No abstract

The effect of zinc (Zn) doping and defect formation on the surface of nickel molybdate (NiMoO 4 ) structures with varying Zn content has been studied to produce one-dimensional electrodes and catalysts for electrochemical energy storage and ethanol oxidation, respectively. Zn-doped nickel molybdate (Ni 1-x Zn x MoO 4 , where x = 0.1, 0.2, 0.4, and 0.6) nanorods were synthesized by a simple wet chemical route. The optimal amount of Zn is found to be around 0.25 above which the NiMoO 4 becomes unstable, resulting in poor electrochemical activity. This result agrees with our density functional theory calculations in which the thermodynamic stability reveals that Ni 1-x Zn x MoO 4 crystallized in the β-NiMoO 4 phase and is found to be stable for x≤0.25. Analytical techniques show direct evidence of the presence of Zn in the NiMoO 4 nanorods, which subtly alter the electrocatalytic activity. Compared with pristine NiMoO 4 , Zn-doped NiMoO 4 with the optimized Zn content was tested as an electrode for an asymmetric supercapacitor and demonstrated an enhanced specific capacitance of 122 F g −1 with a high specific energy density of 43 W h kg −1 at a high power density of 384 W kg −1 . Our calculations suggest that the good conductivity from Zn doping is attributed to the formation of excess oxygen vacancies and dopants play an important role in enhancing the charge transfer between the surface and OH − ions from the electrolyte. We report electrochemical testing, material characterization, and computational insights and demonstrate that the appropriate amount of Zn in NiMoO 4 can improve the storage capacity (∼15%) due to oxygen vacancy interactions.

Fractionation of two Fijian specimens of the sponge Corticium sp. led to the isolation of the known active alkaloid steroid plakinamine A and two new halogenated cyclic peptides, corticiamide A (1) and cyclocinamide B (2). Structural elucidation of 1 and 2 was achieved by an extensive combination of high-field NMR and HRFT MS/MS experiments, and the absolute stereochemistry of 2 was determined by acid hydrolysis and Marfey's analysis. Corticiamide A (1) and cyclocinamide B (2) represent the first peptides to be described from the genus Corticium.

No abstract

No abstract

Chemical investigation of the Western Australian marine brown alga Cystophora harveyi resulted in the isolation of the new linearly fused 6,6,5-tricyclic compound pycnanthuquinone C (1), in addition to four previously reported geranyltoluquinol derivatives. Structures were elucidated by interpretation of spectrometric data. Compounds with the same cyclic skeleton as 1 have been reported to be useful drug leads for the treatment of type 2 diabetes, while compounds 4 and 7 are known constituents of Chinese medicinal herbs. A biosynthetic scheme encompassing all of the geranyltoluquinol derivatives isolated from C. harveyi is proposed.

The degradation of twenty-one low-molecular-weight organic carboxylates has been studied at 90 and 180 °C in a synthetic Bayer liquor consisting of 6 mol kg -1 aqueous NaOH solution for periods of up to 36 days. The reactions were monitored and the major degradation products identified by HPLC and NMR spectroscopy. The carboxylates chosen for study either could be intermediates, or occur as a result of decomposition of organic matter in the Bayer process. Aliphatic carboxylates without hydroxyl substituents were stable at 90 °C but decomposed at 180 °C, except for formate, acetate, oxalate and succinate. The corresponding aromatic carboxylates were stable even at 180 °C. Both aliphatic and aromatic carboxylates with hydroxyl substituents were unstable at 90 °C, except for lactate and 4-hydroxybenzoate. The most frequently detected decomposition products for both aliphatic and aromatic carboxylates were formate, acetate, oxalate, succinate and lactate. Phenolate was also observed for some aromatic carboxylates. These products are briefly discussed with reference to possible mechanisms for the degradation reactions.

The degradation of nineteen low-molecular-weight phenolates, polyalcohols and selected aliphatic and aromatic carboxylates of relevance to the Bayer process has been studied in 6 mol kg -1 NaOH(aq) at 90 °C for up to 36 d, and (for some species) at 180 °C for up to 12 d, using HPLC and 13 C-NMR spectroscopy. Aliphatic polyalcohols degraded readily at 90 °C to lactate, oxalate, acetate, and formate. As observed previously, aliphatic carboxylates with hydroxyl groups also degraded readily at 90 °C but there is evidence that the position of the hydroxyl group may be important. The observed degradation products for most, but not all, of these species can be explained in terms of well-known organic reaction mechanisms. Phenolate adn 5-hydroxyisophthalate were stable at 180 °C but other phenolic species degraded partially at 90 °C. However, the reaction products could not be identified and no trends in reactivity were discernible. Consistent with previous studies both aliphatic and aromatic carboxylates without hydroxyl groups were generally stable in NaOH(aq) even at 180 °C.