Positioning hydrogen reaction sites by constructing CdS/CoNiMoS4 heterojunctions for efficient photocatalytic hydrogen evolution.

The high gravimetric energy density of hydrogen makes it an ideal chemical fuel to address the issues of fossil fuel depletion and environmental pollution. Even though transition metal sulfides (TMSs) have been extensively investigated as substitutes for noble metals, their effectiveness is still doubtful for practical applications. Herein, we introduce a facile and general strategy to fabricate heterojunctions with CdS nanorods and a multimetallic transition metal sulfide (CoNiMoS4) for enhanced photocatalytic activity. The CdS/CoNiMoS4 heterojunction will serve as a dual-function photocatalyst with enhanced visible light absorption capability offered by CdS and high charge transfer efficiency provided by CoNiMoS4 nanostructures. Moreover, CdS/CoNiMoS4 nanostructures exhibit the best photocatalytic performance to generate H2 with an amount of 31.9 mmol g-1 h-1, with a distinguished stability for over 25 h. This synthetic approach may offer a new strategy to create diverse heterojunctions with Earth-abundant multimetallic components, which may broaden their scope of application in catalysis.

Highly stable and durable ZnIn2S4 nanosheets wrapped oxygen deficient blue TiO2(B) catalyst for selective CO2 photoreduction into CO and CH4.

Developing new and highly stable efficient photocatalysts is crucial for achieving high performance and selective photocatalytic CO2 conversion. In this paper, we designed a one-dimensional oxygen-deficient blue TiO2(B) (BT) catalyst for improved electron mobility and visible light accessibility. In addition, hexagonal ZnIn2S4 (ZIS) nanosheets with a low bandgap and great visible light accessibility are employed to produce effective heterostructures with BT. The synthesized materials are tested for photocatalytic conversion of CO2 into solar fuels (H2, CO and CH4). The optimized composite yields 71.6 and 10.3 µmol g-1h-1 of CO and CH4, three and ten times greater than ZIS, respectively. When ZIS nanosheets are combined with a one-dimensional oxygen-deficient BT catalyst, improved electron mobility and visible light accessibility are achieved, charge carriers are effectively segregated, and the transfer process is accelerated, resulting in efficient CO2 reduction. The photocatalytic CO2 conversion activity of the constructed BT/ZIS heterostructures is very stable over a 10-day (240-hour) period, and CO and CH4 production rates increase linearly with time; however, as time goes on, the rates of H2 production decrease. Further, a five-time recycling test confirmed this, revealing essentially equal activity and selectivity throughout the experiment. As a result, CO2 to CO and CH4 conversion has high selectivity and longer durability. The band structure of the BT/ZIS composite is determined using Mott-Schottky measurement, diffuse reflectance spectroscopy, and valence band X-ray photoelectron spectroscopy. This research demonstrates a novel approach to investigating effective, stable, and selective photocatalytic CO2 reduction systems for solar-to-chemical energy conversion.

Gleditsiae fructus regulates osteoclastogenesis by inhibiting the c­Fos/NFATc1 pathway and alleviating bone loss in an ovariectomy model.

Medical and economic developments have allowed the human lifespan to extend and, as a result, the elderly population has increased worldwide. Osteoporosis is a common geriatric disease that has no symptoms and even a small impact can cause fractures in patients, leading to a serious deterioration in the quality of life. Osteoporosis treatment typically involves bisphosphonates and selective estrogen receptor modulators. However, these treatments are known to cause severe side effects, such as mandibular osteonecrosis and breast cancer, if used for an extended period of time. Therefore, it is essential to develop therapeutic agents from natural products that have fewer side effects. Gleditsiae fructus (GF) is a dried or immature fruit of Gleditsia sinensis Lam. and is composed of various triterpenoid saponins. The anti­inflammatory effect of GF has been confirmed in various diseases, and since the anti­inflammatory effect plays a major role in inhibiting osteoclast differentiation, GF was expected to be effective in osteoclast differentiation and menopausal osteoporosis; however, to the best of our knowledge, it has not yet been studied. Therefore, the present study was designed to examine the effect of GF on osteoclastogenesis and to investigate the mechanism underlying inhibition of osteoclast differentiation. The effects of GF on osteoclastogenesis were determined in vitro by tartrate­resistant acid phosphatase (TRAP) staining, pit formation assays, filamentous actin (F­actin) ring formation assays, western blotting and reverse transcription­quantitative PCR analyses. Furthermore, the administration of GF to an animal model exhibiting menopausal osteoporosis allowed for the analysis of alterations in the bone microstructure of the femur using micro­CT. Additionally, assessments of femoral tissue and serum were conducted. The present study revealed that the administration of GF resulted in a reduction in osteoclast levels, F­actin rings, TRAP activity and pit area. Furthermore, GF showed a dose­dependent suppression of nuclear factor of activated T­cells cytoplasmic, c­Fos and other osteoclastogenesis­related markers.

Do Planar Tetracoordinate Fluorine Atoms Exist? Revisiting a Theoretical Prediction.

We re-examined the existence of planar tetracoordinate F (ptF) atoms, which was proposed recently by using high-level ab initio methods such as coupled-cluster singles and doubles with perturbative triples (CCSD(T)) with large basis sets. Our calculations indicate that the planar structures of FIn4+ (D4h), FTl4+ (D4h), FGaIn3+ (C2V), FIn2Tl2+ (D2h), FIn3Tl+ (C2V), and FInTl3+ (C2V) are not the minimum energy states; by contrast, they are transition states. Density functional theory calculations overestimate the size of the cavity formed by the four peripheral atoms, leading to erroneous conclusions regarding the existence of ptF atoms. Our analysis suggests that the preference for non-planar structures in the six cations studied is not due to the pseudo Jahn-Teller effect. Additionally, spin-orbit coupling does not alter the main conclusion that the ptF atom does not exist. If sufficiently large cavity formation by group 13 elements to accommodate the central F- ion is guaranteed, then the existence of ptF atoms is plausible.

Asymmetric gradient orbital interaction of hetero-diatomic active sites for promoting C - C coupling.

Diatomic-site catalysts (DACs) garner tremendous attention for selective CO2 photoreduction, especially in the thermodynamical and kinetical mechanism of CO2 to C2+ products. Herein, we first engineer a novel Zn-porphyrin/RuCu-pincer complex DAC (ZnPor-RuCuDAC). The heteronuclear ZnPor-RuCuDAC exhibits the best acetate selectivity (95.1%), while the homoatomic counterparts (ZnPor-Ru2DAC and ZnPor-Cu2DAC) present the best CO selectivity. In-situ spectroscopic measurements reveal that the heteronuclear Ru-Cu sites easily appear C1 intermediate coupling. The in-depth analyses confirm that due to the strong gradient orbital coupling of Ru4d-Cu3d resonance, two formed *CO intermediates of Ru-Cu heteroatom show a significantly weaker electrostatic repulsion for an asymmetric charge distribution, which result from a side-to-side absorption and narrow dihedral angle distortion. Moreover, the strongly overlapped Ru/Cu-d and CO molecular orbitals split into bonding and antibonding orbitals easily, resulting in decreasing energy splitting levels of C1 intermediates. These results collectively augment the collision probability of the two *CO intermediates on heteronuclear DACs. This work first provides a crucial perspective on the symmetry-forbidden coupling mechanism of C1 intermediates on diatomic sites.

High level ab initio and density functional study of TeF6+ and TeCl6+: Attainability of +7 oxidation state for tellurium.

Discovery of a new oxidation state for an element expands its chemistry. A high oxidation state, such as +7, is rare for sp-block elements except for halogens. In this study, we determined that Te can attain a +7 oxidation state through the existence of a distorted octahedron (DOH) structure of TeCl6+ based on coupled cluster singles and doubles with perturbative triples calculations. We propose a new type of isomerization that resembles pseudorotation. The octahedron structure of TeF6+ bearing one elongated axial bond isomerizes to a DOH via an associated pseudorotation.

Geometric and Electronic Structural Engineering of Isolated Ni Single Atoms for a Highly Efficient CO2 Electroreduction.

Tuning the coordination environment and geometric structures of single atom catalysts is an effective approach for regulating the reaction mechanism and maximize the catalytic efficiency of single-atom centers. Here, a template-based synthesis strategy is proposed for the synthesis of high-density NiNx sites anchored on the surface of hierarchically porous nitrogen-doped carbon nanofibers (Ni-HPNCFs) with different coordination environments. First-principles calculations and advanced characterization techniques demonstrate that the single Ni atom is strongly coordinated with both pyrrolic and pyridinic N dopants, and that the predominant sites are stabilized by NiN3 sites. This dual engineering strategy increases the number of active sites and utilization efficiency of each single atom as well as boosts the intrinsic activity of each active site on a single-atom scale. Notably, the Ni-HPNCF catalyst achieves a high CO Faradaic efficiency (FECO ) of 97% at a potential of -0.7 V, a high CO partial current density (jCO ) of 49.6 mA cm-2 (-1.0 V), and a remarkable turnover frequency of 24 900 h-1 (-1.0 V) for CO2 reduction reactions (CO2 RR). Density functional theory calculations show that compared to pyridinic-type NiNx , the pyrrolic-type NiN3 moieties display a superior CO2 RR activity over hydrogen evolution reactions, resulting in their superior catalytic activity and selectivity.

Synthesis of Pore-Wall-Modified Stable COF/TiO2 Heterostructures via Site-Specific Nucleation for an Enhanced Photoreduction of Carbon Dioxide.

Constructing stable heterostructures with appropriate active site architectures in covalent organic frameworks (COFs) can improve the active site accessibility and facilitate charge transfer, thereby increasing the catalytic efficiency. Herein, a pore-wall modification strategy is proposed to achieve regularly arranged TiO2 nanodots (≈1.82 nm) in the pores of COFs via site-specific nucleation. The site-specific nucleation strategy stabilizes the TiO2 nanodots as well as enables the controlled growth of TiO2 throughout the COFs' matrix. In a typical process, the pore wall is modified and site-specific nucleation is induced between the metal precursors and the organic walls of the COFs through a careful ligand selection, and the strongly bonded metal precursors drive the confined growth of ultrasmall TiO2 nanodots during the subsequent hydrolysis. This will result in remarkably improved surface reactions, owing to the superior catalytic activity of TiO2 nanodots functionalized to COFs through strong NTiO bonds. Furthermore, density functional theory studies reveal that pore-wall modification is beneficial for inducing strong interactions between the COF and TiO2 and results in a large energy transfer via the NTiO bonds. This work highlights the feasibility of developing stable COF and metal oxide based heterostructures via organic wall modifications to produce carbon fuels by artificial photosynthesis.

Long-Term Exposure of MoS2 to Oxygen and Water Promoted Armchair-to-Zigzag-Directional Line Unzippings.

Understanding the long-term stability of MoS2 is important for various optoelectronic applications. Herein, we show that the long-term exposure to an oxygen atmosphere for up to a few months results in zigzag (zz)-directional line unzipping of the MoS2 basal plane. In contrast to exposure to dry or humid N2 atmospheres, dry O2 treatment promotes the initial formation of line defects, mainly along the armchair (ac) direction, and humid O2 treatment further promotes ac line unzipping near edges. Further incubation of MoS2 for a few months in an O2 atmosphere results in massive zz-directional line unzipping. The photoluminescence and the strain-doping plot based on two prominent bands in the Raman spectrum show that, in contrast to dry-N2-treated MoS2, the O2-treated MoS2 primarily exhibits hole doping, whereas humid-O2-treated MoS2 mainly exists in a neutral charge state with tension. This study provides a guideline for MoS2 preservation and a further method for generating controlled defects.

Development of an experimental apparatus to observe ultrafast phenomena by tender X-ray absorption spectroscopy at PAL-XFEL.

Understanding the ultrafast dynamics of molecules is of fundamental importance. Time-resolved X-ray absorption spectroscopy (TR-XAS) is a powerful spectroscopic technique for unveiling the time-dependent structural and electronic information of molecules that has been widely applied in various fields. Herein, the design and technical achievement of a newly developed experimental apparatus for TR-XAS measurements in the tender X-ray range with X-ray free-electron lasers (XFELs) at the Pohang Accelerator Laboratory XFEL (PAL-XFEL) are described. Femtosecond TR-XAS measurements were conducted at the Ru L3-edge of well known photosensitizer tris(bipyridine)ruthenium(II) chloride ([Ru(bpy)3]2+) in water. The results indicate ultrafast photoinduced electron transfer from the Ru center to the ligand, which demonstrates that the newly designed setup is applicable for monitoring ultrafast reactions in the femtosecond domain.

Effective dye degradation by an environment-friendly porous few-layered carbon nitride photocatalyst developed using sequential molecule self-assembly.

Two-dimensional (2D) g-C3N4 (CN) has garnered massive interest for photocatalytic applications owing to its excellent photon contact area, visible-light absorption, and easy transport of photogenerated charge carriers to the surface. However, bulk CN suffers from intrinsically poor charge separation, limited specific surface area, and insufficient visible-light absorption, significantly limiting its photocatalytic efficiency. Exfoliation of bulk crystals into nanosheets with few layers has proven to be an effective and widely used strategy to enhance photocatalytic performance; however, this process is quite complicated, requiring longer times and external energy. Here, a few-layered porous g-C3N4 (PCN) was synthesized using the molecular self-assembly process. This prepared PCN exposes more active sites, leading to enhanced separation of charge carriers, resulting in a higher photocatalytic activity than regular CN. PCN achieved the best photocatalytic degradation (97.46%) of Rhodamine B (RhB) dye in 1 h, which is three times higher than that by CN (32.57%) because of enhanced porosity of the photocatalyst with few layers. This enhanced degradation performance of PCN was caused by increased visible-light absorption and charge separation along with higher number exposed active sites triggered by the high porosity under visible light, which is greater than those of other metal-free photocatalysts reported thus far.

Highly Durable and Fully Dispersed Cobalt Diatomic Site Catalysts for CO2 Photoreduction to CH4.

Dual-atom-site catalysts (DACs) have emerged as a new frontier in heterogeneous catalysis because the synergistic effect between adjacent metal atoms can promote their catalytic activity while maintaining the advantages of single-atom-site catalysts, such as almost 100 % atomic efficiency and excellent hydrocarbon selectivity. In this study, cobalt-based atom site catalysts with a Co2 -N coordination structure were synthesized and used for photodriven CO2 reduction. The resulting CoDAC containing 3.5 % Co atoms demonstrated a superior atom ratio for CO2 reduction catalytic performance, with 65.0 % CH4 selectivity, which far exceeds that of cobalt-based single-atom-site catalysts (CoSACs). The intrinsic reason for the superior activity of CoDACs is the excellent adsorption strength of CO2 and CO* intermediates at dimeric Co active sites.

Ligand-Field Effects in a Ruthenium(II) Polypyridyl Complex Probed by Femtosecond X-ray Absorption Spectroscopy.

We employ femtosecond X-ray absorption spectroscopy of [Ru(m-bpy)3]2+ (m-bpy = 6-methyl-2,2'-bipyridine) to elucidate the time evolution of the spin and charge density upon metal-to-ligand charge-transfer (MLCT) excitation. The core-level transitions at the Ru L3-edge reveal a very short MLCT lifetime of 0.9 ps and relaxation to the lowest triplet metal-centered state (3MC) which exhibits a lifetime of about 300 ps. Time-dependent density functional theory relates ligand methylation to a lower ligand field strength that stabilizes the 3MC state. A quarter of the 3MLCT population appears to be trapped which may be attributed to intramolecular vibrational relaxation or further electron transfer to the solvent. Our results demonstrate that small changes in the ligand field allow control of the photophysical properties. Moreover, this study underscores the high information content of femtosecond L-edge spectroscopy as a probe of valence charge density and spin-state in 4d transition metals.

National Monitoring of Mosquito Populations and Molecular Analysis of Flavivirus in the Republic of Korea in 2020.

The Korea Disease Control and Prevention Agency has established centers at 16 locations to screen vector populations and pathogens. The aims of this study were to determine the relative spatiotemporal distributions of mosquitoes that are flavivirus vectors, and to correlate them with instances of flaviviral disease in the Republic of Korea (ROK). We collected 67,203 mosquitoes in traps at 36 collection sites in 30 urban regions and migratory bird habitats in 2020. The trap index was 36.6, and the predominant mosquito species were the Culex pipiens complex, Armigeres subalbatus, Aedes albopictus, Aedes vexans, and Culex tritaeniorhynchus. The mosquitoes were pooled into 4953 pools to monitor flavivirus infection. We determined that the minimum infection rate of flavivirus was 0.01%. Japanese encephalitis virus (JEV) was detected in only seven pools of Culex orientalis from Sangju, and we isolated JVE from two pools. All detected JEV was found to be genotype V by phylogenetic analysis. To the best of our knowledge, this is the first study to isolate genotype V JVE from Culex orientalis in the ROK. Subsequent geographical and ecological studies on mosquitoes will help improve our understanding of the relative risk of flavivirus infection. Future studies should analyze mosquito species distribution and improve flavivirus monitoring and long-term surveillance.

Molecular evidence of zoonotic Babesia species, other than B. microti, in ixodid ticks collected from small mammals in the Republic of Korea.

The occurrence of tick-borne infectious diseases, including zoonotic babesiosis, has become a serious concern in recent years. In this study, we detected Babesia spp. using polymerase chain reaction (PCR) amplification of the 18S rRNA of the parasites isolated from ixodid ticks collected from small mammals in the Republic of Korea (ROK). Sequence analysis of the PCR amplicon revealed the presence of B. duncani, B. venatorum, B. capreoli/divergens, and, the most prevalent, B. microti in the ticks. The molecular phylogenetic analysis showed that the four species-specific18S rRNA sequences clustered in four distinct clades. This is the first study to provide molecular evidence for the presence of zoonotic Babesia spp. other than B. microti in ticks in the ROK.

Nationwide Incidence of Chigger Mite Populations and Molecular Detection of Orientia tsutsugamushi in the Republic of Korea, 2020.

The Korea Disease Control and Prevention Agency has established regional centers at 16 locations to monitor vectors and pathogens. We investigated the geographical and temporal distribution of chigger mite populations to understand tsutsugamushi disease epidemiology in 2020. To monitor weekly chigger mite populations, 3637 chigger mites were collected from sticky chigger mite traps in autumn. Chigger mites appeared from the first week of October to the third week of December, peaking in the fourth week of October. The predominant species were Leptotrombidium scutellare, Leptotrombidium palpale, Neotrombicula kwangneungensis, Neotrombicula tamiyai, and Leptotrombidium pallidum. To monitor Orientia tsutsugamushi infection in chigger mites, 50,153 chigger mites were collected from 499 trapped wild rodents in spring and autumn, with a chigger index of 100.5. Approximately 50% of chigger mites were pooled into 998 pools, and the minimum infection rate (MIR) of O. tsutsugamushi was 0.1%. Jeongeup had the highest MIR for O. tsutsugamushi (0.7%). The Kato-related genotype was the most common (52.2%), followed by the Karp-related (17.4%), Boryong (13.0%), JG-related (8.7%), Shimokoshi (4.3%), and Kawasaki (4.3%) genotypes. Ecological and geographical studies focusing on the basic ecology and pathology of mites will improve our understanding of tsutsugamushi disease risks in the Republic of Korea.

Nationwide Temporal and Geographical Distribution of Tick Populations and Phylogenetic Analysis of Severe Fever with Thrombocytopenia Syndrome Virus in Ticks in Korea, 2020.

Since 2010, the Korea Disease Control and Prevention Agency has established centers at 16 locations to monitor disease vectors and pathogens. Here, we examined tick populations to understand the geographical and temporal distribution of severe fever with thrombocytopenia syndrome virus (SFTSV) vectors in 2020. From April to November, 63,376 ticks were collected from traps to monitor tick populations, with a trap index of 41.3. Tick incidence varied from April to October, with population peaks observed for nymphs in May, adults in July, and larvae in September. The predominant tick species were Haemaphysalis longicornis, Haemaphysalis spp., H. flava, Ixodes spp., Amblyomma testudinarium, and Ixodes nipponensis. Approximately 50% of the collected ticks were pooled into 2973 groups to detect the rate of SFTSV infection in ticks. The minimum infection rate (MIR) of SFTSV was 0.2%, and Andong had the highest MIR for SFTSV (4.0%). The B3 genotype was the most prevalent (52.2%) followed by B2 (28.6%), B5 (15.9%), B4 (1.6%), and B6 (1.6%). We identified widely distributed tick species and a high degree of diversity in SFTSV strains in ticks from different geographical regions. The results may provide a basis for future epidemiological studies and risk assessments for tick-borne diseases.

Following Metal-to-Ligand Charge-Transfer Dynamics with Ligand and Spin Specificity Using Femtosecond Resonant Inelastic X-ray Scattering at the Nitrogen K-Edge.

We demonstrate for the case of photoexcited [Ru(2,2'-bipyridine)3]2+ how femtosecond resonant inelastic X-ray scattering (RIXS) at the ligand K-edge allows one to uniquely probe changes in the valence electronic structure following a metal-to-ligand charge-transfer (MLCT) excitation. Metal-ligand hybridization is probed by nitrogen-1s resonances providing information on both the electron-accepting ligand in the MLCT state and the hole density of the metal center. By comparing to spectrum calculations based on density functional theory, we are able to distinguish the electronic structure of the electron-accepting ligand and the other ligands and determine a temporal upper limit of (250 ± 40) fs for electron localization following the charge-transfer excitation. The spin of the localized electron is deduced from the selection rules of the RIXS process establishing new experimental capabilities for probing transient charge and spin densities.

Shot noise limited soft x-ray absorption spectroscopy in solution at a SASE-FEL using a transmission grating beam splitter.

X-ray absorption near-edge structure (XANES) spectroscopy provides element specificity and is a powerful experimental method to probe local unoccupied electronic structures. In the soft x-ray regime, it is especially well suited for the study of 3d-metals and light elements such as nitrogen. Recent developments in vacuum-compatible liquid flat jets have facilitated soft x-ray transmission spectroscopy on molecules in solution, providing information on valence charge distributions of heteroatoms and metal centers. Here, we demonstrate XANES spectroscopy of molecules in solution at the nitrogen K-edge, performed at FLASH, the Free-Electron Laser (FEL) in Hamburg. A split-beam referencing scheme optimally characterizes the strong shot-to-shot fluctuations intrinsic to the process of self-amplified spontaneous emission on which most FELs are based. Due to this normalization, a sensitivity of 1% relative transmission change is achieved, limited by fundamental photon shot noise. The effective FEL bandwidth is increased by streaking the electron energy over the FEL pulse train to measure a wider spectral window without changing FEL parameters. We propose modifications to the experimental setup with the potential of improving the instrument sensitivity by two orders of magnitude, thereby exploiting the high peak fluence of FELs to enable unprecedented sensitivity for femtosecond XANES spectroscopy on liquids in the soft x-ray spectral region.

Geographical Distribution of Borrelia burgdorferi sensu lato in Ticks Collected from Wild Rodents in the Republic of Korea.

Lyme disease is a tick-borne zoonotic disease caused by Borrelia burgdorferi sensu lato (s. l.) via transmission cycles involving competent tick vectors and vertebrate reservoirs. Here, we determined the prevalence and distribution of Borrelia genospecies in 738 ticks of at least three species from wild rodents in nine regions of the Republic of Korea (ROK). Ticks were analyzed using nested PCR targeting partial flagellin B gene sequences, followed by sequence analysis. The prevalence of Borrelia infection was 33.6%, and the most common genospecies were B. afzelii (62.5%), B. valaisiana (31.9%), B. yangtzensis (2.4%), B. garinii (1.6%), and B. tanukii (1.6%). Borrelia afzelii was found in all regions except Jeju Island; this predominant genospecies was found in the northern and central sampling regions. Borrelia valaisiana, B. yangtzensis, and B. tanukii were found only in the southern regions with B. valaisiana being the most common, whereas B. yangtzensis and B. tanukii were only found on Jeju Island. Our study is the first to describe the nationwide prevalence of B. burgdorferi s. l. in ticks from wild rodents in the ROK. Continuous surveillance in ticks, animals, humans, and different regions is required to avoid disease distribution and possible transmission to humans in the ROK.