One step NaBH4 reduction of Pt-Ru-Ni catalysts on different types of carbon supports for direct ethanol fuel cells: Synthesis and characterization

The ternary catalyst Pt₇₅Ru₅Ni₂₀ was conducted on various types of carbon supports including functionalized Vulcan XC-72R (f-CB), functionalized multi-walled carbon nanotubes (f-MWCNT), and mesoporous carbon (PC-Zn-succinic) by sodium borohydride chemical reduction method to improve the ethanol electrooxidation reaction (EOR) for direct ethanol fuel cell (DEFC). It was found that the particle size of the metals on f-MWCNT was 5.20 nm with good particle dispersion. The alloy formation of ternary catalyst was confirmed by XRD and more clearly described by SEM element mapping, which was relevant to the efficiency of the catalysts. Moreover, the mechanism of ethanol electrooxidation reaction based on the surface reaction was more understanding. The activity and stability for ethanol electrooxidation reaction (EOR) were investigated using cyclic voltammetry and chronoamperometry, respectively. The highest activity and stability for EOR were observed from Pt₇₅Ru₅Ni₂₀/f-MWCNT due to a good metal-carbon interaction. Ru and Ni presented in Pt-Ru-Ni alloy improved the activity and stability of ternary catalysts for EOR. Moreover, the reduction of Pt content in ternary catalyst led to the catalyst cost deduction in DEFC.     

Melt processing of maleic anhydride grafted poly(lactic acid) and its compatibilizing effect on poly(lactic acid)/poly(butylene adipate-<Emphasis Type="Italic">co</Emphasis>-terephthalate) blend and their composite

Poly(lactic acid) (PLA)/poly(butylene adipate-co-terephthalate) (PBAT) blends were prepared using melt processing. The effects of maleic anhydride grafted PLA (PLA-g-MA) and calcium carbonate (CaCO₃) content on mechanical, thermal, and morphological properties of the blends were investigated. PLA-g-MA was synthesized by varying monomer and initiator contents using a reactive melt-grafting process. Tensile properties of PLA/PBAT blend were enhanced with adding 2 phr of PLA-g-MA. SEM micrographs exhibited the improvement of interfacial adhesion between PLA and PBAT in the compatibilized blend. Moreover, thermal stability of the blends improved with presence of PLA-g-MA. With increasing CaCO₃ content, Young’s modulus of the composites increased.     

Chemical Analysis,Toxicity Study,and Free-Radical Scavenging and Iron-Binding Assays Involving Coffee (Coffea arabica) Extracts

We aimed to analyze the chemical compositions in Arabica coffee bean extracts, assess the relevant antioxidant and iron-chelating activities in coffee extracts and instant coffee, and evaluate the toxicity in roasted coffee. Coffee beans were extracted using boiling, drip-filtered and espresso brewing methods. Certain phenolics were investigated including trigonelline, caffeic acid and their derivatives, gallic acid, epicatechin, chlorogenic acid (CGA) and their derivatives, p-coumaroylquinic acid, p-coumaroyl glucoside, the rutin and syringic acid that exist in green and roasted coffee extracts, along with dimethoxycinnamic acid, caffeoylarbutin and cymaroside that may be present in green coffee bean extracts. Different phytochemicals were also detected in all of the coffee extracts. Roasted coffee extracts and instant coffees exhibited free-radical scavenging properties in a dose-dependent manner, for which drip coffee was observed to be the most effective (p < 0.05). All coffee extracts, instant coffee varieties and CGA could effectively bind ferric ion in a concentration-dependent manner resulting in an iron-bound complex. Roasted coffee extracts were neither toxic to normal mononuclear cells nor breast cancer cells. The findings indicate that phenolics, particularly CGA, could effectively contribute to the iron-chelating and free-radical scavenging properties observed in coffee brews. Thus, coffee may possess high pharmacological value and could be utilized as a health beverage.     

Effect of Silane Coupling Agent and Compatibilizer on Properties of Short Rossells Fiber/Poly(propylene) Composites

Rossells fiber reinforced polypropylene composites were prepared by melt mixing. The fiber content was 20 wt%. Octadecyltrimethoxysilane (OTMS) and maleic anhydride grafted polypropylene (MAPP) were used to improve the adhesion between poly(propylene) (PP) and the fiber. The mechanical, rheological, and morphological properties, and heat distortion temperature (HDT) of the composites were investigated. Tensile strength, impact strength, flexural strength and HDT of MAPP modified PP composites increased with an increase in MAPP content. However, no remarkable effect of MAPP content on the Young's modulus of the composites was found. OTMS resulted in small decreases of tensile strength and Young's modulus, and increase in impact strength. Scanning electron micrographs revealed that MAPP enhanced surface adhesion between the fiber surface and PP matrix.     

Synthesis of Poly(methyl methacrylate) Nanoparticles Initiated by 2,2′‐Azoisobutyronitrile via Differential Microemulsion Polymerization

The synthesis of nanosized poly(methyl methacrylate) initiated by 2,2′‐azoisobutyronitrile via differential microemulsion polymerization has been investigated. Poly(methyl methacrylate) with a molecular weight of around 1 × 10⁶ and a particle size of about 20 nm was achieved under mild reaction conditions. A typical condition was that the surfactant amount required could be as low as 1/130 of the monomer amount in weight, and the surfactant/water ratio could be as low as 1/600, which is much less than the corresponding amounts reported in the literature. “Molecular bricks”, i.e., nanoparticles in which there are only one or two polymer chains, can be achieved using mild conditions by differential microemulsion polymerization, which may have potential applications for making molecular devices.

     

Inclusion complexes and photostability of UV filters and curcumin with beta-cyclodextrin polymers: effect on cross-linkers

Beta-cyclodextrin polymers (pbCD) cross-linked by epichlorohydrin (pbCDE) and citric acid (pbCDC) were prepared in this work. The inclusion complexes of pbCDE and pbCDC with curcumin and two commercial UV filters, 2-ethylhexyl-p-methoxycinnamate (EHMC) and 4-tert-butyl-4′-methoxydibenzoylmethane (DBM) were investigated. The UV absorption of these three compounds observed in water indicated that the water solubility of these three hydrophobic compounds increased. The amount of EHMC was higher in both pbCDE and pbCDC than curcumin and DBM, respectively. The photostability of these three compound inclusion complexes with pbCDE and pbCDC were also studied in water and ethylene glycol. It was found that the photostability of the three compounds improved upon formation of the inclusion complex with pbCDE in an aqueous and ethylene glycol solution. The acidity of the crosslink moiety effects to the inclusion complex formation and the photostability of the guests suggesting that more acidity of citric acid decreased the formation and stability of all guest compounds.     

Protonation of carbon single-walled nanotubes studied using 13C and 1H-13C cross polarization nuclear magnetic resonance and Raman spectroscopies

The reversible protonation of carbon single-walled nanotubes (SWNTs) in sulfuric acid and Nafion was investigated using solid-state nuclear magnetic resonance (NMR) and Raman spectroscopies. Magic-angle spinning (MAS) was used to obtain high-resolution 13C and 1H-13C cross polarization (CP) NMR spectra. The 13C NMR chemical shifts are reported for bulk SWNTs, H2SO4-treated SWNTs, SWNT-Nafion polymer composites, SWNT-AQ55 polymer composites, and SWNTs in contact with water. Protonation occurs without irreversible oxidation of the nanotube substrate via a charge-transfer process. This is the first report of a chemically induced change in a SWNT 13C resonance brought about by a reversible interaction with an acidic proton, providing additional evidence that carbon nanotubes behave as weak bases. Cross polarization was found to be a powerful technique for providing an additional contrast mechanism for studying nanotubes in contact with other chemical species. The CP studies confirmed polarization transfer from nearby protons to nanotube carbon atoms. The CP technique was also applied to investigate water adsorbed on carbon nanotube surfaces. Finally, the degree of bundling of the SWNTs in Nafion films was probed with the 1H-13C CP-MAS technique.     

Phosphorylation of alcohols with N-phosphoryl oxazolidinones employing copper(II) triflate catalysis

[reaction: see text]. Phosphoryl transfer from N-phosphoryl 5,5-diphenyl oxazolidinone is efficiently catalyzed by copper(II) triflate. The utility of this method has been demonstrated in the phosphorylation of representative primary, secondary, tertiary, phenolic, and allylic alcohols. These reaction conditions are significantly milder than employing alkoxides and allow the phosphorylation of biologically relevant molecules.