Multi-active Site Dynamics on a Molecular Cr/Co/Se Cluster Catalyst

This study provides detailed insights into the interconnected reactivity of the three catalytically active sites of an atomically precise nanocluster Cr3(py)3Co6Se8L6 (Cr3(py)3, L = Ph2PNTol–, Ph = phenyl, Tol = 4-tolyl). Catalytic and stoichiometric studies into tosyl azide activation and carbodiimide formation enabled the isolation and crystallographic characterization of key metal-nitrenoid catalytic intermediates, including the tris(nitrenoid) cluster Cr3(NTs)3, the catalytic resting state Cr3(NTs)3(CNtBu)3, and the mono(nitrenoid) cluster Cr3(NTs)(CNtBu)2. Nitrene transfer proceeds via a stepwise mechanism, with the three active sites engaging sequentially to produce carbodiimide. Comparative structural analysis and CNtBu bind-ing studies reveal that the chemical state of neighboring active sites regulates the affinity for substrates of an individual Cr-nitrenoid edge site, intertwining their reactivity through the inorganic support.

Life on the edge: behavioural and physiological responses of Verreaux's sifakas (<i>Propithecus verreauxi</i>) to forest edges

Forest edges change micro-environmental conditions, thereby affecting the ecology of many forest-dwelling species. Understanding such edge effects is particularly important for Malagasy primates because many of them live in highly fragmented forests today. The aim of our study was to assess the influence of forest edge effects on activity budgets, feeding ecology, and stress hormone output (measured as faecal glucocorticoid metabolite – fGCM – levels) in wild Verreaux's sifakas (Propithecus verreauxi), a group living, arboreal lemur. We observed five habituated groups: three living in the forest interior and two at an established forest edge. There was no difference in average daily temperatures between edge and interior habitats; however, within the edge site, the average daily temperature incrementally increased over 450 m from the forest edge towards the interior forest of the edge habitat, and the population density was lower at the edge site. Activity budgets differed between groups living in the two microhabitats, with individuals living near the edge spending more time travelling and less time feeding. Groups living near the edge also tended to have smaller home ranges and core areas than groups in the forest interior. In addition, edge groups had elevated average fGCM concentrations, and birth rates were lower for females living in the edge habitat. Combined with lower levels of fruit consumption at the edge, these results suggest that nutritional stress might be a limiting factor for Verreaux's sifakas when living near a forest edge. Hence, Verreaux's sifakas appear to be sensitive to microhabitat characteristics linked to forest edges; a result with implications for the conservation of this critically endangered lemurid species.

A Batch Experiment of Cesium Uptake Using Illitic Clays with Different Degrees of Crystallinity

Radiocesium released by the severe nuclear accident and nuclear weapon test is a hazardous material. Illitic clays play a key role in the spatial distribution of radiocesium in groundwater environments due to selective uptake sites at the illite mineral, such as frayed edge sites. However, the cesium uptake capabilities of illitic clays are diverse, which could be associated with the illite crystallinity. This study was performed to determine the cesium uptake of illitic clays and evaluate the crystallinity effects on cesium uptake using statistical approaches. A total of 10 illitic clays showed various crystallinity, which was parameterized by the full width at half maximum (FWHM) at 10 Å XRD peak ranging from 0.15 to 0.64. The uptake behavior of illitic clays was well fitted with the Freundlich model (i.e., r2 > 0.946). The uptake efficiency of illitic clays increased with the decrease in dissolved cesium concentrations. The cesium uptake was significantly correlated with the FWHM and cation exchange capacity, suggesting that the uptake becomes higher with decreasing crystallinity through expansion of the edge site and/or formation of ion-exchangeable sites.

Corrosion resistant fluorine-doped graphene nanoribbons for an highly durable PEMFC: combined experiment and ab-initio studies

Pt-supported carbon material-based electrocatalysts are formidably suffering from carbon corrosion when H2O and O2 molecules are present at high voltages in PEMFC. In this study, we discovered that the edge site of a fluorine-doped graphene nanoribbon (F-GNR) was slightly adsorbed with H2O and thermodynamically unfavorable with O atoms after defining the thermodynamically stable structure of F-GNR from DFT calculations. Based on computational predictions, the physicochemical and electrochemical properties of F-GNRs with/without Pt nanoparticles derived from a modified Hummer’s method and the polyol process were investigated as support materials for electrocatalysts and additives in the cathode of a PEMFC, respectively. Pt/F-GNR showed the lowest degradation rate in carbon corrosion, and was effective in the cathode as additives, resulting from the enhanced carbon corrosion durability owing to the improved structural stability and water management. Notably, F-GNR with highly stable carbon corrosion contributed to achieving a more durable PEMFC for long-term operation.

Structures, electronic and magnetic properties of transition metals-doped Mg9O9 tubular clusters

The structures, electronic and magnetic attributes of the transition metal (TM) doping Mg9O9 tubular clusters have been investigated using the PBE functional. The results display that the ScMg9O9 and NiMg9O9 clusters are more structurally stable than the other TMMg9O9 clusters. An Sc atom replaces the Mg atom at the edge site of the Mg9O9 clusters, which leads to the Mg atom transferring to the top of an adjacent O atom. Ni atom prefers to occupy the bridge site of the Mg–O bond at a side of the Mg9O9 clusters. VMg9O9 and FeMg9O9 display more kinetic activity than the other TMMg9O9 clusters. The TM atoms lost certain electrons except for Co, Cu and Zn. The maximum spin value of the TM atoms for the ground-state TMMg9O9 clusters occurs at Mn.