Microstructure array on Si and SiOx generated by micro-contact printing, wet chemical etching and reactive ion etching

A method, combining micro-contact printing (μCP), wet chemical etching and reactive ion etching (RIE), is reported to fabricate microstructures on Si and SiOx. Positive and negative structures were generated based on different stamps used for μCP. The reproducibility of the obtained microstructures shows the methodology reported herein could be useful in Micro-Electro-Mechanical Systems (MEMS), optical and biological sensing applications.     

Cobalt(II), nickel(II) and copper(II) complexes of 5-(2-carboxyphenylazo)-2-thiohydantoin

A new series of hexacoordinate cobalt(II), nickel(II) and copper(II) complexes of 5-(2-carboxyphenylazo)-2-thiohydantoin HL having formulae [LM(OAc)(H₂O)₂] · nH₂O (M = Co^II, Cu^II and Ni^II), [LMCl(H₂O)₂] · nH₂O (M = Co^II and Ni^II), [LCuCl(H₂O)]₂ · 2H₂O, [LCu(H₂O)₃](ClO₄) and [LCu(HSO₄)(H₂O)₂] were isolated and characterized by elemental analyses, molar conductivities and magnetic susceptibilities, and by i.r., electronic and e.s.r. spectral measurements, as well as by thermal (t.g. and d.t.g.) analyses. The i.r. spectra indicate that the ligand HL behaves as a monobasic tridentate towards the three divalent metal ions via an azo-N, carboxylate-O and thiohydantoin-O atom. The magnetic moments and electronic spectral data suggest an octahedral geometry for Co^II complexes, distorted octahedral geometry for both Ni^II and Cu^II complexes with a dimeric structure for [LCuCl(H₂O)]₂ · 2H₂O through bridged chloro ligands. The X-band e.s.r. spectra reveal an axial symmetry for the copper(II) complexes with unsymmetrical M_s = ± 1 signal and G-parameter less than four for the dimeric [LCuCl(H₂O)]₂ · 2H₂O. The thermogravimetry (t.g. and d.t.g.) of some complexes were studied; the order and kinetic parameters of their thermal degradation were determined by applying Coats–Redfern method and discussed.     

A novel route to prepare highly surface active nanogel particles based on nonaqueous emulsion polymerization

The motivation of the current work has stemmed from the fact that the selection of suitable stabilizers for nonaqueous emulsions is still challenging because of lack of general knowledge about the underlying stabilization mechanisms. The preparation and surface activity of new amphiphilic gel nanoparticles in organic solvents were investigated. A new bifunctional surfmer was prepared by reacting polyoxyethylene 4‐nonyl‐2‐propylene‐phenol nonionic reactive surfactant with maleic anhydride followed by esterification with poly(ethylene glycol). This surfmer was used as stabilizer to prepare amphiphilic crosslinked N‐isopropylacrylamide (NIPAm) and 2‐acrylamido‐2‐methylpropane sulfonic acid (AMPS) copolymer nanogel on the basis of nonaqueous radical copolymerization temperature modified method in the presence of toluene and formamide (FA) as solvents and N, N‐methylene bisacrylamide as a crosslinker. The chemical structure of the prepared nanogels was determined by Fourier transform infrared spectroscopy analyses. The morphologies of the prepared nanogels were detected by transmission electron microscopy and scanning electron microscopy techniques. The surface tension of colloidal NIPAm/AMPS dispersions was measured in FA as functions of surface age (time), temperature, and the morphology of the NIPAm/AMPS nanogels. The NIPAm/AMPS nanogels reduced the surface tension of FA from 58.2 to about 30.2 mN/m at 25°C, and a little increase in the surface tension was observed at 40°C. The prepared nanogels show great reduction in interfacial tension values between FA and styrene. The NIPAm/AMPS dispersions exhibited high surface activity and used as stabilizers to prepare crosslinked styrene‐co‐AMPS microgel in the presence of divinylbenzene and FA as organic solvents based on nonaqueous emulsion crosslinking polymerization technique. Copyright © 2013 John Wiley & Sons, Ltd.     

Elaboration of silica colloid/polymer hybrid support for oligonucleotide synthesis

One way to increase the sensitivity of DNA diagnostic assays developed on microarrays is to improve the solid phase that allows the extraction of the target from a biological sample, before detection. Two parameters are influencing the performances of this capture step: (i) the specific surface area being offered for the capture and (ii) the number and the accessibility of oligonucleotide probes immobilized on the surface. In this context, we have developed an attractive approach which fulfills these two points. Our strategy was to elaborate a new material of high specific surface area, suitable to serve as support for both solid-phase oligonucleotide synthesis and in vitro diagnostic assay. This material has consisted of aggregates of colloidal amino-silica nanoparticles covalently linked by poly(ethylene oxide) (PEO) arms. The aggregation of amino-silica particles in the presence of reactive bis-isocyanate PEO was achieved in a controlled manner. The aggregate size and structure were examined by microscopy. The specific surface area of this material was measured by nitrogen adsorption technique. The composition of aggregate was studied by thermogravimetry and X-ray photoelectron spectroscopy. Then, this material has been successfully used as support for oligonucleotide synthesis of high yield and purity. The resulting system will be further evaluated in a diagnostic assay on a microarray.     

非线性欧拉方程组的完美匹配层吸收边界条件

对于非线性Euler方程,提出一类基于完美匹配层(PML)技术的吸收边界条件。首先对线性化的Euler方程设计出PML公式,然后将线性化Euler方程中的通量函数替换成相对应的非线性通量函数,得到非线性的PML方程。考虑到PML方程中包含有一个刚性的源项,文中采用一种隐显Runge-Kutta方法来求解空间半离散后得到的ODE系统。数值实验表明设计的非线性PML吸收边界条件优于传统的特征边界条件。     

SPE and HPLC monitoring of 17-β-estradiol in Egyptian aquatic ecosysetms

Solid-phase extraction and HPLC methods are described for monitoring of 17-β-estradiol residues in Egyptian aquatic ecosystems (water, fish, mollusks, sediment, and drinking water) at the Nile River, Suez Canal region, and northeast of Egypt. Molecular imprinted polymer was prepared and used in extraction. High performance liquid chromatography (HPLC) columns used were Supelcosil C₁₈ and Nucleosil C₁₈. The mobile phases used were different combinations of water and acetonitrile. The concentration of 17-β-estradiol in water, aquatic animals, and sediment samples were of 265.13–7988.12 µg/L, 0.503–96.167, and 0.775–11.884 µg/kg, respectively. Marine lake was contained with high levels of 17-β-estradiol (P < 0.05). Similarly, the Nile River downstream showed high levels of 17-β-estradiol. The detected concentrations in mollusks were significantly higher than those detected in fish. Tilapia fish did not show 17-β-estradiol. Contrarily, low concentrations were detected in the rivulet streams supplied by the Nile River. Besides, 17-β-estradiol was also detected in the sediments at low levels. Detection of 17-β-estradiol in the Egyptian ecosystems attracted attention toward heavy reliance on some esterogenic medicinal products in Egypt. The monitoring of 17-β-estradiol in other water bodies was recommended. Besides, the development of methodologies of bioremediation to eliminate 17-β-estradiol from the Egyptian and other water resources of the world was also suggested.     

Covalently functionalized hexagonal boron nitride nanosheets by nitrene addition

The covalent functionalization of exfoliated hexagonal boron nitride (h-BN) nanosheets by nitrene addition is described. Integration of functionalized h-BN nanosheets within a polycarbonate matrix is demonstrated and was found to afford significant increases in mechanical properties. This integration methodology was further extended by the covalent modification of the h-BN nanosheets with polymer chains of a polycarbonate analogue, and the integration of the polymer modified h-BN within the polymer matrix.     

Lifetime measurements and decay of superdeformed bands in Hg isotopes

The lifetimes of states in Superdeformed (SD) bands in ^192,194Hg have been measured using the Doppler shift attenuation method. Intrinsic quadrupole moments have been extracted for band 1 of ¹⁹²Hg and for bands 1, 2, and 3 of ¹⁹⁴Hg. It was found that the quadrupole moments for the “identical” SD bands in these nuclei are the same. In the same experiment, one-step transitions linking SD states to yrast and near yrast states for bands 1 and 3 of ¹⁹⁴Hg have been identified. From this observation, excitation energies, spins and probable parities have been assigned to SD states in these bands.     

Molecular-level approach to inhibit degradations of alkanethiol self-assembled monolayers in aqueous media

A molecular-level approach is developed to prevent or inhibit the degradation processes of alkanethiol self-assembled monolayers (SAMs). Previous studies revealed two degradation pathways: direct desorption and oxidation-desorption. By use of scanning tunneling microscopy (STM) and atomic force microscopy (AFM), in situ and time-dependent imaging reveals and confirms that degradations of alkanethiol SAMs on gold mainly initiate at defect sites, such as domain boundaries and vacancy islands, and then propagate into the ordered domains. Our approach targets at attaching small molecules with preferred adhesion to the defects. The best candidates are aqueous media containing a small amount of amphiphilic surfactant molecules, such as N,N-dimethylformamide (DMF) or dimethyl sulfoxide (DMSO). High-resolution studies demonstrate that DMSO and DMF molecules attach to SAM surfaces and more favorably at defect sites, forming relatively stable adsorbates. This attachment increases the activation energy sufficiently to inhibit both degradation pathways. The robustness of this approach has been investigated as a function of surfactant concentration, solution temperature, and the stirring condition. Molecular-level mechanisms and energetics for degradation inhibition of SAMs are also discussed in detail.     

Novel emulsions of ionic liquids stabilised solely by silica nanoparticles

We have successfully prepared a series of novel stable emulsions, of both simple and multiple types, containing ionic liquids and stabilised solely by silica nanoparticles.