condition. However, FAU type zeolite significantly decreased the amount of toluene adsorbed in the presence of water in the feed gas stream, mainly due to the hydrophobicity of the catalyst surface. Over Beta type zeolites, the toluene adsorbed was found to be considerably preserved, even after forced desorption temperature-ramping to the warm-up condition of an automotive engine. Li, K, or Ag ion-exchanged Beta zeolites seem to be particularly promising as an HC trap catalyst.     

Immobilization of TiO2 on an ITO substrate to facilitate the photoelectrochemical degradation of an organic dye pollutant

In this study, we developed an immobilized TiO₂ semiconductor on an ITO glass substrate (TiO₂/ITO) and investigated its photocatalytic and electrochemical performance. The TiO₂/ITO samples were prepared via a spin-coating process followed by calcination and were used for the photocatalytic or electrochemical degradation of an organic dye pollutant. The measured photocatalytic performance was comparable to that reported in previous publications; however, a remarkable result was obtained in our electrochemical system. The formation of hydroxyl radicals (OH) strongly dominated the electrochemical system, which resulted in outstanding degradation performance. Therefore, we propose a commercializable photoelectrochemical system that can maximize the degradation of pollutants in wastewater treatment plants.     

The effect of nano-sized BNBT on microstructure and dielectric/piezoelectric properties

(Bi_0.5Na_0.5)_0.94Ba_0.06TiO₃ (abbreviated as BNBT6) ceramic of near MPB composition was synthesized by two different processes. The first one is the addition of pre-synthesized BaTiO₃ and pre-milled Bi₂O₃, Na₂CO₃, BaCO₃ powders and calcination powder milled with a high energy milling machine in order to obtain a nano-particle size. The second one is a conventional one to compare with the former process. The pre-milling and the pre-synthesis process of raw materials lowered the calcination temperature to the extent of 59 °C as compared with conventionally fabricated BNBT6. The particle size of the powder exposed to heavy high energy milling reduced to 50–70 nm, whereas that of the conventionally ball-milled powder without the pre-milling and the pre-synthesis process had a larger size of 280 nm. To investigate the effects of the modified process on the characteristic of BNBT6 ceramics, the dielectric and the piezoelectric properties of sintered specimens fabricated by the two different processes were evaluated. It was found that the properties of the nano-sized BNBT6 ceramic near the MPB composition were increased by the modified mixing and milling method, showing superior characteristics in terms of the piezoelectric/dielectric constant and sintering density compared with those of the conventional process. The modified mixing and milling method was considered to be a new and promising process for lead-free piezoelectric ceramics owing to their excellent piezoelectric/dielectric properties.     

In vivo immunological toxicity in mice of carbon nanotubes with impurities

The longstanding question as to whether carbon nanotubes are intrinsically toxic hinders their widespread industrial application. Here, we clarify the effect of impurities within such tubes through systemic studies of immunological responses in mice by monitoring and examining changes in peripheral T-cell subset and peripheral cytokine levels and histology. Contaminated and clean tubes were subcutaneously implanted in mice. The implanted tubes with impurities clearly induced immunological toxicity and localized alopecia, whereas extremely pure implanted tubes showed good biocompatibility. Our studies suggest that such high-temperature thermal treatment is an effective way to improve the biocompatibility of carbon nanotube.     

Migration of Intergranular Liquid Films and Formation of Core-Shell Grains in Sintered TiC–Ni Bonded to WC–Ni

When TiC–20 wt% Ni powder mixtures are sintered at 1400°C, relatively large TiC grains possibly containing some Ni form with near-equilibrium shapes. When these specimens are heat-treated again at 1400°C in contact with sintered WC–20 wt% Ni pieces, the liquid films between the TiC grains in the contact region migrate against their increasing curvatures, forming (Ti,W)C solid solution behind them. These migrating liquid films reverse their directions on further heat-treatment. As in other alloys, this liquid film migration must be driven by the coherency strain energy produced by W diffusion at the surface of the dissolving TiC grains. Shells of (Ti,W)C solid solution also form around the cores of TiC grains near the contact region, and this process is probably driven by both coherency strain energy and free energy of mixing. At some contact regions, (Ti,W)C precipitates nucleate and grow, probably driven mainly by the free energy of mixing. In powder mixtures, the formation of core-shell grains is expected to be driven by the coherency strain energy, the free energy of mixing, and the capillary effect.