Monitoring Electron Flow in Nickel Single-Atom Catalysts during Nitrogen Photofixation.

An efficient catalytic system for nitrogen (N2) photofixation generally consists of light-harvesting units, active sites, and an electron-transfer bridge. In order to track photogenerated electron flow between different functional units, it is highly desired to develop in situ characterization techniques with element-specific capability, surface sensitivity, and detection of unoccupied states. In this work, we developed in situ synchrotron radiation soft X-ray absorption spectroscopy (in situ sXAS) to probe the variation of electronic structure for a reaction system during N2 photoreduction. Nickel single-atom and ceria nanoparticle comodified reduced graphene oxide (CeO2/Ni-G) was designed as a model catalyst. In situ sXAS directly reveals the dynamic interfacial charge transfer of photogenerated electrons under illumination and the consequent charge accumulation at the catalytic active sites for N2 activation. This work provides a powerful tool to monitor the electronic structure evolution of active sites under reaction conditions for photocatalysis and beyond.

Associations between low-dose triclosan exposure and semen quality in a Chinese population.

BACKGROUND: The antimicrobial agent triclosan (TCS) has attracted much attention worldwide because of its pervasive existence in the human body and environment. TCS exposure has been reported to be associated with decreased male reproductive function. However, few studies have investigated these associations in humans. OBJECTIVE: To examine the relationship between TCS in urine and male semen quality. METHODS: A total of 406 men from a reproductive clinic were enrolled in this study. Urinary TCS concentrations were determined by ultra-high performance liquid chromatography-electrospray ionization tandem mass spectrometry. Sixteen semen parameters were assessed according to the guidelines of World Health Organization (WHO), including parameters for volume, count, motility, and motion. We used multivariate linear regression models and restricted cubic splines to estimate the linear and non-linear associations between TCS exposure and semen parameters, respectively. Logistical regression models were further applied to explore the associations with abnormal semen quality. RESULTS: TCS was detected in 74.6% of urine specimens. The monotonous trend of TCS tertiles and continuous TCS levels with all semen quality parameters were not observed in multivariate linear regression models (p > 0.05). However, compared with those in the lowest tertile, subjects in the second tertile showed significantly higher linearity and wobble (p < 0.05), indicating potential effects on sperm motion. In the models using restricted cubic splines with 3-5 knots, there were no significant non-linear associations between TCS exposure and any semen quality parameter. In addition, TCS tertiles were not associated with the risk of abnormal semen quality (i.e., count and motility) in the logistical regression models. CONCLUSION: Our results revealed that low-level TCS exposure may have limited (none or modest) effects on male semen quality, potentially inducing some fluctuations. Further mechanistic studies on low levels of exposure are needed.

Identification of the Active-Layer Structures for Acidic Oxygen Evolution from 9R-BaIrO3 Electrocatalyst with Enhanced Iridium Mass Activity.

Iridium-based perovskites show promising catalytic activity for oxygen evolution reaction (OER) in acid media, but the iridium mass activity remains low and the active-layer structures have not been identified. Here, we report highly active 1 nm IrOx particles anchored on 9R-BaIrO3 (IrOx/9R-BaIrO3) that are directly synthesized by solution calcination followed by strong acid treatment for the first time. The developed IrOx/9R-BaIrO3 catalyst delivers a high iridium mass activity (168 A gIr-1), about 16 times higher than that of the benchmark acidic OER electrocatalyst IrO2 (10 A gIr-1), and only requires a low overpotential of 230 mV to reach a catalytic current density of 10 mA cm-2geo. Careful scanning transmission electron microscopy, synchrotron radiation-based X-ray absorption spectroscopy, and X-ray photoelectron spectroscopy analyses reveal that, during the electrocatalytic process, the initial 1 nm IrOx nanoparticles/9R-BaIrO3 evolve into amorphous Ir4+OxHy/IrO6 octahedrons and then to amorphous Ir5+Ox/IrO6 octahedrons on the surface. Such high relative content of amorphous Ir5+Ox species derived from trimers of face-sharing IrO6 octahedrons in 9R-BaIrO3 and the enhanced metallic conductivity of the Ir5+Ox/9R-BaIrO3 catalyst are responsible for the excellent acidic OER activity. Our results provide new insights into the surface active-layer structure evolution in perovskite electrocatalysts and demonstrate new approaches for engineering highly active acidic OER nanocatalysts.

Synergizing metal-support interactions and spatial confinement boosts dynamics of atomic nickel for hydrogenations.

Atomically dispersed metal catalysts maximize atom efficiency and display unique catalytic properties compared with regular metal nanoparticles. However, achieving high reactivity while preserving high stability at appreciable loadings remains challenging. Here we solve the challenge by synergizing metal-support interactions and spatial confinement, which enables the fabrication of highly loaded atomic nickel (3.1 wt%) along with dense atomic copper grippers (8.1 wt%) on a graphitic carbon nitride support. For the semi-hydrogenation of acetylene in excess ethylene, the fabricated catalyst shows extraordinary catalytic performance in terms of activity, selectivity and stability-far superior to supported atomic nickel alone in the absence of a synergizing effect. Comprehensive characterization and theoretical calculations reveal that the active nickel site confined in two stable hydroxylated copper grippers dynamically changes by breaking the interfacial nickel-support bonds on reactant adsorption and making these bonds on product desorption. Such a dynamic effect confers high catalytic performance, providing an avenue to rationally design efficient, stable and highly loaded, yet atomically dispersed, catalysts.

Effects of long-term fertilization on calcium-associated soil organic carbon: Implications for C sequestration in agricultural soils.

Although the contribution of calcium ion (Ca2+) to stabilizing organic carbon (OC) in soils has been known for years, we still have a limited understanding of the quantity and molecular composition of Ca2+ bound SOC (Ca-OC) evolution in response to long-term fertilization. Here we report the role of Ca2+ in the accumulation of OC in the topsoil (0-20 cm) from two long-term (25-37 years) fertilization experiment sites. Approximately 4.54-19.27% and 9.00-25.15% of SOC was bound with Ca2+ in the Ferric Acrisol and Fluvic Cambisol, respectively. The application of NPK mineral fertilizers (NPK) decreased (p < 0.05) the Ca-OC stocks from 3.40 t ha-1 to 0.96 t ha-1 and from 2.03 t ha-1 to 1.17 t ha-1 in the Ferric Acrisol and Fluvic Cambisol, respectively. Swine manure (M) addition did not change (p > 0.05) the Ca-OC stock in Ferric Acrisol, but enhanced (p < 0.05) that from 2.03 t ha-1 to 9.75 t ha-1 in Fluvic Cambisol. Fourier transform infrared and carbon (1s)-near X-ray absorption spectroscopies showed that Ca2+ was mainly bound with aromatic carbon and carboxylic carbon. Long-term M fertilization facilitated the binding of Ca2+ with O-alkyl C, suggesting an increment of Ca-linked polysaccharide. Calcium ion was preferentially associated with 13C enriched organic matter (OM). Mineral fertilization promoted the 13C-enriched organic compounds in the Ca-OC, while organic fertilization facilitated the binding of 13C-depleted organic C with Ca2+. This study suggests that Ca-OC may be a potentially vital and stable OC pool in arable soils, and provides direct evidence for the preferential association of OC with Ca2+ in edaphic environments.

Interaction of Hydrogen with Ceria: Hydroxylation, Reduction, and Hydride Formation on the Surface and in the Bulk.

The study reports the first attempt to address the interplay between surface and bulk in hydride formation in ceria (CeO2 ) by combining experiment, using surface sensitive and bulk sensitive spectroscopic techniques on the two sample systems, i.e., CeO2 (111) thin films and CeO2 powders, and theoretical calculations of CeO2 (111) surfaces with oxygen vacancies (Ov ) at the surface and in the bulk. We show that, on a stoichiometric CeO2 (111) surface, H2 dissociates and forms surface hydroxyls (OH). On the pre-reduced CeO2-x samples, both films and powders, hydroxyls and hydrides (Ce-H) are formed on the surface as well as in the bulk, accompanied by the Ce3+ ↔ Ce4+ redox reaction. As the Ov concentration increases, hydroxyl is destabilized and hydride becomes more stable. Surface hydroxyl is more stable than bulk hydroxyl, whereas bulk hydride is more stable than surface hydride. The surface hydride formation is the kinetically favorable process at relatively low temperatures, and the resulting surface hydride may diffuse into the bulk region and be stabilized therein. At higher temperatures, surface hydroxyls can react to produce water and create additional oxygen vacancies, increasing its concentration, which controls the H2 /CeO2 interaction. The results demonstrate a large diversity of reaction pathways, which have to be taken into account for better understanding of reactivity of ceria-based catalysts in a hydrogen-rich atmosphere.

Anomalous self-optimization of sulfate ions for boosted oxygen evolution reaction.

Broadly, the oxygen evolution reaction (OER) has been deeply understood as a significant part of energy conversion and storage. Nevertheless, the anions in the OER catalysts have been neglected for various reasons such as inactive sites, dissolution, and oxidation, amongst others. Herein, we applied a model catalyst s-Ni(OH)2 to track the anionic behavior in the catalyst during the electrochemical process to fill this gap. The advanced operando synchrotron radiation Fourier transform infrared (SR-FTIR) spectroscopy, synchrotron radiation photoelectron spectroscopy (SRPES) depth detection and differential X-ray absorption fine structure (Δ-XAFS) spectrum jointly point out that some oxidized sulfur species (SO42-) will self-optimize new Ni-S bonds during OER process. Such amazing anionic self-optimization (ASO) behavior has never been observed in the OER process. Subsequently, the optimization-derived component shows a significantly improved electrocatalytic performance (activity, stability, etc.) compared to reference catalyst Ni(OH)2. Theoretical calculation further suggests that the ASO process indeed derives a thermodynamically stable structure of the OER catalyst, and then gives its superb catalytic performance by optimizing the thermodynamic and kinetic processes in the OER, respectively. This work demonstrates the vital role of anions in the electrochemical process, which will open up new perspectives for understanding OER and provide some new ideas in related fields (especially catalysis and chemistry).

Establishing a new hot electrons transfer channel by ion doping in a plasmonic metal/semiconductor photocatalyst.

A straightforward strategy is developed to improve the injection efficiency of hot electrons in a Ag/TiO2 plasmonic photocatalyst by introducing Fe as a dopant. The Fe dopant energy level formed within the bandgap of TiO2 provides an extra electron transfer channel for transferring the hot electrons induced by plasmonic Ag nanoparticles.

The impact of extreme heat and heat waves on emergency ambulance dispatches due to external cause in Shenzhen, China.

BACKGROUND: Compared to hospital admissions (HAs), emergency ambulance dispatches (EADs) can be considered a real-time outcome for evaluating the public health impacts of ambient temperature. OBJECTIVES: This study aimed to assess if temperature has a causal effect on cause-specific EADs and its potential main and added effect in Shenzhen from 2013 to 2017. METHODS: A distributed lag nonlinear model (DLNM) with quasi-Poisson distribution was applied to quantify the association between temperature and EADs. Likewise, the fraction of EADs attributable to different temperature ranges was calculated to identify extreme temperature ranges affecting population health. We then explored the main and added wave effects of heatwaves. RESULTS: Ambient temperature showed a U-shaped association with EADs. The minimum risk temperature was 17 °C (16th percentile of the daily mean temperature). Compared with the cold, the relative risk (RR) of heat on EADs presented smaller but the attributable risk larger. The main effects of heatwaves on EADs varied with external causes; and the peak RR of heat on EADs was observed in suicidal behaviors with heatwaves defined as 3 or more days with temperatures above the 75th percentile (RR = 4.53, 95% CI: 1.23-16.68), followed by assault (RR = 2.36, 95% CI: 1.25-4.48) and accidents (RR = 1.72, 95% CI: 1.30-2.28), while the added wave effect was negligible. CONCLUSIONS: Heat was responsible for a higher proportion of EADs than cold. Most of the increase in health risk during warm season can be simply ascribed to the independent effects of daily temperature occurrences whether it is or not on the heat-wave day. And the main effects of heatwaves on cause-specific EADs showed varied change trends, of which the incidence of suicides seems more susceptible, followed by assault and accidents.

Quasi Pd1Ni single-atom surface alloy catalyst enables hydrogenation of nitriles to secondary amines.

Hydrogenation of nitriles represents as an atom-economic route to synthesize amines, crucial building blocks in fine chemicals. However, high redox potentials of nitriles render this approach to produce a mixture of amines, imines and low-value hydrogenolysis byproducts in general. Here we show that quasi atomic-dispersion of Pd within the outermost layer of Ni nanoparticles to form a Pd1Ni single-atom surface alloy structure maximizes the Pd utilization and breaks the strong metal-selectivity relations in benzonitrile hydrogenation, by prompting the yield of dibenzylamine drastically from ∼5 to 97% under mild conditions (80 °C; 0.6 MPa), and boosting an activity to about eight and four times higher than Pd and Pt standard catalysts, respectively. More importantly, the undesired carcinogenic toluene by-product is completely prohibited, rendering its practical applications, especially in pharmaceutical industry. Such strategy can be extended to a broad scope of nitriles with high yields of secondary amines under mild conditions.

Highly Active and Stable Metal Single-Atom Catalysts Achieved by Strong Electronic Metal-Support Interactions.

Developing an active and stable metal single-atom catalyst (SAC) is challenging due to the high surface free energy of metal atoms. In this work, we report that tailoring of the 5d state of Pt1 single atoms on Co3O4 through strong electronic metal-support interactions (EMSIs) boosts the activity up to 68-fold higher than those on other supports in dehydrogenation of ammonia borane for room-temperature hydrogen generation. More importantly, this catalyst also exhibits excellent stability against sintering and leaching, in sharp contrast to the rapid deactivation observed on other Pt single-atom and nanoparticle catalysts. Detailed spectroscopic characterization and theoretical calculations revealed that the EMSI tailors the unoccupied 5d state of Pt1 single atoms, which modulates the adsorption of ammonia borane and facilities hydrogen desorption, thus leading to the high activity. Such extraordinary electronic promotion was further demonstrated on Pd1/Co3O4 and in hydrogenation reactions, providing a new promising way to design advanced SACs with high activity and stability.

Oxidation of Reduced Ceria by Incorporation of Hydrogen.

The interaction of hydrogen with reduced ceria (CeO2-x ) powders and CeO2-x (111) thin films was studied using several characterization techniques including TEM, XRD, LEED, XPS, RPES, EELS, ESR, and TDS. The results clearly indicate that both in reduced ceria powders as well as in reduced single crystal ceria films hydrogen may form hydroxyls at the surface and hydride species below the surface. The formation of hydrides is clearly linked to the presence of oxygen vacancies and is accompanied by the transfer of an electron from a Ce3+ species to hydrogen, which results in the formation of Ce4+ , and thus in oxidation of ceria.

Association between Pancreatic Atrophy and Loss of Insulin Secretory Capacity in Patients with Type 2 Diabetes Mellitus.

AIMS: To examine pancreatic volume (PV) changes among patients with different duration of type 2 diabetes and whether pancreatic atrophy was associated with loss of insulin secretory capacity. METHODS: This cross-sectional study (203 patients with type 2 diabetes, 93 controls without diabetes) was conducted from January 2016 to December 2017. Patients with type 2 diabetes were divided into 3 groups: recently diagnosed (duration ≤ 2 years), midterm (duration 3-9 years), and long term (duration ≥ 10 years). All the patients were scanned with upper abdominal computerized tomography; PV was then calculated by an experienced technician. Absolute insulin deficiency was defined as fasting C - peptide < 0.9 ng/mL. RESULTS: Compared with PV (cm3) in the controls, the mean PV was similar in patients with recently diagnosed type 2 diabetes (68.8 versus 71.0, P = 0.56) but significantly reduced in patients with midterm (68.8 versus 60.8, P < 0.05) and long-term (68.8 versus 53.1, P < 0.001) type 2 diabetes. A similar trend was observed for the PV index (PV adjusted for body surface area and body mass index). Furthermore, rates of pancreatic atrophy and absolute insulin deficiency increased with duration of diabetes. Multiple logistic regression analysis indicated that pancreatic atrophy was associated with higher likelihood of absolute insulin deficiency (odds ratio = 4.47, 95%confidence interval = 1.45-13.8). CONCLUSIONS: PV was reduced in those with midterm and long-term type 2 diabetes compared to individuals without type 2 diabetes. Overall, pancreatic atrophy was associated with the loss of insulin secretory capacity in patients with type 2 diabetes.

Disentangling the size-dependent geometric and electronic effects of palladium nanocatalysts beyond selectivity.

The prominent size effect of metal nanoparticles shapes decisively nanocatalysis, but entanglement of the corresponding geometric and electronic effects prevents exploiting their distinct functionalities. In this work, we demonstrate that in palladium (Pd)-catalyzed aerobic oxidation of benzyl alcohol, the geometric and electronic effects interplay and compete so intensively that both activity and selectivity showed in volcano trends on the Pd particle size unprecedentedly. By developing a strategy of site-selective blocking via atomic layer deposition along with first principles calculations, we disentangle these two effects and unveil that the geometric effect dominates the right side of the volcano with larger-size Pd particles, whereas the electronic effect directs the left of the volcano with smaller-size Pd particles substantially. Selective blocking of the low-coordination sites prevents formation of the undesired by-product beyond the volcano relationship, achieving a remarkable benzaldehyde selectivity and activity at the same time for 4-nm Pd. Disentangling the geometric and electronic effects of metal nanoparticles opens a new dimension for rational design of catalysts.

Rapid Construction of a Replication-Competent Infectious Clone of Human Adenovirus Type 14 by Gibson Assembly.

In 1955, Human adenovirus type 14 (HAdV-B14p) was firstly identified in a military trainee diagnosed as acute respiratory disease (ARD) in the Netherlands. Fifty years later, a genomic variant, HAdV-B14p1, re-emerged in the U.S. and caused large and fatal ARD outbreaks. Subsequently, more and more ARD outbreaks occurred in Canada, the UK, Ireland, and China, in both military and civil settings. To generate a tool for the efficient characterization of this new genomic variant, a full-length infectious genomic clone of HAdV-B14 was successfully constructed using one-step Gibson Assembly method in this study. Firstly, the full genome of HAdV-B14p1 strain GZ01, the first HAdV-B14 isolate in China, was assembled into pBR322 plasmid by Gibson Assembly. The pBRAdV14 plasmid, generated by Gibson Assembly, was analyzed and verified by PCR, restriction enzymes digestion and the sequencing. Secondly, viruses were rescued from pBRAdV14-transfected A549 cells. The integrity of the rescued viruses was identified by restriction enzyme analysis. The complete sequence of the infectious clone was further sequenced. No mutation was found in the infectious clone during the construction when compared with the parental virus and pBR322 sequences. The direct immunofluorescence assay indicated the expression of the hexon protein. Finally, typical virions were observed; the one-step growth curves further showed that the DNA replication and viral reproduction efficiency of pBRAd14 derived viruses was similar with that of wild-type HAdV-B14 strain. The successful construction of the replication-competent infectious clone of pBRAdV14 facilitates the development of vaccine and antiviral drugs against HAdV-B14, as well as provides a novel strategy for rapid construction of infectious viral clones for other large-genome DNA viruses.

A Stable and Efficient Cathode for Fluorine-Containing Proton-Conducting Solid Oxide Fuel Cells.

Substitution of anions such as F- and Cl- can effectively improve the stability of proton-conducting electrolytes at no expense to proton conduction. However, during operation, F- and Cl- in electrolytes can transfer to the cathodes, which reduces the stability of the electrolytes. In this work, F- -doped Ba0.5 Sr0.5 Co0.8 Fe0.2 O3-δ [Ba0.5 Sr0.5 Co0.8 Fe0.2 O2.9-δ F0.1 (F-BSCF)] was prepared as a potential cathode for proton-conducting solid oxide fuel cells with BaCe0.8 Sm0.2 F0.1 O2.85 electrolyte. The incorporation of F- in the cathode depressed F- diffusion from the electrolyte and improved the stability of button cells. Temperature-changing X-ray photoelectron spectroscopy and electronic conductivity relaxation results demonstrated that the incorporation of F- enhanced the oxygen incorporation kinetics at intermediate temperatures and improved the cathode catalytic performance. Moreover, a button cell prepared with this novel cathode was stable for 270 h at a current density of 300 mA cm-2 and 700 °C, which was much superior than those containing a BSCF cathode.

Modulation of Metal and Insulator States in 2D Ferromagnetic VS2 by van der Waals Interaction Engineering.

2D transition-metal dichalcogenides (TMDCs) are currently the key to the development of nanoelectronics. However, TMDCs are predominantly nonmagnetic, greatly hindering the advancement of their spintronic applications. Here, an experimental realization of intrinsic magnetic ordering in a pristine TMDC lattice is reported, bringing a new class of ferromagnetic semiconductors among TMDCs. Through van der Waals (vdW) interaction engineering of 2D vanadium disulfide (VS2 ), dual regulation of spin properties and bandgap brings about intrinsic ferromagnetism along with a small bandgap, unravelling the decisive role of vdW gaps in determining the electronic states in 2D VS2 . An overall control of the electronic states of VS2 is also demonstrated: bond-enlarging triggering a metal-to-semiconductor electronic transition and bond-compression inducing metallization in 2D VS2 . The pristine VS2 lattice thus provides a new platform for precise manipulation of both charge and spin degrees of freedom in 2D TMDCs availing spintronic applications.

Coordination reaction between tetraphenylporphyrin and nickel on a TiO2(110) surface.

In situ metalation of tetraphenylporphyrin (2HTPP) (sub)monolayers with Ni on a TiO2(110) surface to nickel(II)-tetraphenylporphyrin (NiTPP) depends on temperature and order of deposition, and affects conformation and bonding geometry of the porphyrin.

Interaction of oxygen with samarium on Al2O3 thin film grown on Ni3Al(111).

The interaction between oxygen and samarium (Sm) on the well-ordered thin Al2O3 film grown on Ni3Al(111) has been investigated by X-ray photoelectron spectroscopy and synchrotron radiation photoemission spectroscopy. At Sm coverage higher than one monolayer, exposure of oxygen to the Sm films at room temperature leads to the formation of both samarium peroxide (O2(2-)) states and regular samarium oxide (O(2-)) states. By contrast, when exposing O2 to Sm film less than one monolayer on Al2O3, no O2(2-) can be observed. Upon heating to higher temperatures, these metastable O2(2-) states dissociate, supplying active O atoms which can diffuse through the Al2O3 thin film to further oxidize the underlying Ni3Al(111) substrate, leading to the significant increase of the Al2O3 thin film thickness. Therefore, it can be concluded that Sm, presumably in its peroxide form, acts as a catalyst for the further oxidation of the Ni3Al substrate by supplying the active oxygen species at elevated temperatures.

Association between NQO1 Pro187Ser polymorphism and esophageal cancer: a meta-analysis.

NAD(P)H: quinone oxidoreductase 1 (NQO1) is an important enzyme which can catalyze the two-electron reduction of quinoid compounds into hydroquinones. NQO1 Pro187Ser polymorphism can change the enzymatic activity of NQO1, and it has been proposed to be associated with risk of esophageal cancer. We performed a meta-analysis to examine the association between NQO1 Pro187Ser polymorphism and esophageal cancer. Odds ratio (OR) with a 95% confidence interval (95% CI) was used to assess the association. Twelve case-control studies with 1,725 cases with esophageal cancer and 2,341 controls were finally included in the meta-analysis. Overall, there was an obvious association between NQO1 Pro187Ser polymorphism and esophageal cancer (allele model: OR = 1.24, 95% CI 1.06-1.46, P OR = 0.009; homozygote model: OR = 1.59, 1195% CI 1.10-2.30, P OR = 0.013; dominant model: OR = 1.31, 95% CI 1.05-1.64, P OR = 0.018). In the subgroup analysis by ethnicity, there was an obvious association between NQO1 Pro187Ser polymorphism and esophageal cancer in Asians but not in Caucasians. Therefore, the meta-analysis suggests that NQO1 Pro187Ser polymorphism is associated with esophageal cancer risk.