Platinum‐based catalysts occupy a pivotal position in diverse catalytic applications in hydrogen chemistry and electrochemistry, for instance, the hydrogen evolution reactions (HER). While adsorbed ...Pt atoms on supports often cause severe mismatching on electronic structures and HER behaviors from metallic Pt due to the different energy level distribution of electron orbitals. Here, the design of crystalline lattice‐confined atomic Pt in metal carbides using the Pt‐centered polyoxometalate frameworks with strong PtO‐metal covalent bonds is reported. Remarkably, the lattice‐confined atomic Pt in the tungsten carbides (Ptdoped@WCx, both Pt and W have atomic radii of 1.3 Å) exhibit near‐zero valence states and similar electronic structures as metallic Pt, thus delivering matched energy level distributions of the Pt 5dz2 and H 1s orbitals and similar acidic hydrogen evolution behaviors. In alkaline conditions, the Ptdoped@WCx exhibits 40 times greater mass activity (49.5 A mgPt−1 at η = 150 mV) than the Pt@C because of the favorable water dissociation and H* transport. These findings offer a universal pathway to construct urgently needed atomic‐scale catalysts for broad catalytic reactions.
Crystalline lattice‐confined atomic Pt in metal carbides with “real” matched properties as metallic platinum are developed using Pt‐centered polyoxometalate frameworks with strong PtOW/Mo covalent bonds. The WC lattice‐confined Pt atoms exhibit near‐zero valence states, similar electronic structures, and matched hydrogen evolution behaviors as Pt(111) surface; remarkably, they offer 40 times greater mass activity than Pt@C‐20% in alkaline conditions.
A robust cluster-based Eu-MOF has been created by a tetrazolyl-carboxyl linker, which shows great chemical and thermal stability and multiple functions of fluorescent sensor for the detection of ...antibiotics (MDZ, DMZ) and pesticides (DCN).
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•A robust cluster-based Eu-MOF as a fluorescence probe.•Resistance to water, organic solvents and wide pH value range.•Selective detection of MDZ, DMZ and DCN with low detection limit, rapid response.•Detected MDZ and DMZ in calf serum and sensed DCN in lake water.•Combining experiments and calculations to study the sensing mechanism.
As a hot issue of global concern, the abuse of organic pollutants, including pesticides and antibiotics poses a great threat to the human health and ecological environment. Effective and accurate detection of these species is of profound significance in many fields. In this work, a novel 3D metal-organic framework (MOF) Eu2(dtztp)(OH)2(DMF)(H2O)2.5·2H2O (1) was solvothermally synthesized. 1 is a three-dimensional framework based on tetranuclear Eu4(μ3-OH)4(μ2-OH2)8+ clusters, and reveals the great chemical stability and excellent tolerance in water and organic solvents. The MOF also shows strong fluorescence that was undisturbed by the pH in aqueous water (pH = 3–12). Importantly, 1 can quickly detect metronidazole (MDZ) and dimetridazole (DMZ) antibiotics as well as 2,6-dichloro-4-nitroaniline (DCN) pesticide in water with good recyclability and low detection limit. MDZ, DMZ and DCN were also successfully detected in calf serum and lake water, respectively. The mechanism of fluorescence quenching was disclosed through the combination of experiments and density functional theory calculations.
Autophagy is a highly orchestrated intracellular bulk degradation process that is activated by various environmental stresses. The serine/threonine kinase ULK1, like its yeast homologue Atg1, is a ...key initiator of autophagy that is negatively regulated by the mTOR kinase. However, the molecular mechanism that controls the inhibitory effect of mTOR on ULK1-mediated autophagy is not fully understood. Here we identified AMPK, a central energy sensor, as a new ULK1-binding partner. We found that AMPK binds to the PS domain of ULK1 and this interaction is required for ULK1-mediated autophagy. Interestingly, activation of AMPK by AICAR induces 14-3-3 binding to the AMPK-ULK1-mTORC1 complex, which coincides with raptor Ser792 phosphorylation and mTOR inactivation. Consistently, AICAR induces autophagy in TSC2-deficient cells expressing wild-type raptor but not the mutant raptor that lacks the AMPK phosphorylation sites (Ser722 and Ser792). Taken together, these results suggest that AMPK association with ULK1 plays an important role in autophagy induction, at least in part, by phosphorylation of raptor to lift the inhibitory effect of mTOR on the ULK1 autophagic complex.
Convolutional-deconvolution networks can be adopted to perform end-to-end saliency detection. But, they do not work well with objects of multiple scales. To overcome such a limitation, in this work, ...we propose a recurrent attentional convolutional-deconvolution network (RACDNN). Using spatial transformer and recurrent network units, RACDNN is able to iteratively attend to selected image sub-regions to perform saliency refinement progressively. Besides tackling the scale problem, RACDNN can also learn context-aware features from past iterations to enhance saliency refinement in future iterations. Experiments on several challenging saliency detection datasets validate the effectiveness of RACDNN, and show that RACDNN outperforms state-of-the-art saliency detection methods.
Multi‐component MOFs contain multiple sets of unique and hierarchical pores, with different functions for different applications, distributed in their inter‐linked domains. Herein, we report the ...construction of a class of precisely aligned flexible‐on‐rigid hybrid‐phase MOFs with a unique rods‐on‐octahedron morphology. We demonstrated that hybrid‐phase MOFs can be constructed based on two prerequisites: the partially matched topology at the interface of the two frameworks, and the structural flexibility of MOFs with acs topology, which can compensate for the differences in lattice parameters. Furthermore, we achieved domain selective loading of multiple guest molecules into the hybrid‐phase MOF, as observed by scanning transmission electron microscopy–energy‐dispersive X‐ray spectrometry elemental mapping. Most importantly, we successfully applied the constructed hybrid‐phase MOF to develop a dual‐drug delivery system with controllable loading ratio and release kinetics.
A class of precisely aligned flexible‐on‐rigid hybrid‐phase MOFs were synthesized by the heteroepitaxial growth of acs‐topology MOF on the surface of fcu‐topology MOF. Domain‐selective loading of multiple guests into the hybrid‐phase MOFs was achieved by size‐selective encapsulation or selective binding. A dual‐drug delivery system with controllable loading ratio and release kinetics was developed based on the hybrid‐phase MOF.
In this article, we introduce a P-wave between the diquark and antidiquark explicitly to construct the vector tetraquark currents, and study the vector tetraquark states with the QCD sum rules ...systematically, and obtain the lowest vector tetraquark masses up to now. The present predictions support assigning the
Y
(4220 / 4260),
Y
(4320 / 4360),
Y
(4390) and
Z
(4250) to be the vector tetraquark states with a relative P-wave between the diquark and antidiquark pair.
Metallic bowtie nanoarchitectures can produce dramatic electric field enhancement, which is advantageous in single‐molecule analysis and optical information processing. Plasmonic bowtie ...nanostructures were successfully constructed using a DNA origami‐based bottom‐up assembly strategy, which enables precise control over the geometrical configuration of the bowtie with an approximate 5 nm gap. A single Raman probe was accurately positioned at the gap of the bowtie. Single‐molecule surface‐enhanced Raman scattering (SM‐SERS) of individual nanostructures, including ones containing an alkyne group, was observed. The design achieved repeatable local field enhancement of several orders of magnitude. This method opens the door on a novel strategy for the fabrication of metal bowtie structures and SM‐SERS, which can be utilized in the design of highly‐sensitive photonic devices.
Plasmonic bowtie nanostructures were successfully constructed using DNA origami‐based self‐assembly. A single Raman probe was accurately positioned at the gap of the bowtie and single‐molecule SERS of individual nanostructures was observed.
Fundamental understanding of the dynamic behaviors at the electrochemical interface is crucial for electrocatalyst design and optimization. Here, we revisit the oxygen reduction reaction mechanism on ...a series of transition metal (M = Fe, Co, Ni, Cu) single atom sites embedded in N-doped nanocarbon by ab initio molecular dynamics simulations with explicit solvation. We have identified the dissociative pathways and the thereby emerged solvated hydroxide species for all the proton-coupled electron transfer (PCET) steps at the electrochemical interface. Such hydroxide species can be dynamically confined in a "pseudo-adsorption" state at a few water layers away from the active site and respond to the redox event at the catalytic center in a coupled manner within timescale less than 1 ps. In the PCET steps, the proton species (in form of hydronium in neutral/acidic media or water in alkaline medium) can protonate the pseudo-adsorbed hydroxide without needing to travel to the direct catalyst surface. This, therefore, expands the reactive region beyond the direct catalyst surface, boosting the reaction kinetics via alleviating mass transfer limits. Our work implies that in catalysis the reaction species may not necessarily bind to the catalyst surface but be confined in an active region.
Nanostructured‐alloy‐type anodes have received great interest for high‐performance lithium‐ion batteries (LIBs). However, these anodes experience huge volume fluctuations during repeated ...lithiation/delithiation and are easily pulverized and subsequently form aggregates. Herein, an efficient method to stabilize alloy‐type anodes by creating defects on the surface of the metal oxide support is proposed. As a demonstration, PPy‐encapsulated SnS2 nanosheets supported on defect‐rich TiO2 nanotubes were produced and investigated as an anode material for LIBs. Both experimental results and theoretical calculations demonstrate that defect‐rich TiO2 provides more chemical adhesions to SnS2 and discharge products, compared to defect‐poor TiO2, and then effectively stabilizes the electrode structure. As a result, the composite exhibits an unprecedented cycle stability. This work paves the way to designing durable and active nanostructured‐alloy‐type anodes on oxide supports.
PPy‐encapsulated SnS2 nanosheets strongly anchored onto a hydrogen‐treated TiO2 (H–TiO2) support have been successfully prepared as an anode for LIBs. As demonstrated by first principles, theoretical calculations, and experimental results, the superior binding between SnS2 and the H–TiO2 support via abundant Ti–S bonding, which is reinforced by the oxygen vacancy, contributes to the unprecedented cycle stability.
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