Updated Metal Compounds (MOFs, S, OH, N, C) Used as Cathode Materials for Lithium–Sulfur Batteries

Lithium–sulfur (Li–S) batteries have the potential to be as efficient and as widespread as lithium‐ion (Li‐ion) batteries, since sulfur electrode has high theoretical capacity (1672 mA h g_sul^?1) and this element is affordable. However, unlike their ubiquitous lithium ion (Li‐ion) counterparts, it is difficult to realize the commercialization of Li‐S battery. Because the shuttle effect of polysulfide inevitably results in the serious capacity degradation. Tremendous progress is devoted to approach this problem from the aspect of physical confinement and chemisorption of polysulfide. Owing to weak intermolecular interactions, physical confinement strategy, however is not effective when the battery is cycled long‐term. Chemisorption of polysulfide that derived from polar–polar interaction, Lewis acid–base interaction, and sulfur‐chain catenation, are proven to significantly suppress the shuttle effect of polysulfide. It is also discovered that the metal compounds have strong chemical interactions with polysulfide. Therefore, this review focuses on latest metal–organic frameworks metal sulfides, metal hydroxides, metal nitrides, metal carbides, and discusses how the chemical interactions couple with the unique properties of these metal compounds to tackle the problem of polysulfide shuttle effect.     

Updated Metal Compounds (MOFs, ?S, ?OH, ?N, ?C) Used as Cathode Materials for Lithium–Sulfur Batteries

Lithium–sulfur (Li–S) batteries have the potential to be as efficient and as widespread as lithium‐ion (Li‐ion) batteries, since sulfur electrode has high theoretical capacity (1672 mA h g_sul^?1) and this element is affordable. However, unlike their ubiquitous lithium ion (Li‐ion) counterparts, it is difficult to realize the commercialization of Li‐S battery. Because the shuttle effect of polysulfide inevitably results in the serious capacity degradation. Tremendous progress is devoted to approach this problem from the aspect of physical confinement and chemisorption of polysulfide. Owing to weak intermolecular interactions, physical confinement strategy, however is not effective when the battery is cycled long‐term. Chemisorption of polysulfide that derived from polar–polar interaction, Lewis acid–base interaction, and sulfur‐chain catenation, are proven to significantly suppress the shuttle effect of polysulfide. It is also discovered that the metal compounds have strong chemical interactions with polysulfide. Therefore, this review focuses on latest metal–organic frameworks metal sulfides, metal hydroxides, metal nitrides, metal carbides, and discusses how the chemical interactions couple with the unique properties of these metal compounds to tackle the problem of polysulfide shuttle effect.     

Identification and characterization of Cr-, Cd-, and Ni-tolerant bacteria isolated from mine tailings

Eleven bacterial strains were isolated from soil samples collected from mine tailings. Bacterial strains were checked for tolerance against heavy metals (Cr, Cd, Ni), using the agar dilution method. All the strains showed multiple tolerances against heavy metals, but the most promising results appeared in strains BCr3, BCd33, and BNi11: they were tolerant to 15 mM of Cr⁶⁺, 7.5 mM of Cd²⁺, and 10 mM of Ni²⁺, respectively. The effect of heavy metals on bacterial growth was tested together with their ability to grow in different pH, NaCl, and temperature values. Bacterial isolates grew well between pH 7.5 and 8.5. The optimum temperature for maximum growth was between 35 and 37°C, and no significant change in bacterial growth was observed in the presence of 2% NaCl. In addition, the bioaccumulation potential of bacterial strains was investigated. Bacterial strains BCr3, BCd33, and BNi11 showed high bioaccumulation ability of Cr (68.7%), Cd (72.4%), and Ni (69.8%), respectively. All bacterial isolates were identified by 16S rRNA gene sequencing. Analysis of plasmid content revealed that all bacterial isolates contained a single plasmid. Further, polymerase chain reaction together with DNA sequence analysis was used to screen all bacterial strains for the presence metal tolerance genes (czcD, chrA, chrB, czcB, czcC, nccA, and cadA) on both plasmid and chromosomal genomes.     

Binding of Transition Metal Ions [Cobalt,Copper, Nickel and Zinc] with Furanyl-, Thiophenyl-, Pyrrolyl-, Salicylyl-and Pyridyl-Derived Cephalexins as Potent Antibacterial Agents

A method is described for the preparation of novel cephalexin-derived furanyl-, thiophenyl-, pyrrolyl-, salicylyl- and pyridyl-containing compounds showing potent antibacterial activity. The binding of these newly synthesized antibacterial agents with metal ions such as cobalt(II), copper(II), nickel(II) and zinc(II) has been studied and their inhibitory properties against various bacterial species such as Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and Klebsiella pneumoniae are also reported. These results suggest that metal ions to possess an important role in the designing of metal-based antibacterials and that such complexes are more effective against infectious diseases compared to the uncomplexed drugs.     

Biogeochemistry and effects of copper,manganese and zinc added to enclosures in Island Billabong,Magela Creek,northern Australia

Three large plastic enclosures (5 m diam, volume 40 m³) were used to study the effects of copper, manganese and zinc, on the phytoplankton community in Island billabong, a floodplain billabong (waterhole) situated in the Magela Creek in tropical northern Australia. Copper was added to one enclosure, and manganese and zinc to another, to give initial concentrations around ten times the normal wet season values. The enclosures and the billabong were monitored over a ten week period towards the end of the dry season, with the enclosures allowed to stabilise for four weeks before the metals were added.The control enclosure adequately simulated the temperature and pH changes in the billabong. The trends in conductivity, dissolved oxygen and major ion concentrations were similar in the enclosure and the billabong, with the minor differences observed attributed to either epiphytic growth on the enclosure walls (influenced dissolved oxygen, pH and bicarbonate concentration) or ingress of sulphate-rich groundwater into the billabong (influenced sulphate concentration and conductivity). Major differences in both the composition of species and the size of the phytoplankton populations were observed between the three enclosures and between the control enclosure and the billabong. This variability reflects the great natural variability in the phytoplankton communities in tropical lentic systems, and means that enclosures are unlikely to adequately simulate the biological communities in the billabongs.The control enclosure appeared to simulate quite well the longer term changes in total concentration and speciation of the three metals (copper, manganese & zinc) in the billabong. The mean concentrations of copper and zinc were similar in the two systems, although the mean concentration of manganese in the billabong was almost double that in the enclosure, possibly due to ingress of manganese-enriched groundwater. Particulate forms dominated the speciation of copper and manganese. There was considerable short term variation in both total metal concentration and speciation in both the enclosure and the billabong. This variability appears to be a feature of these small tropical waterbodies.The added heavy metals were found to have minimal detrimental effect on the phytoplankton community in each metal-loaded enclosure. The high natural variability in the phytoplankton community in these tropical systems will make it difficult to separate natural changes from those caused by low level contamination from mining operations should this occur.All three metals were rapidly removed from the water column, so that by the end of the six week period, only ca. 5% of each added metal remained in the water column. Association with the particulate matter (phytoplankton, abiotic particulate matter and MnO_x in enclosure 2) followed by sedimentation was the major removal pathway. Epiphytes growing on the enclosure walls appeared to have a minor influence (<10% of the total amount of metal added) on the removal of the added metals. For copper, uptake by phytoplankton followed by sedimentation was the major (65%) removal process. Manganese and zinc, added together, were found to influence each other. The major manganese removal process (60%) was rapid (ca. 3 days) involving bacterial oxidation and sedimentation of the MnO_x formed. This material appeared to have little influence on the behaviour of zinc, possibly because other particulate matter competed more effectively for the zinc. A further 30% of the added manganese was removed via initial adsorption to other particulate matter, possibly phytoplankton. Approximately one third of this adsorbed manganese (10% of the total added) appeared to undergo delayed oxidation some 8 days after the initial additions, and the heavier particles settled out more rapidly. This path was responsible for removing the major amount (ca. 60%) of the added zinc. We hypothesis that the sorbed zinc inhibited the bacterial oxidation of the manganese. A further 25% of the zinc was removed in association with a burst of phytoplankton activity. The occurrence of bursts in the phytoplankton activity, when populations can increase very substantially and then decrease again, all within the space of a day, appears to be an important mechanism for removing copper and zinc from the water column in these tropical water bodies     

王港潮滩重金属Pb、Zn和Cu的积累特征

对15a来王港潮滩重金属积累规律和污染状况进行了研究,第1次测到了王港地区210Pb的本底值为1.16dpm/g,校正了前人对王港地区沉积速率的研究。尝试性地把分形理论引入到环境压力的定量研究中。研究表明,王港潮滩现代平均沉积速率为4.13cm/a;从重金属相关性分析得出:王港潮滩Fe、Zn与Li相关系数非常显著,归一化后,Cu、Zn的归一化值在15a内相对稳定,其中Cu的波动范围在0.4～2之间,Zn在1.5～2.6之间狭小的范围内波动。分形回归分析结果表明,王港潮滩重金属Cu、Zn归一化值的信息维数高,系统的结构松散,自组织程度低。Cu的分维值范围在5～6.5,平均值为5.8085,Zn的分维值范围在在3～6.5,平均值为4.68。王港潮滩重金属的人为污染较轻,主要受地球化学元素的控制;同时,Pb的归一化值的分维值较低,其分维值范围在2～5.5,平均值为3.608,自组织程度较高,说明存在一定程度的Pb污染。     

Comparative microarray analysis of Arabidopsis thaliana and Arabidopsis halleri roots identifies nicotianamine synthase, a ZIP transporter and other genes as potential metal hyperaccumulation factors

The hyperaccumulation of zinc (Zn) and cadmium (Cd) is a constitutive property of the metallophyte Arabidopsis halleri. We therefore used Arabidopsis GeneChips to identify genes more active in roots of A. halleri as compared to A. thaliana under control conditions. The two genes showing highest expression in A. halleri roots relative to A. thaliana roots out of more than 8000 genes present on the chip encode a nicotianamine (NA) synthase and a putative Zn2+ uptake system. The significantly higher activity of these and other genes involved in metal homeostasis under various growth conditions was confirmed by Northern and RT-PCR analyses. A. halleri roots also show higher NA synthase protein levels. Furthermore, we developed a capillary liquid chromatography electrospray ionization quadrupole time-of-flight mass spectrometry (CapLC-ESI-QTOF-MS)-based NA analysis procedure and consistently found higher NA levels in roots of A. halleri. Expression of a NA synthase in Zn2+-hypersensitive Schizosaccharomyces pombe cells demonstrated that formation of NA can confer Zn2+ tolerance. Taken together, these observations implicate NA in plant Zn homeostasis and NA synthase in the hyperaccumulation of Zn by A. halleri. Furthermore, the results show that comparative microarray analysis of closely related species can be a valuable tool for the elucidation of phenotypic differences between such species.     

Engineering of a Low‐Cost,Highly Active,and Durable Tantalate–Graphene Hybrid Electrocatalyst for Oxygen Reduction

The oxygen reduction reaction (ORR) is one of the most important reactions in renewable energy conversion and storage devices. The full deployment of these devices depends on the development of highly active, stable, and low‐cost catalysts. Herein, a new hybrid material consisting of Na₂Ta₈O_21?x/Ta₂O₅/Ta₃N₅ nanocrystals grown on N‐doped reduced graphene oxide is reported. This catalyst shows a significantly enhanced ORR activity by ≈4 orders of magnitude in acidic media and by ≈2 orders of magnitude in alkaline media compared to individual Na₂Ta₈O_21?x on graphene. Moreover, it has excellent stability in both acid and alkaline media. It also has much better methanol tolerance than the commercial Pt/C, which is relevant to methanol fuel cells. The high ORR activity arises not only from the synergistic effect among the three Ta phases, but also from the concomitant nitrogen doping of the reduced graphene oxide nanosheets. A correlation between ORR activity and nitrogen content is demonstrated. Deep insights into the mechanism of the synergistic effect among these three Ta‐based phases, which boosts the ORR's kinetics, are acquired by combining specific experiments and density functional theory calculations.     

Nanocrystalline Nickel and Cobalt Sulfides Formed by a Heavy Metal-Tolerant,Sulfate-Reducing Enrichment Culture

A soil enrichment culture of the sulfate-reducers Desulfosporosinus auripigmenti and Citrobacter freundii and of fermentative bacteria from a former uranium-mining site was studied for its metal retention potential by promoting metal sulfide precipitation. The culture could tolerate up to 30 mM Ni and 40 mM Co. XRD and TEM analyses revealed the formation of amorphous NiS together with nanocrystalline, metastable α-NiS, and nanocrystalline cobalt pentlandite. The α-NiS with a grain size of 5 nm shows probably an example of size-dependent phase stability and/or specific biomineralization precipitation paths. Detailed mineralogical characterizations are necessary to correctly assess the mineral inventory and thus metal bioavailability.