First-principles calculations for carbyne under strain predict that the Peierls transition from symmetric cumulene to broken-symmetry polyyne structure is enhanced as the material is stretched. ...Interpretation within a simple and instructive analytical model suggests that this behavior is valid for arbitrary 1D metals. Further, numerical calculations of the anharmonic quantum vibrational structure of carbyne show that zero-point atomic vibrations eliminate the Peierls distortion in the mechanically free chain, preserving the cumulene symmetry. The emergence and increase of Peierls dimerization under tension then implies a qualitative transition between the two forms, which our computations place around 3% strain. Thus, the competition between the zero-point vibrations and mechanical strain determines a switch in symmetry resulting in the transition from metallic state to a dielectric, with a small effective mass and a high carrier mobility. In any practical realization, it is important that the effect is also chemically modulated by the choice of terminating groups. These findings are promising for applications such as electromechanical switching and band gap tuning via strain, and besides carbyne itself, they directly extend to numerous other systems that show Peierls distortion.
Nanomaterials are anticipated to be promising storage media, owing to their high surface-to-mass ratio. The high hydrogen capacity achieved by using graphene has reinforced this opinion and motivated ...investigations of the possibility to use it to store another important energy carrier – lithium (Li). While the first-principles computations show that the Li capacity of pristine graphene, limited by Li clustering and phase separation, is lower than that offered by Li intercalation in graphite, we explore the feasibility of modifying graphene for better Li storage. It is found that certain structural defects in graphene can bind Li stably, yet a more efficacious approach is through substitution doping with boron (B). In particular, the layered C3B compound stands out as a promising Li storage medium. The monolayer C3B has a capacity of 714 mAh/g (as Li1.25C3B), and the capacity of stacked C3B is 857 mAh/g (as Li1.5C3B), which is about twice as large as graphite’s 372 mAh/g (as LiC6). Our results help clarify the mechanism of Li storage in low-dimensional materials, and shed light on the rational design of nanoarchitectures for energy storage.
The practical recycling of carbon dioxide (CO2) by the electrochemical reduction route requires an active, stable, and affordable catalyst system. Although noble metals such as gold and silver have ...been demonstrated to reduce CO2 into carbon monoxide (CO) efficiently, they suffer from poor durability and scarcity. Here we report three-dimensional (3D) graphene foam incorporated with nitrogen defects as a metal-free catalyst for CO2 reduction. The nitrogen-doped 3D graphene foam requires negligible onset overpotential (−0.19 V) for CO formation, and it exhibits superior activity over Au and Ag, achieving similar maximum Faradaic efficiency for CO production (∼85%) at a lower overpotential (−0.47 V) and better stability for at least 5 h. The dependence of catalytic activity on N-defect structures is unraveled by systematic experimental investigations. Indeed, the density functional theory calculations confirm pyridinic N as the most active site for CO2 reduction, consistent with experimental results.
The challenge in the electrosynthesis of fuels from CO2 is to achieve durable and active performance with cost-effective catalysts. Here, we report that carbon nanotubes (CNTs), doped with nitrogen ...to form resident electron-rich defects, can act as highly efficient and, more importantly, stable catalysts for the conversion of CO2 to CO. The unprecedented overpotential (−0.18 V) and selectivity (80%) observed on nitrogen-doped CNTs (NCNTs) are attributed to their unique features to facilitate the reaction, including (i) high electrical conductivity, (ii) preferable catalytic sites (pyridinic N defects), and (iii) low free energy for CO2 activation and high barrier for hydrogen evolution. Indeed, DFT calculations show a low free energy barrier for the potential-limiting step to form key intermediate COOH as well as strong binding energy of adsorbed COOH and weak binding energy for the adsorbed CO. The highest selective site toward CO production is pyridinic N, and the NCNT-based electrodes exhibit no degradation over 10 h of continuous operation, suggesting the structural stability of the electrode.
Nitrogen‐doped carbon nanotubes (NCNTs) have been considered as a promising electrocatalyst for carbon‐dioxide‐reduction reactions, but two fundamental chemistry questions remain obscure: 1) What are ...the active centers with respect to various defect species and 2) what is the role of defect density on the selectivity of NCNTs? The aim of this work is to address these questions. The catalytic activity of NCNTs depends on the structural nature of nitrogen in CNTs and defect density. Comparing with pristine CNTs, the presence of graphitic and pyridinic nitrogen significantly decreases the overpotential (ca. −0.18 V) and increases the selectivity (ca. 80 %) towards the formation of CO. The experimental results are in congruent with DFT calculations, which show that pyridinic defects retain a lone pair of electrons that are capable of binding CO2. However, for graphitic‐like nitrogen, electrons are located in the π* antibonding orbital, making them less accessible for CO2 binding.
Useful defects: The electrochemical activity of nitrogen‐doped multiwalled carbon nanotubes (see picture) used for the reduction of CO2 was improved by tuning the nitrogen defect sites in the wall structure. Pyridinic nitrogen defects supported the selective formation of CO. DFT calculations confirmed the experimental results.
Robust underwater superoleophobicity – oil repellence that is stable under loading – is achieved by constructing hierarchical macromolecule‐nanoclay hydrogels (see images), inspired by the ...oil‐repellent nature of the composite surface of fish. The synergetic effect of micro‐/nanostructures and the mechanical strength of hybrid hydrogels in general supports the stability of trapped water on the hydrogel surface, endowing hybid hydrogels with robust superoleophobicity (upper right inset) even under loading forces.
Corn gluten meal (CGM) is an important alternative protein source in aquafeed production. However, in turbot (Scophthalmus maximus), CGM could not be effectively utilized because of its low ...digestibility, the reason for which is still unclear. The purpose of the present study was to investigate and elucidate the cause for the poor utilization of CGM by turbot from the view of gut health. An 8-week feeding trial was conducted with turbot individuals (initial body weight 11.4 ± 0.2 g), which were fed with one of four isonitrogenous and isolipidic diets formulated to include 0%, 21.2%, 31.8%, and 42.6% CGM to progressively replace 0%, 33%, 50%, and 67% fish meal (FM) protein in a FM-based diet, respectively. The results showed that CGM caused dose-dependent decreases in (1) growth performance, nutrient digestibility, and feed utilization; (2) activities of brush-border membrane enzymes; (3) intestinal antioxidant indices of superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase activities, and reduced glutathione level; (4) intestinal immune parameters of acid phosphatase activity, complement 3, complement 4, and IgM concentrations. Dose-dependent increases in the severity of the inflammation, with concomitant alterations on microvilli structure and increasing expression of inflammatory cytokine genes of Il-1β, Il-8, and Tnf-α were observed but without a change in the intracellular junctions and the epithelial permeability established by the plasma diamine oxidase activity and D-lactate level examinations. In conclusion, the present work proved that CGM negatively affected the gut health of turbot by inducing enteritis and by decreasing intestinal immunity and antioxidant capacity, which could be one of the reasons for the reduced utilization of CGM by turbot.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A ubiquitous strategy
to superhydrophobize the surfaces of synthetic hydrogels is reported, creating heterogeneous wettability across the surface and the inner network. Such wetting disparity shows ...significant influence on preventing immediate diffusion of substances between the hydrogel and the aqueous environment on different scales.
Bioinformatics and RT-PCR analysis of RNA from four Lentinula edodes samples identified 22 different virus-like contigs comprising 15 novel and 3 previously reported viruses. We further investigated ...the Lentinula edodes negative-stranded RNA virus 1 (LeNSRV1) isolated from a symptomatic sample, whose virion is a filamentous particle with a diameter of ~15 nm and a length of ~1200 nm. RT-PCR analysis detected LeNSRV1 in 10 of the 56 Chinese L. edodes core collection strains and 6 of the 22 monokaryotic strains from the L. edodes strain HNZMD. Genetic variation analysis showed that the sequences encoding the nucleocapsid protein (ORF2) from all the aforementioned LeNSRV1 positive strains are very conservative. The results presented here may enrich our understanding of L. edodes virus diversity and the characteristics of LeNSRV1, and will promote further research on virus-host interaction in L. edodes.
•( (1) Identification of 22 different virus-like contigs comprising 15 novel viruses in L. edodes.•Firstly exhibit the viral particles of a negative-strand RNA mymonavirus LeNSRV1.•Firstly exhibit of the occurrence and genetic variation of LeNSRV1 in Chinese Lentinula edodes core collection and sexual basidiospores.
•Biochemical and biophysical changes of conifers in cold acclimation and the role of cell wall in the freeze tolerance of conifers were discussed.•Two bioinspired strategies for fabrication of ...anti-freezing gel materials were proposed: (1) suppress the freezing point in a colligative manner, (2) introduce nano-confinement of water molecules between hydrophobic network/moieties to inhibit ice recrystallization and growth.•Emerging applications of anti-freezing multiphase gel materials in the energy storage devices including supercapacitors and batteries, sensors, and biocompatibility related applications are summarized.
Anti-freezing gel materials are an important class of materials that have potential applications in many areas of tissue engineering, soft robots, wearable devices in which ice crystal cannot form or the ice crystal growth is damaging at subzero temperatures. In the increasing need for fabrication of new and innovative anti-freezing soft materials, natural biological systems always provide inspiration and examples that have exceptional hierarchical structural designs and unparalleled performance in freeze-tolerance capabilities. The thoughtful understanding of the freeze-tolerance mechanisms of organisms offers great promise in the synthesis and fabrication of anti-freezing organohydrogels that are difficult to engineer through conventional ideas and approaches. In this review, we propose nature-inspired design principles of anti-freezing gel materials based on the observation of the freeze avoidance/tolerance strategies utilized by various organisms, especially the coniferous trees. Then we detail the pioneering development of anti-freezing multiphase gel material's design and fabrication, and illustrate how these gel materials with unprecedented properties and functionalities can be integrated into devices for various applications under these bioinspired design strategies.
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