Preparation and improvement in photovoltaic performance of dye-sensitized solar cells using carbon dioxide

We report preparation and improvement in photovoltaic performance of N719-based dye-sensitized solar cells (DSSCs) using pressurized carbon dioxide (CO₂) as a co-solvent for the absorption process on the TiO₂ photoelectrode surface. Effective absorption of the N719 molecules on the TiO₂ surface was achieved using CO₂ processing, and the absorption time was shortened drastically from 24 h (in the dip process) to less than 3 h. The cells prepared under pressurized CO₂ for the absorption showed greater photovoltaic performance, especially higher short-circuit current density and conversion efficiency, compared with that from typical dip method. It was revealed that the suitable CO₂ pressure for the absorption was 5 MPa and the efficiency was achieved to be more than 7.5 %. Prevention of back electron transfer reactions from TiO₂ to oxidized dyes or iodides was caused currently, because the homogeneous coverage of N719 molecules on the TiO₂ surface was obtained by the use of pressurized CO₂.     

Mechanochromic Photoluminescent Liquid Crystals Containing 5,5′-Bis(2-phenylethynyl)-2,2′-bithiophene

5,5′-Bis(2-phenylethynyl)-2,2′-bithiophene derivative 1 containing dendritic moieties linked through amide groups was synthesized. Compound 1 exhibits a rectangular columnar phase on slow cooling from the isotropic liquid. In contrast, a cubic phase is formed as a metastable liquid-crystalline phase by rapid cooling of the isotropic melt. Mechanical shearing induces a cubic–columnar phase transition, accompanied by the change of a photoluminescent color from yellow-green to green. The infrared spectra of 1 suggest that the mechanical stimuli can induce the partial dissociation of the hydrogen bond. This may lead to more disordering of the π-stacks of chromophores.     

Discovery of a novel acyl-CoA: cholesterol acyltransferase inhibitor: the synthesis, biological evaluation, and reduced adrenal toxicity of (4-phenylcoumarin)acetanilide derivatives with a carboxylic acid moiety

As a part of our research for novel potent and orally available acyl-CoA: cholesterol acyltransferase (ACAT) inhibitors that can be used as anti-atherosclerotic agents, we recently reported the discovery of the (4-phenylcoumarine)acetanilide derivative 1. However, compound 1 showed adrenal toxicity in animal models. In order to search for safer ACAT inhibitors that do not have adrenal toxicity, we examined the inhibitory activity of ACAT in human macrophage and adrenal cells. The introduction of a carboxylic acid moiety on the pendant phenyl ring and the adjustment of the lipophilicity led to the discovery of (2E)-3-[7-chloro-3-[2-[[4-fluoro-2-(trifluoromethyl)phenyl]amino]-2-oxoethyl]-6-methyl-2-oxo-2H-chromen-4-yl]phenyl]acrylic acid (21e), which showed potent ACAT inhibitory activity in macrophages and a selectivity of around 30-fold over adrenal cells. In addition, compound 21e showed high adrenal safety in guinea pigs.     

Molecular Flow and Lanthanum -Catalyzed Bond Interchange in Sodium Phosphate Polymers

Abstract

It is observed that sodium phosphate polymers, in which some of the Na⁺ ions have been replaced by La³⁺ ions, are subject to both simple molecular flow and to bond interchange in the glass transition region. These two relaxation mechanisms are separated, and their relative contributions to the shear viscosity are calculated. It is shown that the bond-interchange mechanism is subject to an activation energy of ca. 50 kcal, while that of the molecular flow is of the order of 200 kcal at Tg + 30°C;the latter is of the WLF form. It is further shown that the La³⁺ ions act as cross-links, at least at low concentrations, and that bond interchange occurs at the site of the La³⁺ ions rather than at random along the polymer chain.     

Si3S-, Si3Se-, Si3Te-Bicyclo[1.1.0]butanes and Si3S2-Bicyclo[1.1.1]pentane

The reaction of trisilirene 1 with propylene sulfide or elemental sulfur produced Si₃S-bicyclo[1.1.0]butane 2, which underwent Si–Si insertion of a second S atom forming Si₃S₂-bicyclo[1.1.1]pentane 3. Analogous reactions of 1 with elemental Se or Te resulted in the formation of heavier analogues of 2, namely, Si₃Se-bicyclo[1.1.0]butane 4 and Si₃Te-bicyclo[1.1.0]butane 5.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.

GRAPHICAL ABSTRACT     

High-speed phase imaging by parallel phase-shifting digital holography

Parallel phase-shifting digital holography can obtain three-dimensional information of a dynamically moving object with high accuracy by using space-division multiplexing of multiple holograms required for phase-shifting interferometry. We demonstrated high-speed parallel phase-shifting digital holography and obtained images of the phase variation of air caused by a compressed gas flow sprayed from a nozzle. In particular, we found the interesting phenomenon of periodic phase distributions. Reconstructed images were obtained at frame rates of 20,000 and 180,000 frames per second.     

Nanocrystals Assembled by the Chemical Reaction of the Dispersion Solvent

The development of methods to pattern nanocrystals with different sizes and shapes remains a challenge. In this study, we demonstrate a unique class of bottom‐up approaches to assemble nanocrystals into patterns. Our approach for patterning nanocrystals focuses on the utilization and control of the chemical reaction of solvents surrounding nanocrystals. The photopolymerization of solvent molecules through a photomask creates time‐dependent concentration gradients of the solvents. Dispersed nanocrystals such as silver nanowires (AgNWs) migrate and are gradually organized and integrated into the polymerizing films based on the concentration gradients. The AgNW‐embedded film properties are determined by the organized AgNW structures and include light transmission and electrical conductivity. Overall, the demonstrated method is very simple, widely applicable to various nanocrystals and solvents, and can thus contribute to the development of a new class of nanocrystal patterning methods.