Monte Carlo simulation of ion transport in non-linear ion mobility spectrometry

A program for Monte Carlo simulation of ion transport in non-linear ion mobility spectrometry, also known as field asymmetric ion mobility spectrometry (FAIMS) or differential mobility spectrometry (DMS), has been developed. Simulations are based on elastic collisions between the ions and the gas particles, and take into account the effects of flow dynamics and asymmetric electric fields. Using this program, the separation and diffusion of the ions moving in a planar DMS filtration gap are demonstrated. Ion focusing in a cylindrical filtration gap is also confirmed. A characteristic compensation voltage is found to provide insight for understanding separation in non-linear ion mobility spectrometry. The simulation program is used to study the characteristics of non-linear ion mobility spectrometry, the effect of the carrier gas flow, and the dependence of the compensation voltage and nonlinear mobility coefficient (α) on the applied asymmetric electric field.     

Electrodes with extremely high hydrogen overvoltages as substrate electrodes for stripping analysis based on bismuth-coated electrodes

Hydrogen evolution bothers stripping analysis significantly. Dioctyl phthalate-based carbon paste electrode exhibits extremely wide cathodic potential window. It is explored as a powerful substrate electrode to solve the problem of hydrogen evolution and further improve reproducibility for stripping analysis using bismuth-coated electrodes for the first time. It was successfully applied to the simultaneous determination of Zn²⁺, Cd²⁺, and Pb²⁺. Linear responses are obtained for Zn²⁺ in the range of 10–100 μg L⁻¹ and for Pb²⁺ and Cd²⁺ in the range of 5–100 μg L⁻¹. The detection limits for Zn²⁺, Cd²⁺, and Pb²⁺ are 0.1 μg L⁻¹, 0.22 μg L⁻¹ and 0.44 μg L⁻¹, respectively. The method has been successfully applied to the determination of Zn²⁺, Cd²⁺, and Pb²⁺ in waste water samples. The detection strategy based on the combination of dioctyl phthalate-based carbon paste electrode and bismuth-coated electrodes holds great promise for stripping analysis.     

Tunable protic ionic liquids as solvent-catalysts for improved synthesis of multiply substituted 1,2,4-triazoles from oxadiazoles and organoamines

More than green alternatives to traditional volatile molecular organic solvents, protic ionic liquids as dual solvent-catalysts have been successfully used to promote reactions of organoamines with oxadiazoles to afford sterically hindered 1,2,4-triazoles. Among the tested protic ionic liquids, pyridinium trifluoroacetate and acetate showed the highest efficiency for the reactions of arylamines and alkylamines, respectively, indicating that tunable catalysis could be readily effected with protic ionic liquid solvent-catalysts by simply tuning their cation and anion counterparts. A general and efficient approach has been developed for synthesis of multiply substituted 1,2,4-triazoles based on the tunable protic ionic liquid solvent-catalyst systems.     

Preparation of high thermal conductive aluminum nitride/cyanate ester nanocomposite using a new macromolecular coupling agent

Novel glycidyl methacrylate–butyl acrylate–maleic anhydride (GBM) terpolymers with different molecular weights were synthesized by radical polymerization and characterized using fourier transform infrared, nuclear magnetic resonance (¹H‐NMR and ¹³ C‐NMR), and gel permeation chromatography. Each GBM terpolymer was used to modify aluminum nitride (AlN), and the modified AlN, coded as AlN(GBM), was added to 2,2′‐bis(4‐cyanatophenyl)isopropylidene (CE) resin for preparing composites. Composites based on original AlN or γ‐(2,3‐epoxypropoxy)propyltrimethoxysilane‐modified AlN (AlN(K)) were also prepared for comparison. Although GBM and γ‐(2,3‐epoxypropoxy)propyltrimethoxysilane have similar reactive groups, the results indicate that GBM shows more attractive integrated advantages, reflected by the fact that CE/AlN(GBM) composites have better thermal stability, higher thermal conductivity, and higher glass transition temperature than those of CE/AlN(K). These properties result from better dispersion of fillers, improved interfacial adhesion between fillers and CE resin, and increased cross‐linking density. This study demonstrates that the nature of the coupling agents is an important factor to develop high performance composites for cutting‐edge industries. Copyright © 2011 John Wiley & Sons, Ltd.     

Fire retardant synergism between melamine and triphenyl phosphate in poly(butylene terephthalate)

The fire retardant efficiency of melamine (MA) and triphenyl phosphate (TPP) in poly(butylene terephthalate) (PBT) was studied by the limiting oxygen index (LOI) and the UL94 test. On adding 10 wt. % MA and 20 wt. % TPP, LOI increased from 20.9 to 26.6 and the UL94 V-0 rating was achieved. SEM and DSC analyses show that the fire retardants are compatible with PBT and facilitate crystallization of PBT. The occurrence of an interaction between MA + TPP and PBT was elucidated by TGA, dynamic FTIR, and pyrolysis/GC/MS. MA + TPP changes the degradation path of PBT and modifies the compositions of the gas and condensed-phase products.     

MOF-Derived Double-Layer Hollow Nanoparticles with Oxygen Generation Ability for Multimodal Imaging-Guided Sonodynamic Therapy

The high reactive oxygen species (ROS) generation ability and simple construction of sonosensitizer systems remain challenging in sonodynamic therapy against the hypoxic tumor. In this work, we rationally prepared MOF-derived double-layer hollow manganese silicate nanoparticle (DHMS) with highly effective ROS yield under ultrasound irradiation for multimodal imaging-guided sonodynamic therapy (SDT). The presence of Mn in DHMS increased ROS generation efficiency because it could be oxidized by holes to improve the electron–hole separation. Moreover, DHMS could produce oxygen in the tumor microenvironment, which helps overcome the hypoxia of the solid tumor and thus enhance the treatment efficiency. In vivo experiments demonstrated efficient tumor inhibition in DHMS-mediated SDT guided by ultrasound and magnetic resonance imaging. This work presents a MOF-derived nanoparticle with sonosensitive and oxygen generating ability, which provides a promising strategy for tumor hypoxia in SDT.     

Electrochemical properties of La0.8Sr0.2FeO3 − δ –La0.45Ce0.55O2 − δ composite cathodes for intermediate temperature SOFC

The electrochemical properties of La_0.8Sr_0.2FeO_3???δ (LSF)–La_0.45Ce_0.55O_2???δ (LDC) composite cathodes coated on LSGM electrolyte were studied by electrochemical impedance spectroscopy and cathodic polarization technique. Results showed that the composite cathodes possessed superior electrochemical performance compared to that of pure LSF cathode. The cathodic overpotential of Cathode C was only 100 mV at 0.3 A cm^?2, and the charge transfer resistance and the gas phase diffusion resistance were decreased to 0.105 Ω cm² and 0.257 Ω cm², respectively at 800 °C. The improvement of the electrochemical performance is contributed to the increase of the triple-phase boundary, enlargement of the effective area for electrode reaction, and increase of the porosity of the cathode by adding LDC to the cathode material.     

3D visualization of the microstructure of Quedius beesoni Cameron using micro-CT

The investigation of the internal morphology of insects is usually performed using classical microtomy yielding optical micrographs of stained thin sections. The achievement of high-quality cross sections for microtomy is time-consuming and the risk of damaging sections is unavoidable. Moreover, the approach is impractical, in particular when quick acquisition of 3D structural information is required. Recently, X-ray computed microtomography (micro-CT) with a high spatial resolution was considered as a potential tool for the morphological classification of insects. We used micro-CT to investigate Quedius beesoni Cameron at the cellular length scale. This method provides a new powerful and nondestructive approach to obtain 3D structural information on the biological organization of insects. The preliminary images presented in this contribution clearly reveal the endoskeleton and the muscles of the head and the thorax with a full 3D structure. We also reconstructed the 3D structure of the brain of Quedius beesoni Cameron, and this is the first reconstruction in Staphylinidae, which will be a great advancement for morphological and phylogenic research. We claim that both the spatial resolution and the contrast characteristic of micro-CT imaging may fulfill the requirements necessary for zoological insect morphology and phylogeny, in particular, when a classification of a rare and unique insect specimen is required.     

Nickel(II) complexes bearing pyrazolylimine ligand: synthesis,structure, and catalytic properties for vinyl‐type polymerization of norbornene

Two nickel(II) complexes of {2‐[C₃HN₂(R₁)₂‐3,5]}[C(R₂)?N(C₆H₃ⁱPr₂‐2,6)]NiBr₂ (complex 1 : R₁ = CH₃, R₂ = 2,4,6‐trimethylphenyl; complex 2 : R₁ = R₂ = Ph) were synthesized and characterized. The solid‐state structure of complex 1 has been confirmed by X‐ray single‐crystal analysis. Activated by methylaluminoxane (MAO), complexes 1 and 2 are capable of catalyzing the polymerization of norbornene with moderate activities [up to 10.56 × 10⁵ gPNBE (mol Ni h)^?1] with high molecular weights (M_w?13.56 × 10⁵ g mol^?1) and molecular weight distributions were around 2. The influences of polymerization parameters such as reaction temperature and Al–Ni molar ratio on catalytic activity and molecular weight of the polynorbornene were investigated in detail. The obtained polynorbornenes were characterized by means of ¹H‐NMR and FTIR techniques. The analytical results of polymer structures indicated that the norbornene polymerization is vinyl‐type polymerization rather than ROMP. Copyright © 2009 John Wiley & Sons, Ltd.