ZnO thin films epitaxially grown by electrochemical deposition method with constant current

The electrochemical deposition (ECD) method is well suited to the preparation of large area devices and has several advantages, although the deposited films have a crystallinity problem. A constant current deposition method was employed for preparation of ZnO thin films in this study, because it was expected that the growth rate of the films could be controlled by means of the current density. The intensity of X-ray diffraction (XRD) peaks, and the size and shape of grains of ZnO films grown on polycrystalline Au substrates were observed to depend on the cathodic current density. On the basis of those results, deposition of ZnO on a Pt layer epitaxially grown on c-sapphire was carried out. The results of ?-scan XRD measurements showed in-plane orientation in agreement with the in-plane direction of the Pt substrate layer, which suggests that the ZnO thin film was epitaxially grown by the ECD method.     

Synthesis of the Ag+-Bipyridine Complexes Anchored within MCM-41 and their Photocatalytic Reactivity for N2O Reduction with CO

Bipyridine derivatives were covalently anchored on the surface of the mesopores of MCM-41 porous material and the further introduction of Ag⁺ ions led to the formation of Ag⁺ bipyridine complexes by the chelation of the Ag⁺ ions with the bipyridine units. The successful covalent immobilization of the bipyridine derivatives as well as the Ag⁺ bipyridine complexes has been confirmed by various spectroscopic investigations such as FT-IR, UV-vis, and XPS analyses. It was found that the anchored bipyridine derivatives on the surface of MCM-41 prevent the reduction and agglomeration of the Ag⁺ species even after evacuation treatment at 573 K. Thus, the anchored Ag⁺ ions chelated with the bipyridine units inside the mesopores of MCM-41 were observed to exhibit photocatalytic reactivity for N₂O reduction with CO.     

Electronic Communication in the Mixed-valence States of Cyclobutadienecobalt Complexes having Two Ferrocenes and Two Anthraquinones

Two geometric isomers, Z and E forms of (η⁴-cyclobutadiene)(η⁵-cyclopentadienyl) cobalt simultaneously containing two ferrocene moieties and two anthraquinone moieties, 1 and 2, respectively, were synthesized, and their crystal structures were determined. These molecules formed double mixed-valence states caused by ferrocene–ferrocenium and anthraquinone–anthrasemiquinone electronic communications. In both 1 and 2, the thermodynamic stability of the mixed-valence state for the ferrocene moieties was higher than that of the anthraquinone moieties because of the orbital coupling of the CB–Co bridging unit. The comproportionation constant, K _c, for the ferrocene moieties was similar between 1 and 2, whereas the mixing coefficient, α, and the off-diagonal matrix-coupling element in the Marcus-Hush two-state model, H _AB, evaluated from analysis of the intervalence charge transfer (IVCT) band were larger for 1 than for 2. These results suggest the existence of higher electrostatic repulsion between two ferrocenium cations in 1 than in 2 and the occurrence of through-bond electronic communication. K _c for the anthraquinone moieties in the E form is smaller than that of the Z form, probably due to the through-space electronic interaction.     

Mechano‐ and Photochromism from Bulk to Nanoscale: Data Storage on Individual Self‐Assembled Ribbons

A Pt(II) complex, bearing an oligo‐ethyleneoxide pendant, is able to self‐assemble in ultralong ribbons that display mechanochromism upon nanoscale mechanical stimuli, delivered through atomic force microscopy (AFM). Such observation paves the way to fine understanding and manipulation of the mechanochromic properties of such material at the nanoscale. AFM allows quantitative assessment of nanoscale mechanochromism as arising from static pressure (piezochromism) and from shear‐based mechanical stimuli (tribochromism), and to compare them with bulk pressure‐dependent luminescence observed with diamond‐anvil cell (DAC) technique. Confocal spectral imaging reveals that mechanochromism only takes place within short distance from the localized mechanical stimulation, which allows to design high‐density information writing with AFM nanolithography applied on individual self‐assembled ribbons. Each ribbon hence serves as an individual microsystem for data storage. The orange luminescence of written information displays high contrast compared to cyan native luminescence; moreover, it can be selectively excited with visible light. In addition, ribbons show photochromism, i.e., the emission spectrum changes upon exposure to light, in a similar way as upon mechanical stress. Photochromism is here conveniently used to conceal and eventually erase information previously written with nanolithography by irradiation.     

Status of uptake of mercury by the fresh water diatom, Synedra ulna

Synedra, a fresh water diatom, took up mercuric chloride rapidly from the surrounding water into the cells attaining the maximum level during the first 7 h. The comparison of mercury uptake by dividing cells with that of non-dividing, heat killed cells and their silicate shells showed that some factors other than cell-division or photosynthesis were responsible for mercury uptake by Synedra cells. About 20% of the total amount of mercury found in dividing cells was taken up by passive adsorption and could be eliminated by washing with distilled water or medium. About 50% of the mercury could not be eluted even with cysteine solution and was accumulated in the inner part of cells. Synedra took up 0·45 μm filterable or ionic mercury rather than particulate mercury larger than 0·45 μm.     

Physical Properties of Two Isomers of Conjugated Linoleic Acid

Thermal properties, powder X-ray diffraction patterns and FT-IR absorption spectra of crystals of two isomers of conjugated linoleic acid (CLA), 9-cis, 11-trans-CLA (c9t11), 10-trans, 12-cis-CLA (t10c12) were examined. To search for polymorphic modifications, we carefully performed crystallization from melt and solution phases, and isolated one type of crystalline form in c9t11 and t10c12. The melting temperature (T _m) was 14.9 °C, enthalpy of fusion (ΔH) was 38.7 kJ/mol, and entropy of fusion (ΔS) was 134 J/mol K for c9t11, and T _m = 19.8 °C, ΔH = 35.6 kJ/mol and ΔS = 122 J/mol K for t10c12. The X-ray diffraction and FT-IR measurements indicated O_⊥ subcell packing in the crystals of c9t11 and t10c12, and long spacing values of 4.22 nm for c9t11 and 3.88 nm for t10c12. The unique molecular structures of the two isomers of CLA are discussed in comparison to the polymorphism of oleic acid, petroselinic acid, elaidic acid and linoleic acid, all of which are unsaturated fatty acids having the same carbon number of 18 as that of the two CLA isomers.     

Effect of hydrophilic group on thin film formation using redox-active surfactants with an azobenzene group

Thin films of organic pigments were prepared at higher than pH 1 by the contact plating method using an anionic surfactant (AZNa, first figure of this article (part c) (n = 4)) containing an azobenzene moiety. The effects of hydrophilic group of the surfactants on the rate of following reaction of the reduction product were studied by cyclic voltammetry. The positive shift of the reduction peak potential of AZNa compared to those of cationic and non-ionic surfactants was ascribed to higher rate of following reaction of reduction product due to the presence of the anionic hydrophilic group of the surfactant. The present investigation revealed that the anionic hydrophilic group accelerates the cleavage of the NN bond of the azobenzene group. This phenomenon enabled us to prepare the organic thin film at higher pH condition.     

Polymorphic and microstructural behaviors of palm oil/lecithin blends crystallized under shear

There has been much work on polymorphism and crystal habit of quiescently crystallized palm oil. However, researchers have found it difficult to probe the process of sheared crystallization. The effect of surface-active molecules as nucleation agents or habit modifiers was demonstrated in quiescent systems. The aim of this work is to explore the effects of shear and specific lecithins (soy and sunflower) on palm oil crystallization by monitoring crystallization under shear using a synchrotron radiation source, as well as microscopy and DSC. It was found that increasing shear led to increasing β′ stabilization in all situations. Soybean lecithin had little effect on behavior. Sunflower lecithin led to even greater β′ stabilization. The different lecithins interact with the crystallizing fat changing rates of nucleation and crystal growth. Thus, the structure of the overall system can be dramatically altered. Microscopy revealed very different structures even if the polymorphism of the different systems was similar. Consequently, specific interactions can be manipulated in order to control the system. In particular, control of lecithin composition affects the stability of the different polymorphs. Palm oil crystallization under realistic processing conditions has been characterized. Under these conditions, increasing shear rates give higher β′ stability. Specific lecithins have different effects. In particular, soybean lecithin is β′ stabilizing, whereas sunflower lecithin has limited effects. Thus the overall structure of lecithin is important in determining the efficacy. This can be applied to control the structure and properties of different systems such as shortenings or spreads where crystalline interactions create the macro-structure that determines product properties.     

Soil improvement using plant-derived urease-induced calcium carbonate precipitation

This study addresses a soil improvement technique using plant-derived urease-induced calcium carbonate (CC) precipitation (PDUICCP) as an alternative to microbially induced carbonate precipitation (MICP). A crude extract of crushed watermelon (Citrullus lanatus) seeds was used as the urease source along with calcium chloride (CaCl₂) and urea (CO (NH₂)₂) for CC precipitation. Test specimens (φ?=?2.3?cm, h?=?7.1?cm) made from commercially available Mikawa sand (mean diameter, D₅₀?=?870?µm) were cemented, and estimated unconfined compressive strength (UCS) of several kPa to MPa was obtained by changing the concentration of CaCl₂- urea, urease activity, curing time, and temperature. The increase of curing time and that of the CaCl₂-urea concentration from 0.3?M to 0.7?M caused an increase in estimated UCS value. The average estimated UCS obtained after 14?days’ curing time for 0.7?M CaCl₂-urea and 3.912 U/mL urease was around 3.0?MPa and for 0.3 and 0.5?M CaCl₂-urea and 0.877 U/mL urease, it was around 1.5–2.0?MPa at 25?°C. By changing each of the abovementioned parameters, it may be possible to apply this method for strength improvement of loose sand, to mitigate the liquefaction, protection and restoration of limestone monuments and statuaries, and artificial soft rock formations. Crude urease from crushed watermelon seeds has the potential to replace commercially available urease for carbonate precipitation and for use as a low environmental impact type soil improvement method.     

Crystal growth and structure of R2Ir2O7 (R = Pr, Eu) using molten KF

Single crystals of R₂Ir₂O₇ (R = Pr, Eu) have been synthesized using molten KF at 1373 K. The pyrochlore compounds crystallize in a cubic space group (No. 227, origin choice 2), with Z = 8. At room temperature, the lattice parameters are a = 10.3940(4) Å, V = 1122.92(7) Å³ and a = 10.274(3) Å, V = 1084.5(6) Å³ for Pr₂Ir₂O₇ and Eu₂Ir₂O₇, respectively. In this paper, we report the crystal growth of R₂Ir₂O₇ (R = Pr, Eu) and their structure determinations from single crystal X-ray diffraction experiments at temperatures of 110, 115, and 298 K.