Facile Synthesis of Highly Dispersed and Well-Alloyed Bimetallic Nanoparticles on Oxide Support.

Supported alloy catalysts play a pivotal role in many heterogeneous catalytic processes of socioeconomic and environmental importance. But the controlled synthesis of supported alloy nanoparticles with consistent composition and tight size distribution remains a challenging issue. Herein, a simple yet effective method for preparation of highly dispersed, homogeneously alloyed bimetallic nanoparticles on oxide supports is reported. This method is based on solid solution of metal cations in parent oxide and strong electrostatic adsorption of a secondary metal species onto the oxide surface. In the reductive annealing process, hydrogen spillover occurs from the surface metal with a higher reduction potential to the solute metal in solid solution, leading to metal exsolution and homogenous alloying of the metals on the oxide surface. The ceria-supported Ni-Pt alloy is chosen as a model catalyst and hydrazine monohydrate decomposition is chosen as a probe reaction to demonstrate this method, and particularly its advantages over the conventional impregnation and galvanic replacement methods. A systematic application of this method using different oxides and base-noble metal pairs further elucidates its applicability and generality.

[Coexistence strategies of invaded gobies in the Dianchi Lake, Yunnan, China]. / äº‘å—æ»‡æ± å ¥ä¾µè™¾è™Žé±¼ç±»çš„å ±å­˜ç­–ç•¥.

Gobiids are widespread invasive species, with many species from this group usually invade into the same ecosystem simultaneously. Understanding the mechanisms underlying the coexi-stence of different gobiid species in the sympatric habitats is a key issue in fish invasion ecology. Incorporating morphological analyses, spatial distribution survey, and trophic analyses, we examined the coexistence strategy of Mugilogobius myxodermus and related species (the earlier invaders) in Dianchi Lake, Yunnan, China. Our results showed significant differences in morphology and spatial distribution among the four invasive gobies species (i.e., M. myxodermus, Micropercops swinhonis, Rhinogobius giurinus and Rhinogobius cliffordpopei). The spatial niche index of M. myxodermus was the highest. Food composition between M. myxodermus and other gobies was significantly different, with the former mainly feeding on Chydorus ovalis and Cypris sp. The trophic diversity index of M. myxodermus was the highest. Overall, we found that morphological differences, spatial niche diffe-rentiation, and trophic niche differentiation contributed to the coexistence of the gobies in Dianchi Lake, which could help M. myxodermus reduce interspecific competition. Importantly, the feeding strategy is the key factor determining population size and habitas of M. myxodermus during their competition with the other gobies, and finally contributing to the dominant position in the study area.

Sex dimorphism of Yunnanilus analis and its habitat adaptation in Xingyun Lake, Yunnan, China.

Yunnanilus is a group of endemic fish inhabit in Yun-Gui Plateau and its adjacent areas. They show the characteristic of sex dimorphism, which could be an important reason for their adaptation to karst habitats. Here, we used Yunnanilus analis as the model to understand the sex dimorphism characteristics and its adaptation to the karst habitats. The sex dimorphism, female fecundity, and food specialization of Y. analis were investigated in Xingyun Lake, Jiangchuan, Yunnan. Our results showed that Y. analis exhibit sex size dimorphism (sex dimorphism index=0.23; female with larger body size). There were stains on the transverse sections at females body, but not in males. Males had dark longitudinal lines at their body sides. Morphological differences between males and females were confirmed by the results of one-way analyses of variance (ANOVA), multivariate statistical analyses, principal component analyses, discriminant analyses, and one-way analyses of similarity (ANOSIM) on total length, standard body length, fork length, head width vs. heal length, and the distance between the starting point of ventral fin to the starting point of pectoral fin vs. standard body length. Fecundity of female fish was 1364.5±489.3 (470-2430) eggs, which were positively correlated with their body size. Both female and male Y. analis mainly feed on Chironomid larvae and mayfly naiads. Their food composition was somehow similar, with significantly statistical difference. In conclusion, fecundity selection pressure and food specialization should be the main factors contributing to the evolution of Y. analis' sex dimorphism. More importantly, sex dimorphism of Y. analis is a significant adaptation to the karstic habitats.

Free-standing Pt-Ni nanowires catalyst for H2 generation from hydrous hydrazine.

Free-standing Pt-Ni nanowires were fabricated by a one-pot solvothermal method. Nanowires with an optimal Pt/Ni ratio of 1.86 exhibited a high activity and a 100% H2 selectivity for hydrous hydrazine decomposition at mild temperatures, which are comparable to the levels of supported catalysts. Our study reveals for the first time that basic support is not a prerequisite for achieving favorable catalytic performance and provides a renewed perspective for the design of advanced catalysts for on-demand H2 generation from hydrous hydrazine.

NiPt Nanoparticles Anchored onto Hierarchical Nanoporous N-Doped Carbon as an Efficient Catalyst for Hydrogen Generation from Hydrazine Monohydrate.

Catalytic decomposition of the hydrogen-rich hydrazine monohydrate (N2H4·H2O) represents a promising hydrogen storage/production technology. A rational design of advanced N2H4·H2O decomposition catalysts requires an overall consideration of intrinsic activity, number, and accessibility of active sites. We herein report the synthesis of a hierarchically nanostructured NiPt/N-doped carbon catalyst using a three-step method that can simultaneously address these issues. The chelation of metal precursors with polydopamine and thermolysis of the resulting complexes under reductive atmosphere resulted in a concurrent formation of N-doped carbon substrate and catalytically active NiPt alloy nanoparticles. Thanks to the usage of a silica nanosphere template and dopamine precursor, the N-doped carbon substrate possesses a hierarchical macroporous-mesoporous architecture. This, together with the uniform dispersion of tiny NiPt nanoparticles on the carbon substrate, offers opportunity for creating abundant and accessible active sites. Benefiting from these favorable attributes, the NiPt/N-doped carbon catalyst enables a complete and rapid hydrogen production from alkaline N2H4·H2O solution with a rate of 1602 h-1 at 50 °C, which outperforms most existing catalysts for N2H4·H2O decomposition.

[Ecomorphological traits explaining the competition exclusion between Oryzias and mosqui-tofish].

The theory of ecomorphology predicts that species with similar morphological traits can occupy similar ecological niche, which may cause competitive exclusion. To apply this theory into fish invasion ecology research is of significance for understanding the interaction between native and invasive species. Here, we compared the morphological difference between two native (Oryzias pectoralis, Oryzias curvinotus) and one invasive species (Gambusia affinis) to explore the competitive exclusion among them. The results showed that despite O. pectoralis and O. curvinotus were sympa-tric species, they varied in spatial distribution. Such a result supported the theory of ecomorphology, which predicts that two species with similar morphological traits might have strong competition. Moreover, their population density exhibited a significant negative relationship with that of G. affinis. The morphology of G. affinis and both Oryzias species were more similar when comparing to other fish in the assemblage. Results from the cluster analysis showed that G. affinis and Oryzias species were close in a branch, with extremely low spatial niche overlap between invasive mosquitofish and native Oryzias species. There was significant negative correlation between the population abundance of mosquitofish and Oryzias species. All the results suggested that mosquitofish led to population decline of both Oryzias species, due to the ecomorphological similarity. More studies are needed to better understand the mechanisms of G. affinis invasion in habitats of native Oryzias species.

Noble-Metal-Free Ni-W-O-Derived Catalysts for High-Capacity Hydrogen Production from Hydrazine Monohydrate.

Development of active and earth-abundant catalysts is pivotal to render hydrazine monohydrate (N2H4·H2O) viable as a hydrogen carrier. Herein, we report the synthesis of noble-metal-free Ni-W-O-derived catalysts using a hydrothermal method in combination with reductive annealing treatment. Interestingly, the thus-prepared Ni-based catalysts exhibit remarkably distinct catalytic properties toward N2H4·H2O decomposition depending upon the annealing temperature. From a systematic phase/microstructure/chemical state characterization and the first-principles calculations, we found that the variation of the apparent catalytic properties of these Ni-based catalysts should stem from the formation of different Ni-W alloys with distinct intrinsic activity, selectivity, and distribution state. The thereby chosen Ni-W alloy nanocomposite catalyst prepared under an optimized condition showed high activity, nearly 100% selectivity, and excellent stability toward N2H4·H2O decomposition for hydrogen production. Furthermore, this noble-metal-free catalyst enables rapid hydrogen production from commercially available N2H4·H2O solution with an intriguingly high hydrogen capacity of 6.28 wt % and a satisfactory dynamic response property. These results are inspiring and momentous for promoting the use of the N2H4·H2O-based H2 source systems.

Exposure to tetracycline perturbs the microbiome of soil oligochaete Enchytraeus crypticus.

Microbial symbiosis is essential for the normal development and growth of hosts. Past attention has mostly been paid to its effects on plants and vertebrates. The effects of environmental pressures such as antibiotics on the microbiome of soil fauna remain largely elusive. We used bacterial 16S rRNA gene high-throughput sequencing to examine the response of microbiome of soil invertebrate Enchytraeus crypticus to oral tetracycline exposure. After two-week exposure, tetracycline-free oat was used as food to monitor the restoration of E. crypticus microbiome. The results showed that Proteobacteria, Actinobacteria and Planctomycetes were the three dominant phyla in all samples, Rhizobiaceae and Kaistia were the most abundant family and genus in all samples, respectively. After 14 days tetracycline exposure, Planctomycetes declined dramatically from 33.05% to 3.28% (P = 0.016), but Actinobacteria elevated substantially from 2.47% to 23.65% (P = 0.004). The alpha-diversity of microbial community increased significantly after tetracycline exposure compared to the control (P = 0.014). Terminating tetracycline exposure led to the recovery of E. crypticus microbiome back to the background level within 14 days. Our results suggest that while tetracycline can disturb the microbiome in E. crypticus significantly, the effects of the antibiotic on E. crypticus microbiome may not be permanent but reversibly diminish after stopping exposure for a period of time. The results may contribute to extending our understanding of the effect of antibiotics on microbiome of soil invertebrates. CAPSULE: The microbiome of E. crypticus exposed to tetracycline is perturbed and reversibly restored after terminating the exposure.

Tuning the Surface Composition of Ni/meso-CeO2 with Iridium as an Efficient Catalyst for Hydrogen Generation from Hydrous Hydrazine.

Selective decomposition of hydrous hydrazine (N2 H4 ⋅H2 O) over metal catalysts provides a promising means for onboard or portable hydrogen source applications. Studies on N2 H4 ⋅H2 O decomposition catalysts mainly focus on the effects of bulk composition and structure on their performances, instead of the surface-composition-dependent properties. Herein, the synthesis of an Ir-modified Ni/meso-CeO2 catalyst is reported by using a combination of colloidal solution combustion synthesis and galvanic replacement methods. A combination of structural characterization, control experiments, and DFT calculations reveals that the Ni-Ir alloy resulting from calcination treatment exerts a profound effect on the catalytic properties. The resulting Ni@Ni-Ir/meso-CeO2 catalyst shows excellent catalytic performance towards hydrogen generation from N2 H4 ⋅H2 O, which compares favorably with the Ni-Ir bimetallic catalysts reported to date.

1-[6-(Hydroxy-meth-yl)-2-pyrid-yl]-3-(2,4,6-trimethyl-benz-yl)-1H-imidazol-3-ium bromide.

In the title compound, C(19)H(22)N(3)O(+)·Br(-), the imidazole ring is approximately coplanar with the pyridine ring [dihedral angle = 0.88 (13)°] and nearly perpendicular to the benzene ring [dihedral angle = 81.70 (13)°]. O-H⋯Br and C-H⋯Br hydrogen bonding helps to stabilize the crystal structure.