ELECTROCHEMICAL DEPOSITION OF MAGNESIUM IN ETHEREAL GRIGNARD SALT SOLUTION WITH IONIC LIQUID ADDITIVE

The electrochemical deposition of magnesium was investigated in ethereal Grignard salt solution with tetraethylammonium bistrifluoro-methanesulfonimidate additive, using cyclic voltammetry, potentiostatic transients, and scanning electron microscope measurements. The voltammograms showed the presence of reduction and oxidation peaks associated with the deposition and dissolution of magnesium. From the analysis of the experimental current transients, it was shown that the magnesium deposition process was characterized as a three-dimensional nucleation. The deposited product obtained from potentiostatic reduction presented a generally uniform and dense film.

Surface-Relevant Regulable DNA Toroids Induced by Dopamine

Dopamine (2-(3,4-dihydroxyphenyl)ethylamine) is known as a natural chemical neurotransmitter and is also a cytotoxic and genotoxic molecule for cell apoptosis. In this work, the interaction of DNA with dopamine was investigated. Though the electrostatic interaction of DNA and dopamine was weak in aqueous solution, dopamine condensed circular pBR322 DNA into toroids on the mica surface cooperatively with ethanol. The formed DNA toroids came from the shrinking of DNA that was driven by ethanol-enhanced DNA-dopamine electrostatic interaction. The size of the DNA toroids could be modulated by varying the concentration of dopamine. This study offers useful information about the DNA condensation induced by monovalent cations and the sample preparation for AFM measurement and application.

Facile synthesis of PtRu/C electrocatalyst with high activity and high loading for passive direct methanol fuel cell by synergetic effect of ultrasonic radiation and mechanical stirring

The PtRu/C electrocatalyst with high loading (PtRu of 60 wt%) was prepared by synergetic effect of ultrasonic radiation and mechanical stirring. Physicochemical characterizations show that the size of PtRu particles of as-prepared PtRu/C catalyst is only several nanometers (2-4 nm), and the PtRu nanoparticles were homogeneously dispersed on carbon surface. Electrochemistry and single passive direct methanol fuel cell (DMFC) tests indicate that the as-prepared PtRu/C electrocatalyst possessed larger electrochemical active surface (EAS) area and enhanced electrocatalytic activity for methanol oxidation reaction (MOR). The enhancement could be attributed to the synergetic effect of ultrasound radiation and mechanical stirring, which can avoid excess concentration of partial solution and provide a uniform environment for the nucleation and growth of metal particles simultaneously hindering the agglomeration of PtRu particles on carbon surface.

Crystal Growth Transition from Flat-On to Edge-On Induced by Solvent Evaporation in Ultrathin Films of Polystyrene-b-Poly(ethylene oxide)

The transition of lamellar crystal orientation from flat-on to edge-on in ultrathin films of polystyrene-b-poly(ethylene oxide) (PS-b-PEO) via solvent vapor (toluene) treatment Was investigated. When the as-prepared film was treated in saturated solvent vapor, breakout crystals could form quickly, and then they transformed from square single crystals (flat-on lamellae) to dendrites and finally to nanowire crystals (edge-on lamellae). Initially, heterogeneous nucleation tit the polymer/substrate interface dominated the structure evolution, leading to flat-on lamellar crystals orientation. And the transition from faceted habits to dendrites indicated a transition of underlying mechanism from nucleation-controlled to diffusion-limited growth. As the solvent molecules gradually diffused into the polymer/substrate interface, it will subsequently weaken the polymer-substrate interaction.

两种草乌炮制品中生物碱成分的电喷雾质谱比较

Aconite alkaloids in two kinds of processed Radix Aconiti Kusnezoffii(RAK) were analyzed by ESI-MS.The results indicate that there are not diester-alkaloids detected in the two kinds of processed RAK by comparison with crude RAK,which show that both steaming process and boiling process decrease toxicity.As the same time,a simple,rapid and sensitive method is provided to analyze aconite alkaloids in different sorts of processed RAK using ESI-MS.

Crystalline morphology of poly(L-lactic acid) thin films

Crystalline morphologies of spin-coated poly(L-lactic acid) (PLLA) thin films under different conditions are investigated mainly with atomic force microscopy (AFM) technique. When PLLA concentration in chloroform is varied from 0.01 to 1% gradually, disordered structure, rod-shape and larger spheres aggregates are observed in thin films subsequently. Under different annealing temperature, such as at 78, 102, 122 degrees C, respectively, we can find most rod-like crystalline aggregates. Interestingly, we observed that nucleation sites locate at the edge of the holes at the original crystalline stage. Then, these holes developed to form chrysanthemum-like and rods subsequently with annealing time meanwhile the size and the shape of crystalline aggregate are changed. In addition. effect of substrate and solvent on morphology is also discussed. On the other hand, the possible mechanism of crystalline morphology evolution is proposed.

Study on the formation of beta-crystal during the crystallization process of polypropylene reactor granule

A notable amount of PP beta-crystal (30%, by X-ray diffraction pattern) has been found in the PP samples as polymerized at normal static isothermal crystallization conditions without using any extra nucleating agents. Existence of catalyst residues in the sample is decisive, which slows down the crystallization rate facilitating the formation of beta-form spherulites. Comparatively, high molecular weight PP favors the formation of beta-form spherulites, deducting from no beta-crystal detected in the degraded samples. Finally, high isotacticity is also required for obtaining qualitative beta-form spherulites, demonstrated by increased beta-crystal content after removal of weak crystalline fraction of the sample.

Synthesis and characterization of high-quality ZnS, ZnS : Mn2+, and ZnS : Mn2+/ZnS (core/shell) luminescent nanocrystals

High-quality ZnS, ZnS:Mn2+, and ZnS:Mn2+/ZnS (core/shell) nanocrystals (NCs) were synthesized via a high-boiling solvent process and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), electron paramagnetic resonance (EPR), X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) spectra. The monodisperse ZnS NCs (size = 8 nm), which self-assembled into several micrometer-sized domains, were achieved by adopting poly(ethylene glycol) (PEG) in the reaction process (without using a size-selection process). The obtained ZnS:Mn2+ and ZnS:Mn2+/ZnS core/shell NCs are highly crystalline and quasimonodisperse with an average particle size of 6.1 and 8.4 nm, respectively. All of the as-formed NCs can be well dispersed in hexane to form stable and clear colloidal solutions, which show strong visible emission (blue for ZnS and red-orange for ZnS:Mn2+ and ZnS:Mn2+/ZnS) under UV excitation. The growth of a ZnS shell on ZnS:Mn2+ NCs, that is, the formation of ZnS:Mn2+/ZnS core/shell NCs, resulted in a 30% enhancement in the PL intensity with respect to that of bare ZnS:Mn2+ NCs due to the elimination of the surface defects.

The effect of multiwall carbon nanotube on the crystallization, morphology, and rheological properties of nylon1010 nanocomposites

Nanocomposites based on poly(iminosebacoyl imino-decamethylene) (PA1010) and multiwall carbon nanotubes (MWNTs) were successfully prepared by melt blending technique. environmental scanning electron microscope micrographs of the fracture surfaces showed that not only is there an evenly dispersion of MWNTs throughout the PA1010 matrix but also a strongly interfacial adhesion with the matrix. The combined effect of more defects on MWNTs and low temperature buckling fracture is mainly responsible for the broken tubes. Differential scanning calorimeter results showed that the MWNTs acted as a nucleation agent and increased the crystallization rate and decreased crystallite size. In the linear region, rheological measurements showed a distinct change in the frequency dependence of storage modulus, loss modulus, and complex viscosity particularly at low frequencies. We conclude that the rheological percolation threshold might occur when the content of MWNTs is over 2 wt% in the composites.

Crystallization and orientation of syndiotactic polystyrene in nanorods

Syndiotactic polystyrene (sPS) nanorods of 200 and 80 nm diameters were prepared by infiltrating porous anodic alumina oxide templates with polymer melt, and the crystallinity and orientation of various forms of sPS crystals in the nanorods were studied by FTIR spectroscopy and electron diffraction. For sPS crystallized from amorphous state at lower temperatures, a-form crystals were found in the nanorods with random orientation and the same degree of crystallinity as that in the bulk. However, for sPS crystallized from molten state at 260 degrees C, while no preferred orientation was found for the chains in the melt, the beta-crystals formed in the nanorods oriented preferentially with the c-axis aligning perpendicular to the axial direction of the nanorod, and the degree of crystallinity was significantly lower than that in the bulk. The crystallinity decrease was more profound for nanorods of smaller diameter. These results were also supported by electron diffraction data and can be attributed to competition between nucleation and crystal growth in the nanotemplates.

Assembly process of CuHCF/MPA multilayers on gold nanoparticles modified electrode and characterization by electrochemical SPR

Gold nanoparticles were deposited onto 2-mercaptoethylamine (MEA)-assembled planar gold thin film to construct gold nanoparticles modified electrode by virtue of a solution-based self-assembly strategy. Subsequently, 3-mercaptopropionic acid (MPA)-bridged copper hexacyanoferrate (CuHCF) multilayers were constructed on the as-prepared gold nanoparticles modified electrode. The resulted multilayer nanostructures were investigated by electrochemical surface plasmon resonance (EC-SPR) and atomic force microscopy (AFM) with primary emphasis upon the effect of the gold nanoparticles on the MPA/CuHCF multilayers growth and their surface morphology. Compared with the multilayer system on a planar gold electrode, the different electrochemical and optical properties might result from higher curvature effect and extraordinary surface-to-volume ratio characteristic of gold nanoparticles and the nanoparticle-selective growth of CuHCF. A dendrimer-like assembly process was proposed to explain the experiment results. This new motif of multilayer on the gold nanoparticles modified electrode was different from that of on a planar gold electrode, indicating a potential application of EC-SPR technique in the study of nanocomposite materials.

Sulfonated polyimides bearing benzimidazole groups for proton exchange membranes

A series of sulfonated polymides containing benzimidazole groups were synthesized using 4,4'-binaphthyl-1,1',8,8'-tetracarboxylic dianhydride (BTDA), 4,4'-diaminodiphenyl ether-2,2'-disulfonic acid (ODADS) as the sulfonated diamine, and 2-(3',5-diaminophenyl)benzimidazole (a) or 6,4'-diamino-2-phenylbenzimidazole (b) as the nonsulfortated diamine. The electrolyte properties of the synthesized polyimides Ia-x, Ib-x, x refers to molar percentage of the sulfonated diamine) were investigated and compared with those of polyimides (Ic-x) from BTDA, ODADS, and m-phenylenediamine (c). All synthesized polyimides possessed high molecular weights revealed by their high viscosity, and formation of tough and flexible membranes. Polyintides with benzimidazole groups exhibited much better swelling capacity than those without benzimiclazole groups. This was attributed to the strong interchain interaction through basic benzimidazole functions and sulfonic acid groups. The sulfortated polyimides that are incorporated with 1, 1',8,8'-binaphthalimide exhibited better hydrolytic stability than that with 1,4,5,8-naphthalimide. Polyimide membranes with good water stability as well as high proton conductivity were developed. Polyimide membrane (Ia - 90), for example, did not lose mechanical properties after being soaked in boiling water for tOOO h, while its proton conductivity was still at a high level (compared to that of Nafion 117).

Tunable synthesis, growth mechanism, and magnetic properties of La0.5Ba0.5MnO3

La0.5Ba0.5MnO3 products with novel flowerlike, microcube, and nanocube structures were successfully synthesized by a simple hydrothermal route by controlling the alkalinity of the reaction solutions. The synthesized products were systematically studied by X-ray powder diffraction, field-emission scanning electron microscopy, transmission electron microscopy, and energy dispersive X-ray spectroscopy. The results showed that the formation of the flowerlike structures with a layer assembly experienced a nucleation-aggregation-crystallization growth process, while the cubic structures experienced a nucleation-crystallization growth process due to the effect of different alkalinity in the reaction solutions. The higher alkalinity also led to a decrease in the size in the cubic structures. Suitable temperature and pressure were demonstrated to be crucial to the formation of the flowerlike structures by carrying out further control experiments. The measurement of the magnetic properties of three samples obtained at different alkaline conditions indicated that the size of the La0.5Ba0.5MnO3 products had an obvious influence on their properties; however, the dependence of the properties upon the morphology of the La0.5Ba0.5MnO3 products was minor.

Non-isothermal crystallisation kinetics of polyamide 6/mesoporous silica nanocomposites

Non-isothermal crystallisation kinetics of a polyamide 6/mesoporous silica nanocomposite (PA6-MS) has been investigated by differential scanning calorimetry (DSC) at different cooling rates. Mandelkern, Jeziorny-Ziabicki and Ozawa methods were applied to describe this crystallisation process. The analyses show that the mesoporous silica particles act as nucleating agents in the composite and that the Avrami exponent n varies from 3.0 to 4.6. The addition of mesoporous silica influenced the mechanism of nucleation and the growth of polyamide 6 (PA6) crystallites.

Dewetting of thin polystyrene films under confinement

The dewetting behavior of thin polystyrene (PS) film has been investigated by placing an upper plate with a ca. 140 nm gap from the underlying substrate with the spin-coated thin polymer films. Three different kinds of dewetting behaviors of thin PS film have been observed after annealing according to the relative position of the PS film to the upper plate. Since the upper plate is smaller than the underlying substrate, a part of the polymer film is not covered by the plate. In this region (I), thin PS film dewetting occurs in a conventional manner, as previously reported. While in the region covered by the upper plate (III), the PS film exhibits unusual dewetted patterns. Meanwhile, in the area right under the edge of the plate (II) (i.e., the area between region I and region III), highly ordered arrays of PS droplets are formed. Formation mechanisms of different dewetted patterns are discussed in detail. This study may offer an effective way to improve the understanding of various dewetting behaviors and facilitate the ongoing exploration of utilizing dewetting as a patterning technique.