Pentafluorophenylammonium triflate as an efficient, environmentally friendly and novel organocatalyst for synthesis of bis-indolyl methane derivatives

A simple, inexpensive, environmentally friendly and efficient route for the synthesis of bis-indolyl methane derivatives by the reaction of indole or N-methyl indole with aldehydes using pentafluorophenylammonium triflate (PFPAT) as a catalyst is described. PFPAT organocatalyst is air-stable, cost-effective, easy to handle, and easily removed from the reaction mixtures.     

B2-PPW91: a promising double-hybrid density functional for the electric response properties

A new double-hybrid density functional, termed B2-PPW91, is presented which includes the Becke88 (B88) exchange in conjunction with Perdew-Wang91 (PW91) gradient-corrected correlation functional. The fitting parameters are obtained by minimization of mean absolute error of the static dipole polarizability of 4d transition metal monohalides against the CCSD(T)∕aug-cc-pVTZ∕SDD results. The performance of proposed functional has been assessed for estimation of other response properties, such as dipole moment and excitation energy, for the same species. We then proceed to explore the validity of B2-PPW91 method for calculation of the dipole polarizability of some 5d transition metal monofluorides. In all cases, the improvement compared to common density functional methods and even previously reported double-hybrid functionals such as B2-PLYP and mPW2-PLYP has been observed. This indicates that the utility of double-hybrid density functional methods can be further extended to study linear and non-linear optical properties of transition metal containing molecules.     

Voltammetric and amperometric determination of hydrogen peroxide using a carbon-ceramic electrode modified with a nanohybrid composite made from single-walled carbon nanotubes and silver nanoparticles

A nanohybrid composite material was prepared from single-walled carbon nanotubes and silver nanoparticles, and used to fabricate a modified carbon-ceramic electrode. The preparation of the composite is facile and efficient. The nanohybrid composite deposited on the carbon-ceramic electrode was characterized by X-ray diffraction and cyclic voltammetry. The new electrode displays favorable electrocatalytic ability towards hydrogen peroxide (H₂O₂) and can be used to electrocatalytically reduce this species. Under the optimum conditions, the current measured during hydrodynamic amperometry is linearly related to the concentration of H₂O₂ over the concentration range from 0.01 to 8 mM, with a detection limit of 2?×?10^?7 M at a signal-to-noise ratio of 3 and sensitivity of 3.23 μA/mM. The electrode exhibits good reproducibility, long-term stability and negligible interference by dopamine, uric acid, and other important biological compounds. The electrode was successfully applied to the determination of H₂O₂ in honey samples, and the recovery was 101.2%.

Preparation, optimization and thermal characterization of a novel conductive thermoset nanocomposite containing polythiophene nanoparticles using dynamic thermal analysis

Polythiophene nanoparticles as a conductive filler was prepared with average diameter of 20-35 nm and its molecular structure was confirmed by the FT-IR, TEM, XRD and UV-vis analysis. A new conductive epoxy nanocomposite was synthesized by curing of diglycidyl ether of bisphenol A/4,4′-(4,4′ Isopropylidenediphenoxy) bis (Phthalic Anhydride) involving various percentages of polythiophene nanoparticles. DSC and DMTA studies revealed that low percentage of the polythiophene nanoparticles, i.e. 1%, results in improved crosslink density as evidenced by increasing in the glass transition temperature. The addition of polythiophene nanoparticles into the epoxy matrix resulted in a significant increment in the electrical conductivity, mechanical properties, thermal stability and activation energy of thermal degradation. The advanced isoconversional method is utilized to describe the curing behavior and thermal degradation process of the neat epoxy and epoxy nanocomposite. We have utilized the Coats-Redfern and Criado methods to find the solid state thermal degradation reaction mechanism. For the nanocomposite, the mechanism was recognized to be two-dimensional diffusion (D₂) reaction and it changes to a nucleation and growth (A₄) for pure epoxy system.     

Synthesis and application of the uniform particle size of nano-γ-Fe2O3: dispersed nanoparticles of γ-Fe2O3 for green synthesis of aminophosphonates

China started nanotechnology research from 1990s, and has paid much attention to nanoeducation since then. Scientific discoveries from nanoresearch have been introduced timely into high school textbooks, and more specific courses such as Nanomaterials and Nanofabrication are being taught at both college and graduate levels. In this paper, nanotechnology courses at the Graduate University of Chinese Academy of Sciences, Beijing University, and Tsinghua University are chosen to be overviewed, which could be a good indicator of Chinese nanoeducation because of high-quality science and engineering education in these schools. Research institutes also contribute in popularizing nanoscience knowledge through activities such as public open days. These combined efforts substantially promote the public acceptance and understanding of nanoscience and technology in China.     

The de Jongh property for Basic Arithmetic

We prove that Basic Arithmetic, BA, has the de Jongh property, i.e., for any propositional formula A(p ₁,..., p _n ) built up of atoms p ₁,..., p _n , BPC \({\vdash}\) A(p ₁,..., p _n ) if and only if for all arithmetical sentences B ₁,..., B _n , BA \({\vdash}\) A(B ₁,..., B _n ). The technique used in our proof can easily be applied to some known extensions of BA.     

Highly stereoselective construction of functionalized cyclopropanes from the reaction between acetylenic esters and C-H acids in the presence of triphenylarsine

A one-pot triphenylarsine-catalyzed synthesis of trans-cyclopropane derivatives is achieved by means of the reaction between acetylenic esters and C-H acids in the presence of triphenylarsine. This procedure is simple and proceeds under mild reaction conditions. Its success depends on the choice of solvent, temperature and C-H acid used.     

Determination of dual glass transition temperatures of a PC/ABS blend using two TMA modes

An inherent challenge with polymer blends is the difficulty in resolving the glass transition, T _g, for the smaller mass fraction component. The objective of this work was to determine the practical scanning conditions for identifying the dual T _g’s for a 75:25 polycarbonate/acrylonitrile-butadiene-styrene (PC/ABS) blend using a thermomechanical analyzer (TMA). Scanning rates up to 20°C min⁻¹ using dilatometer and expansion modes were studied. Heating and cooling rates were found to affect both T _g values but the effects were not simple relationships. T _g values could either increase or decrease depending on the scanning rate applied. Higher rates resulted in large thermal lags which opened the accuracy of measurements to question. Generally, higher rates tended to display only one T _g but the duality of T _g’s can be detected with scanning rates between 0.5 and 5°C min⁻¹ for both modes.