Isothermal Titration Calorimetry and Transmission Electron Microscopy of Main-Chain Viologen Polymer Containing Bromide as Counerions

Polyelectrolytes are an important class of macromolecules that contain dissociable ionic groups. When introduced into polar solvent, usually the universal solvent water, dissociation takes place so that electrically charged macromolecule is suspended in solution. The electrostatic interaction is operative between ionized groups inside the macromolecule, between the macromolecules, between the counterions, and between the macromolecule and counterion. Since this interaction is characterized by its long-range nature, the solution exhibits various interesting properties including the polyelectrolyte behavior very different from solutions of neutral polymers

A New Method of Synthesizing Black Birnessite Nanoparticles: From Brown to Black Birnessite with Nanostructures

A new method for preparing black birnessite nanoparticles is introduced. The initial synthesis process resembles the classical McKenzie method of preparing brown birnessite except for slower cooling and closing the system from the ambient air. Subsequent process, including wet-aging at 7◦C for 48 hours, overnight freezing, and lyophilization, is shown to convert the brown birnessite into black birnessite with complex nanomorphology with folded sheets and spirals. Characterization of the product is performed by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), thermogravimetric analysis (TGA), and N2 adsorption (BET) techniques. Wet-aging and lyophilization times are shown to affect the architecture of the product. XRD patterns show a single phase corresponding to a semicrystalline birnessite-based manganese oxide. TEM studies suggest its fibrous and petal-like structures. The HRTEM images at 5 and 10 nm length scales reveal the fibrils in folding sheets and also show filamentary breaks. The BET surface area of this nanomaterial was found to be 10.6m2/g. The TGA measurement demonstrated that it possessed an excellent thermal stability up to 400◦C. Layerstructured black birnessite nanomaterial containing sheets, spirals, and filamentary breaks can be produced at low temperature (−49◦C) from brown birnessite without the use of cross-linking reagents

Free-Surface Problems in Electrokinetic Micro- and Nanofluidics

With the development of novel micro- and nanofluidic devices, applications of flows with moving interfaces are in increasing demand. Problems in ultra-small scale with moving boundaries, which have not yet been exploited rigorously, are discussed with focus on electrokinetic flows. A generic formulation for moving interfaces, applicable to micro- and nanoscale electrokinetic flows, is provided, and actual free-surface problems in electroosmosis and electrophoresis are presented

Synthesis, Characterization, and Catalytic Performance of Sb 2

Antimony selenide has many potential applications in thermoelectric, photovoltaic, and phase-change memory devices. A novel method is described for the rapid and scalable preparation of antimony selenide (Sb2Se3) nanorods in the presence of hydrazine hydrate and/or permanganate at 40°C. Crystalline nanorods are obtained by the addition of hydrazine hydrate in a reaction mixture of antimony acetate and/or chloride and sodium selenite in neutral and basic media, while amorphous nanoparticles are formed by the addition of KMnO4 in a reaction mixture of antimony acetate/chloride and sodium selenite. The powder X-ray diffraction pattern confirms orthorhombic phase crystalline Sb2Se3 for the first and second reactions with lattice parameters a=1.120 nm, b=1.128 nm, and c=0.383 nm and amorphous Sb2Se3 for the third reaction. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high-resolution TEM (HRTEM) images show the diameter of nanorods for the first and second reactions to be in the order of 100 nm to 150 nm and about 20 nm particles for the third reaction. EDX and XPS suggest that the nanorods are pure Sb2Se3. The UV-vis analysis indicates a band gap of 4.14 and 4.97 eV for the crystalline and amorphous Sb2Se3, respectively, corresponding to a blue shift. The photocatalytic study shows that the decolorization of Rhodamine in solution by nanoparticles is slightly greater than nanorods

A Comparative Study on the Uptake of Polycyclic Aromatic Hydrocarbons by Anodonta Californiensis

Uptake of polycyclic aromatic hydrocarbons (PAHs) by the freshwater bivalve mollusc Anodonta californiensis was examined in the presence and absence of surfactant in order to gain further insight into mixture toxicity and to predict whether certain mixtures have negative and/or positive effects on aquatic organisms. In the presence of surfactant, the uptake of anthracene or chrysene was higher than that of naphthalene, given the same concentration in the solution. In the absence of surfactant, the trend was similar, but the uptakes were increased by approximately 100% compared to those in the presence of surfactant. On the uptake of naphthalene, the presence of anthracene showed only minor influence. The uptake of anthracene was affected by both naphthalene and chrysene. The uptake of chrysene was influenced by neither naphthalene nor anthracene. There was no observable displacement of divalent cations from the surface of the gill membrane by any of the PAHs studied