A manganese superoxide dismutase mimic based on cis,cis-1,3,5-triaminocyclohexane

A novel manganese(iii) complex with a water soluble cis,cis-1,3,5-triaminocyclohexane-based ligand was synthesised and shown to exhibit superoxide dismutase activity.     

A Stable Integrated Photoelectrochemical Reactor for H2 Production from Water Attains a Solar‐to‐Hydrogen Efficiency of 18 % at 15 Suns and 13 % at 207 Suns

The major challenge in solar water splitting to H₂ and O₂ is in making a stable and affordable system for large‐scale applications. We have designed, fabricated, and tested a photoelectrochemical reactor characterized as follows: 1) it comprises an integrated device to reduce the balance of the system cost, 2) it utilizes concentrated sunlight to reduce the photoabsorber cost, and 3) it employs and alkaline electrolyte to reduce catalyst cost and eliminate external thermal management needs. The system consists of an III‐V‐based photovoltaic cell integrated with Ni foil as an O₂ evolution catalyst that also protects the cell from corrosion. At low light concentration, without the use of optical lenses, the solar‐to‐hydrogen (STH) efficiency was 18.3 %, while at high light concentration (up to 207 suns) with the use of optical lenses, the STH efficiency was 13 %. Catalytic tests conducted for over 100 hours at 100–200 suns showed no sign of degradation nor deviation from product stoichiometry (H₂/O₂=2). Further tests projected a system stability of years.     

Molecular basis for water-promoted supramolecular chirality inversion in helical rosette nanotubes

Helical rosette nanotubes (RNTs) are obtained through the self-assembly of the GwedgeC motif, a self-complementary DNA base analogue featuring the complementary hydrogen bonding arrays of both guanine and cytosine. The first step of this process is the formation of a 6-membered supermacrocycle (rosette) maintained by 18 hydrogen bonds, which then self-organizes into a helical stack defining a supramolecular sextuple helix whose chirality and three-dimensional organization arise from the chirality, chemical structure, and conformational organization of the GwedgeC motif. Because a chiral GwedgeC motif is predisposed to express itself asymmetrically upon self-assembly, there is a natural tendency for it to form one chiral RNT over its mirror image. Here we describe the synthesis and characterization of a chiral GwedgeC motif that self-assembles into helical RNTs in methanol, but undergoes mirror image supramolecular chirality inversion upon the addition of very small amounts of water (<1% v/v). Extensive physical and computational studies established that the mirror-image RNTs obtained, referred to as chiromers, result from thermodynamic (in water) and kinetic (in methanol) self-assembly processes involving two conformational isomers of the parent GwedgeC motif. Although derived from conformational states, the chiromers are thermodynamically stable supramolecular species, they display dominant/recessive behavior, they memorize and amplify their chirality in an achiral environment, they change their chirality in response to solvent and temperature, and they catalytically transfer their chirality. On the basis of these studies, a detailed mechanism for supramolecular chirality inversion triggered by specific molecular interactions between water molecules and the GwedgeC motif is proposed.     

Adsorption of phosphate and nitrate anions on ammonium-functionalized MCM-48: effects of experimental conditions

In this study, ammonium-functionalized MCM-48 (Mobil Composite Material No. 48) was used as an adsorbent to remove nitrate (NO(-)(3)) and monobasic phosphate (H(2)PO(-)(4)) anions from aqueous solutions. The effects of operating conditions such as temperature, adsorbent loading, initial anion concentration, pH, and the presence of competitive ions on the adsorption performances were examined. Results showed that adsorption capacity decreased with increasing temperature. The adsorption capacity increased with adsorbent loading and initial anion concentration. The removal of nitrate was maximum at pH<8, while phosphate removal was maximized at pH 5. The adsorption was almost unaffected by the presence of competitive ions in the case of phosphate anions. However, their presence adversely affected nitrate adsorption. Desorption of both anions was rapidly achieved within 10 min using NaOH at 0.01 M. Regeneration tests showed that the adsorbent retained its capacity after 5 adsorption-desorption cycles.     

Electrical properties and Pockels effect in BaTiO_{3}/SrTiO_{3} superlattices

The electrical and linear electro-optical properties of BaTiO $_{3}$ (BT)/SrTiO $_{3}$ (ST) superlattices epitaxially grown on ST substrate are theoretically investigated using a microscopic quantum mechanical model based on the orbital approximation in correlation with the dipole–dipole interaction. Both the first-, second-, and third-order electronic polarizabilities were considered in this calculation in order to obtain accurate results for both the spontaneous local electric field, spontaneous polarization, relative dielectric constant, and linear electro-optic coefficients (Pockels constants) of BT/ST superlattices. The calculations show that the spontaneous local electric field, spontaneous polarization and linear electro-optic coefficients of BT/ST superlattices increase with their content in BT while the relative dielectric constant increases with their content in ST. Moreover, we have shown that significant enhancement of the linear electro-optic coefficients can be achieved in BT/ST superlattices. This enhancement, which concerns the ST as well as the BT layers, arises from the combined effects of strain, induced in the BT layers by the epitaxial growth, and internal polarizing electric field originating in the BT layers and acting on the electronic clouds of the polarizable constituent ions of the system.     

蜂窝夹芯圆环的拓扑优化设计及尺度效应研究

采用尺度关联的一体化设计方法开展了旋转周期圆环结构的拓扑优化设计研究,以宏观 结构的最大刚度为目标,研究了材料表征体胞尺度、构型以及不同载荷作用形式对蜂窝夹芯 圆环结构优化结果的影响. 所提出的无量纲结构构型因子实现了优化结构的结构效率量化评 估. 结合SIMP材料模型和周长控制方法,实现了宏观结构和细观表征体胞的优化设计,获得 清晰的材料分布. 数值算例表明,尺度关联的一体化设计方法能有效地完成圆环结构的拓扑 优化设计,设计结果充分反映体胞尺度效应对旋转周期圆环结构夹芯构型的影响.     

Electrochemical reactivity of In-Pb solid solution as a negative electrode for rechargeable Mg-ion batteries

A composite In-Pb:carbon was successfully synthetized by a two-step mechanochemical synthesis in order to obtain an adequate particles size and structure to investigate the electrochemical reactivity of the In-Pb solid solution towards Mg.A potential synergetic coupling of electroactive elements In and Pb was examined using electrochemical and ex situ X-ray diffraction analyses.The potential profile of the solid solution indicates the formation of Mg₂Pb and Mg In.However,the diffraction study suggests a peculiar electrochemically-driven amorphization of Mg In during the magnesiation,in strong contrast to Mg In crystallization in In-based and In Bi-based electrodes reported in the literature.Combining In and Pb favors the amorphization of Mg In and a high first magnesiation capacity of about 550 m Ah g^-1,but is thereafter detrimental to the material’s reversibility.These results emphasize the possible influence of electrochemically-driven amorphization and crystallization processes on electrochemical performance of battery materials.     

Experimental Investigation of Pure Spinel Mn3O4 Properties Synthesized through Chemical Spray Pyrolysis for Future Gas Sensor Application

The semiconductor realization is a very significant stage in gas sensor application. Herein, the Mn₃O₄ semiconductor was deposited using chemical spray pyrolysis. The effect of deposition temperature on structural, vibrational optical and electrical Mn₃O₄ thin layers properties were investigated through: X-ray diffraction, Raman spectroscopy, UV-visible spectrophotometer, and two points electrometers respectively. The X-ray diffraction showed the appearance of spinel phase of tetragonal Mn₃O₄ with strong formation direction along (101) plan and without any secondary phase indicating the formation of pure Mn₃O₄. The Raman spectroscopy confirmed the results obtained in XRD and certified the high-quality formation of Mn₃O₄. In addition, the crystallinity improvement (the increase of crystallite size and the decrease of dislocation density) was caused by the increasing of deposition temperature from 350 °C to 450 °C. Optical properties such as transmittance, absorbance and band gap energy were extracted by UV-Visible spectrophotometer. Thus, low transmittance, high absorbance and small band gap energy were observed at the highest substrate temperature (450 °C). The electrical conductivity showed good values between 4.83 and 13.89 mS.cm⁻¹. These properties make Mn₃O₄ an appropriate material to be used as a sensitive layer in gas sensors applications.