Metal-Nanoparticle-Catalyzed Hydrogen Generation from Formic Acid.

To meet the ever-increasing energy demand, the development of effective, renewable, and environmentally friendly sources of alternative energy is imperative. Hydrogen (H2) is a renewable, clean energy carrier, which exhibits a threefold energy density compared to gasoline; H2 is considered one of the most promising alternative energy carriers for enabling a secure, clean energy future. However, the realization of a hydrogen economy is restricted by several unresolved issues. Particularly, one of the most difficult challenges is the development of a safe, efficient hydrogen storage and delivery system. To this end, hydrogen storage techniques based on liquid-phase chemical hydrogen storage materials have become an attractive choice. Formic acid (FA) with a high volumetric capacity of 53 g H2/L demonstrates promise as a safe, convenient liquid hydrogen carrier. However, generating H2 from FA in a controlled manner at ambient temperature is still challenging, which primarily depends on the catalyst used. Hence, for practical purposes, it is imperative to develop high-performance heterogeneous catalysts for the dehydrogenation of FA. Ultrasmall metal NPs with a high surface-to-volume ratio and "clean" surface, and hence a high density of active sites exposed to reactants, are of significance for heterogeneous catalysis. However, the size of these "clean" ultrasmall metal NPs inevitably increase, and these particles undergo aggregation during synthesis and catalysis because of their high surface energy. The immobilization of metal NPs into appropriate support materials affords considerable advantages for catalytic applications, which not only offers spatial confinement to control the nucleation and growth of particles, but also prevents them from aggregation; hence, catalytic performance is significantly enhanced. In addition, the functionalization of the support with electron-rich groups is beneficial to the formation of intermediates for FA dehydrogenation, which in turn promotes the catalytic performance. In this Account, studies of hydrogen generation from FA using heterogeneous catalysts were reviewed, mainly focusing on the results reported by our group. By varying support materials (metal-organic frameworks, silica, graphene, and porous carbons) and synthetic strategies, a wide range of highly active metal NP catalysts for efficient H2 generation from FA under mild conditions were developed. In addition, the design and synthetic strategies were described, by which the size and composition of the NPs, as well as the well-defined NPs-support interactions, can be controlled for the enhancement of catalytic performance for the FA dehydrogenation. Furthermore, the performance of the prepared catalysts for the effective release of H2 from FA for the purpose of liquid-phase chemical hydrogen storage was discussed. Finally, the challenges, expected improvements, and future opportunities in this research area were summarized.

Synthesis of honeycomb-like mesoporous pyrite FeS2 microspheres as efficient counter electrode in quantum dots sensitized solar cells.

Honeycomb-like mesoporous pyrite FeS2 microspheres, with diameters of 500-800 nm and pore sizes of 25-30 nm, are synthesized by a simple solvothermal approach. The mesoporous FeS2 microspheres are demonstrated to be an outstanding counter electrode (CE) material in quantum dot sensitized solar cells (QDSSCs) for electrocatalyzing polysulfide electrolyte regeneration. The cell using mesoporous FeS2 microspheres as CE shows 86.6% enhancement in power conversion efficiency (PCE) than the cell using traditional noble Pt CE. Furthermore, it also shows 11.4% enhancement in PCE than the cell using solid FeS2 microspheres as CE, due to the mesoporous structure facilitating better contact with polysulfide electrolyte and fast diffusion of redox couple species in electrolyte.

High-salt diet enhances hippocampal oxidative stress and cognitive impairment in mice.

Previous evidence suggests that a high-salt (HS) diet may increase oxidative stress and contribute to the development of hypertension that is already present. Oxidative stress is thought to play a critical role in the development of neurodegenerative diseases. Lower dietary sodium intake putatively contributes to a lower rate of cognitive impairment; however, the specific effects of HS diet on cognitive function remain poorly understood. In this work, C57BL/6J mice were administered a normal-salt (NS) diet (0.4% NaCl) or a HS diet (7.0% NaCl) for 12 weeks, and cognitive ability and oxidative stress in the brain were measured. It was found that the HS diet significantly impaired retention of spatial memory. Additionally, superoxide anion production in the hippocampus was significantly increased in the HS diet mice compared with that in the NS mice. Interestingly, the antioxidant defense capacities for HS diet mice were markedly reduced in the hippocampus, but not in the cerebral cortex, compared with the NS mice. Taken together, these data demonstrate that HS diet directly impairs retention of spatial memory, which may be related to the increased oxidative stress observed in the hippocampus.

MXene/Silk Fibroin Strengthened PVA-Based Eutectogel with Excellent Self-Healing Ability and Environmental Adaptability: Design, Synthesis, and Sensing Application.

A superelastic self-healing eutectogel was designed and prepared using poly (vinyl alcohol) (PVA) as the bulk skeleton material, while silk fibroin (SF) and two-dimensional (2D) MXene (Ti3C2TX) as reinforcing fillers. In brief, the eutectogel possesses a high tensile strength of 7.63 MPa, and its elongation at break reached 1115.2%, higher than most reported polymers (<1000%). In addition, the eutectogel-assembled sensor has a high ionic conductivity of 0.61 S/m and a high strain sensitivity of 5.17 kPa-1. Moreover, eutectogel shows excellent self-healing ability and can achieve self-healing quickly within 10 min, while its tensile strength and elongation at break can be restored to 84.7% and 97.4% of the initial levels. Besides, a stable electrical signal can be transmitted after 200 cycles at 30% strain. Finally, the eutectogel can withstand various environmental conditions, such as atmospheric or even vacuum evaporation and low-temperature freezing, while maintaining good mechanical and sensing performances. The assembled flexible sensors based on the eutectogel demonstrate their significant application prospects in wearable devices, especially human physiological monitoring.

Prenatal arsenic metabolite exposure is associated with increased newborn mitochondrial DNA copy number: evidence from a birth cohort study.

While mitochondria are susceptible to environmental detriments, little is known about potential associations between arsenic metabolites and mitochondria DNA copy number (mtDNAcn). We attempted to examine whether maternal urinary arsenic metabolite levels in different trimesters were related to neonatal cord blood mtDNAcn. We included 819 mother-newborn pairs embedded in an in-progress birth cohort survey performed from April 2014 to October 2016 in Wuhan, China. We determined maternal urinary arsenic species concentrations in different trimesters. We determined cord blood mtDNAcn using quantitative real-time polymerase chain reaction. In covariate-adjusted models, each one-unit increment of dimethylated arsenic (DMA) and total arsenic (TAs) in the third trimester was related to 8.43% (95% CI 1.13%, 16.26%) and 12.15% (95% CI 4.35%, 20.53%) increases in mtDNAcn, respectively. The dose-response trend with statistical significance was observed across tertiles of DMA and TAs in the third trimester with mtDNAcn (DMA percent changes (%Δ) = 25.60 (95% CI 6.73, 47.82), for the highest vs the lowest tertile (P = 0.02); TAs %Δ = 40.31 (95% CI 19.25, 65.10), for the highest vs the lowest tertile (P = 0.0002)). These findings may prove the relationships between prenatal arsenic species levels and neonatal mitochondrial dysfunction.

Altered cord blood mitochondrial DNA content and prenatal exposure to arsenic metabolites in low-arsenic areas.

While mitochondria are susceptible to environmental detriments, little is known about potential associations between arsenic metabolites and mitochondria DNA copy number (mtDNAcn). We attempted to examine whether arsenic metabolism in different trimesters was related to cord blood mtDNAcn alteration. We included 819 mother-newborn pairs embedded in an in-progress birth cohort survey performed from April 2014 to October 2016 in Wuhan, China. We determined maternal urinary arsenic species concentrations in different trimesters using HPLC-ICPMS. We decided on cord blood mtDNAcn using quantitative real-time polymerase chain reaction. In covariate-adjusted models, each two-fold increment of dimethylated arsenic (DMA) and total arsenic (TAs) in the 3rd trimester were related to 8.43% (95% CI: 1.13%, 16.26%) and 12.15% (95% CI:4.35%, 20.53%) increases in mtDNAcn, respectively. The dose-response trend with statistical significance was observed across tertiles of DMA and TAs in the 3rd trimester with mtDNAcn. These findings may prove the relationships between arsenic species and mitochondrial dysfunction.

Polarized micropores in a novel 3D metal-organic framework for selective adsorption properties.

A novel 3D porous metal-organic framework with 1D polarized channels was synthesized, and its adsorption properties for gas separation and chemical sensing were studied. The framework shows a preferential adsorption of CO(2) over N(2) with a selectivity of 22:1. It also exhibits a very good sensitivity to water with respect to most of the organic solvents in view of chemical sensing applications.

Two-Dimensional Nanosheet-Enhanced Waterborne Polyurethane Eutectogels with Ultrastrength and Superelasticity for Sensitive Strain Sensors.

Sensing materials that are ultrastrong but still superelastic and highly sensitive are crucial for meeting the requirements of future flexible sensors. However, these requirements are challenging to satisfy simultaneously due to the internal constraints among these properties. Here, an ultrastrong and superelastic eutectogel is designed and prepared using a waterborne polyurethane (WPU) network enhanced by two-dimensional (2D) nanosheets in a deep eutectic solvent. The 2D nanosheet-induced noncovalent cross-linking endows the prepared eutectogel with superelasticity and flexibility, and its elongation at break reaches 2071%, higher than those of most polymers (<1000%). Meanwhile, this eutectogel also exhibits a high tensile strength (21.6 MPa), which is strong enough to support 20 000 times its own weight. Such a composite design provides a feasible route for preparing eutectogels with outstanding comprehensive functions without trade-offs among these features. In addition, the eutectogel-assembled sensor possesses a high ionic conductivity of 0.225 S/m and a high strain sensitivity of 1.18 kPa-1. Furthermore, it can be integrated into the sensing arrays for multidimensional signal monitoring without diminishing its pristine strength and flexibility. Surprisingly, the eutectogel can be quickly disintegrated in ethanol due to the WPU's pseudoplastic behavior, providing a competitive way to dispose of waste electronic devices.

Effect of Cationic Modified Microcrystalline Cellulose on the Emulsifying Properties and Water/Oil Interface Behavior of Soybean Protein Isolate.

Stabilizing emulsion using complex biopolymers is a common strategy. It would be very interesting to characterize the impact of charge density on the emulsifying properties of complex polyelectrolytes carrying opposite charges. In this study, cationic modified microcrystalline celluloses (CMCC) of different charge densities were prepared and mixed with soy protein isolate (SPI) for emulsion applications. CMCC-1 to 3 with various cationic charge values were successfully prepared as characterized by zeta-potential and FTIR. The positive charge density's effects on solubility, thermogravimetric properties, and rheological properties were studied. Complexes of SPI-CMCC with various zeta-potential values were then obtained and used to stabilize soybean oil emulsions. The results show that emulsions stabilized by complexes of SPI and CMCC-3 at a ratio of 1:3 had the best emulsification ability and stability. However, the interfacial tension-reducing ability of complexes decreased continuously with increasing cationic charge value, while the rheological results show that complexes of SPI-CMCC-3 at a ratio of 1:3 formed a stronger viscoelastic network than other complexes. Our results indicate that this SPI-CMCC complex formula showed excellent emulsification performance, which could be adjusted and promoted by changing the charge density. This complex formula is promising for fabrication of emulsion-based food and cosmetic products.

Ultralight GO-Hybridized CNTs Aerogels with Enhanced Electronic and Mechanical Properties for Piezoresistive Sensors.

Extremely low density carbon nanotubes/graphene hybrid aerogels (CNG) are highly potential active materials for fabricating flexible devices, owing to synergistic effects with one (nanotubes) and two (graphene) dimensional characters in a single structure. However, conquering the long-standing dilemma among low electronic conductivity and inferior mechanical properties for CNG remains a challenging task. Here, an ultralight CNG aerogel (1.52 mg cm-3) with prominent electronic conductivity and mechanical resilience is facilely fabricated through a triple roles design of the sodium dodecyl sulfate (SDS), namely anchoring metal ions, dispersing carbon nanotubes, and inducing self-assembly. It is demonstrated that the Ba2+ can be effectively anchored into the GO interlayers by coupling it with the SDS to reinforce the intersheet interactions, thereby achieving remarkable improvement in mechanical properties (Young's moduli up to 18.3 kPa). Density functional theory calculations reveal that the anchored Ba2+ acting as molecular bridges can availably reduce the tunneling barrier between the GO sheets and facilitate the multidirectional and fast transport of electronics, inducing the high electrical conductivity of CNG (12.55 S cm-1). Taking advantage of these features, potential applications in flexible sensing devices have been demonstrated utilizing the remarkable CNG as an active material, giving extraordinary sensing performance including high sensitivity (48.6 kPa-1), ultralow detection limit (10 Pa), and ultrafast response (18 ms).

Three new spirostanol glycosides from Helleborus thibetanus.

An ongoing chemical investigation on n-BuOH extract of roots and rhizomes of Helleborus thibetanus afforded three new spirostanol glycosides (1-3). Their structures were elucidated by extensive analysis of 1 D, 2 D NMR spectra, together with IR and MS methods and acid hydrolysis. This is the first report of the isolation of spirostanol glycoside with xylose at C-24 of the aglycone in Helleborus.

Fluorine Doping Strengthens the Lithium-Storage Properties of the Mn-Based Metal-Organic Framework.

The electrochemical properties of the metal-organic framework (MOF)-based composite as electrode material can be significantly improved by means of partial destruction of the full coordination of linkers to metal ions and replacing with other small ions, which make metal centers become more accostable and consequently more effective for the lithiation/delithiation process. In this paper, F- was chosen to replace some of the benzenedicarboxylate (BDC) linkers because of its better interaction with the Li+ than the oxide ion. What's more, the formed M-F bond promotes the Li+ to transfer at the active material interface and protects the surface from HF attacking. The as-synthesized F-doped Mn-MOF electrode maintains a reversible capacity of 927 mA h g-1 with capacity retention of 78.5% after 100 cycles at 100 mA g-1 and also exhibits a high discharge capacity of 716 mA h g-1 at 300 mA g-1 and 620 mA h g-1 at 500 mA g-1 after 500 cycles. Even at 1000 mA g-1, the electrode still maintains a high reversible capacity of 494 mA h g-1 after 500 cycles as well as a Coulombic efficiency of nearly 100%, which is drastically increased compared with pure Mn-MOF material as expected.

Diazoxide accelerates wound healing by improving EPC function.

Endothelial cell dysfunction is the primary cause of microvascular complications in diabetes. Diazoxide enables beta cells to rest by reversibly suppressing glucose-induced insulin secretion by opening ATP-sensitive K+ channels in the beta cells. This study investigated the role of diazoxide in wound healing in mice with streptozotocin (STZ)-induced diabetes and explored the possible mechanisms of its effect. Compared to the controls, mice with STZ-induced diabetes exhibited significantly impaired wound healing. Diazoxide treatment (30 mg/kg/d, intragastrically) for 28 days accelerated wound closure and stimulated angiogenesis in the diabetic mice. Circulating endothelial progenitor cells (EPCs) increased significantly in the diazoxide-treated diabetic mice. The adhesion, migration, and tube formation abilities of bone marrow (BM)-EPCs were impaired by diabetes, and these impairments were improved by diazoxide treatment. The expression of both p53 and TSP-1 increased in diabetic mice compared to that in the controls, and these increases were inhibited significantly by diazoxide treatment. In vitro, diazoxide treatment improved the impaired BM-EPC function and diminished the increased expression of p53 and TSP-1 in cultured BM-EPCs caused by high glucose levels. We conclude that diazoxide improved BM-EPC function in mice with STZ-induced diabetes, possibly via a p53- and TSP-1-dependent pathway.

Graphene-Wrapped Ni(OH)2 Hollow Spheres as Novel Electrode Material for Supercapacitors.

Graphene-wrapped Ni(OH)2 hollow spheres were prepared via electrostatic interaction between poly(diallyldimethylammonium chloride) (PDDA) modified Ni(OH)2 and graphene oxide (GO) in an aqueous dispersion, followed by the reduction of GO. Morphological and structural analysis by field-emission scanning electron microscopy, X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy and thermogravimetric analysis confirmed the successful coating of graphene on Ni(OH)2 hollow spheres with a content of 3.8 wt%. And then its application as electrode material for supercapacitor has been investigated by cyclic voltammetry (CV) and galvanostatic charge-discharge tests. Results show that the sample displays a high capacitance of 1368 F g(-1) at a current density of 1 A g(-1), much better than that of pure Ni(OH)2, illustrating that such composite is a promising candidate as electrode material for supercapacitors.

Porous CuCo2O4 nanocubes wrapped by reduced graphene oxide as high-performance lithium-ion battery anodes.

A composite of porous CuCo2O4 nanocubes well wrapped by reduced graphene oxide (rGO) sheets has been synthesized by a facile microwave-assisted solvothermal reaction and applied as anode in lithium ion batteries (LIBs). The porous structure of the CuCo2O4 nanocubes not only provides a high surface area for contact with the electrolyte, but also assists by accommodating volume change upon charging-discharging. Impedance measurements and transmission electron microscopy show that incorporation of rGO further decreases the charge transfer resistance and improves the structural stability of the composite. As an anode material for a LIB, the composite exhibits a high stable capacity of ∼ 570 mA h g(-1) at a current density of 1000 mA g(-1) after 350 cycles. With a high specific surface area and a low charge transfer resistance, the composite anode shows impressive performance especially at high current density. The LIB shows a high capacity of ∼ 450 mA h g(-1) even at a high current density of 5000 mA g(-1), demonstrating the composite's potential for applications in LIBs with long cycling life and high power density.

Simvastatin attenuates radiation-induced tissue damage in mice.

The aim of this study was to investigate the protective effect of simvastatin against radiation-induced tissue injury in mice. Mice were radiated with 4 Gy or 8 Gy after 20 mg/kg/d simvastatin treatment over 2 weeks. Morphological changes were observed in the jejunum and bone marrow, and apoptotic cells were determined in both tissues. Peripheral blood cells were counted, and the superoxide dismutase (SOD) activity and the malondialdehyde (MDA) level in tissues of both thymus and spleen were measured. Compared with the radiation-only group, 20 mg/kg/d simvastatin administration significantly increased the mean villi height and decreased apoptotic cells in jejunum tissue, and stimulated regeneration and reduced apoptotic cells in bone marrow. Peripheral blood cell analysis revealed that simvastatin treatment induced a larger number of red blood cells and increased the hemoglobin level present after 4 Gy of radiation. Interestingly, it was also found that the number of peripheral endothelial progenitor cells was markedly increased following simvastatin administration. Antioxidant determination for tissues displayed that simvastatin therapy increased the SOD activity after both 4 and 8 Gy of radiation, but only decreased the MDA level after 4 Gy. Simvastatin ameliorated radiation-induced tissue damage in mice. The radioprotective effect of simvastatin was possibly related to inhibition of apoptosis and improvement of oxygen-carrying and antioxidant activities.

Activation of alpha 7 nicotinic acetylcholine receptor protects mice from radiation-induced intestinal injury and mortality.

Radiation-induced gastrointestinal syndrome occurs when the body is exposed to a high dose of radiation. Currently, safe and effective radioprotectants are not available. Apoptosis was reported to play a primary role in radiation-induced injury. Recent evidence suggests that stimulation of α7 nicotinic acetylcholine receptor (α7nAChR) prevents cell death by inhibition of apoptosis. In this study, we demonstrated that a single dose of PNU282987 (100 µg/kg, i.p.), a selective α7nAChR agonist, protected mice from intestinal injury and significantly improved survival when administered prior to lethal 8 Gy total body irradiation. In vitro, PNU282987 protected against 8 Gy radiation-induced cell death in human umbilical venous endothelial cells by inhibiting apoptosis. We conclude that activation of α7nAChR may provide a new therapeutic pathway for the treatment of radiation-induced damage and mortality.

Simple synthesis of amorphous NiWO4 nanostructure and its application as a novel cathode material for asymmetric supercapacitors.

This study reports a simple synthesis of amorphous nickel tungstate (NiWO4) nanostructure and its application as a novel cathode material for supercapacitors. The effect of reaction temperature on the electrochemical properties of the NiWO4 electrode was studied, and results demonstrate that the material synthesized at 70 °C (NiW-70) has shown the highest specific capacitance of 586.2 F g(-1) at 0.5 A g(-1) in a three-electrode system. To achieve a high energy density, a NiW-70//activated carbon asymmetric supercapacitor is successfully assembled by use of NiW-70 and activated carbon as the cathode and anode, respectively, and then, its electrochemical performance is characterized by cyclic voltammetry and galvanostatic charge-discharge measurements. The results show that the assembled asymmetric supercapacitor can be cycled reversibly between 0 and 1.6 V with a high specific capacitance of 71.1 F g(-1) at 0.25 A g(-1), which can deliver a maximum energy density of 25.3 Wh kg(-1) at a power density of 200 W kg(-1). Furthermore, this asymmetric supercapacitor also presented an excellent, long cycle life along with 91.4% specific capacitance being retained after 5000 consecutive times of cycling.

Syntheses, structures and chemical sensing properties of three complexes with mixed ligands of carboxylate and bipyridine.

Three mixed-ligand coordination polymers, [Cu(oda)(2,2'-bipy)](2) (1), Ni(2)(oda)(2)(4,4'-bipy)·DMF (2), and [{Ni(oda)(H(2)O)(2)}(2)(µ-4,4'-bipy)]·2H(2)O (3) were synthesized and characterized. Complex 1 features a 1D chain via intermolecular π-π interactions. Complex 2 is a novel 3D microporous coordination polymer with 1D polarized channels. Complex 3 forms a 3D network via extensive hydrogen bonding interactions. Thermogravimetric analyses have been studied. The chemical sensing properties have been investigated in situ by quartz crystal microbalance (QCM). Complex 1 has a good sensitivity to toluene, complexes 2 and 3 have exceptionally high selectivity and sensitivity to water over organic solvents.