Fabrication of spatially periodic double roughness structures by directional viscous fingering and spinodal dewetting for water-repellent surfaces

Water-repellent and self-cleaning properties of lotus leaves are considered to be due to its double roughness structure, protrusion structure (approximately 20 microm) and hairy structure (0.2-1.0 microm). In this study, attempts to fabricate a spatially periodic double roughness structure by two far-from-equilibrium self-organization phenomena, a directional viscous fingering and a spinodal dewetting, were made. A mixture of an octylsilyl titanium dioxide particle having an average diameter of 35 nm suspended in volatile silicone, decamethyl cyclopentasiloxane, and octyl p-methoxycinnamate was spread on a glass plate by dragging an applicator across the top. Formation of a stripe pattern parallel to the direction of dragging, called directional viscous fingering, was sometimes observed. Influences of spreading conditions on the pattern formation were analyzed. In addition, attempts were made to apply the stripe pattern formation to the preparation of a water repellent surface. We have succeeded in preparing a highly water-repellent surface by immersing a glass plate, on which a spatially periodic stripe pattern having a characteristic wavelength of 200-700 microm was formed, in water, after the completion of evaporation of decamethyl cyclopentasiloxane. In this case, dewetting patterns having a characteristic wavelength at around 5 microm were formed at the bottom part of the stripe patterns. Neither the surface on which only the mesoscopic spatially periodic stripe pattern was formed nor the one on which only the microscopic dewetting pattern was formed showed high water-repellent properties, indicating that the coexistence of the two different scales of patterns increased the water-repellent properties of the hydrophobic surface.     

Local structure of Pt and Pd ions in Ce(1-x)TixO2: x-ray diffraction, x-ray photoelectron spectroscopy, and extended x-ray absorption fine structure

Ce(1-x-y)Ti(x)Pt(y)O(2-delta) (x=0.15; y=0.01) and Ce(1-x-y)Ti(x)Pd(y)O(2-delta) (x=0.25; y=0.02 and 0.05) are found to be good CO oxidation catalysts [T. Baidya et al., J. Phys. Chem. B 110, 5262 (2006); T. Baidya et al., J. Phys. Chem. C 111, 830 (2007)]. A detailed structural study of these compounds has been carried out by extended x-ray absorption fine structure along with x-ray diffraction and x-ray photoelectron spectroscopy. The gross cubic fluorite structure of CeO(2) is retained in the mixed oxides. Oxide ion sublattice around Ti as well as Pt and Pd ions is destabilized in the solid solution. Instead of ideal eight coordinations, Ti, Pd, and Pt ions have 4+3, 4+3, and 3+4 coordinations creating long and short bonds. The long Ti-O, Pd-O, and Pt-O bonds are approximately 2.47 A (2.63 A for Pt-O) which are much higher than average Ce-O bonds of 2.34 A.     

Transformation of environment map by changing the captured position in a cuboidal room

Optical Review - In this paper, we consider the use of an environment map as a photographic support tool for understanding the condition of surrounding light. It is well known that an environment...     

Synthesis of chiral and modifiable hexahydroxydiphenoyl compounds

A reliable method for synthesizing each enantiomer of the hexahydroxydiphenoyl (HHDP) compounds has been developed. The synthesis involved atropselective construction of the aryl-aryl bond of the HHDP compounds. This construction relied on the CuCl(2)·n-BuNH(2)-mediated intramolecular coupling of bis(4-O-benzylgallate) on two simple chiral auxiliaries, both of which were derived from l-(+)-tartaric acid. The coupling reaction realized complete or near-perfect atropselectivity. The two auxiliaries induced opposite axial chirality despite their identical origin. The diastereoselectivities of these couplings were probably controlled kinetically. Modifications of the free phenolic hydroxy groups and the carbonyl groups in the resulting HHDP compounds demonstrated the potential derivatization of a wide variety of HHDP analogues.     

In situ time-resolved XAFS study of the reaction mechanism of bromobenzene homocoupling mediated by [Ni(cod)(bpy)

A homocoupling reaction mechanism of bromobenzene mediated by the [Ni(cod)(bpy)] (cod = 1,5-cyclooctadiene; bpy = 2,2'-bipyridine) complex was investigated by means of in situ time-resolved X-ray absorption fine structure (XAFS) and factor analysis. A dimer intermediate [Ni(bpy)(Ph)Br](2) proposed in the previous studies by other groups is too dilute to observe with the XAFS technique; however, the structures and concentrations on the time course of a reactant [Ni(cod)(bpy)], an intermediate [Ni(bpy)(Ph)Br(dmf)(2)], and a byproduct [Ni(bpy)Br(2)(dmf)] during reaction are revealed by this combination.     

Alkali-Metal-Promoted Pt/TiO(2) Opens a More Efficient Pathway to Formaldehyde Oxidation at Ambient Temperatures

Addition of alkali metal ions significantly promotes the activity of the Pt/TiO(2) catalyst for the HCHO oxidation reaction by stabilizing an atomically dispersed Pt-O(OH)(x) alkali metal species and opening a new low-temperature reaction pathway. The atomically dispersed Na-Pt-O(OH)(x) species can effectively activate H(2) O and catalyze the facile reaction between surface OH and formate species to total oxidation products.     

Completely β-selective glycosylation using 3,6-O-(o-xylylene)-bridged axial-rich glucosyl fluoride

A completely β-selective glycosylation that does not rely on neighboring group participation is described. The novelty of this work is the design of the glycosyl donor locked into the axial-rich form by the o-xylylene bridge between the 3-O and 6-O of d-glucopyranose. The synthesized 2,4-di-O-benzyl-3,6-O-(o-xylyene)glucopyranosyl fluoride could efficiently react with various alcohols in a SnCl(2)-AgB(C(6)F(5))(4) catalytic system. The mechanism composed of the glycosylation and isomerization cycles was revealed through comparative experiments using acidic and basic molecular sieves. The achieved perfect stereocontrol is attributed to the synergy of the axial-rich conformation and convergent isomerization caused by HB(C(6)F(5))(4) generated in situ.     

Recognition and one-pot extraction of right- and left-handed semiconducting single-walled carbon nanotube enantiomers using fluorene-binaphthol chiral copolymers

Synthesized single-walled carbon nanotubes (SWNTs) are mixtures of right- and left-handed helicity and their separation is an essential topic in nanocarbon science. In this paper, we describe the separation of right- and left-handed semiconducting SWNTs from as-produced SWNTs. Our strategy for this goal is simple: we designed copolymers composed of polyfluorene and chiral bulky moieties because polyfluorenes with long alkyl-chains are known to dissolve only semiconducting SWNTs and chiral binaphthol is a so-called BINAP family that possesses a powerful enantiomer sorting capability. In this study, we synthesized 12 copolymers, (9,9-dioctylfluorene-2,7-diyl)x((R)- or (S)-2,2'-dimethoxy-1,1'-binaphthalen-6,6-diyl)y, where x and y are copolymer composition ratios. It was found that, by a simple one-pot sonication method, the copolymers are able to extract either right- or left-handed semiconducting SWNT enantiomers with (6,5)- and (7,5)-enriched chirality. The separated materials were confirmed by circular dichroism, vis-near IR and photoluminescence spectroscopies. Interestingly, the copolymer showed inversion of SWNT enantiomer recognition at higher contents of the chiral binaphthol moiety. Molecular mechanics simulations reveal a cooperative effect between the degree of chirality and copolymer conformation to be responsible for these distinct characteristics of the extractions. This is the first example describing the rational design and synthesis of novel compounds for the recognition and simple sorting of right- and left-handed semiconducting SWNTs with a specific chirality.     

Single-step thioetherification by indium-catalyzed reductive coupling of carboxylic acids with thiols

Direct thioetherification from a variety of aromatic carboxylic acids and thiols using a reducing system combined with InBr(3) and 1,1,3,3-teramethyldisiloxane (TMDS) in a one-pot procedure is demonstrated. It was also found that a system combined with InI(3) and TMDS underwent thioetherification of aliphatic carboxylic acids with thiols.