Showing papers by "Jun Lu published in 2017"
TL;DR: This work designs a parent 3D atomic laminate, (Mo2/3Sc1/3)2AlC, with in-plane chemical ordering, and by selectively etching the Al and Sc atoms, shows evidence for 2D Mo1.33C sheets with ordered metal divacancies and high electrical conductivities.
Abstract: The exploration of two-dimensional solids is an active area of materials discovery. Research in this area has given us structures spanning graphene to dichalcogenides, and more recently 2D transition metal carbides (MXenes). One of the challenges now is to master ordering within the atomic sheets. Herein, we present a top-down, high-yield, facile route for the controlled introduction of ordered divacancies in MXenes. By designing a parent 3D atomic laminate, (Mo2/3Sc1/3)2AlC, with in-plane chemical ordering, and by selectively etching the Al and Sc atoms, we show evidence for 2D Mo1.33C sheets with ordered metal divacancies and high electrical conductivities. At ∼1,100 F cm−3, this 2D material exhibits a 65% higher volumetric capacitance than its counterpart, Mo2C, with no vacancies, and one of the highest volumetric capacitance values ever reported, to the best of our knowledge. This structural design on the atomic scale may alter and expand the concept of property-tailoring of 2D materials. Vacancies in 2D materials can influence their properties, however controlling their formation remains a challenge. Here the authors show that selective etching of a 3D laminate with in-plane chemical ordering results in formation of MXenes with ordered divacancies, as well as elevated conductance and supercapacitance.
461 citations
TL;DR: In this article, a template-directed polymerization of cobalt phthalocyanine on carbon nanotubes for a high-performance CO 2 reduction reaction was proposed, which can selectively reduce CO 2 to CO with a large faradic efficiency (∼90%), exceptional turnover frequency (4,900hr −1 at η ǫ = 0.5 V), and excellent longterm durability.
339 citations
TL;DR: In this paper, Li foils are simply burned in a CS 2 vapour for the cathode design, which shows promising battery performance and can be used in the commercialization of Li-S batteries.
Abstract: Facile and scalable fabrication of high-performing sulfur cathodes is challenging in the commercialization of Li–S batteries. The authors report a strategy of simply burning Li foils in a CS 2 vapour for the cathode design, which shows promising battery performa…
329 citations
TL;DR: In this paper, the authors review recent progress in the development and application of advanced characterization techniques such as in situ transmission electron microscopy for high-performance lithium-ion batteries, using three representative electrode systems, and discuss how these tools help researchers understand the battery process and design better battery systems.
Abstract: To meet future needs for industries from personal devices to automobiles, state-of-the-art rechargeable lithium-ion batteries will require both improved durability and lowered costs. To enhance battery performance and lifetime, understanding electrode degradation mechanisms is of critical importance. Various advanced in situ and operando characterization tools developed during the past few years have proven indispensable for optimizing battery materials, understanding cell degradation mechanisms, and ultimately improving the overall battery performance. Here we review recent progress in the development and application of advanced characterization techniques such as in situ transmission electron microscopy for high-performance lithium-ion batteries. Using three representative electrode systems—layered metal oxides, Li-rich layered oxides and Si-based or Sn-based alloys—we discuss how these tools help researchers understand the battery process and design better battery systems. We also summarize the application of the characterization techniques to lithium–sulfur and lithium–air batteries and highlight the importance of those techniques in the development of next-generation batteries.
312 citations
TL;DR: In this paper, the authors summarized the scientific discoveries enabled by in situ transmission electron microscopy, and specifically emphasized the applicability of this technique to address the critical challenges in the rechargeable ion battery electrodes, electrolyte and their interfaces.
Abstract: An in-depth understanding of material behaviours under complex electrochemical environment is critical for the development of advanced materials for the next-generation rechargeable ion batteries. The dynamic conditions inside a working battery had not been intensively explored until the advent of various in situ characterization techniques. Real-time transmission electron microscopy of electrochemical reactions is one of the most significant breakthroughs poised to enable radical shift in our knowledge on how materials behave in the electrochemical environment. This review, therefore, summarizes the scientific discoveries enabled by in situ transmission electron microscopy, and specifically emphasizes the applicability of this technique to address the critical challenges in the rechargeable ion battery electrodes, electrolyte and their interfaces. New electrochemical systems such as lithium–oxygen, lithium–sulfur and sodium ion batteries are included, considering the rapidly increasing application of in situ transmission electron microscopy in these areas. A systematic comparison between lithium ion-based electrochemistry and sodium ion-based electrochemistry is also given in terms of their thermodynamic and kinetic differences. The effect of the electron beam on the validity of in situ observation is also covered. This review concludes by providing a renewed perspective for the future directions of in situ transmission electron microscopy in rechargeable ion batteries. In situ TEM is a powerful tool that helps to understand energy storage behaviors of various materials. This review summarizes the critical discoveries, enabled by in situTEM, in rechargeable ion batteries, and foresees its bright future for extensive applications.
282 citations
TL;DR: In this article, a facile and binder-free method is developed for the in situ and horizontal growth of ultrathin mesoporous Co3O4 layers on the surface of carbon fibers in the carbon cloth (ultrathin Co 3O4/CC) as high-performance air electrode for the flexible Zn-air battery.
Abstract: A facile and binder-free method is developed for the in situ and horizontal growth of ultrathin mesoporous Co3O4 layers on the surface of carbon fibers in the carbon cloth (ultrathin Co3O4/CC) as high-performance air electrode for the flexible Zn–air battery. In particular, the ultrathin Co3O4 layers have a maximum contact area on the conductive support, facilitating the rapid electron transport and preventing the aggregation of ultrathin layers. The ultrathin feature of Co3O4 layers is characterized by the transmission electron microscopy, Raman spectra, and X-ray absorption fine structure spectroscopy. Benefiting from the high utilization degree of active materials and rapid charge transport, the mass activity for oxygen reduction and evolution reactions of the ultrathin Co3O4/CC electrode is more than 10 times higher than that of the carbon cloth loaded with commercial Co3O4 nanoparticles. Compared to the commercial Co3O4/CC electrode, the flexible Zn–air battery using ultrathin Co3O4/CC electrode exhibits excellent rechargeable performance and high mechanical stability. Furthermore, the flexible Zn–air battery is integrated with a flexible display unit. The whole integrated device can operate without obvious performance degradation under serious deformation and even during the cutting process, which makes it highly promising for wearable and roll-up optoelectronics.
282 citations
TL;DR: A battery that reversibly intercalates magnesium monochloride cations with excellent rate and cycle performances in addition to the large capacity is shown.
Abstract: Magnesium rechargeable batteries potentially offer high-energy density, safety, and low cost due to the ability to employ divalent, dendrite-free, and earth-abundant magnesium metal anode. Despite recent progress, further development remains stagnated mainly due to the sluggish scission of magnesium-chloride bond and slow diffusion of divalent magnesium cations in cathodes. Here we report a battery chemistry that utilizes magnesium monochloride cations in expanded titanium disulfide. Combined theoretical modeling, spectroscopic analysis, and electrochemical study reveal fast diffusion kinetics of magnesium monochloride cations without scission of magnesium-chloride bond. The battery demonstrates the reversible intercalation of 1 and 1.7 magnesium monochloride cations per titanium at 25 and 60 °C, respectively, corresponding to up to 400 mAh g−1 capacity based on the mass of titanium disulfide. The large capacity accompanies with excellent rate and cycling performances even at room temperature, opening up possibilities for a variety of effective intercalation hosts for multivalent-ion batteries. Magnesium rechargeable batteries potentially offer high-energy density, safety, and low cost. Here the authors show a battery that reversibly intercalates magnesium monochloride cations with excellent rate and cycle performances in addition to the large capacity.
274 citations
TL;DR: An important innate immune signalling pathway that functions in intestinal epithelial cells and may present useful targets in the modulation of host defences against viral pathogens is highlighted.
Abstract: Rotavirus, a leading cause of severe gastroenteritis and diarrhoea in young children, accounts for around 215,000 deaths annually worldwide. Rotavirus specifically infects the intestinal epithelial cells in the host small intestine and has evolved strategies to antagonize interferon and NF-κB signalling, raising the question as to whether other host factors participate in antiviral responses in intestinal mucosa. The mechanism by which enteric viruses are sensed and restricted in vivo, especially by NOD-like receptor (NLR) inflammasomes, is largely unknown. Here we uncover and mechanistically characterize the NLR Nlrp9b that is specifically expressed in intestinal epithelial cells and restricts rotavirus infection. Our data show that, via RNA helicase Dhx9, Nlrp9b recognizes short double-stranded RNA stretches and forms inflammasome complexes with the adaptor proteins Asc and caspase-1 to promote the maturation of interleukin (Il)-18 and gasdermin D (Gsdmd)-induced pyroptosis. Conditional depletion of Nlrp9b or other inflammasome components in the intestine in vivo resulted in enhanced susceptibility of mice to rotavirus replication. Our study highlights an important innate immune signalling pathway that functions in intestinal epithelial cells and may present useful targets in the modulation of host defences against viral pathogens.
252 citations
TL;DR: The remarkably high photoelectrochemical and photocatalytic performances of the heterojunctions are mainly attributed to the synergetic effect of efficient photogenerated electron-hole separation, decreased electron transfer resistance from interfacial chemical hydroxy residue bonds, and oxidizing groups originating from Ti3+-TiO2 and O-g-C3N4.
Abstract: To improve the utilization of visible light and reduce photogenerated electron/hole recombination, Ti3+ self-doped TiO2/oxygen-doped graphitic carbon nitride (Ti3+-TiO2/O-g-C3N4) heterojunctions were prepared via hydrothermal treatment of a mixture of g-C3N4 and titanium oxohydride sol obtained from the reaction of TiH2 with H2O2. In this way, exfoliated O-g-C3N4 and Ti3+-TiO2 nanoparticles were obtained. Simultaneously, strong bonding was formed between Ti3+-TiO2 nanoparticles and exfoliated O-g-C3N4 during the hydrothermal process. Charge transfer and recombination processes were characterized by transient photocurrent responses, electrochemical impedance test, and photoluminescence spectroscopy. The photocatalytic performances were investigated through rhodamine B degradation test under an irradiation source based on 30 W cold visible-light-emitting diode. The highest visible-light photoelectrochemical and photocatalytic activities were observed from the heterojunction with 1:2 mass ratio of Ti3+-TiO2 ...
236 citations
TL;DR: This review will discuss methods to conquer challenges of susceptibility to nuclease degradation, rapid excretion through renal filtration and insufficient binding affinity, and highlight recent developments of chemical modifications and technological advances that may enable early aptamers to be translated into clinical therapeutics.
Abstract: Nucleic acid aptamers have minimal immunogenicity, high chemical synthesis production, low cost and high chemical stability when compared with antibodies. However, the susceptibility to nuclease degradation, rapid excretion through renal filtration and insufficient binding affinity hindered their development as drug candidates for therapeutic applications. In this review, we will discuss methods to conquer these challenges and highlight recent developments of chemical modifications and technological advances that may enable early aptamers to be translated into clinical therapeutics.
208 citations
TL;DR: By localizing the encapsulated MNPs closer to the surface of MOFs, the resultant MNPs@MOF composites not only exhibit effective selectivity derived from MOF cavities, but also enhanced catalytic activity due to the spatial regulation of MNPs as close as possible to the MOF surface.
Abstract: Composites incorporating metal nanoparticles (MNPs) within metal-organic frameworks (MOFs) have broad applications in many fields. However, the controlled spatial distribution of the MNPs within MOFs remains a challenge for addressing key issues in catalysis, for example, the efficiency of catalysts due to the limitation of molecular diffusion within MOF channels. Here we report a facile strategy that enables MNPs to be encapsulated into MOFs with controllable spatial localization by using metal oxide both as support to load MNPs and as a sacrificial template to grow MOFs. This strategy is versatile to a variety of MNPs and MOF crystals. By localizing the encapsulated MNPs closer to the surface of MOFs, the resultant MNPs@MOF composites not only exhibit effective selectivity derived from MOF cavities, but also enhanced catalytic activity due to the spatial regulation of MNPs as close as possible to the MOF surface.
TL;DR: An effective strategy combining anion substitution, defect engineering, and the dopant effect to address the above two critical issues is shown and this strategy is demonstrated on a hybrid catalyst consisting of sulfur-deficient cobalt oxysulfide single crystals and nitrogen-doped graphene nanomeshes.
Abstract: A critical bottleneck limiting the performance of rechargeable zinc-air batteries lies in the inefficient bifunctional electrocatalysts for the oxygen reduction and evolution reactions at the air electrodes. Hybridizing transition-metal oxides with functional graphene materials has shown great advantages due to their catalytic synergism. However, both the mediocre catalytic activity of metal oxides and the restricted 2D mass/charge transfer of graphene render these hybrid catalysts inefficient. Here, an effective strategy combining anion substitution, defect engineering, and the dopant effect to address the above two critical issues is shown. This strategy is demonstrated on a hybrid catalyst consisting of sulfur-deficient cobalt oxysulfide single crystals and nitrogen-doped graphene nanomeshes (CoO0.87 S0.13 /GN). The defect chemistries of both oxygen-vacancy-rich, nonstoichiometric cobalt oxysulfides and edge-nitrogen-rich graphene nanomeshes lead to a remarkable improvement in electrocatalytic performance, where CoO0.87 S0.13 /GN exhibits strongly comparable catalytic activity to and much better stability than the best-known benchmark noble-metal catalysts. In application to quasi-solid-state zinc-air batteries, CoO0.87 S0.13 /GN as a freestanding catalyst assembly benefits from both structural integrity and enhanced charge transfer to achieve efficient and very stable cycling operation over 300 cycles with a low discharge-charge voltage gap of 0.77 V at 20 mA cm-2 under ambient conditions.
TL;DR: A water-soluble nucleolin aptamer-paclitaxel conjugate that selectively accumulates in ovarian tumor issues displaying reduced toxicity and improved activity profiles is reported.
Abstract: Paclitaxel (PTX) is among the most commonly used first-line drugs for cancer chemotherapy. However, its poor water solubility and indiscriminate distribution in normal tissues remain clinical challenges. Here we design and synthesize a highly water-soluble nucleolin aptamer-paclitaxel conjugate (NucA-PTX) that selectively delivers PTX to the tumor site. By connecting a tumor-targeting nucleolin aptamer (NucA) to the active hydroxyl group at 2' position of PTX via a cathepsin B sensitive dipeptide bond, NucA-PTX remains stable and inactive in the circulation. NucA facilitates the uptake of the conjugated PTX specifically in tumor cells. Once inside cells, the dipeptide bond linker of NucA-PTX is cleaved by cathepsin B and then the conjugated PTX is released for action. The NucA modification assists the selective accumulation of the conjugated PTX in ovarian tumor tissue rather than normal tissues, and subsequently resulting in notably improved antitumor activity and reduced toxicity.
TL;DR: A short review of state-of-the-art research advances in rational design of diverse Bi2×3 electrodes and their electrochemical energy storage performance for H, Li, and Na and supercapacitors is presented in this paper.
TL;DR: In this article, the effect of GOPS on the electrical and electronic properties of poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonate) (PEDOT:PSS) was investigated.
Abstract: Poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonate) (PEDOT:PSS) has been reported as a successful functional material in a broad variety of applications. One of the most important advantages of PEDOT:PSS is its water-solubility, which enables simple and environmental friendly manufacturing processes. Unfortunately, this also implies that pristine PEDOT:PSS films are unsuitable for applications in aqueous environments. To reach stability in polar solvents, (3-glycidyloxypropyl)trimethoxysilane (GOPS) is typically used to cross-link PEDOT:PSS. Although this strategy is widely used, its mechanism and effect on PEDOT:PSS performance have not been articulated yet. Here, we present a broad study that provides a better understanding of the effect of GOPS on the electrical and electronic properties of PEDOT:PSS. We show that the GOPS reacts with the sulfonic acid group of the excess PSS, causing a change in the PEDOT:PSS film morphology, while the oxidation level of PEDOT remains unaffected. This is at the origin of the observed conductivity changes. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 814–820
TL;DR: In this paper, a phase of molybdenum sulfide (amorphous chain-like MoS3) was used as an anode material of a Na3V2(PO4)3 cathode to achieve high capacity and cycling stability.
Abstract: The search for earth-abundant and high-performance electrode materials for sodium-ion batteries represents an important challenge to current battery research. 2D transition metal dichalcogenides, particularly MoS2, have attracted increasing attention recently, but few of them so far have been able to meet expectations. In this study, it is demonstrated that another phase of molybdenum sulfide—amorphous chain-like MoS3—can be a better choice as the anode material of sodium-ion batteries. Highly compact MoS3 particles infiltrated with carbon nanotubes are prepared via the facile acid precipitation method in ethylene glycol. Compared to crystalline MoS2, the resultant amorphous MoS3 not only exhibits impressive gravimetric performance—featuring excellent specific capacity (≈615 mA h g−1), rate capability (235 mA h g−1 at 20 A g−1), and cycling stability but also shows exceptional volumetric capacity of ≈1000 mA h cm−3 and an areal capacity of >6.0 mA h cm−2 at very high areal loadings of active materials (up to 12 mg cm−2). The experimental results are supported by density functional theory simulations showing that the 1D chains of MoS3 can facilitate the adsorption and diffusion of Na+ ions. At last, it is demonstrated that the MoS3 anode can be paired with an Na3V2(PO4)3 cathode to afford full cells with great capacity and cycling performance.
TL;DR: In this paper, a MAX phase alloy with out-of-plane chemical order, Mo2ScAlC2, was presented, with a formation enthalpy of −−24meV/atom.
TL;DR: Amorphous MoS3 largely preserves its chain-like structure during repetitive battery cycling without generating any free polysulfide intermediates and is also fully cyclable in the carbonate electrolyte under a relatively high temperature of 55 °C.
Abstract: Many problems associated with Li–S and Na–S batteries essentially root in the generation of their soluble polysulfide intermediates. While conventional wisdom mainly focuses on trapping polysulfides at the cathode using various functional materials, few strategies are available at present to fully resolve or circumvent this long-standing issue. In this study, we propose the concept of sulfur-equivalent cathode materials, and demonstrate the great potential of amorphous MoS 3 as such a material for room-temperature Li–S and Na–S batteries. In Li–S batteries, MoS 3 exhibits sulfur-like behavior with large reversible specific capacity, excellent cycle life, and the possibility to achieve high areal capacity. Most remarkably, it is also fully cyclable in the carbonate electrolyte under a relatively high temperature of 55 °C. MoS 3 can also be used as the cathode material of even more challenging Na–S batteries to enable decent capacity and good cycle life. Operando X-ray absorption spectroscopy (XAS) experiments are carried out to track the structural evolution of MoS 3 . It largely preserves its chain-like structure during repetitive battery cycling without generating any free polysulfide intermediates.
TL;DR: A Na-ion solid-state electrolyte, Na3 P0.62 As0.38 S4, is developed with an exceptionally high conductivity and enhanced moisture stability and dual effects of alloying element As (lattice expansion and a weaker AsS bond strength) are responsible for the superior conductivity.
Abstract: A Na-ion solid-state electrolyte, Na3 P0.62 As0.38 S4 , is developed with an exceptionally high conductivity of 1.46 mS cm-1 at 25 °C and enhanced moisture stability. Dual effects of alloying element As (lattice expansion and a weaker AsS bond strength) are responsible for the superior conductivity. Improved moisture stability is regulated by shifting low-energy moisture reactions to high-energy ones due to As.
TL;DR: It is indicated that NAFPD is a frequent clinical entity, associated with significantly increased risk of metabolic syndrome and its components, and the normal pancreatic fat percentage threshold of 6.2% may be recommended for use in future prospective studies.
Abstract: Objective Growing evidence suggests that individuals with excessive fat in the pancreas are at an increased risk of chronic metabolic disorders. The aim was to systematically review studies on non-alcoholic fatty pancreas disease (NAFPD) with a view to determine its prevalence, associations with metabolic co-morbidities, and to suggest normal pancreatic fat percentage threshold. Methods Three electronic databases (MEDLINE, Scopus, and Embase) were queried. Studies in humans were eligible for inclusion if they provided data on NAFPD and/or pancreatic fat percentage. Where possible, data were pooled using random-effects meta-analysis and the effect of covariates analysed using meta-regression. Results Pooling data on pancreatic fat percentage from nine studies (1209 healthy individuals who underwent magnetic resonance imaging), yielded the weighted mean and weighted standard deviation of 4.48% and 0.87%, respectively. Pooling data on NAFPD from eleven studies (12,675 individuals), yielded the pooled prevalence of 33% (95% confidence interval, 24% - 41%). Meta-regression analysis showed that the prevalence of NAFPD was independent of age and sex. The presence of NAFPD was associated with a significantly increased risk of arterial hypertension (risk ratio 1.67; 95% confidence interval, 1.32–2.10; p Conclusion The findings indicate that NAFPD is a frequent clinical entity, associated with significantly increased risk of metabolic syndrome and its components. The normal pancreatic fat cut-off point of 6.2% may be recommended for use in future prospective studies.
TL;DR: The results show that 2D holey ACN maintained the holey morphology at different sodiation stages because Co3O4 are converted to extremely small interconnected Co nanoparticles and these Co nanoparticle could be well dispersed in a Na2O matrix.
Abstract: A general template-directed strategy is developed for the controlled synthesis of two-dimensional (2D) assembly of Co3O4 nanoparticles (ACN) with unique holey architecture and tunable hole sizes that enable greatly improved alkali-ion storage properties (demonstrated for both Li and Na ion storage) The as-synthesized holey ACN with 10 nm holes exhibit excellent reversible capacities of 1324 mAh/g at 04 A/g and 566 mAh/g at 01 A/g for Li and Na ion storage, respectively The improved alkali-ion storage properties are attributed to the unique interconnected holey framework that enables efficient charge/mass transport as well as accommodates volume expansion In situ TEM characterization is employed to depict the structural evolution and further understand the structural stability of 2D holey ACN during the sodiation process The results show that 2D holey ACN maintained the holey morphology at different sodiation stages because Co3O4 are converted to extremely small interconnected Co nanoparticles and th
TL;DR: It is shown that crystalline 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA), an organic solid, is highly amenable to host divalent metal ions, i.e., Mg2+ and Ca2+, in aqueous electrolytes, where the van der Waals structure is intrinsically superior in hosting charge-dense ions.
Abstract: We report that crystalline 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA), an organic solid, is highly amenable to host divalent metal ions, i.e., Mg2+ and Ca2+, in aqueous electrolytes, where the van der Waals structure is intrinsically superior in hosting charge-dense ions. We observe that the divalent nature of Mg2+ causes unique squeezing deformation of the electrode structure, where it contracts and expands in different crystallographic directions when hosting the inserted Mg-ions. This phenomenon is revealed experimentally by ex situ X-ray diffraction and transmission electron microscopy, and is investigated theoretically by first-principles calculations. Interestingly, hosting one Mg2+ ion requires the coordination from three PTCDA molecules in adjacent columns of stacked molecules, which rotates the columns, thus reducing the (011) spacing but increasing the (021) spacing. We demonstrate that a PTCDA Mg-ion electrode delivers a reversible capacity of 125 mA h g–1, which may include a minor c...
TL;DR: In this paper, a review focuses on recent developments in the last three years of various sulfur integration methods at the cathode that result in improved electrochemical performance, increased energy density, cyclic stability, and a higher capacity over the mainstream lithium-ion battery.
Abstract: The lithium-ion battery, with a relatively small energy density of ∼250 W h kg−1, has dominantly powered many devices requiring small energy demands. However, there remains a need for a cheaper and smaller type of battery with higher energy density for energy-intensive storage purposes in the automotive, aircraft, and household energy sectors. With its higher specific capacity (1675 mA h g−1) and lower costs, the lithium–sulfur (Li–S) battery represents the most promising next generation battery. The main focus of scientific inquiry surrounding Li–S batteries lies at the cathode, where sulfur chemically bonds to lithium. Current challenges pertaining to the high performance cathode such as the dissolution of sulfur into the electrolyte and electrode volume changes are highlighted. This review focuses on recent developments in the last three years of various sulfur integration methods at the cathode that result in improved electrochemical performance, increased energy density, cyclic stability, and a higher capacity over the mainstream lithium-ion battery. In particular, the most recent approaches were systematically examined and compared including the use of carbon and non-carbon composites to stabilize sulfur. Ideal material hosts for sulfur atoms in the cathode for outstanding Li–S batteries were outlined and thoroughly discussed. Critical understanding and relevant knowledge were summarized aiming to provide general guidance for rational design of high-performance cathodes for advanced Li–S batteries.
TL;DR: Predictive theory and verifying materials synthesis indicate a potentially large family of thermodynamically stable phases, with Kagomé-like and in-plane chemical ordering, and with incorporation of elements previously not known for MAX phases, including the common Y.
Abstract: The enigma of MAX phases and their hybrids prevails. We probe transition metal (M) alloying in MAX phases for metal size, electronegativity, and electron configuration, and discover ordering in these MAX hybrids, namely, (V2/3Zr1/3)2AlC and (Mo2/3Y1/3)2AlC. Predictive theory and verifying materials synthesis, including a judicious choice of alloying M from groups III to VI and periods 4 and 5, indicate a potentially large family of thermodynamically stable phases, with Kagome-like and in-plane chemical ordering, and with incorporation of elements previously not known for MAX phases, including the common Y. We propose the structure to be monoclinic C2/c. As an extension of the work, we suggest a matching set of novel MXenes, from selective etching of the A-element. The demonstrated structural design on simultaneous two-dimensional (2D) and 3D atomic levels expands the property tuning potential of functional materials.
TL;DR: An induced-fit conformational coupling between the partial agonist and AgoPAM binding sites is revealed, involving rearrangements of the transmembrane helices 4 and 5 (TM4 and TM5) and transition of the intracellular loop 2 (ICL2) into a short helix and likely prime GPR40 to a more active-like state and explain the binding cooperativity between these ligands.
Abstract: Clinical studies indicate that partial agonists of the G-protein-coupled, free fatty acid receptor 1 GPR40 enhance glucose-dependent insulin secretion and represent a potential mechanism for the treatment of type 2 diabetes mellitus. Full allosteric agonists (AgoPAMs) of GPR40 bind to a site distinct from partial agonists and can provide additional efficacy. We report the 3.2-A crystal structure of human GPR40 (hGPR40) in complex with both the partial agonist MK-8666 and an AgoPAM, which exposes a novel lipid-facing AgoPAM-binding pocket outside the transmembrane helical bundle. Comparison with an additional 2.2-A structure of the hGPR40-MK-8666 binary complex reveals an induced-fit conformational coupling between the partial agonist and AgoPAM binding sites, involving rearrangements of the transmembrane helices 4 and 5 (TM4 and TM5) and transition of the intracellular loop 2 (ICL2) into a short helix. These conformational changes likely prime GPR40 to a more active-like state and explain the binding cooperativity between these ligands.
TL;DR: The present results, by combined analytical electron microscopy and ab initio calculations, open avenues for processing of noble-metal-containing layered ceramics that have not been synthesized from elemental sources, along with tunable properties such as stable electrical contacts for high-temperature power electronics or gas sensors.
Abstract: Substitution of Si with Au and Ir in Ti3SiC2 through a solid-state diffusion process allows the synthesis of Ti3AuC2, Ti3Au2C2 and Ti3IrC2 phases able to form Ohmic contacts with SiC stable at high temperatures under ambient air conditions.
TL;DR: In this paper, simultaneous anionic and cationic redox reactions in Li5FeO4 electrodes have been reported, which enables its high capacity and eliminates the undesired oxygen gas release.
Abstract: Anionic redox reactions in cathodes of lithium-ion batteries are allowing opportunities to double or even triple the energy density. However, it is still challenging to develop a cathode, especially with Earth-abundant elements, that enables anionic redox activity for real-world applications, primarily due to limited strategies to intercept the oxygenates from further irreversible oxidation to O2 gas. Here we report simultaneous iron and oxygen redox activity in a Li-rich anti-fluorite Li5FeO4 electrode. During the removal of the first two Li ions, the oxidation potential of O2− is lowered to approximately 3.5 V versus Li+/Li0, at which potential the cationic oxidation occurs concurrently. These anionic and cationic redox reactions show high reversibility without any obvious O2 gas release. Moreover, this study provides an insightful guide to designing high-capacity cathodes with reversible oxygen redox activity by simply introducing oxygen ions that are exclusively coordinated by Li+. It is challenging to exploit anionic redox activity to boost performance of battery electrodes, especially for anti-fluorite structures. Here the authors report simultaneous anionic and cationic redox in Li5FeO4, which enables its high capacity and eliminates the undesired oxygen gas release.
TL;DR: This investigation demonstrates that GOS, which is dependent onTLR4, is taken up by macrophages and stimulates TLR4/Akt/NF-κB, TLR 4/AKT/mTOR and MAPK signalling pathways and exerts impressive immuno-stimulatory activity.
Abstract: Alginate, a natural acidic polysaccharide extracted from marine brown seaweeds, is composed of different blocks of β-(1, 4)-D-mannuronate (M) and its C-5 epimer α-(1, 4)-L-guluronate (G). Alginate-derived guluronate oligosaccharide (GOS) readily activates macrophages. However, to understand its role in immune responses, further studies are needed to characterize GOS transport and signalling. Our results show that GOS is recognized by and upregulates Toll-like receptor 4 (TLR4) on RAW264.7 macrophages, followed by its endocytosis via TLR4. Increased expression of TLR4 and myeloid differentiation protein 2 (MD2) results in Akt phosphorylation and subsequent activation of both nuclear factor-κB (NF-κB) and mechanistic target of rapamycin (mTOR). Moreover, GOS stimulates mitogen-activated protein kinases (MAPKs); notably, c-Jun N-terminal kinase (JNK) phosphorylation depends on TLR4 initiation. All these events contribute to the production of inflammatory mediators, either together or separately. Our findings also reveal that GOS induces cytoskeleton remodelling in RAW264.7 cells and promotes macrophage proliferation in mice ascites, both of which improve innate immunity. Conclusively, our investigation demonstrates that GOS, which is dependent on TLR4, is taken up by macrophages and stimulates TLR4/Akt/NF-κB, TLR4/Akt/mTOR and MAPK signalling pathways and exerts impressive immuno-stimulatory activity.
TL;DR: In this paper, a self-assembly V2O5·nH2O nanoflakes with ultrathin flower petals were obtained after heat treatment at 300 °C.
Abstract: The high-capacity cathode material V2O5·nH2O has attracted considerable attention for metal ion batteries due to the multielectron redox reaction during electrochemical processes. It has an expanded layer structure, which can host large ions or multivalent ions. However, structural instability and poor electronic and ionic conductivities greatly handicap its application. Here, in cell tests, self-assembly V2O5·nH2O nanoflakes shows excellent electrochemical performance with either monovalent or multivalent cation intercalation. They are directly grown on a 3D conductive stainless steel mesh substrate via a simple and green hydrothermal method. Well-layered nanoflakes are obtained after heat treatment at 300 °C (V2O5·0.3H2O). Nanoflakes with ultrathin flower petals deliver a stable capacity of 250 mA h g−1 in a Li-ion cell, 110 mA h g−1 in a Na-ion cell, and 80 mA h g−1 in an Al-ion cell in their respective potential ranges (2.0–4.0 V for Li and Na-ion batteries and 0.1–2.5 V for Al-ion battery) after 100 cycles.
TL;DR: It is demonstrated that ultrasmall (∼5 nm) iron selenide (FeSe2) nanoparticles exhibited a remarkable activity for sodium-ion storage and exhibited a large specific capacity, high rate capability, and excellent cycling stability at both low and high current rates by virtue of their advantageous nanosizing effect.
Abstract: Sodium-ion batteries are potential low-cost alternatives to current lithium-ion technology, yet their performances still fall short of expectation due to the lack of suitable electrode materials with large capacity, long-term cycling stability, and high-rate performance. In this work, we demonstrated that ultrasmall (∼5 nm) iron selenide (FeSe2) nanoparticles exhibited a remarkable activity for sodium-ion storage. They were prepared from a high-temperature solution method with a narrow size distribution and high yield and could be readily redispersed in nonpolar organic solvents. In ether-based electrolyte, FeSe2 nanoparticles exhibited a large specific capacity of ∼500 mAh/g (close to the theoretical limit), high rate capability with ∼250 mAh/g retained at 10 A/g, and excellent cycling stability at both low and high current rates by virtue of their advantageous nanosizing effect. Full sodium-ion batteries were also constructed from coupling FeSe2 with NASICON-type Na3V2(PO4)3 cathode and demonstrated imp...