Proton transfer reactions within the pyridazine-methanol cluster ion

The multiphoton ionization of the hydrogen-bonding cluster pyridazine-methanol (C4H4N2-CH3OH) was studied using a time-of-flight mass spectrometer at the wavelengths of 355 and 532 nm. At both wavelengths, a series of protonated C4H4N2-(CH3OH)(n)-H+ cluster ions were obtained. Relevant ab initio calculations were performed with HF and B3LYP methods. Equilibrium geometries of both neutral and ionic C4H4N2-CH3OH clusters, and dissociation channels and dissociation energies of ionic clusters, are presented. The results show that when C4H4N2-CH3OH is vertically ionized, C4H4N2H+ and CH3O are the dominant products via proton transfer reaction. A high energy barrier makes another channel corresponding to the production of C4H4N2H+ and CH2OH disfavored. (C) 2002 Elsevier Science B.V. All rights reserved.

Mercury selective electrochemical sensor based on a double armed crown ether as ionophore

PVC based membranes of a double armed crown ether, N, N'-dibenzyl, 1,4,10,13-tetraoxa-7, 16-diaza cyclooctadecane (I) as ionophore with sodium tetra phenyl borate (NaTPB) as anion excluder and with many plasticizing solvent mediators have been prepared and used for Hg(II) ion determination. The membrane with DBBP (dibutyl butyl phosphonate ) as plasticizer with various ingredients in the ratio PVC: I: NaTPB: DBBP (150: 12: 2: 100) shows the best results in terms of working concentration range (3.1x10-5-1.0x10-tM) with a Nernstian slope (29.0′0.5 mV/decade of activity). The electrode works in the pH range 2.1-4.5. The response time of the sensor is 15s and it can be used for about 4 months in aqueous as well as in non-aqueous medium. It has good stability and reproducibility. The potentiometric selectivity coefficient values for mono-, di-, and trivalent cations are tabulated. The sensor is highly selective for Hg2+ in the presence of normal interferents like cadmium, silver, sodium and iron.

Calibration of a solid-state copper ion-selective electrode in cupric ion buffers containing chloride

It is shown that near-Nernstian calibration slopes can be obtained with a Cu1.8Se electrode in a range of cupric ion buffers in spite of a high chloride content. Best results are obtained with the ligands ethylenediamine, glycine and histidine. The onset of cupric ion toxicity towards marine organisms falls within the pCu calibration range obtained with glycine, and the Cu1.8Se electrode could, therefore, be useful for monitoring cupric ion activity in bioassays in sea-water media.

Environmentally friendly synthesis of highly monodisperse biocompatible gold nanoparticles with urchin-like shape

We report a facile and environmentally friendly strategy for high-yield synthesis of highly monodisperse gold nanoparticles with urchin-like shape. A simple protein, gelatin, was first used for the control over shape and orientation of the gold nanoparticles. These nanoparticles, ready to use for biological systems, are promising in the optical imaging-based disease diagnostics and therapy because of their tunable surface plasmon resonance (SPR) and excellent surface-enhanced Raman scattering (SERS) activity.

Perovskite-Like Mixed Oxides (LaSrMn1-x Ni (x) O4+delta, 0 a parts per thousand currency sign x a parts per thousand currency sign 1) as Catalyst for Catalytic NO Decomposition: TPD and TPR Studies

Catalytic NO decomposition on LaSrMn1-x Ni (x) O4+delta (0 a parts per thousand currency sign x a parts per thousand currency sign 1) is investigated. The activity of NO decomposition increases dramatically after the substitution of Ni for Mn, but decreases when Mn is completely replaced by Ni (x = 1.0). The optimum value is at x = 0.8. These indicate that the catalytic performance of the samples is contributed by the synergistic effect of Mn and Ni. O-2-TPD and H-2-TPR experiments are carried out to explain the change of activity. The former indicates that only when oxygen vacancy is created, could the catalyst show enhanced activity for NO decomposition; the latter suggests that the best activity is obtained from catalyst with the most matched redox potentials (in this work, the biggest Delta T and Delta E values).

G-quadruplex-based DNAzyme for sensitive mercury detection with the naked eye

Hg2+ is able to inhibit the peroxidase-like DNAzyme function of a T-containing G-quadruplex DNA via Hg2+-mediated T-T base pairs, which enables the visual detection of Hg2+ in the TMB-H2O2 reaction system with high selectivity and sensitivity.

Controlled Synthesis of Ln(3+) (Ln = Tb, Eu, Dy) and V5+ Ion-Doped YPO4 Nano-/Microstructures with Tunable Luminescent Colors

YPO4 nano/microcrystals with multiform crystal phases and morphologies, such as hexagonal nano/submicroprisms, spherical-like nanoparticles, and nanorods with different length/diameter ratios as well as tetragonal nanospindles, have been synthesized via a facile hydrothermal route. A series of controlled experiments indicate that the pH values in the initial solution, phosphorus sources, and the organic additive trisodium citrate (Cit(3-)) are responsible for crystal phase and shape determination of final products. It is found that Cit(3-) as a ligand and shape modifier has the dynamic effect by adjusting the growth rate of different facets under different experimental conditions, resulting in the formation of various geometries of the final products. The possible formation mechanisms for products with diverse architectures have been presented.

"Dual-Parallel-Channel" Shape-Gradient Surfaces: Toward Oriented and Reversible Movement of Water Droplets

In this paper, we prepared "dual-parallel-channel" shape-gradient surfaces, on which water droplets can reversibly and orientedly move between two adjacent pools under the guidance of an external voltage. Furthermore, it is found that the motion speed is governed by several parameters, including bath condition, gradient angle, and the working voltage. In this self-transportation process of water droplets, the external voltage works like a traffic light, which can give "moving", "stopping", "turning" and "straight-going" signals to the Water droplets.

Raspberry-like Hierarchical Au/Pt Nanoparticle Assembling Hollow Spheres with Nanochannels: An Advanced Nanoelectrocatalyst for the Oxygen Reduction Reaction

In this contribution, we for the first time report the synthesis of raspberry-like hierarchical Au/Pt nanoparticle (NP) assembling hollow spheres (RHAHS) with pore structure and complex morphology through one in situ sacrificial template approach without any post-treatment procedure. This method has some clear advantages including simplicity, quickness, high quality, good reproducibility, and no need of a complex post-treatment process (removing templating). Furthermore, the present method could be extended to other metal-based NP assembling hollow spheres. Most importantly, the as-prepared RHAHS exhibited excellent electrocatalytic activity for oxygen reduction reaction (ORR). For instance, the present RHAHS-modified electrode exhibited more positive potential (the half-wave potential at about 0.6 V), higher specific activity, and higher mass activity for ORR than that of commercial platinum black (CPB). Rotating ring-disk electrode (RRDE) voltarnmetry demonstrated that the RHAHS-modified electrode could almost catalyze a four-electron reduction of O-2 to H2O in a 0.5 M air-saturated H2SO4 solution.

Studies on principal components and antioxidant activity of different Radix Astragali samples using high-performance liquid chromatography/electrospray ionization multiple-stage tandem mass spectrometry

The principal components, isoflavonoids and astragalosides, in the extract of Radix Astragali were detected by a high-performance liquid chromatography Couple to electrospray ionization ion trap multiple-stage tandem mass spectrometry (HPLC-ESI-IT-MSn) method. By comparing the retention time (t(R)) of HPLC, the ESI-MSn data and the structures of analyzed Compounds with the data of reference compounds and in the literature, 17 isoflavonoids and 12 astragalosides have been identified or tentatively deduced. By Virtue of the extracted ion chromatogram (EIC) mode, simultaneous determination of isoflavonoids and astragalosides could be achieved when the different components formed overlapped peaks. And this method has been utilized to analyze the constituents in extracts of Radix Astragali from Helong City and of different growth years. Then the antioxidant activity of different samples has been Successfully investigated by HPLC-ESI-MS method in multiple selected ion monitoring(MIM) mode, applying the spin trapping technology, and the Ferric Reducing Antioxidant Power (FRAP) assay was applied to support the result.

Purification, sequencing and biological activity of polypeptide from velvet antler

The velvet antler polypeptide CNT14 was extracted and purified by gel filtration, ion exchange chromatography and RP C, which showed a single peak in HPLC chromatography and a single band in SDS-PAGE. The molecular weight measured by MALDI/TOF/MS spectrum was 1479. 9028. The polypeptide consisted mostly of Glu, Leu, Val, Pro. The amino acid sequence of the polypeptide was detected with ESI-MS/ MS, and the sequence was E-P-T-V-L-D-E-V-C-L-A-H-G-P. The experiments of biological activity of polypeptide CNT14 in vivo were carried out, and the results show that CNT14 has stimulant effects on the growth of rat HT22 cells. Then we produced the polypeptide CNT14 according the amino acid sequence by solid phase synthesis, confirmed the sequence of the polypeptide to be consistent with the amino acid sequence of polypeptide CNT14 which was separated from the velvet antler.

Weak epitaxy growth affording high-mobility thin films of disk-like organic semiconductors

Thin films of phthalocyanine compounds show weak epitaxial growth on a monodomain film of a rod-like molecule (see figure). The resulting organic electronic devices exhibit high charge carrier mobilities close to those of the single-crystal devices.

Active site structure of NO decomposition on perovskite(-like) oxides: An investigation from experiment and density functional theory

Active site structure for NO decomposition carried out on perovskite-like oxides were discussed based on the N-2 yield measured from LaSrNi1-x,AlxO4 with different B-site cations and from La2-ySryCuO4 with different crystal phases. Results show that the active site contains two oxygen vacancies, two transition metals, and one lattice-oxygen, with the oxygen vacancy locating on the apex of MO6 octahedron, and the lattice oxygen locating between the two transition metals (i.e., M-O-M plane). Density functional theory (DFT) analysis to the structure shows that this new active site is the most active structure for NO adsorbing, and hence, for NO decomposition. The similar trend of the relative energies that are required for the formation of oxygen vacancies with f form (calculated from DFT), the amount of oxygen vacancies, and the activities (N-2 yield) certifies this result further.

The luminescence of Eu3+ ion in Ca2Al2SiO7

Ca2Al2SiO7:Eu3+ was prepared by the sol-gel method. Through the emission spectrum of Eu3+ ion, the fluorescence parameters such as Omega(i) (i = 2,4) and radiative transition probabilities of D-5(0)-F-7(j) were calculated. The Pb2+ ion with bigger radius has an effect on the fluorescence spectra of Eu3+ which can be explained by the structure of the matrix. Simultaneously, the energy transfers between mercury-like ions (Pb2+ and Bi3+) and Eu3+ ion were observed. The D-5(4) and D-5(2) energy levels of Eu3+ are the resonance ones for Pb2+ ion.

Mercaptoethane sulfonate protected, water-soluble gold and silver nanoparticles: Syntheses, characterization and their building, multilayer films with polyaniline via ion-dipole interactions

Mercaptoethane sulfonate protected, water-soluble gold and silver nanoparticles (Au-MES and Ag-MES) are synthesized by one-phase method and characterized by TEM, TGA and XPS techniques, UV-vis and FTIR spectra. Both Au-MES and Ag-MES nanoparticles are soluble in the water up to 2.0 mg/ml and the stability of AU-MES is much better than that of Ag-MES. When dissolved in the water. they behave like a polyanion and can be used to build multilayer films with polyaniline (PANI) by way of layer-by-layer. A new approach is presented to fabricate the Multilayer films of Au-MES/PANI and Ag-MES/PAN]. The assembly mechanism of these multilayer films is also discussed. We anticipate highly conducting PANI films can be obtained by doping with these nanoparticles.