Deposition of the Monodispersed Pt Nanodots on a Substrate by Using the Pt Nanoparticle-Containing Dendrimer Micelle Aqueous Solution

Dendritic polyphenylazomethine (DPA) can form complexes with an unambiguous number of various metal ions, allowing the preparation of size-controlled sub-nanometer metal particles. Upon the deposition of the obtained metal nanoparticles on a substrate, the diameters usually tend to grow larger due to the aggregations. We now report that the deposition of such platinum (Pt) particles obtained by one of the DPA dendrimers (DPAG4) on a substrate without such aggregations. First, Pt nanoparticles supported in DPAG4 (DPAG4–Pt) were prepared from the complex between DPAG4 and 14PtCl₄ (DPAG4–14PtCl₄) in an organic solvent by a hydride reduction. The micelles of the dendrimer-surfactant composite containing monodispersed Pt nanoparticles in the shell are prepared in metal free buffer solutions. Because of the electro charge repulsion among the DPAG4 micelles, the monodispersed Pt particles prepared by DPAG4 can be deposited on the substrate without aggregation.     

Quantum size titanium oxide templated with a π-conjugated dendrimer: crystal structure in the quantum size domain

Metal-based nanoparticles templated with dendrimers have recently attracted much interest to control particle sizes strictly. However, the standard deviation of the obtained particles is larger than that of the single-mass Au clusters (0.2 nm). We succeeded the subnanosize-control of TiO₂ particles (both of rutile and anatase crystal structures based on the difference in the synthesis methods) with a standard deviation of 0.2 nm, using finely controlled metal assembly on a phenylazomethine dendrimer (DPA G4). The optical absorption spectra of the obtained particles revealed that the quantum size effect and the difference in the crystal structure, such as rutile and anatase, exists less than 2 nm particle sizes. A semi-empirical effective mass approximation, introduced a new concept; apparent reduced mass, describes the size dependency and the difference based on the crystal structure in the bandgap energy of the indirect and direct transition.     

Study on the foaming of CaO-SiO2-FeO slags: Part II. Dimensional analysis and foaming in iron and steelmaking processes

An empirical equation for the foaming index Σ of a CaO-SiO₂-FeO slag was obtained by dimensional analysis. The effect of second-phase particles on slag foaming was well described by calculating the viscosity of the mixture using the modified Einstein equation. The anticipated foaming in basic oxygen furnace (BOF), electric arc furnace (EAF), and bath-smelting processes was estimated using the parameter Σ for various operating conditions and slag compositions. For BOF operations, it is predicted that foaming is most extreme in the middle of the blow, and a stable foam in EAF is achieved with less basic slags with low FeO contents. For bath smelting, foam heights of 5 m are possible, and a higher degree of prereduction prior to smelting will reduce foaming (because of smaller gas evolution) and possibly increase production rates. Running the process at a higher pressure will also reduce foam heights, because the volume of gas generated is less. Kimihisa Ito, Research Associate, formerly with the Department of Metallurgical Engineering and Materials Science, Carnegie Mellon University     

Reaction Kinetics of FeO Containing Molten Slags

The kinetic study of FeO‐containing slag is valuable if we consider slag‐gas and slag‐metal reactions in steelmaking process. In the present work, the reduction rate of Fe_tO‐SiO₂–TiO₂–MO_x (MO_x = CaO, MgO, AlO_1.5, PO_2.5) melts in equilibrium with solid iron by CO gas was measured using the thermobalance system at 1673 K. A rate equation was developed based on the results obtained. The mechanisms of the reaction and the effect of P₂0₅ as a surfactant were discussed. Solid CaO was reacted with FeO‐containing slag at 1573 to 1673 K. The CaO–slag interface was analyzed by SEM and EDX, and the reacted layers were identified. The rate of solid CaO dissolution into a stagnant FeO‐containing slag at hot‐metal temperatures was explained by the FeO diffusion in slag phase.     

Electrochemical Catalytic Reduction of Oxygen by a Self-Doped Polyaniline–Co-Porphyrin Complex-Modified Glassy Carbon Electrode

The four-electron reduction of oxygen to water takes place on a glassy carbon electrode by electrocatalysis using the Co-porphyrin–polyaniline complex. The four-electron transfer processes were confirmed by electrochemical measurements such as cyclic voltammetry, rotating disk voltammetry (RDV), and rotating ring-disk voltammetry (RRDV). The number of electrons transferred was determined on the basis of the Koutecky–Levich plot in RDV. Large amounts of H₂O₂ formation were not detected by RRDV. RRDV revealed that the direct four-electron reduction of oxygen proceeded without the formation of H₂O₂. The process obeys a mechanism in which the four-electron reduction takes place through a multiple electron injection from the polyaniline to the cobalt complex after electron transfer from Co to oxygen. The four-electron reduction of oxygen also proceeds in a pseudo-neutral medium (pH 6.2). Poly(2,3-dicarboxyaniline) acts as an excellent electron mediator from the electrode to the Co-porphyrin matrix and shows stable redox activity over a wide pH range due to the self-dopable carboxy substituents in the polymer chain.     

Identification of molecular target of AMP-activated protein kinase activator by affinity purification and mass spectrometry

We show an efficient method to identify molecular targets of small molecular compounds by affinity purification and mass spectrometry. Binding proteins were isolated from target cell lysate using affinity columns, which immobilized the active and inactive compounds. All proteins bound to these affinity columns were eluted by digestion using trypsin and then were identified by mass spectrometry. The specific binding proteins to the active compound, a candidate for molecular targets, were determined by subtracting the identified proteins in an inactive compound-immobilized affinity column from that in an active compound-immobilized affinity column. This method was applied to identification of molecular targets of D942, a furancarboxylic acid derivative, which increases glucose uptake in L6 myocytes through AMP-activated protein kinase (AMPK) activation. To elucidate the mechanism of AMPK activation by D942, affinity columns that immobilized D942 and its inactive derivative, D768, were prepared, and the binding proteins were purified from L6 cell lysate. NAD(P)H dehydrogenase [quinone] 1 (complex I), which was shown as one of the specific binding proteins to D942 by subtracting the binding proteins to D768, was partially inhibited by D942, not D768. Because inhibition of complex I activity led to a decrease in the ATP/AMP ratio, and the change in the ATP/AMP ratio triggered AMPK activation, we identified complex I as a potential protein target of AMPK activation by D942. This result shows our approach can provide crucial information about the molecular targets of small molecular compounds, especially target proteins not yet identified.     

Synthesis and thermal characteristics of poly(thioarylene)s by thermal polymerization

Thermal polymerization of bis[4-(4-bromophenylthio)phenyl] disulfide (I), bis[4-(4-bromophenyloxy)phenyl] disulfide (II) and bis[(4-(4-bromophenylsulfony)phenyloxy)phenyl] disulfide (III) was carried out at 250°C in diphenyl ether. The resulting poly(thioarylene)s show high crystallinity and high thermal stability. The blends and copolymers of poly(thioarylene) were also prepared, whose thermal properties were investigated by DSC measurements.     

Two-point separation in far-field super-resolution fluorescence microscopy based on two-color fluorescence dip spectroscopy, Part I: Experimental evaluation

The two-point resolution of a novel two-color far-field super-resolution fluorescence microscopy was evaluated by measuring fluorescent beads 100 nm in diameter. This microscopy is based on a combination of two-color fluorescence dip spectroscopy and a phase-modulation technique for a laser beam. By simply introducing two-color laser light, the size of the fluorescent image of a bead was shrunk down to a diameter of 250 nm from the diffraction-limited image with a diameter of 360 nm. For two closely adjacent fluorescent beads with a separation distance of 350 nm, the two-color microscope clearly gave separated fluorescence images, while the conventional one-color fluorescence microscope could not resolve them. It has been proved that our technique breaks Rayleigh's diffraction limit.     

Electrocatalysis of the Reduction of Dioxygen by π-Conjugated Polymer Complexes with Dinuclear Cobalt Porphyrin

Catalysis of polymer complexes using polyanilines and dinuclear cobalt porphyrin (Co₂P) was investigated by electrochemical measurement. Poly(2,3-dicarboxyaniline) with CoTPPS–CoTMPyP acts as an excellent catalyst for a four-electron reduction of oxygen even under pseudo-neutral conditions. Various polymer complexes were made using synthesized electroresponsive polymers. The selectivity of the four-electron reduction dramatically decreases with an increase in the potential gap between the polymer and the porphyrin. This result indicates that a sequential electron transfer takes place from the polymer to the porphyrin with a potential similar to that of the cobalt porphyrin.