Long-range flow-induced alignment of self-assembled rosette nanotubes on Si/SiOx and poly(methyl methacrylate)-coated Si/SiOx

Helical rosette nanotubes are obtained through the self-assembly of low molecular weight synthetic modules in water. Here we demonstrate that despite their dynamic nature, these materials respond very well to directional fluid flow and assume long-range order on flat substrates. Persistence length, order, and packing of the rosette nanotubes were found to depend dramatically on the surface properties of both the substrate and the nanotubes and vary from well-ordered long-range 2D films to bundled nanotubes or amorphous conglomerates. While flow-induced long-range alignment of dynamic nanostructures is unprecedented, the chemical tunability of the rosette nanotubes is anticipated to offer a versatile means for investigating the basis of interfacial forces in self-assembled organo-silicon devices and their effect on the stability and physical properties of organic nanostructures on electroactive surfaces.     

The assay of pterostilbene in spiked matrices by liquid chromatography tandem mass spectrometry and isotope dilution method

Pterostilbene (trans‐3,5‐dimethoxy‐4‐hydroxystilbene) is an active component found in several plant species, exhibiting important pharmacological properties. A new and reliable method of assaying this phyto compound in various matrices is presented; the assay is based on (1) the selectivity of liquid chromatography (LC) hyphenated with electrospray ionisation (ESI), (2) the specificity of a two‐step mass spectrometric analysis (MS/MS) and (3) the accuracy of the isotope dilution method. The labelled analogue may be conveniently synthesised in a few steps. The sensitivity of the method is confirmed by the very low limit of detection (LOD) and limit of quantitation (LOQ) values achieved in the assay of pterostilbene in two distinct fortified matrices, and is further supported by the observed accuracy values. Copyright © 2010 John Wiley & Sons, Ltd.     

Phosphorylated cellulose for water purification: a promising material with outstanding adsorption capacity towards methylene blue

Cellulose - Enhancing the sorption properties of cellulose is a prerequisite for its efficient use in water purification as an alternative to costly activated carbon. Here, solvent-free...     

Single‐Crystal‐like Nanoporous Spinel Oxides: A Strategy for Synthesis of Nanoporous Metal Oxides Utilizing Metal‐Cyanide Hybrid Coordination Polymers

Development of a new method to synthesize nanoporous metal oxides with highly crystallized frameworks is of great interest because of their wide use in practical applications. Here we demonstrate a thermal decomposition of metal‐cyanide hybrid coordination polymers (CPs) to prepare nanoporous metal oxides. During the thermal treatment, the organic units (carbon and nitrogen) are completely removed, and only metal contents are retained to prepare nanoporous metal oxides. The original nanocube shapes are well‐retained even after the thermal treatment. When both Fe and Co atoms are contained in the precursors, nanoporous Fe?Co oxide with a highly oriented crystalline framework is obtained. On the other hand, when nanoporous Co oxide and Fe oxide are obtained from Co‐ and Fe‐contacting precursors, their frameworks are amorphous and/or poorly crystallized. Single‐crystal‐like nanoporous Fe?Co oxide shows a stable magnetic property at room temperature compared to poly‐crystalline metal oxides. We further extend this concept to prepare nanoporous metal oxides with hollow interiors. Core‐shell heterostructures consisting of different metal‐cyanide hybrid CPs are prepared first. Then the cores are dissolved by chemical etching using a hydrochloric acid solution (i.e., the cores are used as sacrificial templates), leading to the formation of hollow interiors in the nanocubes. These hollow nanocubes are also successfully converted to nanoporous metal oxides with hollow interiors by thermal treatment. The present approach is entirely different from the surfactant‐templating approaches that traditionally have been utilized for the preparation of mesoporous metal oxides. We believe the present work proves a new way to synthesize nanoporous metal oxides with controlled crystalline frameworks and architectures.     

Dielectric Properties of Colossal-Dielectric-Constant Na1/2La1/2Cu3Ti4O12 Ceramics Prepared by Spark Plasma Sintering

In the current study, we report on the dielectric behavior of colossal-dielectric-constant Na_1/2La_1/2Cu₃Ti₄O₁₂ (NLCTO) ceramics prepared by mechanochemical synthesis and spark plasma sintering (SPS) at 850 °C, 900 °C, and 925 °C for 10 min. X-ray powder diffraction analysis showed that all the ceramics have a cubic phase. Scanning electron microscope observations revealed an increase in the average grain size from 175 to 300 nm with an increase in the sintering temperature. SPS NLCTO ceramics showed a room-temperature colossal dielectric constant (>10³) and a comparatively high dielectric loss (>0.1) over most of the studied frequency range (1 Hz–40 MHz). Two relaxation peaks were observed in the spectra of the electrical modulus and attributed to the response of grain and grain boundary. According to the Nyquist plots of complex impedance, the SPS NLCTO ceramics have semiconductor grains surrounded by electrically resistive grain boundaries. The colossal dielectric constant of SPS NLCTO ceramics was attributed to the internal barrier layer capacitance (IBLC) effect. The high dielectric loss is thought to be due to the low resistivity of the grain boundary of SPS NLCTO.     

Quasistatic frictional thermo‐piezoelectric contact problem

We consider here a mathematical model describing the bilateral frictional contact between a thermo‐piezoelectric body and a thermally conductive foundation. We model the behavior of the material with a linear thermo‐electro‐elastic constitutive law. The process is assumed to be quasistatic and the contact is modeled with a nonlocal version of Coulomb's dry friction law, in which the frictional heat generated in the process, is taken into account. We drive a variational formulation of the problem and establish the existence of its weak solution.     

Entropy solutions of anisotropic elliptic nonlinear obstacle problem with measure data

We prove the existence of an entropy solution for a class of nonlinear anisotropic elliptic unilateral problem associated to the following equation $$\begin{aligned} -\sum _{i=1}^{N} \partial _i a_i(x,u, \nabla u) -\sum _{i=1}^{N}\partial _{i}\phi _{i}( u)=\mu , \end{aligned}$$where the right hand side $$\mu $$ belongs to $$L^{1}(\Omega )+ W^{-1, \vec {p'}}(\Omega )$$. The operator $$-\sum _{i=1}^{N} \partial _i a_i(x,u, \nabla u) $$ is a Leray–Lions anisotropic operator and $$\phi _{i} \in C^{0}({\mathbb {R}}, {\mathbb {R}})$$.     

Adsorption of Toluene and Water over Cationic-Exchanged Y Zeolites: A DFT Exploration

In this study, density functional theory (DFT) calculations have been performed to investigate the adsorption mechanisms of toluene and water onto various cationic forms of Y zeolite (LiY, NaY, KY, CsY, CuY and AgY). Our computational investigation revealed that toluene is mainly adsorbed via π–interactions on alkalis exchanged Y zeolites, where the adsorbed toluene moiety interacts with a single cation for all cases with the exception of CsY, where two cations can simultaneously contribute to the adsorption of the toluene, hence leading to the highest interaction observed among the series. Furthermore, we find that the interaction energies of toluene increase while moving down in the alkaline series where interaction energies are 87.8, 105.5, 97.8, and 114.4 kJ/mol for LiY, NaY, KY and CsY, respectively. For zeolites based on transition metals (CuY and AgY), our calculations reveal a different adsorption mode where only one cation interacts with toluene through two carbon atoms of the aromatic ring with interaction energies of 147.0 and 131.5 kJ/mol for CuY and AgY, respectively. More importantly, we show that water presents no inhibitory effect on the adsorption of toluene, where interaction energies of this latter were 10 kJ/mol (LiY) to 47 kJ/mol (CsY) higher than those of water. Our results point out that LiY would be less efficient for the toluene/water separation while CuY, AgY and CsY would be the ideal candidates for this application.     

Gas‐phase pyrolytic reactions of esters of 2‐pyridine and 8‐quinoline sulfonic acid

The rates of gas‐phase thermal elimination reaction of esters of 2‐pyridine sulfonic acid and 8‐quinoline sulfonic acid have been measured over at least 50° for each compound. The relative rates of the first‐order unimolecular decomposition at 500 K for the primary:secondary esters suggest that C O bond breaking is kinetically more significant than C H bond breaking, leading to a transition state of carbocationic character. This is consistent with the electron‐donating effect provided by the methoxy substituent in 2‐p‐methoxyphenylethyl of 2‐pyridine and 8‐quinoline sulfonate esters stabilizing the carbocation center. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 771–775, 2000