Rumen fermentation affects ruminants productivity and the environmental impact of ruminant production. The release to the atmosphere of methane produced in the rumen is a loss of energy and a cause ...of climate change, and the profile of volatile fatty acids produced in the rumen affects the post-absorptive metabolism of the host animal. Rumen fermentation is shaped by intracellular and intercellular flows of metabolic hydrogen centered on the production, interspecies transfer, and incorporation of dihydrogen into competing pathways. Factors that affect the growth of methanogens and the rate of feed fermentation impact dihydrogen concentration in the rumen, which in turn controls the balance between pathways that produce and incorporate metabolic hydrogen, determining methane production and the profile of volatile fatty acids. A basic kinetic model of competition for dihydrogen is presented, and possibilities for intervention to redirect metabolic hydrogen from methanogenesis toward alternative useful electron sinks are discussed. The flows of metabolic hydrogen toward nutritionally beneficial sinks could be enhanced by adding to the rumen fermentation electron acceptors or direct fed microbials. It is proposed to screen hydrogenotrophs for dihydrogen thresholds and affinities, as well as identifying and studying microorganisms that produce and utilize intercellular electron carriers other than dihydrogen. These approaches can allow identifying potential microbial additives to compete with methanogens for metabolic hydrogen. The combination of adequate microbial additives or electron acceptors with inhibitors of methanogenesis can be effective approaches to decrease methane production and simultaneously redirect metabolic hydrogen toward end products of fermentation with a nutritional value for the host animal. The design of strategies to redirect metabolic hydrogen from methane to other sinks should be based on knowledge of the physicochemical control of rumen fermentation pathways. The application of new -omics techniques together with classical biochemistry methods and mechanistic modeling can lead to exciting developments in the understanding and manipulation of the flows of metabolic hydrogen in rumen fermentation.
A mechanical bond presents a combination of the best features of covalent and supramolecular chemistries (stability and structural integrity), plus a unique dynamic nature, that makes it a very ...interesting tool for materials chemistry. Here, we overview the chemistry of the mechanical bond applied to polymers, metal-organic frameworks (MOFs) and carbon nanotubes. We first describe synthetic strategies towards polycatenanes and polyrotaxanes, and highlight their potential impact in polymer chemistry, exemplified by their use to make stimuli-responsive gels and as binders in battery electrodes. We continue by showing how to include mechanically interlocked components in MOFs, and analyse the distinctive dynamic properties of the final constructs. Finally, we describe the strategies towards mechanically interlocked derivatives of single-walled carbon nanotubes (SWNTs), and discuss the potential of the mechanical bond to tackle some of the classic problems of SWNT chemistry.
An overview of the progress in mechanically interlocked materials is presented. In particular, we focus on polycatenanes, polyrotaxanes, metal-organic rotaxane frameworks (MORFs), and mechanically interlocked derivatives of carbon nanotubes (MINTs).
Custom‐made macrocyclic receptors for fullerenes are proving a valuable alternative to achieve the affinity and selectivity required to meet challenges such as the selective extraction of higher ...fullerenes, their chiral resolution, or the self‐assembly of functional molecular materials. In this Minireview, we highlight some of the important breakthroughs that this class of fullerene hosts has already produced.
All wrapped up: In the field of fullerene recognition, chemists are currently facing new challenges dealing with the selective extraction of higher fullerenes, their chiral resolution, or their organization in molecular materials. In this regard, the new generation of macrocyclic hosts looks particularly promising and has already allowed important breakthroughs.
π-π Interactions are the dominating supramolecular forces in systems like carbon nanostructures, which are inherently constituted by large conjugated π-systems. Their skilful use has allowed the ...construction of fascinating supramolecular ensembles, thus opening a new avenue in carbon chemistry. In this tutorial review, we provide a short introduction to carbon nanostructures, and show the basic concepts of π-π interactions involving fullerenes, carbon nanotubes, and graphene.
A concise tutorial review on the basic concepts of π-π interactions involving fullerenes, carbon nanotubes, and graphene.
In the last five years, we have developed synthetic methods towards encapsulation of single‐walled carbon nanotubes (SWNTs) into organic macrocycles, to form rotaxane‐type molecules. These are the ...first examples of mechanically interlocked SWNT derivatives (MINTs). In this article, the motivation to continue developing the chemistry of SWNTs at a time well past their hype is discussed and our synthetic strategy and characterization methodology is explained in detail, stressing the general aspects. In particular, special emphasis is placed on the importance of adequate control experiments and bulk spectroscopic and analytical data to determine the structure of SWNT derivatives, as opposed to relying only (or mostly) on microscopy. Also our experimental results are used as pretext to reflect on more general/conceptual issues pertaining to the chemistry of SWNTs and mechanically interlocked molecules.
If you liked'em then you should've put a ring on them! In this Concept paper it is discussed why it is interesting to make rotaxane‐type derivatives of single‐walled carbon nanotubes (SWNTs), how to do it, and what they might be useful for.
Maximizing the flow of metabolic hydrogen (H) in the rumen away from CH4 and toward volatile fatty acids (VFA) would increase the efficiency of ruminant production and decrease its environmental ...impact. The objectives of this meta-analysis were: (i) To quantify shifts in metabolic hydrogen sinks when inhibiting ruminal methanogenesis in vitro; and (ii) To understand the variation in shifts of metabolic hydrogen sinks among experiments and between batch and continuous cultures systems when methanogenesis is inhibited. Batch (28 experiments, N = 193) and continuous (16 experiments, N = 79) culture databases of experiments with at least 50% inhibition in CH4 production were compiled. Inhibiting methanogenesis generally resulted in less fermentation and digestion in most batch culture, but not in most continuous culture, experiments. Inhibiting CH4 production in batch cultures resulted in redirection of metabolic hydrogen toward propionate and H2 but not butyrate. In continuous cultures, there was no overall metabolic hydrogen redirection toward propionate or butyrate, and H2 as a proportion of metabolic hydrogen spared from CH4 production was numerically smaller compared to batch cultures. Dihydrogen accumulation was affected by type of substrate and methanogenesis inhibitor, with highly fermentable substrates resulting in greater redirection of metabolic hydrogen toward H2 when inhibiting methanogenesis, and some oils causing small or no H2 accumulation. In both batch and continuous culture, there was a decrease in metabolic hydrogen recovered as the sum of propionate, butyrate, CH4 and H2 when inhibiting methanogenesis, and it is speculated that as CH4 production decreases metabolic hydrogen could be increasingly incorporated into formate, microbial biomass, and perhaps, reductive acetogenesis in continuous cultures. Energetic benefits of inhibiting methanogenesis depended on the inhibitor and its concentration and on the in vitro system.
Schiff-condensation reactions carried out between 1,6-diaminopyrene (DAP) and the tritopical 1,3,5 benzenetricarbaldehyde (BTCA) or 2,4,6-triformylphloroglucinol (TP) ligands give rise to the ...formation of two-dimensional imine-based covalent-organic frameworks (COFs), named IMDEA-COF-1 and -2, respectively. These materials show dramatic layer-packing-driven fluorescence in solid state arising from the three-dimensional arrangement of the pyrene units among layers. Layer stacking within these 2D-COF materials to give either eclipsed or staggered conformations can be controlled, at an atomic level through chemical design of the building blocks used in their synthesis. Theoretical calculations have been used to rationalize the different preferential packing between both COFs. IMDEA-COF-1 shows green emission with absolute photoluminescence quantum yield of 3.5% in solid state. This material represents the first example of imine-linked 2D-COF showing emission in solid state.
The physical properties of ultrathin transition metal dichalcogenides (2D-TMDCs) make them promising candidates as active nanomaterials for catalysis, optoelectronics, and biomedical applications. ...Chemical modification of TMDCs is expected to be key in modifying/adding new functions that will help make such promise a reality. We present a mild method for the modification of the basal planes of 2H-MoS2 and WS2. We exploit the soft nucleophilicity of sulfur to react it with maleimide derivatives, achieving covalent functionalization of 2H-TMDCs under very mild conditions. Extensive characterization proves that the reaction occurs through Michael addition. The orthogonality and versatility of the thiol–ene “click” chemistry is expected to allow the à la carte chemical manipulation of TMDCs.
Single-walled carbon nanotubes (SWNTs) present one of the most interesting collections of properties among nanomaterials. Some sort of chemical modification of SWNTs is often used as a strategy to ...make the most of their intrinsic properties. In the last few years, the mechanical bond has been added to the chemistry toolbox for SWNT modification. In this Tutorial Review, we first discuss the characteristics of the mechanical bond that make it appealing for materials science in general and SWNTs in particular. We then describe the potential advantages of making mechanically-interlocked derivatives of SWNTs (MINTs), as compared to covalent or classic supramolecular derivatives of SWNTs. We go on to explain the different methods of synthesis of MINTs, highlighting their common features as an indication towards possible future synthetic strategies. Finally, we illustrate with examples how the making of MINTs can contribute to modifying the surface properties of SWNTs, modulating their electronic properties, and linking them to functional molecular fragments. The overall objective of this Review is to introduce the reader to the application of the chemistry of the mechanical bond to SWNTs: why it is relevant, how it is done in practice, what it has shown already as potential contributions towards applications, and what could be done in the future.
An introduction to mechanically interlocked derivatives of single-walled carbon nanotubes: their main structural features, their potential advantages compared to covalent and supramolecular derivatives, how to synthesize them, and their most promising fields for application.
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