Nanomaterials that form as heterostructures have applications in catalysis, plasmonics, and electronics. Multielement nanoparticles can now be synthesized through a variety of routes, but how ...thermodynamic phases form in such structures and how specific interfaces between them can be designed and synthesized are still poorly understood. We explored how palladium-tin alloys form mixed-composition phases with metals with known but complex miscibilities. Nanoparticles with up to seven elements were synthesized, and many form triphase heterostructures consisting of either three-interface or two-interface architectures. Density functional theory calculations and experimental work were used to determine the balance between the surface and interfacial energies of the observed phases. From these observations, design rules have been established for making polyelemental systems with specific heterostructures, including tetraphase nanoparticles with as many as six junctions.
Polyelemental nanoparticle libraries Chen, Peng-Cheng; Liu, Xiaolong; Hedrick, James L. ...
Science,
06/2016, Letnik:
352, Številka:
6293
Journal Article
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Multimetallic nanoparticles are useful in many fields, yet there are no effective strategies for synthesizing libraries of such structures, in which architectures can be explored in a systematic and ...site-specific manner. The absence of these capabilities precludes the possibility of comprehensively exploring such systems. We present systematic studies of individual polyelemental particle systems, in which composition and size can be independently controlled and structure formation (alloy versus phase-separated state) can be understood. We made libraries consisting of every combination of five metallic elements (Au, Ag, Co, Cu, and Ni) through polymer nanoreactor–mediated synthesis. Important insight into the factors that lead to alloy formation and phase segregation at the nanoscale were obtained, and routes to libraries of nanostructures that cannot be made by conventional methods were developed.
Colloidal crystal engineering with nucleic acid-modified nanoparticles is a powerful way for preparing 3D superlattices, which may be useful in many areas, including catalysis, sensing, and ...photonics. To date, the building blocks studied have been primarily based upon metals, metal oxides, chalcogenide semiconductors, and proteins. Here, we show that metal-organic framework nanoparticles (MOF NPs) densely functionalized with oligonucleotides can be programmed to crystallize into a diverse set of superlattices with well-defined crystal symmetries and compositions. Electron microscopy and small-angle X-ray scattering characterization confirm the formation of single-component MOF superlattices, binary MOF-Au single crystals, and two-dimensional MOF nanorod assemblies. Importantly, DNA-modified porphyrinic MOF nanorods (PCN-222) were assembled into 2D superlattices and found to be catalytically active for the photooxidation of 2-chloroethyl ethyl sulfide (CEES, a chemical warfare simulant of mustard gas). Taken together, these new materials and methods provide access to colloidal crystals that incorporate particles with the well-established designer properties of MOFs and, therefore, increase the scope of possibilities for colloidal crystal engineering with DNA.
Ammonia–borane (AB) is a promising chemical hydrogen‐storage material. However, the development of real‐time, efficient, controllable, and safe methods for hydrogen release under mild conditions is a ...challenge in the large‐scale use of hydrogen as a long‐term solution for future energy security. A new class of low‐cost catalytic system is presented that uses nanostructured Ni2P as catalyst, which exhibits excellent catalytic activity and high sustainability toward hydrolysis of ammonia–borane with the initial turnover frequency of 40.4 mol(H2) mol(Ni2P)−1 min−1 under air atmosphere and at ambient temperature. This value is higher than those reported for noble‐metal‐free catalysts, and the obtained Arrhenius activation energy (Ea=44.6 kJ mol−1) for the hydrolysis reaction is comparable to Ru‐based bimetallic catalysts. A clearly mechanistic analysis of the hydrolytic reaction of AB based on experimental results and a density functional theory calculation is presented.
A low‐cost catalytic system using nanostructured Ni2P as the catalyst was established for the hydrolysis of ammonia–borane. This system exhibits excellent catalytic activity and high sustainability under an air atmosphere and at ambient temperature.
Quantum key distribution (QKD)1,2 offers a long-term solution to secure key exchange. Due to photon loss in transmission, it was believed that the repeaterless key rate is bounded by a linear ...function of the transmittance, O(η) (refs. 3,4), limiting the maximal secure transmission distance5,6. Recently, a novel type of QKD scheme has been shown to beat the linear bound and achieve a key rate performance of O(η) (refs. 7–9). Here, by employing the laser injection technique and the phase post-compensation method, we match the modes of two independent lasers and overcome the phase fluctuation. As a result, the key rate surpasses the linear bound via 302 km and 402 km commercial-fibre channels, over four orders of magnitude higher than existing results5. Furthermore, our system yields a secret key rate of 0.118 bps with a 502 km ultralow-loss fibre. This new type of QKD pushes forward long-distance quantum communication for the future quantum internet.Phase-matching quantum key distribution is implemented with a 502 km ultralow-loss optical fibre. The fluctuations of the laser initial phases and frequencies are suppressed by the laser injection technique and the phase post-compensation method.
Amino acids are known regulators of cellular signaling and physiology, but how they are sensed intracellularly is not fully understood. Herein, we report that each aminoacyl-tRNA synthetase (ARS) ...senses its cognate amino acid sufficiency through catalyzing the formation of lysine aminoacylation (K-AA) on its specific substrate proteins. At physiologic levels, amino acids promote ARSs bound to their substrates and form K-AAs on the ɛ-amine of lysines in their substrates by producing reactive aminoacyl adenylates. The K-AA marks can be removed by deacetylases, such as SIRT1 and SIRT3, employing the same mechanism as that involved in deacetylation. These dynamically regulated K-AAs transduce signals of their respective amino acids. Reversible leucylation on ras-related GTP-binding protein A/B regulates activity of the mammalian target of rapamycin complex 1. Glutaminylation on apoptosis signal-regulating kinase 1 suppresses apoptosis. We discovered non-canonical functions of ARSs and revealed systematic and functional amino acid sensing and signal transduction networks.
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•Amino acids modify ɛ-amines of lysines•Each tRNA synthetase is the aminoacyl transferase of its cognate amino acid•Aminoacylations can be reversed by deacetylases•Aminoacylations transmit amino acid signals to regulate cellular functions
He et al. reveal that tRNA synthetases sense sufficiency of amino acids and act as aminoacyl transferases to modify ɛ-amines of lysines in proteins, with leucylation of RagA/B regulating mTORC1 activity and glutaminylation of ASK1 inhibiting apoptosis. Lysine aminoacylation marks are removed by SIRT1 and SIRT3.
Quantum walks are the quantum mechanical analog of classical random walks and an extremely powerful tool in quantum simulations, quantum search algorithms, and even for universal quantum computing. ...In our work, we have designed and fabricated an 8x8 two-dimensional square superconducting qubit array composed of 62 functional qubits. We used this device to demonstrate high fidelity single and two particle quantum walks. Furthermore, with the high programmability of the quantum processor, we implemented a Mach-Zehnder interferometer where the quantum walker coherently traverses in two paths before interfering and exiting. By tuning the disorders on the evolution paths, we observed interference fringes with single and double walkers. Our work is an essential milestone in the field, brings future larger scale quantum applications closer to realization on these noisy intermediate-scale quantum processors.
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To ensure a long-term quantum computational advantage, the quantum hardware should be upgraded to withstand the competition of continuously improved classical algorithms and ...hardwares. Here, we demonstrate a superconducting quantum computing systems Zuchongzhi 2.1, which has 66 qubits in a two-dimensional array in a tunable coupler architecture. The readout fidelity of Zuchongzhi 2.1 is considerably improved to an average of 97.74%. The more powerful quantum processor enables us to achieve larger-scale random quantum circuit sampling, with a system scale of up to 60 qubits and 24 cycles, and fidelity of FXEB=(3.66±0.345)×10-4. The achieved sampling task is about 6 orders of magnitude more difficult than that of Sycamore Nature 574, 505 (2019) in the classic simulation, and 3 orders of magnitude more difficult than the sampling task on Zuchongzhi 2.0 arXiv:2106.14734 (2021). The time consumption of classically simulating random circuit sampling experiment using state-of-the-art classical algorithm and supercomputer is extended to tens of thousands of years (about 4.8×104 years), while Zuchongzhi 2.1 only takes about 4.2 h, thereby significantly enhancing the quantum computational advantage.
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•Summarize current strategies used to construct ultramicroporous MOFs.•List the latest progress in gas separation made by ultramicroporous MOFs.•Smaller pore size can enhance the ...host-guest interaction and improve the gas capacity and selectivity.•Providing a guide for future research into creating ultramicroporous MOFs and tuning the pore size precisely.
Metal-organic frameworks (MOFs) have emerged as a new generation of porous materials that demonstrate great promise in diverse application fields, especially gas separation, due to the energy-efficient economy. One of the striking advantages of MOFs relies on their tunable pore sizes, which plays a crucial role in the separation efficiency and selectivity since smaller pore can introduce stronger host–guest interaction. Thus, fabrication of ultramicroporous (pore size < 0.7 nm) MOFs for gas separation and purification has gained increasing attention because they allow molecular-scale resolution for gas separation. In this review, we summarized several typical design strategies and synthesis methods to create ultramicroporous MOFs. We also address the latest progress for gas separation made by ultramicroporous MOFs in critical gas separation processes, especially CO2 separation, C2H4 purification, C3H6 purification, noble gas separation, and isotope separation. We anticipate that this review will provide an important guide for future research into fabricating ultramicroporous MOFs, and provide perspective on the future directions of ultramicroporous MOFs in terms of gas separation.
Whether species demography and diversification are driven primarily by extrinsic environmental changes such as climatic oscillations in the Quaternary or by intrinsic biological interactions like ...coevolution between antagonists is a matter of active debate. In fact, their relative importance can be assessed by tracking past population fluctuations over considerable time periods.
We applied the pairwise sequentially Markovian coalescent approach on the genomes of 11 temperate Juglans species to estimate trajectories of changes in effective population size (N
e) and used a Bayesian-coalescent based approach that simultaneously considers multiple genomes (G-PhoCS) to estimate divergence times between lineages.
N
e curves of all study species converged 1.0 million yr ago, probably reflecting the time when the walnut genus last shared a common ancestor. This estimate was confirmed by the G-PhoCS estimates of divergence times. But all species did not react similarly to the dramatic climatic oscillations following early Pleistocene cooling, so the timing and amplitude of changes in N
e differed among species and even among conspecific lineages.
The population histories of temperate walnut species were not driven by extrinsic environmental changes alone, and a key role was probably played by species-specific factors such as coevolutionary interactions with specialized pathogens.
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