Electron Reservoir Effect of Adjacent Fe Nanoclusters Boosts Atomic Fe Active Sites on Porous Carbon for the Both Electrocatalytic Oxygen Reduction and CO2 Reduction Reaction.

Electrochemical oxygen reduction reaction (ORR) and carbon dioxide reduction reaction (CO2RR) are greatly significant in renewable energy-related devices and carbon-neutral closed cycle, while the development of robust and highly efficient electrocatalysts has remained challenges. Herein, a hybrid electrocatalyst, featuring axial N-coordinated Fe single atom sites on hierarchically N, P-codoped porous carbon support and Fe nanoclusters as electron reservoir (FeNCs/FeSAs-NPC), is fabricated via in situ thermal transformation of the precursor of a supramolecular polymer initiated by intermolecular hydrogen bonds co-assembly. The FeNCs/FeSAs-NPC catalyst manifests superior oxygen reduction activity with a half-wave potential of 0.91 V in alkaline solution, as well as high CO2 to CO Faraday efficiency (FE) of surpassing 90% in a wide potential window from -0.40 to -0.85 V, along with excellent electrochemical durability. Theoretical calculations indicate that the electron reservoir effect of Fe nanoclusters can trigger the electron redistribution of the atomic Fe moieties, facilitating the activation of O2 and CO2 molecules, lowering the energy barriers for rate-determining step, and thus contributing to the accelerated ORR and CO2RR kinetics. This work offers an effective design of electron coupling catalysts that have advanced single atoms coexisting with nanoclusters for efficient ORR and CO2RR.

The Association Between Elevated Myocardial Injury-Related Biomarker (TnI) and Increased Mortality in Patients With Severe Fever With Thrombocytopenia Syndrome.

OBJECTIVES: The objective of this study was to investigate the dynamic profiles of myocardial injury biomarkers and their association with mortality in patients with severe fever with thrombocytopenia syndrome (SFTS). DESIGN: A retrospective cohort study. SETTINGS: Union Hospital in Wuhan, China. PATIENTS: A total of 580 patients with SFTS, observed between May 2014 and December 2021, were included in the final analysis. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: In total, 580 patients with SFTS were enrolled in the study, comprised of 469 survivors and 111 nonsurvivors, with a 21-day fatality rate of 19.1%. The elevation of troponin I (TnI) was observed in 61.6% patients (357/580) with SFTS upon admission, and 68.4% patients (397/580) developed an abnormal TnI level during hospitalization. Multivariate logistic regression identified age, viral load, platelet count, creatinine level, and TnI level as potential risk factors for mortality in patients with SFTS. The results of restricted cubic splines revealed that when the TnI level (baseline TnI: 1.55 [lg (ng/L+1)], peak value: TnI 1.90 [lg (ng/L+1)]) exceeded a certain threshold, the predicted mortality of patients with SFTS increased alongside the rise in TnI levels. Mortality rate surpassed 40% among patients with SFTS with TnI greater than or equal to 10 times the upper limit of normal at admission (43.8%) or during hospitalization (41.7%). Older age, a history of cardiovascular disease, and higher d -dimer levels were potential risk factors for elevated TnI levels in patients with SFTS. CONCLUSIONS: Elevated TnI levels were prevalent among patients with SFTS and were strongly associated with an increased risk of mortality.

Boosting Hydrogen Production of a MOF-based Multicomponent Photocatalyst with Clean Interface via Facile One-pot Electrosynthesis.

Hydrogen production from photocatalysis via the usage of multicomponent photocatalysts represents a promising pathway for carbon peaking and carbon neutrality, owing to their structural advantages in dealing with the three crucial processes in photocatalysis, namely, light harvesting, charge transfer, and surface redox reactions. We demonstrate the fabrication of a MOF-based multicomponent photocatalyst, denoted as semiconductor/MOF/cocatalyst, by a one-pot electrochemical synthetic route. The as-fabricated multicomponent photocatalyst has a clean interface among the components, leading to close connections that contribute to high-quality heterojunction and facilitate photogenerated charge transfer and separation, thereby the efficient hydrogen evolution. The hydrogen production rate of the resultant ZrO2 /Zr-MOF/Pt is 1327 µmol ⋅ g-1 ⋅ h-1 , which is much higher than that of ZrO2 /Zr-MOF (15 µmol ⋅ g-1 ⋅ h-1 ) and pure Zr-MOF (10.1 µmol ⋅ g-1 ⋅ h-1 ), as well as the photodeposited-Pt products ZrO2 /Zr-MOF/PtPD (287 µmol ⋅ g-1 ⋅ h-1 ) and Zr-MOF/PtPD (192 µmol ⋅ g-1 ⋅ h-1 ) obtained by the step-wise synthetic approach. The work gives a good inspiration for the rational design and construction of MOF-based multicomponent photocatalysts through the one-pot electrosynthesis.

Orientation transitions and chiral assemblies of para-terphenyl molecules on Cd(0001).

The interplay between orientation transition and chiral self-assemblies of para-terphenyl (P3P) molecules on the Cd(0001) surface has been investigated using low temperature scanning tunneling microscopy and density functional theory calculations. Three distinct molecular orientations have been discerned from the self-assembled thin films of P3P. At the low coverage, flat-lying molecules appear in the homochiral domains with the incommensurate registry to the substrate. With the coverage increasing, the incoming molecules are incorporated into the first layer with edge-on orientation and form the self-assembled zigzag chains. The alternative arrangement of zigzag chains with opposite chirality leads to the formation of a c(4 × 2) superstructure, in which the tilted molecules exhibit orientational frustration and fuzzy noises. The analysis of the tunneling spectra reveals that the electronic structure of P3P layers is contingent upon the hybridization between the electronic states of P3P molecules and the Cd(0001) surface. These results provide important insights into the interplay between orientational transition and chiral assembly of P3P molecules on metal substrates.

Boosting Oxygen Evolution Performance of Nickel-Iron Layered Double Hydroxides by Controlling Oxygen Vacancies and Structural Disorder via n-Butyllithium Treatment.

Nickel-iron-based layered double hydroxides (NiFe-LDHs) are promising catalysts for the oxygen evolution reaction (OER) because of their high activity, availability, and low cost. Defect engineering, particularly the formation of oxygen vacancies, can improve the catalytic activity of NiFe-LDHs. However, the controllable introduction of uniform oxygen vacancies remains challenging. Herein, an n-butyllithium treatment method is developed to tune oxygen vacancy defects and change the degree of amorphization in NiFe-LDHs via deep reduction, followed by partial oxidization at low temperatures. Interestingly, the Ni in the NiFe-LDHs is selectively reduced to the alloy state by n-butyllithium, whereas Fe is not. The different structural transformations of Ni and Fe during the treatment successfully produce an oxygen-defect-rich amorphous/crystalline electrocatalyst. Under optimal conditions, the treated NiFe-LDHs exhibit high OER activity with an overpotential of 223 mV at 10 mA cm-2 (68 mV lower than that of a commercial IrO2 electrocatalyst) and long-term stability. Notably, the n-butyllithium treatment can be applied to other electrocatalysts, such as CoFe-LDHs and IrO2 (treated IrO2 with an overpotential of 197 mV at 10 mA cm-2). This n-butyllithium reduction/partial oxidization treatment constitutes a novel top-down strategy for the controllable modification of metal oxide structures, with various energy-related applications.

Epitaxial growth of Si thin films with hexagonal close-packed structures on metal substrates.

We have studied the epitaxial growth of Si thin films on the Cd(0001) surface using low-temperature scanning tunneling microscopy. When deposited at low temperatures (100 K), Si atoms form dendritic islands with triangular shapes, indicating the existence of anisotropic edge diffusion in the process of Si film growth. After annealing to elevated temperatures, the triangular dendritic Si islands become hexagonal compact islands. Moreover, the 2D Si islands located on two different substrate terraces exhibit different heights due to the influence of quantum-well states in Cd(0001) films. Based on high-resolution scanning tunneling microscopy images, it is observed that the first, second, and third Si layers show the pseudomorphic 1 × 1 structure. In particular, the first and second layer islands reveal the opposite triangles, indicating the hexagonal close-packed stacking of Si atoms. These results provide important information for the growth of pristine Si films on metal substrates and the understanding of Si-metal interaction.

Structural transition and interconversion between the 2D self-assembled structures of pentacene.

The 2D self-assemblies and structural transitions of pentacene on a Cd(0001) surface have been investigated with low temperature scanning tunneling microscopy (STM). With increasing coverage, pentacene molecules show a structural evolution from the initial disordered gas-like phase through the porous network phase to the herringbone phase, and finally to the brickwall phase at the full monolayer. In particular, orientational frustration and cooperative rotation of pentacene molecules take place in the herringbone phase. Furthermore, successive STM scanning leads to structural interconversions between the porous network phase, herringbone phase, and brickwall phase, indicating the metastability of the 2D assembled structures of pentacene on Cd(0001). These structural transitions and interconversion can be attributed to the interplay between the repulsive electrostatic forces resulting from the charge transfer from the substrate to pentacene and the attractive effects originating from dipole-dipole interactions and intermolecular van der Waals forces.

Spontaneous chiral resolution of pentahelicene molecules on Cd(0001).

Chiral resolution is of fundamental importance to conglomerate or racemate crystallization. Here we demonstrate that the spontaneous chiral resolution of pentahelicene racemates occurred in the monolayer domains. When deposited on a Cd(0001) surface, pentahelicene molecules crystallize into a commensurate (6 × 6)R0° structure built mainly from homochiral trimers. Spontaneous chirality separation takes place in the form of opposite mirror domains, where 2D enantiomorphism is not expressed by the oblique adlattice, but by the supramolecular chirality of the pentahelicene trimers. Furthermore, annealing the sample or extreme close-packing lead to the presence of lattice handedness through the formation of a porous network structure or an edge-on phase. These results provide valuable insight for 2D conglomerate crystallization and stereochemical recognition.

Graphene-supported single-atom catalysts and applications in electrocatalysis.

Supported metal nanostructures are the most extensively studied heterogeneous catalysts, benefiting from easy separation, regeneration and affordable cost. The size of the supported metal species is one of the decisive factors in determining the activity of heterogeneous catalysts. Particularly, the unsaturated coordination environment of metal atoms preferably act as the active centers, minimizing these metal species can significantly boost the specific activity of every single metal atom. Single-atom catalysts/catalysis (SACs), containing isolated metals atomically dispersed on or coordinated with the surface of a support material, represent the ultimate utilization of supported metals and maximize metal usage efficiency. Graphene, a two-dimensional star material, exhibiting extraordinary physical and chemical properties, has been approved as an excellent platform for constructing SACs. When atomically dispersed metal atoms are strongly anchored on the graphene surface, featuring ultra-high surface area and excellent electronic properties, SACs offer a great potential to significantly innovate the conventional heterogeneous catalysis, especially in the field of electrocatalysis. In this review, a detailed discussion of graphene-supported SACs, including preparation approaches, characterization techniques and applications on typical electrocatalytic reactions is provided. The advantages and unique features of graphene-supported SACs as efficient electrocatalysts and the upcoming challenges for improving their performance and further practical applications are also highlighted.

Homochiral to heterochiral transition in a pentahelicene monolayer on Bi(111).

We report the nucleation and two dimensional (2D) crystallization of the helical aromatic hydrocarbon pentahelicene ([5]H) on the semimetallic Bi(111) surface studied via low-temperature scanning tunneling microscopy. Individual homochiral dimers and heterochiral trimers appear on the substrate at a low coverage. With an increase in the coverage, a chiral phase transition takes place from the 2D conglomerate of [5]H dimers to the 2D racemate of [5]H trimers. The heterochiral [5]H trimers reveal a wavy arrangement due to the swing of 5[H] trimer rows after every second or third trimers. The swing mechanism of the trimer rows can be attributed to the steric repulsion between the adjacent trimers with same handedness.

Polymer dependent acoustic mode coupling and Hooke's law spring constants in stacked gold nanoplates.

Metal nanoparticles are excellent acoustic resonators and their vibrational spectroscopy has been widely investigated. However, the coupling between vibrational modes of different nanoparticles is less explored. For example, how the intervening medium affects the coupling strength is not known. Here, we investigate how different polymers affect coupling in Au nanoplate-polymer-Au nanoplate sandwich structures. The coupling between the breathing modes of the Au nanoplates was measured using single-particle pump-probe spectroscopy, and the polymer dependent coupling strength was determined experimentally. Analysis of the acoustic mode coupling gives the effective spring constant for the polymers. A relative motion mode was also observed for the stacked Au nanoplates. The frequency of this mode is strongly correlated with the coupling constant for the breathing modes. The breathing mode coupling and relative motion mode were analyzed using a coupled oscillator model. This model shows that both these effects can be described using the same spring constant for the polymer. Finally, we present a new type of mass balance using the strongly coupled resonators. We show that the resonators have a mass detection limit of a few femtograms. We envision that further understanding of the vibrational coupling in acoustic resonators will improve the coupling strength and expand their potential applications.

Strain-Relief Patterns and Kagome Lattice in Self-Assembled C60 Thin Films Grown on Cd(0001).

We report an ultra-high vacuum low-temperature scanning tunneling microscopy (STM) study of the C60 monolayer grown on Cd(0001). Individual C60 molecules adsorbed on Cd(0001) may exhibit a bright or dim contrast in STM images. When deposited at low temperatures close to 100 K, C60 thin films present a curved structure to release strain due to dominant molecule-substrate interactions. Moreover, edge dislocation appears when two different wavy structures encounter each other, which has seldomly been observed in molecular self-assembly. When growth temperature rose, we found two forms of symmetric kagome lattice superstructures, 2 × 2 and 4 × 4, at room temperature (RT) and 310 K, respectively. The results provide new insight into the growth behavior of C60 films.

TLR5 activation in hepatocytes alleviates the functional suppression of intrahepatic CD8+ T cells.

The liver is an immune-privileged organ with a tolerogenic environment for maintaining liver homeostasis. This hepatic tolerance limits the intrahepatic CD8+ T-cell response for eliminating infections. The tolerant microenvironment in the liver is orchestrated by liver-specific immunoregulatory cells that can be functionally regulated by pathogen-associated molecular patterns (PAMPs). Here, we report that flagellin, a key PAMP of gut bacteria, modulates the intrahepatic CD8+ T-cell response by activating the TLR5 signalling pathway of hepatocytes. We found that mice treated with Salmonella-derived recombinant flagellin (SF) by hydrodynamic injection had a significantly elevated IFN-γ production by the intrahepatic lymphocytes in 7 days after injection. This was correlated with a reduced immune suppressive effect of primary mouse hepatocytes (PMHs) in comparison with that of PMHs from mock-injected control mice. In vitro co-culture of SF-treated PMHs with splenocytes revealed that hepatocyte-induced immune suppression is alleviated through activation of the TLR5 but not the NLRC4 signalling pathway, leading to improved activation and function of CD8+ T cells during anti-CD3 stimulation or antigen-specific activation. In an acute HBV replication mouse model established by co-administration of SF together with an HBV-replicating plasmid by hydrodynamic injection, SF significantly enhanced the intrahepatic HBV-specific CD8+ T-cell response against HBV surface antigen. Our results clearly showed that flagellin plays a role in modulating the intrahepatic CD8+ T-cell response by activating the TLR5 pathway in PMHs, which suggests a potential role for gut bacteria in regulating liver immunity.

Inhomogeneous photocarrier dynamics and transport in monolayer MoS2 by ultrafast microscopy.

Monolayer MoS2 as a member of two-dimensional transition metal dichalcogenides (TMDs) has attracted considerable attention due to its superior optoelectronic properties. Understanding the photocarrier dynamics and transport in these two dimensional systems is beneficial for applications from photovoltaics to sensing. However, various structural defects strongly impact the dynamics and transport of photocarriers. Especially there lacks a precise measuring and understanding of photocarrier transport in TMDs. Here, femtosecond transient absorption spectroscopy and microscopy were employed to study the photocarrier dynamics and transport in monolayer MoS2. Defect correlated photocarrier dynamics are observed across the monolayer MoS2 where exciton formation and nonradiative recombination are the two dominant decay processes. To the best of our knowledge, we report two distinct photocarrier transport regimes in MoS2 for the first time with diffusion coefficients of [Formula: see text] cm2 s-1 and [Formula: see text] cm2 s-1, by taking advantages of ultrafast microscopy with ∼20 nm spatial precision and ∼200 fs temporal resolution. These two regimes are ascribed to fast hot photocarrier diffusion and slow phonon-limited thermal diffusion, respectively. The results indicate that the initial fast photocarrier transport is less dependent on structural defects compared to photocarrier relaxation dynamics which may be useful for hot photocarrier extraction applications.

Long Lifetime and Coupling of Acoustic Vibrations of Gold Nanoplates on Unsupported Thin Films.

Radiation losses due to energy transfer to acoustic waves in the surroundings lead to short vibrational lifetimes of plasmonic nanoresonators and severely limits their applications in quantum technologies and mass sensing. Here we demonstrate a general method for improving the acoustic vibration lifetimes of Au nanoplates (flat structures with edge lengths of several microns and thicknesses of 10-40 nm) by using unsupported thin films instead of thick substrates, which blocks the outgoing acoustic waves. We experimentally confirm the vibrational quality factor improvement of Au nanoplates on Si3N4 and Al2O3/Si3N4 thin films with thicknesses less than 100 nm. Through this substrate phonon engineering, we successfully observe strong vibrational coupling between two Au nanoplates. Furthermore, the increased vibrational lifetimes allow us to study the vibrations of the nanoplates relative to the substrate and, for stacked nanoplates, relative to each other. The frequencies of these relative vibrational modes are well described by a simple coupled mass model, which provides the effective spring constants between interfaces separated by surface bonded molecules. We also demonstrate that the continuous thin films can be used for small plasmonic nanostructures (dimensions of several hundred nm), with similar increases in the vibrational lifetimes.

A Graphene-Supported Single-Atom FeN5 Catalytic Site for Efficient Electrochemical CO2 Reduction.

Electrochemical conversion of CO2 into valued products is one of the most important issues but remains a great challenge in chemistry. Herein, we report a novel synthetic approach involving prolonged thermal pyrolysis of hemin and melamine molecules on graphene for the fabrication of a robust and efficient single-iron-atom electrocatalyst for electrochemical CO2 reduction. The single-atom catalyst exhibits high Faradaic efficiency (ca. 97.0 %) for CO production at a low overpotential of 0.35 V, outperforming all Fe-N-C-based catalysts. The remarkable performance for CO2 -to-CO conversion can be attributed to the presence of highly efficient singly dispersed FeN5 active sites supported on N-doped graphene with an additional axial ligand coordinated to FeN4 . DFT calculations revealed that the axial pyrrolic nitrogen ligand of the FeN5 site further depletes the electron density of Fe 3d orbitals and thus reduces the Fe-CO π back-donation, thus enabling the rapid desorption of CO and high selectivity for CO production.

Hexagonal Monolayer Ice without Shared Edges.

When adsorbed on solids, water molecules are usually arranged into a honeycomb hydrogen-bond network. Here we report the discovery of a novel monolayer ice built exclusively from water hexamers but without shared edges, distinct from all conventional ice phases. Water grown on graphite crystalizes into a robust monolayer ice after annealing, attaining an exceedingly high density of 0.134 Å^{-2}. Unlike chemisorbed ice on metal surfaces, the ice monolayer can translate and rotate on graphite terraces and grow across steps, confirming its two-dimensional nature. First-principles calculations identify the monolayer ice structure as a robust self-assembly of closely packed water hexamers without edge sharing, whose stability is maintained by maximizing the number of intralayer hydrogen bonds on inert surfaces.

Chinese woodchucks with different susceptibility to WHV infection differ in their genetic background exemplified by cytochrome B and MHC-DRB molecules.

BACKGROUND: Chinese woodchucks (M. himalayana) were recently found to be susceptible to woodchuck hepatitis virus (WHV) infection. In this study, we aimed to determine the susceptibility to WHV infection of M. himalayana from different areas and their association with the animal genetic background exemplified by cytochrome B and MHC-DRB molecules. METHODS: Animals from four different areas in Qinghai province were inoculated with WHV59 strains. The virological markers including WHV surface antigen (WHsAg), WHV core antibody (WHcAb), and WHV DNA in serum were measured by ELISA and Real-time PCR, respectively. The sequences of cytochrome B gene and MHC-DRB molecules were obtained and sorted with Clustalx software. The nucleotide variation sites were identified using MEGA5 software. RESULTS: The animals from four different areas had different susceptibility to WHV infection. Animals from TR and TD areas had a high level of long-lasting viremia, while those from GD and WL areas had a low level of transient viremia after WHV inoculation. All of the animals belong to the same subspecies M. himalayana robusta identified by cytochrome B gene sequences. Based on their nucleotide variation pattern, 8 alleles of cytochrome B gene were identified, and 7 MHC-DRB alleles were identified. Allele A of cytochrome B and Allele Mamo-DRB1*02 of MHC-DRB was found to be frequent in animals from TR and TD areas, while Allele H of cytochrome B and Allele Mamo-DRB1*07 of MHC-DRB was predominant in animals from GD and WL areas. CONCLUSION: Chinese woodchucks from different areas differed in their susceptibility to WHV infection, though they belong to the same subspecies M. himalayana robusta. The genetic background exemplified by cytochrome B and MHC-DRB differed in Chinese woodchucks with different susceptibility to WHV infection.

Ultrafast carrier dynamics and third-order nonlinear optical properties of AgInS2/ZnS nanocrystals.

Broad photoluminescence (PL) emission, a large Stokes shift and extremely long-lived radiative lifetimes are the characteristics of ternary I-III-VI semiconductor nanocrystals (NCs), such as CuInS2 and AgInS2. However, the lack of understanding regarding the intriguing PL mechanisms and photo-carrier dynamics limits their further applications. Here, AgInS2 and AgInS2/ZnS NCs were chemically synthesized and their carrier dynamics were studied by time-resolved PL spectroscopy. The results demonstrated that the surface defect state, which contributed dominantly to the non-radiative decay processes, was effectively passivated through ZnS alloying. Femtosecond transient absorption spectroscopy was also used to investigate the carrier dynamics, revealing the electron storage at the surface state and donor state. Furthermore, the two photon absorption properties of AgInS2 and AgInS2/ZnS NCs were measured using an open-aperture Z-scan technique. The improved third-order nonlinear susceptibility [Formula: see text] of AgInS2 through ZnS alloying demonstrates potential application in two photon PL biological imaging.

Chirality switching of the self-assembled CuPc domains induced by electric field.

Chiral switching of the self-assembled domains of CuPc molecules on the Cd(0001) surface has been investigated by means of a low temperature scanning tunneling microscopy (STM). With the coverage increasing, the CuPc molecules show the structural evolutions from an initial gas-like state to a network phase, a square phase, and finally to a compact phase at full monolayer. In the network and square phases, the achiral CuPc molecules reveal both the point chirality and chiral domains. In particular, the chirality of network domain can be switched from one enantiomer to another driven by the electric filed from a STM tip, which can also lead to the lattice rotation of network phase. These results demonstrate that (i) there is strong interaction between the CuPc molecules and STM tip; (ii) the adsorbed CuPc molecules carry considerable net charge or polarizability due to the charge transfer; (iii) the network phase has a low barrier for the interconversion between right- and left-handed domains. Our findings are significant for the understanding and control of the domain's chirality in the self-assembled structures.