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Pregnancy toxemia (PT) is the most frequent metabolic disease of sheep during late pregnancy, which can lead to enormous economic losses in sheep farm industry. However, the underlying mechanism of PT in sheep has not been fully elucidated. High levels of β-hydroxy butyric acid (BHBA) exist in PT sheep. The AMP-activated protein kinase (AMPK) pathway plays a major role in regulating liver function. The aim of this study was to explore the effects of gradient concentrations of BHBA on lipid metabolism of sheep hepatocytes and the underlying molecular mechanism in vitro. The results showed that 0.6, 1.2 mmol/L BHBA could activate AMPKα, promoted the expressions of peroxisome proliferator-activated receptor alpha (PPARα) and its target genes, and inhibited the expressions of sterol regulatory element binding protein-1c (SREBP-1c) as well as its downstream genes. When the concentration of BHBA was beyond 1.2 mmol/L, the expressions of the above-mentioned proteins and genes were just the opposite. However, the expressions of adipose triglyceride lipase (ATGL) and hormone-sensitive lipase (HSL) did not change significantly. The levels of very low density lipoprotein (VLDL), triglyceride (TG) and cholesterol (T-CHOL) showed a gradually increasing trend with the increase of BHBA concentration. According to the results above, it demonstrates that high levels of BHBA can inhibit the expression of the AMPK pathway and cause lipid metabolism disorders in sheep hepatocytes, which may lead to the occurrence of PT.

Nonlinear optical (NLO) microscopy relies on multiple light-matter interactions to provide unique contrast mechanisms and imaging capabilities that are inaccessible to traditional linear optical imaging approaches, making them versatile tools to understand a wide range of complex systems. However, the strong excitation fields that are necessary to drive higher-order optical processes efficiently are often responsible for photobleaching, photodegradation, and interruption in many systems of interest. This is especially true for imaging living biological samples over prolonged periods of time or in accessing intrinsic dynamics of electronic excited-state processes in spatially heterogeneous materials. This perspective outlines some of the key limitations of two NLO imaging modalities implemented in our lab and highlights the unique potential afforded by the quantum properties of light, especially entangled two-photon absorption based NLO spectroscopy and microscopy. We further review some of the recent exciting advances in this emerging filed and highlight some major challenges facing the realization of quantum-light-enabled NLO imaging modalities.

Abstract With the enhancement of environmental protection consciousness, concerns have been raised about non-toxic and biodegradable leather retanning agents. According to the European standard 2002/231/EC, the free formaldehyde content of leather products should be less than 150 mg/kg. As one of the retanning agents in the market, the content of free formaldehyde in the Multifunctional retanning agent (MTA) is 372.22 mg/kg and higher than the limit value. In this work, glutaraldehyde as an alternative of formaldehyde was used to modify acrylic polymer and an amphoteric acrylic retanning agent was prepared. Then it was used in retanning process, and its retanning and assistant-dyeing properties were investigated. The results showed that the free formaldehyde content of amphoteric acrylic retanning agent modified with glutaraldehyde was only 4.17 mg/kg. Meanwhile, the presence of amino groups in the amphoteric acrylic retanning agent improved the dyeing properties of leather by electrostatic attraction. Compared with the leather treated with anionic acrylic retanning agent, the residual dye concentration of the dyeing effluent of the retanned leather with amphoteric acrylic retanning agent decreased from 17.4 mg/L to 10.0 mg/L, and the dyed leather had better resistances to friction and water-washing. In addition, the BOD5/COD value of the wastewater after Mannich base polymer retanning was only 0.32, indicating that the retanning agent was biodegradable. Moreover, the leather retanned with amphoteric acrylic retanning agent had good thermal stability, fullness and physical and mechanical properties. Graphical abstract

Magnesium alloys, a novel functional material for the fabrication of fracturing tools, are being paid more and more attentions recently due to their relatively high mechanical properties and fast dissolubility ability after fracturing. In this study, the novel extruded Mg–10Gd–3Y–0.3Zr–xNi alloys will be reported and their microstructure, mechanical and corrosion behaviors will be also studied. The results show that Ni contents influence phase precipitation behaviors. With adding 0.2 wt% Ni, a large amount of Zr7Ni10 phases will be precipitated insides α-Mg matrix, directly leading to degradation of strength and large corrosion rate. With further increasing Ni contents, the precipitation phases can be changed from Mg5RE to 18R-LPSO structure, resulting in higher mechanical properties and faster corrosion rate. Moreover, adding Ni element also change the texture orientation by influencing the precipitation behavior of the alloys. The alloys invented in this paper have attained the highest compressive and tensile properties among all the reported dissoluble magnesium alloys. This work is beneficial in understanding the role of Ni in the magnesium alloys and provides more materials alternatives for the fabrication of dissoluble fracturing tools.

Chemical looping combustion (CLC) is a clean and efficient flame-free combustion technology, which combust the fuels by lattice oxygen from a solid oxygen carrier with inherent CO2 capture. The development of oxygen carriers with low cost and high redox performance is crucial to the whole efficiency of CLC process. As the solid by-product from the sulfuric acid production, pyrite cinder presented excellent redox performance as an oxygen carrier in CLC process. The main components in pyrite cinder are Fe2O3, CaSO4, Al2O3 and SiO2 in which Fe2O3 is the active component to provide lattice oxygen. In order to systematic investigate the functions of supports (CaSO4, Al2O3 and SiO2) in pyrite cinder, three oxygen carriers (Fe2O3-CaSO4, Fe2O3-Al2O3 and Fe2O3-SiO2) were prepared and evaluated in this study. The results showed that Fe2O3-CaSO4 displayed high redox activity and cycling stability in the multiple redox cycles. However, both Fe2O3-Al2O3 and Fe2O3-SiO2 experienced serious deactivation during redox reactions. It indicated that the inert Fe-Si solid solution (Fe2SiO4) was formed in the spent Fe2O3-SiO2 sample, which decreased the oxygen carrying capacity of this sample. The XPS results showed that the oxygen species on the surface of Fe2O3-CaSO4 could be fully recovered after the 20 redox cycles. It can be concluded that CaSO4 is the key to the high redox activity and cycling stability of pyrite cinder.

Adhesion molecules play an important role in urinary calculus formation. The expressions of adhesion molecules in renal tubular has been reported in some animals. However, the role of adhesion molecules in the process of sheep urinary calculus formation is still unclear. The magnesium ammonium phosphate (MAP) is the main component of sheep urinary calculus. In this paper, the sheep renal tubular epithelial cells (RTECs) were isolated and treated with MAP, the expressions of osteopontin (OPN), intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1) and apoptosis-related indicators caspase-3, Bcl-2 and Bax in RTECs were observed, the viability of RTECs was detected by Cell Counting Kit-8 (CCK-8). The levels of superoxide dismutase (SOD) and malondialdehyde (MDA), and the expressions of inflammatory factors Interleukin-6 (IL-6), Interleukin-1 (IL-1), Interleukin-17 (IL-17) and tumor necrosis factor-α (TNF-α) were measured by enzyme-linked immunosorbent (ELISA). The histopathological observation of kidney in urolithiasis sheep was made. The results showed that MAP could reduce the viability and SOD activity, enhance the activity of MDA significantly and promote the expressions of IL-1, IL-6, IL-17 and TNF-α of RTECs. By western blot and qPCR methods, the expressions of ICAM-1, VCAM-1 and OPN increased in 48 h. In addition, the expression of caspase-3 increased significantly and the ratio of Bcl-2/Bax reduced with exposure to MAP. The renal tissue structure was seriously damaged, the RTECs in urolithiasis sheep were degenerative and necrotic.

Despite silicon being a promising candidate for next-generation lithium-ion battery anodes, self-pulverization and the formation of an unstable solid electrolyte interface, caused by the large volume expansion during lithiation/delithiation, have slowed its commercialization. In this work, we expand on a controllable approach to wrap silicon nanoparticles in a crumpled graphene shell by sealing this shell with a polydopamine-based coating. This provides improved structural stability to buffer the volume change of Si, as demonstrated by a remarkable cycle life, with anodes exhibiting a capacity of 1038 mA h/g after 200 cycles at 1 A/g. The resulting composite displays a high capacity of 1672 mA h/g at 0.1 A/g and can still retain 58% when the current density increases to 4 A/g. A systematic investigation of the impact of spray-drying parameters on the crumpled graphene morphology and its impact on battery performance is also provided.

Lithium–sulfur (Li–S) batteries represent a promising high-density energy storage technology. The use of conductive polymers to enhance the performance of Li–S batteries has received much attention. In this work, a convenient and low-cost in-cell electropolymerization method is developed for the preparation of a conductive polymer, poly(3,4-ethylenedioxythiophene) (PEDOT), as a cathode binder inside a Li–S battery. The cell with this electropolymerized PEDOT (ePEDOT) shows notably improved specific capacity, cycling stability, and rate performance in comparison with the cell using the chemically synthesized commercial PEDOT:PSS (cPEDOT:PSS) as the binder. The performance enhancement is attributed to the formation of tightly integrated interfaces between ePEDOT and other components in the sulfur cathode. Moreover, this study revealed that the electrochemical dedoping of PEDOT is likely to occur during the Li–S battery cycling and thus the contribution of PEDOT (and some other conductive polymers) to the enhancement of the electrical conductivity of the sulfur cathode may not be as significant as expected.

Because of the low cost and easy availability, iron oxides have been widely used in chemical looping combustion. However, pure iron oxides often suffered from a loss of oxygen carrying capacity in ...

Pt-based electrocatalysts are considered as one of the most promising choices to facilitate the oxygen reduction reaction (ORR), and the key factor enabling their success is to reduce the required amount of platinum. Herein, we focus on illuminating both the theoretical mechanisms which enable enhanced and sustained ORR activity and the practical methods to achieve them in catalysts. The various multi-step pathways of ORR are firstly reviewed and the rate-determining steps based on the reaction intermediates and their binding energies are analyzed. We then explain the critical aspects of Pt-based electrocatalysts to tune oxygen reduction properties from the viewpoints of active sites exposure and altering the surface electronic structure, and further summarize representative research progress towards practically achieving these activity enhancements with a focus on platinum size reduction, shape control and core Pt elimination methods. We finally outline the remaining challenges and provide our perspectives with regard to further enhancing their activities.

There is accumulating evidence showing that apoptosis induced by endoplasmic reticulum (ER) stress plays a key role in pancreatic β cell dysfunction and insulin resistance. 3β-Hydroxysteroid-Δ24 Reductase (DHCR24) is a multifunctional enzyme located in the endoplasmic reticulum (ER), which has been previously shown to protect neuronal cells from ER stress-induced apoptosis. However, the role of DHCR24 in type 2 diabetes is only incompletely understood so far. In the present study, we induced ER stress by tunicamycin (TM) treatment and showed that infection of MIN6 cells with Ad-DHCR24-myc rendered these cells resistant to caspase-3-mediated apoptosis induced by TM, while cells transfected with siRNAs targeting DHCR24 were more sensitive to TM. Western blot analysis showed that TM treatment induced upregulation of Bip protein levels in both cells infected with Ad-LacZ (the control group) and Ad-DHCR24-myc, indicating substantial ER stress. Cells infected with Ad-LacZ exhibited a rapid and strong activation of ATF6 and p38, peaking at 3 h after TM exposure. Conversely, cells infected with Ad-DHCR24-myc showed a higher and more sustained activation of ATF6 and Bip than control cells. DHCR24 overexpression also inhibited the generation of intracellular reactive oxygen species (ROS) induced by ER stress and protected cells from apoptosis caused by treatment with both cholesterol and hydrogen peroxide. In summary, these data demonstrate, for the first time, that DHCR24 protects pancreatic β cells from apoptosis induced by ER stress.

NiFe2O4 exhibits a desirable application prospect in chemical looping process because of the high redox activity and oxygen carrying capacity. However, phase segregation resulting from the outward ...

Multimodal all-optical imaging involving coregistered femtosecond transient absorption microscopy (TAM), time-integrated photoluminescence (PL), and steady-state modalities such as confocal reflectance and transmission offers an appealing approach to gain a comprehensive understanding of complex electronic excited-state phenomena in spatially heterogeneous systems. A unique combination of these modalities allows us to unravel not only the competing electronic excited-state dynamical processes but also the underlying morphological information with simultaneous high temporal and spatial resolution. However, correlating the various images obtained from time-resolved and time-independent modalities is generally nontrivial and particularly challenging when the electronic dynamics under study evolve in both time and space. Here, we demonstrate a new approach for rationally correlating time-resolved microscopy with coregistered time-integrated or steady-state modalities. Specifically, our approach involves an extended global lifetime analysis of the time-resolved microscopic data set to separate distinct dynamical processes taking place on commensurate time scales, and the resulting decay-associated amplitude maps (DAAMs) were applied to explore correlations with the images acquired using time-independent modalities. The feasibility of our approach was validated through analyzing a multimodal data set acquired from a thin film of chloride-containing mixed lead halide perovskites (CH3NH3PbI3-xClx) using femtosecond transient absorption, time-integrated PL, and confocal reflectance microscopies. Analysis of the results obtained enable us to gain new insight into the complex ultrafast relaxation dynamics in this highly heterogeneous system.

We report charge recombination rates in lead iodide perovskites with alloys of formamidinium (FA) and methylammonium (MA) cations, FAxMA1–xPbI3, 0 ≤ x ≤ 0.9, prepared through ion exchange with mini...

Polymeric materials are emerging as an important component for organic electronics due to their combined features of soft materials and organic semiconductor/conductor. Different from solid-state bulk materials, polymers are synthesized and modulated with a facile method, with their controllable properties. Therefore, polymers have been recently used in Schottky junction devices that demonstrate features of enhanced performances, flexibility, and easy processing. Polymer-based Schottky junctions have drawn a lot of interest in several prototype applications like photodetectors, energy harvesters, and gas sensors. With this review, we summarize recent progress in synthesis and modulation of polymers and fabrication of polymer-based Schottky junction devices. Designs of applications of sensory devices like photodetectors, energy harvesters, and gas sensors are also presented.

Hypothesis Organophosphorus-based ligands represent a versatile set of solvent extraction reagents whose chemical makeup plays an important role in extraction mechanism. We hypothesize that the branching of the extractant hydrophobic tail and its oil-phase solvation affect the liquid/liquid interfacial structure. Understanding the structure mediated adsorption and interfacial ordering becomes key in designing ligands with enhanced selectivity and efficiency for targeted extractions. Experiment We employed vibrational sum frequency generation spectroscopy and interfacial tension measurements to extract thermodynamic adsorption energies, map interfacial ordering, and rationalize disparate behaviors of model di-(2-ethylhexyl) phosphoric acid and dioctyl phosphoric acid ligands at the hexadecane water interface. Findings With increased surface loading, ligands with branched hydrophobic tails formed stable interfaces at much lower concentrations than those observed for ligands with linear alkyl tails. The lack of an oil phase and associated solvation results in markedly different interfacial properties, and thus measurements made at air/liquid surfaces cannot be assumed to correlate with the processes occurring at buried liquid/liquid interfaces. We attribute these differences in the surface mediated self-assembly to key variations in hydrophobic interactions and tail solvation taking place in the oil phase demonstrating that interactions in both the polar and nonpolar phases are essential to understand self-assembly and function.

The Fe2O3-Al2O3 oxygen carrier is regarded to a promising candidate for chemical looping combustion (CLC). However, Fe2O3-Al2O3 oxygen carrier was often subjected to a decrease of oxygen carrying capacity. The deactivation mechanism of Fe2O3-Al2O3 oxygen carrier in chemical looping combustion was investigated over consecutive 20 cycles. The Fe2O3-Al2O3 oxygen carrier exhibited relatively poor redox stability in a fixed bed reactor. The physico-chemical properties of cycled Fe2O3-Al2O3 oxygen carrier were characterized by different characterization methods. No carbon deposit was detected in the reduction process, indicating that carbon deposition was not the cause for Fe2O3-Al2O3 oxygen carrier deactivation under this experimental condition. The characterization results showed that the deactivation of Fe2O3-Al2O3 oxygen carrier in redox cycles was mainly attributed to thermal sintering. The cycled Fe2O3-Al2O3 oxygen carrier showed lower surface area, lower reducibility and oxygen mobility than that of fresh sample. After a certain number of redox cycles, Fe diffusion and enrichment at the surface of cycled oxygen carrier was observed. The surface Fe is unstable under high reaction temperature, leading to accelerate thermal sintering. A deactivation mechanism of Fe2O3-Al2O3 oxygen carrier in CLC was proposed based on the Fe diffusion and surface sintering.

Calcium molybdate (CaMoO4) is the main component of powellite and is a predominant intermediate in the pyrometallurgical and hydrometallurgical process of molybdenum. The extraction of Mo from CaMoO4 by a combination of phosphoric acid and hydrochloric acid was investigated. For further understanding of the leaching mechanism, the effects of five key factors were studied to describe the leaching kinetics. The results indicated that the dissolution rate of CaMoO4 was independent of the stirring speed. Mo extraction significantly increased with increasing HCl concentration and temperature, but decreased with increasing particle size. A shrinking core model with surface chemical reaction was found to withstand the dissolution of CaMoO4. The apparent activation energy was calculated to be 70.879 kJ/mol, and a semi-empirical equation was derived for the rate of reaction.

Summary Limiting global temperature rises is increasingly dependent on the development of energy-efficient carbon-capture methods. Here, we report a simple CO2-separation cycle using an aqueous bis(iminoguanidine) (BIG) sorbent that reacts with CO2 and crystallizes into an insoluble bicarbonate salt. X-ray diffraction analysis of the bicarbonate crystals revealed “anti-electrostatic” hydrogen-bonded (HCO3−)2 dimers, stabilized by guanidinium cations and water. Mild heating of the crystals releases the CO2 and regenerates the BIG sorbent quantitatively, thereby closing the CO2-separation cycle. Experimental and computational investigations support a CO2-release mechanism consisting of surface-initiated low-barrier proton transfer from guanidinium groups to bicarbonate anions with the formation of carbonic acid dimers, followed by CO2 and H2O release in the rate-limiting step, with a measured activation energy of 102 ± 12 kJ/mol. The minimum energy required for sorbent regeneration is 151.5 kJ/mol CO2, which is 24% lower than the regeneration energy of monoethanolamine, a benchmark industrial sorbent.

This perspective article reviews recent progress in rational synthesis of conductive polymer hydrogels utilizing doping principles and their applications in advanced sensor technologies., Conductive polymer hydrogels are emerging as an advanced electronic platform for sensors by synergizing the advantageous features of soft materials and organic conductors. Doping provides a simple yet effective methodology for the synthesis and modulation of conductive polymer hydrogels. By utilizing different dopants and levels of doping, conductive polymer hydrogels show a highly flexible tunability for controllable electronic properties, microstructures, and structure-derived mechanical properties. By rationally tailoring these properties, conductive polymer hydrogels are engineered to allow sensitive responses to external stimuli and exhibit the potential for application in various sensor technologies. The doping methods for the controllable structures and tunable properties of conductive polymer hydrogels are beneficial to improving a variety of sensing performances including sensitivity, stability, selectivity, and new functions. With this perspective, we review recent progress in the synthesis and performance of conductive polymer hydrogels with an emphasis on the utilization of doping principles. Several prototype sensor designs based on conductive polymer hydrogels are presented. Furthermore, the main challenges and future research are also discussed.

The present study aimed to investigate the protective effect of quercetin on polychlorinated biphenyls (PCB)-induced liver and embryo damage in pregnant Sprague–Dawley rats. Pregnant rats were divided into five groups, and then were orally gavaged daily with peanut oil (vehicle) or a commercial PCB mixture (Aroclor 1254) — with or without co-treatment with 75, 150, or 300 mg/kg quercetin — on gestation days (GD) 4–7. At GD 9, all rats were euthanized, and their blood, liver, and uterus were collected. Expressions of CYP450 mRNA and protein in liver, cytokines (IFNγ, IL-2, IL-4, and IL-6) and IFNγ/IL-4 ratios in liver and sera, liver morphology, and the status of implanted embryos were analyzed. The results showed Aroclor 1254 treatment alone caused hepatic cord damage (i.e. cell disorganization, swelling, decreased cytoplasm, vacuolization), and that quercetin co-treatment appeared to mitigate this damage. Similarly, levels of CYP1A1 and CYP2B1 mRNA in livers of Aroclor 1254-only-treated rats were significantly higher than those in rats co-treated with quercetin. Hepatic and sera levels of IFNγ, IL-2, IL-6, and IFNγ/IL-4 ratios, and the ratio of delayed-development embryos, all increased in Aroclor 1254-treated rats, but were relatively decreased as a result of quercetin co-treatments. IL-4 levels were decreased by Aroclor 1254 and tended to increase back to normal when quercetin was used. The results indicated that quercetin imparted a protective effect against Aroclor 1254-induced toxicity in pregnant rats, in part, by modulating levels of important pro-inflammatory cytokines and reducing induced CYP1A1 and CYP2B1 expression.

Establishing a direct relationship between the mass change of iron-based oxygen carrier and gas production is crucial for the efficient operation and the control of the lattice oxygen release in biomass chemical looping gasification. In this study, a thermogravimetric fixed-bed reactor was designed to achieve the simultaneous measurement of the mass change and gas composition in the reduction of the oxygen carrier. Three oxygen carriers of pure iron (III) oxide, natural hematite, and red mud were used as candidates. The phase transfer of the oxygen carrier along with the biomass pyrolysis/gasification was studied. The mass loss rates and the gas composition were matched by three significant phase transition stages. The phase transitions from Fe2O3 to Fe3O4, Fe3O4 to FeO, and FeO to Fe occurred when CO appeared, CO/CO2 = 0.97, and CO/CO2 = 2.61, respectively. The extent of oxygen carrier reduction was 28.61% of pure iron (III) oxide, whereas the oxygen carrier reduction molar ratio was 74.50% of red mud. X-ray diffraction (XRD) spectrums showed the oxygen carrier was reduced to the metallic iron phase. Sintering and agglomeration were found in the reacted oxygen carriers of the scanning electron microscope (SEM) images.

Background Laminitis, an inflammation of the claw laminae, is one of the major causes of bovine lameness, which can lead to enormous economic losses and animal welfare problems in dairy farms. Angelica polysaccharide (AP) is proved to possess anti-inflammatory properties. But the role of AP on inflammatory response of the claw dermal cells has not been reported. The aim of this study was to investigate the anti-inflammatory effects of AP on lipopolysaccharide (LPS)-induced primary claw dermal cells of dairy cow and clarify the potential mechanisms. In the current research, the primary claw dermal cells were exposed to gradient concentrations of AP (10, 50, 100 µg/mL) in the presence of 10 µg/mL LPS. The levels of cytokines and nitric oxide (NO) were detected with ELISA and Griess colorimetric method. The mRNA expressions of TLR4, MyD88 and chemokines were measured with qPCR. The activation of NF-κB and MAPK signaling pathways was detected with western blotting. Results The results indicated that AP reduced the production of inflammatory mediators (TNF-α, IL-1β, IL-6 and NO), downregulated the mRNA expression of TLR4, MyD88 and some pro-inflammatory chemokines (CCL2, CCL20, CXCL2, CXCL8, CXCL10), and suppressed the NF-κB and MAPK signaling pathways evidenced by inhibition of the phosphorylation of IκBα, p65 and ERK, JNK, p38. Conclusions Our results demonstrated that AP may exert its anti-inflammatory effects on claw dermal cells of dairy cow by regulating the NF-κB and MAPK signaling pathways.

Iron-based oxygen carriers often underwent severe phase segregation in the process of chemical looping, resulting in the reduction of the cyclic performance of oxygen carriers. The phase segregation characteristics of Fe2O3/Al2O3 calcined at different temperature (900 °C, 1100 °C, 1300 °C) were investigated in this study. The obtained samples were recorded as 900-FeAl, 1100-FeAl and 1300-FeAl, respectively. XPS results showed that the surface oxygen vacancies of Fe2O3/Al2O3 increased with the increase of calcination temperature. In the redox cycles, the deactivation rate of the three samples were 5.57% (900-FeAl), 6.99% (1100-FeAl) and 31.69% (1300-FeAl), respectively. After 20 cycles, the 1300-FeAl presented serious surface sintering and the largest enrichment degree of surface Fe (137.05%). It can be inferred that the severe enrichment of surface Fe leads to the serious sintering, which aggravates the deactivation of the 1300-FeAl in cyclic reactions. The low calcination temperature (900 °C, 1100 °C) makes the Fe2O3/Al2O3 exhibit rich pore structure, which generates space barrier for the outward migration of Fe cation and inhibits the phase segregation of Fe2O3/Al2O3. The results of this study are of great significance to understand the phase segregation of iron-based oxygen carriers, and provide guiding value for the synthesis of high-performance iron-based oxygen carriers.

MXenes, a kind of two-dimensional material of early transition metal carbides and carbonitrides, have emerged as a unique class of layered-structured metallic materials with attractive features, as good conductivity comparable to metals, enhanced ionic conductivity, hydrophilic property derived from their hydroxyl or oxygen-terminated surfaces, and mechanical flexibility. With tunable etching methods, the morphology of MXenes can be effectively controlled to form nanoparticles, single layer, or multi-layer nanosheets, which exhibit large specific surface areas and is favorable for enhancing the sensing performance of MXenes based sensors. Moreover, MXenes are available to form composites with other materials facilely. With structure design, MXenes or its composite show enhanced mechanical flexibility and stretchability, which enabled its wide application in the fields of wearable sensors, energy storage, and electromagnetic shielding. In this review, recent progress in MXenes is summarized, focusing on its application in wearable sensors including pressure/strain sensing, biochemical sensing, temperature, and gas sensing. Furthermore, the main challenges and future research are also discussed.

Increasing the tuber number per plant and promoting tuber formation are important goals for potato production. Thus, it is of significance to understand how environmental factors affect tuber formation, which relates to the development of agronomical practices. The objective of this research was to test whether changing the CO₂ or N supply level could alter the C : N ratio in potatoes, and whether a change of the C : N ratio in potatoes closely correlates with tuber formation in potato plants. Potato plantlets were grown in greenhouse with varied CO₂ or N levels. The C and N concentrations of plants were measured, and the tuber number and tuber weight were recorded after different growth times. The results show that the C : N ratios in the potato plants increased with increasing CO₂ concentration and that potato plants treated with higher CO₂ concentrations form tubers earlier. A decrease in the N supply also resulted in a higher C : N ratio and earlier tuber formation. Therefore the hypothesis proposed previously is supported by the present work. In addition, the results that C concentration in plants remained stable under different CO₂ or N levels imply that the variation of C : N ratio in the potato plants is mainly due to a change of N concentrations which decreased as the environmental CO₂ concentration increased, while increased as the N supply level increased.

Flexible pressure sensors are the cornerstone of electronic skins with tactile function. However, flexible pressure sensors tend to have disadvantages of slow response speed and large hysteresis, which are caused mainly by the viscoelasticity and interfacial adhesion of flexible materials. In this letter, we adopted silicon nanowire (SiNW) arrays to fabricate a pressure sensor with a piezo-capacitance when the SiNWs are bending under pressure, which avoided the viscoelasticity and interfacial adhesion accompanying with common flexible materials. The sensor recorded unprecedented low hysteresis (~2.26%) and an extremely short response time (~3 ms). With high sensitivity (up to ~8.2 kPa−1), large response capacitance, ultralow detection limit (0.1 Pa), and good repeatability and stability, the sensor holds potential applications in advanced electronic skins, especially when high-precision and high-speed sensing are required.

Oxygen carrier (OC) plays an important role in the successful operation of chemical looping process. A detailed understanding of the structural evolution of the materials is crucial to design high performance OCs for this technology. In this study, Fe2O3 particles were used as oxygen carrier to investigate the morphology and microstructure changes induced by redox reaction during chemical looping process, which were performed in the single and multiple redox cycles. X-ray diffraction (XRD), Hg intrusion method and scanning electron microscope (SEM) were used to characterize the changes in phase composition, pore size distribution and morphology. Our results indicated that the surface area of Fe2O3 particles decreased during the redox cycles even though more macro-pores (>1000 nm) formed for these particles. Sintering was attributed to the surface area decrease of Fe2O3 particles in the redox process. Because of the outward Fe cation diffusion, porous structure in the interior of Fe2O3 particles was formed, which led to the crushing strength of the OC particles decreased significantly. In the reduction process, the aggregation of unstable Fe3O4 could cause the surface sintering of OC particles in the transformation of Fe2O3 into Fe3O4. Such findings can not only explain the performance of iron-based OCs in redox reaction, but can also provide theoretical guidance for the synthesis of iron-based OCs.

Pt-based nanomaterials are regarded as the most efficient electrocatalysts for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs). However, widespread adoption of PEMFCs requires solutions to major challenges encountered with ORR catalysts, namely high cost, sluggish kinetics, and low durability. Herein, a new efficient method utilizing Co-based metal-organic frameworks is developed to produce PtCo bimetallic nanoparticles embedded in unique nitrogen-doped hollow porous carbon capsules. The obtained catalyst demonstrates an outstanding ORR performance, with a mass activity that is 5.5 and 13.5 times greater than that of commercial Pt/C and Pt black, respectively. Most importantly, the product exhibits dramatically improved durability in terms of both electrochemically active surface area (ECAS) and mass activity compared to commercial Pt/C and Pt black catalysts. The remarkable ORR performance demonstrated here can be attributed to the structural features of the catalyst (its alloy structure, high dispersion and fine particle size) and the carbon support (its nitrogen dopant, large surface area and hollow porous structure).

Iridium dioxide, IrO2, is second to the most active RuO2 catalyst for the oxygen evolution reaction (OER) in acid, and is used in proton exchange membrane water electrolyzers due to its high durability. To improve the activity of IrO2-based catalysts, we prepared RuO2@IrO2 core-shell nanocatalysts using carbon-supported Ru as the template. At 1.48 V, the OER specific activity of RuO2@IrO2 is threefold that of IrO2. While the activity volcano plots over wide range of materials have been reported, zooming into the top region to clarify the rate limiting steps of most active catalysts is important for further activity enhancement. Here, we verified theory-proposed sequential water dissociation pathway in which the O O bond forms on a single metal site, not via coupling of two adsorbed intermediates, by fitting measured polarization curves using a kinetic equation with the free energies of adsorption and activation as the parameters. Consistent with theoretical calculations, we show that the OER activities of IrO2 and RuO2@IrO2 are limited by the formation of O adsorbed phase, while the OOH formation on the adsorbed O limits the reaction rate on RuO2.

Phosphorus (P) is a major limiting factor for plant productivity in many ecosystems and agriculture. The projected increase in atmospheric CO 2 is likely to result in changes in plant mineral consumption and growth. We studied phosphorus depletion by common bean plants cultured hydroponically under ambient (377 ± 77 µmol mol −1 ) or elevated (650 ± 32 µmol mol −1 ) CO 2, in media of low or high phosphorus. Compared to ambient CO 2 environment, under elevated CO 2 : 1) maximum phosphorus depletion rate increased by 98% at low phosphorus and 250% at high phosphorus, and phosphorus was depleted about 2 to 5 weeks sooner; 2) leaf acid phosphatase (APase) activity and leaf chlorophyll content both increased significantly; 3) root-to-shoot ratio increased significantly at high phosphorus, although it was unaffected at low phosphorus; 4) lateral root respiration rate had no change, suggesting that CO 2 did not affect phosphorus depletion via metabolic changes to the roots; 5) total biomass at final harvest was significantly higher at both low- and high- phosphorus. Our data show that the increased rate and amount of phosphorus depletion during growth under elevated CO 2 occurred in association with alteration in leaf biochemical properties, i.e., enhanced activities of leaf APase and increased leaf chlorophyll content.

Ammonia oxidation reaction (AOR) is sluggish, especially at ambient temperature. To make kinetic study in electrochemical cell more informative and relevant to the catalysts' performance in direct ammonia fuel cells (DAFCs) operating at about 100 °C, it is desirable to study the AOR kinetics at elevated temperatures. However, ammonia evaporation accelerates with increasing temperature causing decrease of ammonia concentration with time. We show here a feasible solution to this issue - let argon gas bubble through concentrated ammonia before entering the electrochemical cell so that the solution can be kept ammonia saturated and oxygen free. Repeatable AOR polarization curves were obtained at temperatures up to 60 °C. The AOR activities are characterized by the average currents at 0.5 V versus RHE measured at 20 mV s-1 in potential cycles below the potential of peak current. For PtIr/C, the PGM mass activities are 25 A g-1 at 25 °C and 225 A g-1 at 60 °C. The results for Pt/C and Ir/C and discussion of the causes for their distinct kinetic behavior will be presented at the meeting.

In this paper, the low-temperature thermally induced phase separation (L-TIPS) method was adopted to prepare a high-performance polyvinylidene fluoride (PVDF) hydrophobic membrane for membrane distillation (MD) with non-solvent polyethylene glycol-400 (PEG400) and solvent triethyl phosphate as a fully water-soluble mixed diluent. In the process of L-TIPS membrane formation, the unidirectional regulatory role of coagulation bath temperature on cross-section radius of the PVDF hollow-fiber membrane was analyzed. The results show that the tensile strength of the membrane increases with the increase of the external coagulation bath water temperature, which is the opposite of the general rule. PEG400 is employed to regulate the membrane structure, and more specifically to increase the cellular structure (a positive impact on tensile strength) and reduce the sphere-packed aggregation structure (a negative impact on tensile strength). When the coagulation bath temperature is 60 °C, the tensile strength of the membrane reaches 6.21 MPa (more than 2–4 times higher than the hydrophobic membranes reported). Meanwhile, the PVDF hollow-fiber hydrophobic membrane also has a high flux, the vacuum membrane distillation flux reaches 30.6 kg m−2 h−1, which is 14.6 times higher than that at the coagulation bath temperature of 15 °C.

Rationally designed precursors of N-doped carbon are crucial for high performance carbon materials of supercapacitor electrodes. Herein, we report a scalable preparation of hierarchically structured N-doped carbon of micro/meso porous nanofiber morphology by using a supramolecular assembled polypyrrole as the precursor. The influences of the dose of supramolecular dopant on final products after carbonization and sequential chemical activation were investigated. The interconnected nanofiber backbone allows better electron transport and the optimized hierarchically porous structure of the material exhibits a large specific surface area of 2113.2 m2 g−1. The N content of the carbon is as high as 6.49 atom%, which is favorable to improve the supercapacitive performance via additional reversible redox reaction over pure carbon. The hierarchically porous N-doped carbon electrode delivered an outstanding specific capacitance of 435.6 F g−1 at 0.5 A g−1, significantly higher than that of the control sample derived from undoped polypyrrole samples. Moreover, the capacitance retention is as high as 96.1% after 5000 cycles. This precursor's structural control route is readily applicable to various conducting polymers, and provides a methodology to design carbon materials with advanced structure for developing high-performance supercapacitor electrode materials.

With the vigorous development of industry and information technology, people's requirements for sensors are becoming more and more diversified and universal. It is still a challenge to find a new type of pressure sensor with low cost, simple preparation, wider pressure test range, and higher sensitivity. Hereby, we report a novel flexible pressure sensor with a wide pressure detection range and robust mechanical properties, taking advantage of transition metal sulfide NiS2, adsorbed in melamine sponge as the active substance. The flexible sensor deforms under pressure with a internal microstructure change and a corresponding conductivity ramping. The addition of elastic polyvinylidene fluoride after curing improves the impact resistance and enables higher stability. Experiments show that the resistance pressure sensor responds within a wide range of 50 kPa with a high sensitivity of below 0.0345 kPa−1 and a fast response time of 0.64 s. Its excellent performance makes the sensor promising for wearable electronics and health monitoring devices.

In chemical looping combustion, iron-based oxygen carriers often experienced serious phase segregation, which reduced the cyclic stability of the oxygen carriers. In this work, Fe2O3/Al2O3 (FA) was doped with different metals (Sr, La and Ce) to improve the redox performance during cyclic reactions. The mechanism of dopants on FA was explored by experimental research and characterization analysis. The promotion effect of different dopants on the redox performance of FA followed the sequence: Sr > La > Ce. It was shown that the deactivation of Ce-FA and La-FA was obvious in 20 cycles. The results of 100 successive cycles indicated that the surface structure of Sr-FA remained stable and no sintering was observed. The Sr-FA achieved stable oxygen carrying capacity (4%) in 100 redox cycles. The characterization results indicated that the addition of Sr could effectively increase the concentration of oxygen vacancies, thus inhibiting the phase segregation of FA. The enrichment degree of surface Fe of FA, Sr-FA, La-FA and Ce-FA were 135.7%, 43.47%, 128.0% and 140.0%, respectively. The results of this study provide guidance for the preparation of iron-based oxygen carriers with high redox performance.

The chemical looping combustion (CLC) is an advanced combustion technique that can separate carbon dioxide (CO 2 ) simultaneously. The recyclability and stability of oxygen carriers is very important for the economical efficiency of CLC. The major factor for the deactivation of oxygen carriers is sintering. For most CLC studies, the focus were all on the reactivity of the oxygen carriers, but very few effort was contributed to the sintering properties of the oxygen carriers. This article addressed the characteristic and decay kinetics of surface area for iron oxide in the reduction process of CLC. The results showed that increasing the reaction temperature accelerated the decrease rate of surface area for iron oxide. In addition, with the reduction degree deepening, the grain size of iron oxide increased. Sintering kinetics of surface area decay based on a power law expression model was investigated. The activation energy for surface area decrease of iron oxide in the reduction process was calculated as 89.94 kJ/mol. Sintering and oxygen vacancies creation were the two causes for microstructural variation of iron oxide during the reduction process. Sintering leads to the decrease of surface area for iron oxide, while oxygen vacancies creation results in the porous structure forming.

In the NIPS method, polyethylene glycol-400 (PEG400) was a common water-soluble additive and usually played the role of a pore-forming agent due to NIPS double-diffusion. In this paper, the new role of non-solvent PEG400 in the low temperature thermally-induced phase separation (L-TIPS) was analyzed. PEG400 were used to regulate the phase separation mechanism of the dope solution, and then to improve the membrane structure and performance. The membrane structure was regulated by gradually increasing the PEG400 content, the role evolution of water-soluble non-solvent PEG400 on the phase transformation mechanism and the effect on tensile strength of the polyvinylidene fluoride (PVDF) membrane were studied. The results show that the increase of PEG400 content can increase the cloud point temperature of dope solution, accelerate the thermally induced phase separation (TIPS) effect and inhibit the negative effect of the non-solvent induced phase separation (NIPS) effect on membrane structure. Meanwhile, the increase of PEG400 content can shift the TIPS effect of the dope solution system from solid-liquid phase separation to liquid-liquid phase separation and inhibit the growth of PVDF spherulites during the TIPS process. The dual role mechanism of PEG400 together eliminates the NIPS finger-like voids and the TIPS sphere-packed aggregation structure, which have the negative impact on tensile strength of the PVDF membrane. The PVDF membrane shows excellent mechanical properties; the tensile strength of the membrane reaches 3.12 MPa (more than 3–6 times higher than the membranes reported), pure water flux reaches 391 L m−2 h−1, and the rejection rate of carbon ink is 100%.