Abstract
The development of covalent organic frameworks (COFs) with efficient charge transport is of immense interest for applications in optoelectronic devices. To enhance COF charge transport ...properties, electroactive building blocks and dopants can be used to induce extended conduction channels. However, understanding their intricate interplay remains challenging. We designed and synthesized a tailor‐made COF structure with electroactive hexaazatriphenylene (HAT) core units and planar dioxin (D) linkages, denoted as HD‐COF. With the support of theoretical calculations, we found that the HAT units in the HD‐COF induce strong, eclipsed π–π stacking. The unique stacking of HAT units and the weak in‐plane conjugation of dioxin linkages leads to efficient anisotropic charge transport. We fabricated HD‐COF films to minimize the grain boundary effect of bulk COFs, which resulted in enhanced conductivity. As a result, the HD‐COF films showed an electrical conductivity as high as 1.25 S cm
−1
after doping with tris(4‐bromophenyl)ammoniumyl hexachloroantimonate.
We report the synthesis and characterization of a two-dimensional (2D) conjugated Ni(II) tetraaza14annulene-linked metal organic framework (NiTAA-MOF) where NiTAA is a macrocyclic MN4 (M = metal, N ...= nitrogen) compound. The structure of NiTAA-MOF was elucidated by Fourier-transform infrared, X-ray photoemission, and X-ray diffraction spectroscopies, in combination with density functional theory (DFT) calculations. When chemically oxidized by iodine, the insulating bulk NiTAA-MOF (σ < 10–10 S/cm) exhibits an electrical conductivity of 0.01 S/cm at 300 K, demonstrating the vital role of ligand oxidation in the electrical conductivity of 2D MOFs. Magnetization measurements show that iodine-doped NiTAA-MOF is paramagnetic with weak antiferromagnetic coupling due to the presence of organic radicals of oxidized ligands and high-spin Ni(II) sites of the missing-linker defects. In addition to providing further insights into the origin of the induced electrical conductivity in 2D MOFs, both pristine and iodine-doped NiTAA-MOF synthesized in this work could find potential applications in areas such as catalase mimics, catalysis, energy storage, and dynamic nuclear polarization-nuclear magnetic resonance (DNP-NMR).
Heterointerfaces may exhibit unexpected physical properties distinct from intrinsic properties of component materials. In particular, metal–organic interfaces can drive unique interfacial spin ...moments, which are often called molecular spinterface. Here, van der Waals stacking of molecular layers may lead to variations in the intra/interlayer exchange coupling resulting in multiple ground states, which is highly desired for multifunctional magnetic devices. In this report, the emergence of molecular multispinterface of paramagnetic cobalt‐octaethyl‐porphyrin (CoOEP) layers in a Fe/CoOEP heterostructure is demonstrated through the interfacial layer and a successive antiferromagnetic molecular spin chain. The disentangled interfacial ferromagnetic spins lead to multiple magnetic ground states and behave as additional spin‐dependent scattering centers, as evidenced through the magnetotransport study. In addition, the antiferromagnetic molecule spin chain derives tunable exchange bias, which signifies the dominance of the antiferromagnetic interfacial interaction. Theoretical calculations demonstrate spin configurations of the molecular chain and the antiferromagnetic interfacial coupling through oxygen intermediaries. The development of the molecular multispinterface and controllable exchange bias therein will provide a promising route for the active control of multivalued data processing at the nanoscale.
Heterointerfaces of paramagnetic planar CoOEP molecules on a ferromagnetic Fe film develop unique interfacial molecular magnetism, which also derives successive antiferromagnetic molecular spin chain. This multispinterface leads to tunable exchange bias and multiple magnetic ground states and behaves as additional spin‐dependent scattering centers, as evidenced through magnetometry and magnetotransport and their origin is unveiled by density functional theory calculations.
We demonstrate high-performance polymer solar cells using the plasmonic effect of multipositional silica-coated silver nanoparticles. The location of the nanoparticles is critical for increasing ...light absorption and scattering via enhanced electric field distribution. The device incorporating nanoparticles between the hole transport layer and the active layer achieves a power conversion efficiency of 8.92% with an external quantum efficiency of 81.5%. These device efficiencies are the highest values reported to date for plasmonic polymer solar cells using metal nanoparticles.
We report the synthesis and characterization of a two-dimensional (2D) MX2Y2-type (M = metal, X, Y = N, S, O, and X ≠ Y) copper 1,3,5-triamino-2,4,6-benzenetriol metal–organic framework ...(Cu3(TABTO)2-MOF). The role of oxygen in the synthesis of this MOF was investigated. Copper metal is formed along with the MOF when the synthesis is done in argon as suggested by XRD. When the reaction was exposed to air with vigorous stirring, copper metal was not observed by XRD. However, if there is no stirring, then copper metal is formed, and we learned that this is because oxygen was not allowed to enter the solvent due to the formation of a MOF film at the air/water interface. For the sample synthesized in argon (Cu3(TABTO)2-Ar), an insulating Cu3(TABTO)2-Ar pellet (σ < 10–10 S cm–1) became a metallic conductor with an electrical conductivity of 0.78 S cm–1 at 300 K after exposure to iodine vapor. This work provides further insights into the role of oxygen in the synthesis of redox-active ligand-based MOFs, expands the family of 2D redox-active ligand-based electrically conductive MOFs, and offers more opportunities in sensing, photocatalytic, electronic, and energy-related applications.
Understanding national trends of heart failure (HF) is crucial for establishing prevention and treatment strategies. We aimed to investigate the 11-year trends of HF in the South Korean population.
...Using the Korean National Health Insurance Service database, we identified 3,446,256 patients with HF between 2004 and 2014.
The prevalence of HF was 1.42% in 2004, steadily increasing to 1.98% in 2014. However, the age-adjusted prevalence of HF remained stable (1.43% in 2014). The incidence of HF was 6.1/1000 person-years in 2004 and remained at similar levels, reaching 5.4/1000 person-years in 2014. The age-adjusted incidence of HF slowly decreased to 3.94/1000 person-years in 2014. The event rate for hospitalized patients with HF remained stable increasing from 1.40 in 2004 to 1.87/1000 person-years in 2014, and the age-adjusted event rate of hospitalized HF decreased to 1.22 in 2014.
In South Korea, between 2004 and 2014, the prevalence of HF increased while the incidence of HF remained stable. Furthermore, the age-adjusted HF prevalence was stable, and the age-adjusted incidence decreased. This indicates that the aging population is the main cause of the increasing national burden associated with HF and that further attention is warranted in the management of HF in older adults.
Sucrose-nonfermentation1-related protein kinase1 (SnRK1) is an evolutionarily conserved energy sensor protein that regulates gene expression in response to energy depletion in plants. Efforts to ...elucidate the functions and mechanisms of this protein kinase are hampered, however, by inherent growth defects of snrk1 -null mutant plants. To overcome these limitations and study SnRK1 functions in vivo, we applied a method combining transient expression in leaf mesophyll protoplasts and stable expression in transgenic plants. We found that both rice (Oryza sativa) and Arabidopsis (Arabidopsis thaliana) SnRK1 activities critically influence stress-inducible gene expression and the induction of stress tolerance. Genetic, molecular, and chromatin immunoprecipitation analyses further revealed that the nuclear SnRK1 modulated target gene transcription in a submergencedependent manner. From early seedling development through late senescence, SnRKl activities appeared to modulate developmental processes in the plants. Our findings offer insight into the regulatory functions of plant SnRK1 in stressresponsive gene regulation and in plant growth and development throughout the life cycle.
The substantial amount of pollutants produced by crop burning leads to particulate matter (PM2.5) formation through chemical reactions in the atmosphere. In this study, we quantitatively examined the ...characteristics of PM2.5 component concentration changes and the production mechanism of sulfate (SO42−) due to crop burning in China, during a period of high PM2.5 concentrations in South Korea. Crop burning emissions were obtained from the Fire INventory from NCAR (FINN), and simulations were conducted using the Community Multi-scale Air Quality (CMAQ) model. The concentrations of PM2.5, nitrate, ammonium, organic carbon, and elemental carbon caused by crop burning were the highest in Northeast China, while the SO42− concentration was higher in the Shandong Peninsula and the Yellow Sea. SO42− was mainly produced through the oxidation reaction by hydrogen peroxide (H2O2) (H2O2 + S(IV) = S(VI) + H2O) (1.44 μg/m3, 80.49%). H2O2 that contributed to SO42− production was primarily produced through the self-reaction of hydroperoxy radical (HO2). Moreover, HO2, which contributed to the production of H2O2, was mainly formed through the decomposition of peroxynitric acid (PNA), which is produced by nitric oxide (NOx) emissions from crop burning. SO42− in the Yellow Sea was reported to be predominantly produced by the oxidation of sulfur dioxide (SO2) by hydroxyl radical (OH) (OH + SO2 = SULF + HO2); however, our study suggests that the PNA formed by NOx emissions from crop burning could contribute to an increase in H2O2, which subsequently promotes SO42− production. The produced SO42− was then transported across the Yellow Sea, impacting the elevated PM2.5 concentrations in Jeju Island, a suburban area of South Korea. These findings demonstrate that the mechanisms of SO42− production by crop burning emissions differ from those of anthropogenic emissions.
Display omitted
•Characteristics of transboundary transport of SO42− concentrations induced by crop burning were investigated.•The SO42− due to crop burning was primarily produced by the reaction of H2O2 with S(IV), differing from that by anthropogenic emissions.•The H2O2 was produced through the self-reaction of HO2, which was formed by the decomposition reaction of PNA.•The transported SO42− contributed to an increase in the proportion of SO42− in the PM2.5 concentrations in South Korea.
The development of complex nanostructures containing a homo- and heteromixture of two or more metals is a considerable challenge in nanotechnology. However, previous approaches are considerably ...limited to the number of combinations of metals depending on the compatibility of elements, and to the complex shape control of the nanostructure. In this study, a significant step is taken toward resolving these limitations via the utilization of a low-energy argon-ion bombardment. The multilayer films are etched and re-sputtered on the sidewall of the pre-pattern, which is a secondary sputtering phenomenon. In contrast to the precursor mixing method, most metallic combinations can be fabricated. The degree of mixing is tuned by the control of the sequence and thickness of multilayers. In addition, the feature shape and dimensions are controlled by changing the pre-pattern or by controlling the ion-beam angle. Using this method, the shortest response time (2 s to 1% H
) in comparison with those of Pd-based H
sensors reported previously and a limit of detection below 1 parts per million (ppm) for Pd/Au and Pd/Pt bimetallic line arrays are achieved. This study is expected to realize a family of polyelements that can be used in various applications.
Ordered graphitic carbon nanosheets (GCNs) were, for the first time, synthesized by the direct condensation of multifunctional phenylacetyl building blocks (monomers) in the presence of phosphorous ...pentoxide. The GCNs had highly ordered structures with random hole defects and oxygenated functional groups, showing paramagnetism. The results of combined structural and magnetic analyses indicate that the hole defects and functional groups are associated with the appearance and stabilization of unpaired spins. DFT calculations further suggest that the emergence of stabilized spin moments near the edge groups necessitates the presence of functionalized carbon atoms around the hole defects. That is, both hole defects and oxygenated functional groups are essential ingredients for the generation and stabilization of spins in GCNs.
Ordered graphitic carbon nanosheets (GCNs) were prepared by the direct dehydration of phenylacetyl units using powerful dehydrating agent, phosphorous pentoxide (P2O5). The GCNs, with random hole defects and remnant oxygenated groups, displayed paramagnetism. The correlation between structure and magnetism was manifested by experiments and calculations.
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