Room-Temperature Laser Planting of High-Loading Single-Atom Catalysts for High-Efficiency Electrocatalytic Hydrogen Evolution.

Despite stunning progress in single-atom catalysis (SAC), it remains a grand challenge to yield a high loading of single atoms (SAs) anchored on substrates. Herein, we report a one-step laser-planting strategy to craft SAs of interest under an atmospheric temperature and pressure on various substrates including carbon, metals, and oxides. Laser pulses render concurrent creation of defects on the substrate and decomposition of precursors into monolithic metal SAs, which are immobilized on the as-produced defects via electronic interactions. Laser planting enables a high defect density, leading to a record-high loading of SAs of 41.8 wt %. Our strategy can also synthesize high-entropy SAs (HESAs) with the coexistence of multiple metal SAs, regardless of their distinct characteristics. An integrated experimental and theoretical study reveals that superior catalytic activity can be achieved when the distribution of metal atom content in HESAs resembles the distribution of their catalytic performance in a volcano plot of electrocatalysis. The noble-metal mass activity for a hydrogen evolution reaction within HESAs is 11-fold over that of commercial Pt/C. The laser-planting strategy is robust, opening up a simple and general route to attaining an array of low-cost, high-density SAs on diverse substrates under ambient conditions for electrochemical energy conversion.

Optimizing Porous Metal-Organic Layers for Stable Zinc Anodes.

Aqueous zinc-ion batteries (ZIBs) have been considered as alternative stationary energy storage systems, but the dendrite and corrosion issues of Zn anodes hinder their practical applications. Here we report a series of two-dimensional (2D) metal-organic frameworks (MOFs) with Zr12 clusters, which act as artificial solid electrolyte interphase (SEI) layers to prevent dendrites and corrosion of Zn anodes. The Zr12-based 2D MOF layers were formed by incubating 3D layer-pillared Zr-MOFs in ZnSO4 aqueous electrolytes, which replaced the pillar ligands with terminal SO42-. Furthermore, the pore sizes of Zr12-based 2D MOF layers were systematically tuned, leading to optimized Zn2+ conduction properties and protective performance for Zn anodes. In contrast to the traditional 2D-MOFs with Zr6 clusters, Zr12-based 2D MOF layers as artificial SEI significantly reduced the polarization and increased the stability of Zn anodes in MOF@Zn||MOF@Zn symmetric cells and MOF@Zn||MnO2 full cells. In situ experiments and DFT computations reveal that the enhanced cell performance is attributed to the unique Zr12-based layered structure with intrinsic pores to allow fast Zn2+ diffusion, surface Zr-SO4 zincophilic sites to induce uniform Zn deposition, and inhibited hydrogen evolution by 2D MOF Zr12 layers.

Noninvasive Photodelamination of van der Waals Semiconductors for High-Performance Electronics.

Atomically thin 2D van der Waals semiconductors are promising candidate materials for post-silicon electronics. However, it remains challenging to attain completely uniform monolayer semiconductor wafers free of over-grown islands. Here, the observation of the energy-funneling effect and ambient photodelamination phenomenon in inhomogeneous few-layer WS2 flakes under low-illumination fluencies down to several nW µm-2 and its potential as a noninvasive atomic-layer etching strategy for selectively stripping the local excessive overlying islands are reported. Photoluminescent tracking on the photoetching traces reveals relatively fast etching rates of around 0.3-0.8 µm min-1 at varied temperatures and an activation energy of 1.7 eV. By using crystallographic and electronic characterization, the noninvasive nature of the low-power photodelamination and the highly preserved lattice quality are also confirmed in the as-etched monolayer products, featuring a comparable density of atomic defects (≈4.2 × 1013 cm-2 ) to pristine flakes and a high electron mobility of up to 80 cm2 V-1 s-1 at room temperature. This approach opens a noninvasive postetching route for thickness uniformity management in 2D van der Waals semiconductor wafers for electronic applications.

Oxidation kinetics and non-Marcusian charge transfer in dimensionally confined semiconductors.

Electrochemical reactions represent essential processes in fundamental chemistry that foster a wide range of applications. Although most electrochemical reactions in bulk substances can be well described by the classical Marcus-Gerischer charge transfer theory, the realistic reaction character and mechanism in dimensionally confined systems remain unknown. Here, we report the multiparametric survey on the kinetics of lateral photooxidation in structurally identical WS2 and MoS2 monolayers, where electrochemical oxidation occurs at the atomically thin monolayer edges. The oxidation rate is correlated quantitatively with various crystallographic and environmental parameters, including the density of reactive sites, humidity, temperature, and illumination fluence. In particular, we observe distinctive reaction barriers of 1.4 and 0.9 eV for the two structurally identical semiconductors and uncover an unusual non-Marcusian charge transfer mechanism in these dimensionally confined monolayers due to the limit in reactant supplies. A scenario of band bending is proposed to explain the discrepancy in reaction barriers. These results add important knowledge into the fundamental electrochemical reaction theory in low-dimensional systems.

Cryogenic electron ptychographic single particle analysis with wide bandwidth information transfer.

Advances in cryogenic transmission electron microscopy have revolutionised the determination of many macromolecular structures at atomic or near-atomic resolution. This method is based on conventional defocused phase contrast imaging. However, it has limitations of weaker contrast for small biological molecules embedded in vitreous ice, in comparison with cryo-ptychography, which shows increased contrast. Here we report a single-particle analysis based on the use of ptychographic reconstruction data, demonstrating that three dimensional reconstructions with a wide information transfer bandwidth can be recovered by Fourier domain synthesis. Our work suggests future applications in otherwise challenging single particle analyses, including small macromolecules and heterogeneous or flexible particles. In addition structure determination in situ within cells without the requirement for protein purification and expression may be possible.

Impact of financial inclusion and green bond financing for renewable energy mix: implications for financial development in OECD economies.

The study aims to empirically estimate the nexus of green bond financing with renewable energy index OECD countries. Using the OECD countries data over the period of the 2011-2019, the study estimated the nexus between constructs. To justify the study findings and present widespread policy implications on recent topicality Padroni unit root test, FMOLS and DOLS technique is applied. For robustness analysis, long-run sensitivity analysis using FMOLS extension is used, and a comparative picture of green bond financing nexus with renewable energy index is presented. The study presented the consistent effects of green bond financing on renewable energy index indicators. This asymmetrical role of green bonds is confirmed on renewable energy indicators over the sample period. OECD countries injected 31% role of green bond financing on renewable energy index constructs, and it raised 9.4% of per unit energy efficiency in renewable energy systems; by this, the study findings warrant maximum support through public office, energy ministries, and departments for energy efficiency optimization. The study presents multiple policy implications to enhance renewable energy generation for energy efficiency through different alternative sources. Despite growing literature, the empirical discussion on this topicality is still shattered and less studied, which is extended and contributed by recent research. Furthermore, efficient regulation in the renewable energy sector may convert financial uncertainty into a huge opportunity. Investing in renewable energy stocks might help investors diversify their portfolios.

Three-dimensional electron ptychography of organic-inorganic hybrid nanostructures.

Three dimensional scaffolded DNA origami with inorganic nanoparticles has been used to create tailored multidimensional nanostructures. However, the image contrast of DNA is poorer than those of the heavy nanoparticles in conventional transmission electron microscopy at high defocus so that the biological and non-biological components in 3D scaffolds cannot be simultaneously resolved using tomography of samples in a native state. We demonstrate the use of electron ptychography to recover high contrast phase information from all components in a DNA origami scaffold without staining. We further quantitatively evaluate the enhancement of contrast in comparison with conventional transmission electron microscopy. In addition, We show that for ptychography post-reconstruction focusing simplifies the workflow and reduces electron dose and beam damage.

Low-dose phase retrieval of biological specimens using cryo-electron ptychography.

Cryo-electron microscopy is an essential tool for high-resolution structural studies of biological systems. This method relies on the use of phase contrast imaging at high defocus to improve information transfer at low spatial frequencies at the expense of higher spatial frequencies. Here we demonstrate that electron ptychography can recover the phase of the specimen with continuous information transfer across a wide range of the spatial frequency spectrum, with improved transfer at lower spatial frequencies, and as such is more efficient for phase recovery than conventional phase contrast imaging. We further show that the method can be used to study frozen-hydrated specimens of rotavirus double-layered particles and HIV-1 virus-like particles under low-dose conditions (5.7 e/Å2) and heterogeneous objects in an Adenovirus-infected cell over large fields of view (1.14 × 1.14 µm), thus making it suitable for studies of many biologically important structures.

Influenza virus H1N1 induced apoptosis of mouse astrocytes and the effect on protein expression.

OBJECTIVE: To investigate the effects of influenza A virus H1N1 infection on the proliferation and apoptosis of mouse astrocytes cells and its protein expression. METHODS: After mouse astrocytes was infected with purified influenza A virus H1N1 in vitro, viral integration and replication status of the cells were detected by RT-PCR assay, cell proliferation and apoptosis was determined by MTT method and flow cytometry, respectively. Associated protein expression was detected by Western blotting. RESULTS: Agarose gel electrophoresis showed H1N1 virus can infect astrocytes and can be copied. MTT staining showed H1N1 virus infection can inhibit the proliferation of mouse astrocytes, which makes cell viability decreased significantly. Flow cytometry showed that the proportion of Annein V staining positive vascular endothelial cells in the influenza A virus group was significantly higher than that in the control group. Western blot analysis showed after 24 h and 32 h of infection, there were cells caspase-3 protein and the expression of its active form (lysed caspase-3 protein) increased. The proportion of Bax/Bcl-2 also increased. CONCLUSIONS: Influenza A virus can infect human vascular endothelial cells and proliferation and it can induce apoptosis of endothelial cells.