Stripping voltammetric determination of Pb(II) and Cd(II) based on the multiwalled carbon nanotubes-Nafion-bismuth modified glassy carbon electrodes

In this work, a new method for the simultaneous determination of Pb(II) and Cd(II) on the multiwalled carbon nanotubes (MWNT)-Nafion-bismuth modified glassy carbon electrode (GCE) using square-wave anodic stripping voltammetry has been studied. Scanning electron microscopy was used to investigate the characteristics of the MWNT-Nafion-bismuth modified GCE.

Microchip Micellar Electrokinetic Chromatography Based on One Functionalized Ionic Liquid and Its Excellent Performance on Proteins Separation

Herein, one water-soluble functionalized ionic liquid (IL), 1-butyl-3-methylimidazolium dodecanesulfonate (BAS), was designed, investigated and successfully applied to microchip micellar electrokinetic chromatography (MEKC) construction. It possessed the properties of both IL and surfactant. A fairly stable pH value similar to 7.4, which was fit to pH values of general biological buffers, was nicely placed at the optimum concentration of 20 mM BAS solution. While applying BAS solution as running buffer in poly(dimethylsiloxane) (PDMS) microfluidic systems, significantly enhanced electroosmotic flow (8-fold) and resolutions between analytes were obtained than that using other supporting electrolytes or surfactants.

Control for oriented growth of large size KCl crystals by the competition between spontaneous and induced nucleation/growth on a Langmuir-Blodgett film

Langmuir-Blodgett (LB) film of stearic acid was used as template to induce the nucleation and growth of KCl crystals when the KCl solution was cooled from 50 to 25 degrees C. When the LB film template was vertically dipped into the solution, only induced crystals with (1 1 0) orientation were formed. However, if the template was horizontally placed into solutions, both the induced nuclei at the solution/film interface and spontaneous nuclei formed in solution were simultaneously absorbed onto the LB film, and then grew further to form crystals. X-ray diffraction (XRD) patterns and optical microscopy images showed that the orientation and morphology of the crystals were controlled properly by changing the orientation and position of the LB films in the solutions.

Effects of ammonia and cetyltrimethylammonium bromide (CTAB) on morphologies of ZnO nano- and micromaterials under solvothermal process

Submicrometer zinc oxide (ZnO) with different morphologies including spindle-like, pencil-like, branch rod-like and frizzy flower-like shapes, have been hydrothermally synthesized in mixed solvents of ethanol and water at 140 degrees C. It was found that the volumes of added ammonia, surfactant (cetyltrimethylammonium bromide, CTAB), and mixed solvent play crucial roles in morphological control of ZnO nanostructures. Increasing the volume of ammonia added to the reaction system, the shape of ZnO evolves from spindle into branch rod-like. Synergetic influence between CTAB and ammonia can only be observed at high concentration of ammonia.

Direct electron transfer of horseradish peroxidase and its electrocatalysis based on carbon nanotube/thionine/gold composites

Horseradish peroxidase (HRP) was incorporated into multiwalled carbon nanotube/thionine/Au (MTAu) composite film by electrostatic interactions between positively charged HRP and negatively charged MTAu composite. The results of electrochemical impedance spectroscopy (EIS) confirmed adsorption of HRP on the surface of MTAu modified GC electrode.

Design of Fluorescent Assays for Cyanide and Hydrogen Peroxide Based on the Inner Filter Effect of Metal Nanoparticles

We have demonstrated the design of a new type fluorescent assay based on the inner filter effect (IFE) of metal nanoparticles (NPs), which is conceptually different from the previously reported metal NPs-based fluorescent assays. With a high extinction coefficient and tunable plasmon absorption feature, metal NPs are expected to be capable of functioning as a powerful absorber to tune the emission of the fluorophore in the IFE-based fluorescent assays. In this work, we presented two proof-of-concept examples based on the IFE of Au NPs by choosing MDMO-PPV as a model fluorophore, whose fluorescence could be tuned by the absorbance of Au NPs with a much higher sensitivity than the corresponding absorbance approach.

Electrochemical Sensing and Biosensing Platform Based on Chemically Reduced Graphene Oxide

In this paper, the characterization and application of a chemically reduced graphene oxide modified glassy carbon (CR-GO/GC) electrode, a novel electrode system, for the preparation of electrochemical sensing and biosensing platform are proposed. Different kinds of important inorganic and organic electroactive compounds (i.e., probe molecule (potassium ferricyanide), free bases of DNA (guanine (G), adenine (A), thymine (T), and cytosine (C)), oxidase/dehydrogenase-related molecules (hydrogen peroxide (H2O2/beta-nicotinamide adenine dinucleotide (NADH)), neurotransmitters (dopamine (DA)), and other biological molecules (ascorbic acid (AA), uric acid (UA), and acetaminophen (APAP)) were employed to study their electrochemical responses at the CR-GO/GC electrode, which shows more favorable electron transfer kinetics than graphite modified glassy carbon (graphite/GC) and glassy carbon (GC) electrodes.

Realization of negative differential resistance and switching devices based on copper phthalocyanine by the control of evaporation rate

We have observed, respectively, a negative differential resistance (NDR) and switching conduction in current-voltage (I-V) characteristics of organic diodes based on copper phthalocyanine (CuPc) film sandwiched between indium-tin-oxide (ITO) and aluminum (Al) by controlling the evaporation rate. The NDR effect is repeatable which can be well, controlled by sweep rate and start voltage, and the switching exhibits write-once-read-many-times (WORM) memory characteristics. The traps in the organic layer and interfacial dipole have been used to explain the NDR effect and switching conduction. This opens up potential applications for CuPc organic semiconductor in low power memory and logic circuits.

NMR and pattern recognition studies on the acute biochemical effects of Lu(NO3)(3)

Pattern recognition methods were applied to the analysis of 600 MHz H-1 NMR spectra of urine from rats dosed with compounds that induced organ-specific damage in the liver and kidney. Male Wistar rats were separated into groups (n=4) and each was treated with one of following compounds: HgCl2, CCl4, Lu(NO3)(3) and Changle (a kind of rare earth complex mixed with La, Ce, Pr and Nd). Urine samples from the rats dosed with HgCl2, CCl4 and Lu(NO3)(3) were collected over a 24 h time course and the samples from the rats administrated with Changle were gained after 3 months. These samples were measured by 600 MHz NMR spectroscopy. Each spectrum was data-processed to provide 223 intensity-related descriptors of spectra. Urine spectral data corresponding to the time intervals, 0-8 h (HgCl2 and CCl4), 4-8 (Lu(NO3)(3)) h and 90 d (Changle) were analyzed using principal component analysis (PCA). Successful classification of the toxicity and biochemical effects of Lu(NO3)(3) was achieved.

Diffusion and single molecule dynamics on biomolecular interface binding energy landscape

We propose a new approach to study the diffusion dynamics on biomolecular interface binding energy landscape. The resulting mean first passage time (MFPT) has 'U'curve dependence on the temperature. It is shown that the large specificity ratio of gap to roughness of the underlying binding energy landscape not only guarantees the thermodynamic stability and the specificity [P.A. Rejto, G.M. Verkhivker, in: Proc. Natl. Acad. Sci. 93 (1996) 8945; C.J. Tsai, S. Kumar, B. Ma, R. Nussinov, Protein Sci. 8 (1999) 1181; G.A. Papoian, P.G. Wolynes, Biopolymers 68 (2003) 333; J. Wang, G.M. Verkhivker, Phys. Rev. Lett. 90 (2003) 198101] but also the kinetic accessibility. The complex kinetics and the associated fluctuations reflecting the structures of the binding energy landscape emerge upon temperature changes. The theory suggests a way of connecting the models/simulations with single molecule experiments by analysing the kinetic trajectories.

Solvent and polymer concentration effects on the surface morphology evolution of immiscible polystyrene/poly(methyl methacrylate) blends

The effects of solvent nature on the surface topographies of polystyrene (PS)/poly(methyl methacrylate) (PMMA) blend films spin-coated onto the silicon wafer were investigated. Four different solvents, such as ethylbenzene, toluene, tetrahydrofuran and dichloromethane, were chosen. They are better solvents for PS than that for PMMA. When dichloromethane, tetrahydrofuran and toluene were used, PMMA-rich phase domains protruded from the background of PS. When ethylbenzene was used, PS-rich phase domains elevated on the average height of PMMA-rich phase domains. In addition, continuous pits, networks and isolated droplets consisted of PS formed on the blend film surfaces with the decrease of polymer concentrations. The mechanism of the surface morphology evolution was discussed in detail.

Polymer concentration, shear and stretch field effects on the surface morphology evolution during the spin-coating

Polymer concentration and shear and stretch field effects on the surface morphology evolution of three different kinds of polymers (polystyrene (PS), polybutadiene (PB) and polystyrene-b-polybutadiene-b-polystyrene (SBS)) during the spin-coating were investigated by means of atomic force microscopy (AFM). For PS and SBS, continuous film, net-like structure and particle structure were observed at different concentrations. For PB, net-like structures were not observed and continuous films and radial array of droplets emerged. Moreover, we compared surface morphology transitions on different substrate locations from the center to the edge. For PS, net-like structure, broken net-like structure and irregular array of particles were observed. For SBS, net-like structure, periodically orientated string-like structure and broken-line structure appeared. But for PB, flower-like holes in the continuous film, distorted stream-like structure and irregular distributions of droplets emerged. These different transitions of surface morphologies were discussed in terms of individual material property.

Studies on the stability of polyazamacrocycle-Eu (Tb) by potentiometry and its catalytic hydrolysis on phosphate diester

The stability constants and species distributions of complexes of two lanthanide ions, Eu (III) and Tb(III), with a macrocyclic ligand, 3,6, 9, 17 20, 23-hexaazo-29, 30-dihydroxy-13, 27-dimethyl-tricylco-[23,3,1,1(11,15)] triaconta-1 (28) 11,13,15 (30), 25 26-hexane (BDBPH), in 1: 1 and 2: 1 system, were determined potentiometrically in 50% ethanol solution, at 35.0 degrees C and I = 0.100 mol/L (KCl). The two metal ions could form deprotonated mono- or dinuclear complexes with BDBPH with high stability after the three protons of the ligand completely neutralized. At higher pH values, Eu(M) could not form hydroxo complexes with BDBPH, while Tb(III) could form hydroxo complexes in the types of M2L(OH) M2L(OH)(2) and M2L (OH)(2). The kinetic study on the hydrolysis reaction of his (4-nitrophenyl) phosphate (BNPP) catalyzed by Tb-BDBPH system (2:1) was carried out in aqueous solution (pH 7.0 similar to 10.0) at 35 degrees C with I = 0.1000 mol/L (KCl). The second-order rate constant k(BNPP) (2.3 x 10(-3) (mol/L)(-1)center dot s(-1)) was determined. The dinuclear monohydroxo species, L-Tb-2-OH, is kinetically active species.

Microperoxidase-11 modified electrode and its electrocatalytic activity on the reduction of O-2 and H2O2

Microperoxidase-11 (MP-11) was immobilized on the surface of a silanized glass carbon electrode by means of the covalent bond with glutaraldehyde. The measurements of cyclic voltammetry demonstrated that the formal redox potential of immobilized MP-11 was -170 mV. which is significantly more positive than that of MP-11 in a solution or immobilized on the surface of electrodes prepared with other methods. This MP-11 modified electrode showed a good electrocatalytic activity and stability for the reduction of oxygen and hydrogen peroxide.