Search

Gram-scale preparation of CoFe-LDH for highly efficient electrochemical water oxidation.

Magnetic materials with ingeniously designed structures may be utilized as highly efficient microwave absorbing materials (MAMs) working at ultralow matching thicknesses. However, it remains a challenge to decrease the matching thickness by synergistically tailoring the composition and structure of magnetic MAMs. In this work, a series of magnetic MAMs have been synthesized by sequentially annealing Fe-bdc nanorods in air and hydrogen. The results show that with the increase in hydrogen reduction temperature, the Fe

Extending effective absorption bandwidth at a low filling ratio is still a challenge for metal-organic framework-derived microwave absorbing materials. Herein, varied complex structures based on CNTs have been built on Co/C particles derived from ZIF-67 via melamine-involved annealing routes. It was found that cobalt nanoparticles derived from ZIF-67 act as catalysts for the growth of CNTs, effectively promoting and controlling the content of melamine. Due to the effective control of the CNT-containing complex structure, excellent microwave absorption performance was achieved at a rather low filling ratio of 20 wt%, which can be attributed to improved attenuation ability and ameliorated impedance matching. Results show that highly graphitic CNTs benefit the formation of the electron transport network and enhancement of conduction loss. Unique one-dimensional complex structure and abundant Co/C interfaces strengthen the polarization loss. When the dielectric loss was optimized at different frequencies, appropriate impedance matching was also gained to realize a broad effective absorption bandwidth of 5.6 and 4.4 GHz in Ku and X bands, respectively. This work may provide novel insights into the synthesis and design of CNT-containing metal-organic framework-derived materials with lightweight features and wide frequency response.

Precise control of the dielectric properties of metal–organic framework-derived carbon-based composites is required to extend the effective absorption bandwidth. Herein, ZIF-67 particles with different sizes have been prepared by changing the content and solvent, and they have been converted into Co/C composite particles at different pyrolysis temperatures. The electromagnetic properties of Co/C particles with different filling ratios have been investigated. The results showed that a higher pyrolysis temperature, larger filling ratio and smaller particle size have a positive effect on the increase of complex permittivity especially at low frequencies. The filling ratio and particle size should have an effect on inter-particle conduction loss by affecting electrical conduction networks, while the pyrolysis temperature decides conduction loss, as well as dipole polarization within individual particles. When the balance between dielectric loss and impedance matching is achieved, an extended effective absorption bandwidth in both Ku and X bands can be obtained. With a filling ratio of only 30 wt%, the effective absorption bandwidth of samples with a size of ∼1000 nm and ∼400 nm covered the whole Ku and X bands, respectively. This research offers a facile route to obtain excellent light weight microwave absorbing materials for practical application and deeper insights into the regulation of dielectric properties to achieve an extended effective absorption bandwidth.

Understanding the limitations of electrocatalytic activity and developing advanced catalysts with enhanced activity are of exceptional importance for future hydrogen energy applications. Due to the complexity of electrolytic hydrogen evolution in alkaline media, there are limited non-noble metal catalysts to afford large scale applications. Tungsten-based catalysts exhibit favorable stability but relatively low activity owing to their strong H* adsorption characteristics. In this work, cobalt hydroxides/cubic phase WN nanoparticles with strengthened interfaces and adjustable nitrogen vacancies anchored on multi-walled carbon nanotubes (Co(OH)2/c-WN1−x/CNTs) are exploited as highly efficient alkaline hydrogen evolution electrocatalysts, which exhibit remarkable activity with an overpotential of 78 mV at 10 mA cm−2 and a low Tafel slope of 43 mV dec−1 in 1 M KOH media. Density-functional theory calculations revealed that the interfacial combinations of Co(OH)2/c-WN1−x were tuned to facilitate the kinetics of hydrogen evolution, where Co(OH)2 promoted the adsorption of water molecules and the H–OH dissociation, and cubic phase WN with nitrogen vacancies (c-WN1−x) accelerated hydrogen generation by optimizing the hydrogen adsorption free energy.

Currently, the need for safe and effective methods for relieving allergies is an important concern. In this study, we evaluated the role of Lactobacillus rhamnosus GG (LGG) in alleviating β-conglycinin (β-CG)-induced allergies and elucidated the related molecular mechanisms. Typical allergy symptoms and inflammatory factors in the serum showed that LGG intervention effectively alleviated β-CG induced allergy in mice, which was better than natural recovery (NR). Intestinal villi were restored and lower levels of CD4+ T cells infiltrated after LGG intervention. We evaluated whether LGG intervention weakened the proliferation ability of the spleen cells of allergic mice, balancing between T/B cells and Th1/Th2 and Th17/Treg cytokines. Transcriptome analysis revealed that 4106 differentially expressed mRNAs were identified by comparing the LGG group and β-CG group, and 546 differentially expressed mRNAs were identified by comparing the LGG group and NR group. KEGG pathway analysis identified that the T cell receptor (TCR) signaling pathway was significantly enriched upon LGG intervention, and the upregulated Ifnar2 and the downregulated Tgfbr2, Il13r2 and Il4ra were further validated by qPCR analysis. Therefore, the above results fully revealed the important role of LGG in alleviating β-CG-induced allergies.

Multimetal high-entropy alloys (HEAs) have been recognized as potential catalysts that can possibly replace the conventional metal oxides and noble metals for use in energy conversion and water splitting such as oxygen evolution reactions (OERs). However, their higher catalysis is restrained by the difficulty in the synthesis of HEAs with desirable morphologies and deformed crystal lattice structures. In this work, an advanced approach was developed to fabricate the smallest possible HEA (i.e., MnFeCoNiCu) with deformed nanoparticles supported on the carbon cloth (CC) surface. The nanoparticles were characterized to be single face-centered cubic (FCC) crystals with highly deformed lattices, giving rise to various defects (such as twins, dislocations and stacking faults). The high surface tension caused by these defects leads to a substantial reduction in the overpotential down to 263 mV for the production of 10 mA cm−2 with a very low Tafel slope of 43 mV dec−1 and a rather small charge transfer resistance of 0.644 Ω in 1.0 M KOH, which is exceptionally lower than that of RuO2 and the state-of-the-art HEAs and competitive in comparison to most metal oxides. This work proves that the lattice deformation manipulates the displacement of atoms over the nanoparticle surface that facilitates their catalytic activities that are higher than those of the state-of-the-art counterparts reported in the literature. It also provides an insight into the performance improvement of other nanostructures in energy applications.

Pu-erh tea is produced from the leaves of large-leaf tea species (Camellia sinensis var. assamica) in the Yunnan province of China and divided into ripened pu-erh tea (RIPT, with pile-fermentation) and raw pu-erh tea (RAPT) according to processing methods. RIPT extract showed more potent anti-diabetic effects on two-hour postprandial blood glucose (2h-PBG) and fasting blood glucose (FBG) than RAPT extract. UHPLC-Q-TOF/MS and UHPLC-PDA analyses found that 17 newly formed components and the increased components after fermentation, such as quinic acid, gallic acid, caffeine, puerin I and so on, might be the main contributors to the enhanced activities of RIPT. In addition, the probiotic role of RIPT to some beneficial gut bacteria, such as lactobacillus, Prevotellaceae NK3B31 group, Alloprevotella and Prevotella, was observed in our study. These results might provide a clue to anti-diabetic mechanism and active components of pu-erh tea, and use as a functional beverage worth to be further studied.

Li3VO4 (LVO) anode materials with controllable morphologies ranging from spherical-assemblies, single-crystal nanorods, and flower shapes to bulk-shapes were fabricated via a solvothermal approach using different alcohols (i.e., ethanol, methanol, propanol, and butanol). XRD, SEM, BET, Raman and FTIR and galvanostatic charge/discharge measurements were carried out to correlate their structure/morphology with their electrochemical characteristics. The experimental results reveal that both structure and morphology play important roles in the Li+ ion storage of LVO, which degrades in the sequential order from nanorods, to spheres, to flowers and finally to bulk. The LVO nanorods are hierarchical and have a small particle size, high specific surface area, and high crystallinity; thus, they exhibit the largest Li+ ion diffusion coefficient and best electrochemical performance among the four electrodes. Moreover, coating carbon on the single-crystal LVO nanorods further enhances their Li+ ion storage ability. Consequently, the carbon-coated LVO nanorods deliver a high reversible capacity of 440 mA h g−1 at 0.1 A g−1 with good cycling stability and demonstrate great practical application. In addition, the results promote a better fundamental understanding of the Li+ ion storage behavior in LVO and provide insight into the optimal design of LVO and other vanadium-based electrode materials. MOE (Min. of Education, S’pore) Accepted version

© 2018 The Royal Society of Chemistry. Constructed wetlands (CWs) have been widely used as an ecological technology for removing nutrients from aquatic ecosystems. However, the treatment efficiency of surface flow constructed wetlands (SFCWs) in winter is generally low. To enhance the nutrient removal performance of SFCWs in winter, we developed a novel hardy submerged plant-benthic fauna system by adding Chironomus riparius (C. riparius) larvae and planting Potamogeton crispus L. in SFCWs. Compared to a system without C. riparius, the paired system greatly enhanced TN and TP removal with the average removal efficiencies of 54.73% and 94.76%, respectively. Furthermore, the paired system improved NO 3- -N removal efficiency by 29.51% and reached NH 4+ -N removal efficiency as high as 86.20% simultaneously. The mass balance analysis indicated that C. riparius larvae enhanced substrate absorption and plant uptake in the CWs. The results of microbial analysis agreed with the nutrient removal performance, showing that C. riparius larvae influence the abundance and community structure of microbes related to N removal. As a whole, this study provides a promising ecological strategy for performance intensification of SFCWs in winter.

Herein, we demonstrate a facile method to prepare hollow-structured oxygen-vacancy-rich Fe2O3/MnO2 nanorods. Our results show that oxygen vacancies are induced by nanoscale ion intermixing between Fe and Mn ions during the annealing process. Owing to their unique core–shell hollow nanostructure and the presence of oxygen vacancies, the Fe2O3/MnO2 nanorods show excellent electrochemical performances as an anode material for lithium ion batteries and a reversible capacity higher than 700 mA h g−1 after 2000 cycles.

In the present study, we report a synthetic strategy for the direct fabrication of hybrid vertical graphene/lithium titanate–CNTs arrays via atomic layer deposition in combination with chemical vapor deposition. A novel array architecture was formed where active lithium titanate (Li4Ti5O12, LTO) was uniformly sandwiched by a vertical graphene backbone and an interconnected CNTs shell. The hybrid omnibearing conductive network was identified to be an extremely stable porous structure and demonstrated superior ultra-high rate capability (146 mA h g−1 at 50C and 131 mA h g−1 at 100C) with a capacity of 136 mA h g−1 at 20C after 10 000 cycles when used as an electrode in lithium ion batteries. This special electrode construction strategy is expected to provide a new route for the manufacture of electrochemical energy storage with ultra-high rate capability and ultra-stability.

Herein we converted Fe–Ni hydroxide nanosheets into an Fe–Ni phosphide nanoparticle-stack array on Ni foam by low-temperature phosphorization treatment for promoting the specific surface area of Fe–Ni phosphide and further improving its oxygen evolution reaction (OER) activities. The alkaline electro-activated Fe–Ni–P nanoparticle-stack array exhibits exceptional OER activities in both alkaline and neutral media.

Vertically aligned carbon nanotube (CNT) arrays have aroused considerable interest because of their remarkable mechanical properties. However, the mechanical behaviour of as-synthesized CNT arrays could vary drastically at a macro-scale depending on their morphologies, dimensions and array density, which are determined by the synthesis method. Here, we demonstrate a coaxial carbon@boron nitride nanotube (C@BNNT) array with enhanced compressive strength and shape recoverability. CNT arrays are grown using a commercially available thermal chemical vapor deposition (TCVD) technique and an outer BNNT with a wall thickness up to 1.37 nm is introduced by a post-growth TCVD treatment. Importantly, compared to the as-grown CNT arrays which deform almost plastically upon compression, the coaxial C@BNNT arrays exhibit an impressive ∼4-fold increase in compressive strength with nearly full recovery after the first compression cycle at a 50% strain (76% recovery maintained after 10 cycles), as well as a significantly high and persistent energy dissipation ratio (∼60% at a 50% strain after 100 cycles), attributed to the synergistic effect between the CNT and outer BNNT. Additionally, the as-prepared C@BNNT arrays show an improved structural stability in air at elevated temperatures, attributing to the outstanding thermal stability of the outer BNNT. This work provides new insights into tailoring the mechanical and thermal behaviours of arbitrary CNT arrays which enables a broader range of applications. MOE (Min. of Education, S’pore) Published version

In the present paper, hollow-porous α-Fe2O3 microspheres are prepared via cation etching of zinc citrate microspheres and subsequent thermal treatment. The superior performance of the as-obtained α-Fe2O3 microspheres as an anode material for lithium ion batteries is evaluated. After 1000 cycles, the capacity still remains more than 1100 mA h g−1 at a current rate of 1 A g−1. Meanwhile, the crystal size induced phase transition of Fe2O3 microspheres (α → γ → β) is observed during cycling by the measurements of ex situ XRD and TEM, which is responsible for their abnormal performance fluctuation.

The 3D configuration of graphene materials has been intensively investigated due to their novel properties in biomedical, electrical and optical applications. But few reports have been intentionally carried out to understand the biological influence of 3D graphene materials so far. Herein, we presented an evaluation of the in vitro cytotoxicity of 3D graphene sheets fabricated by carbonization of polydopamine (PDA) films on a template of aligned nanopore arrays (NPAs) on a stainless steel surface. The prepared 3D graphene sheets with a thickness of ∼20 nm displayed a nanoporous architecture that can be readily tuned by the NPA template to control the morphology of the 3D configuration. The in vitro toxicity of the nanoporous 3D graphene sheets with pore sizes of ∼50 nm and ∼240 nm was evaluated using NIH-3T3 fibroblasts as the representative mammal fibroblast cell type. The NPA structure exhibits enhanced properties in cell attachment, spreading, proliferation, and the assembly of focal adhesions and actin filament associated proteins. Morphology-dependent cytotoxicity aroused by the 3D graphene configuration should be attributed to the engulfment of the carbon nanospheres embedded in the 3D configuration and the lack of both focal adhesions and actin filament associated proteins assembling at the nanoscale.

Carbon nanotubes (CNTs) are synthesized through a novel low cost self-vaporized chemical vapor deposition (SCVD) technique from an indecomposable solid carbon source for the first time. This method was manipulated to avoid the injection of flammable gasses, by producing gaseous carbon (e.g. CO) through an in situ catalyzed gasification of the intermediate product induced by KOH. Simultaneously, the as-produced gaseous carbons will deposit onto the pre-imbedded Ni nanocatalyst surface and form CNTs. The growth mechanism is discussed in detail by adjusting the KOH amount. The as-prepared CNTs are rich in oxygen and deficiencies, which endow them with abundant active sites for electrochemical applications. Superior supercapacitor performance is achieved with a specific capacitance 6 times higher than that of commercial CNTs. This technique represents a novel, convenient approach toward large scale production of CNTs directly from a solid carbon precursor, and would show promising applications in various industrial fields.

The present paper reports the use of TEM to investigate the electrochemical behavior of a copper subject to the both free corrosion and polarization in a 0.1 M NaCl + 5 × 10−4 M Na2S aqueous solution at the nano scale. The pure copper is found to be transformed into nano-crystalline Cu2S in the thin region of the copper needle in the solution at open circuit conditions. However, a rough Cu2S layer is formed in the active region of electrochemical polarization, which is then converted to the passive CuS layer with a uniform thickness at higher potentials. Upon the continuous increase of an applied potential, cubic CuS particles with sizes of ∼100 nm are precipitated on the needle surface due to the breakdown of the passive layer. Meanwhile, the growth of a large amount of nanosized CuCl particles is also found, indicating that Cl− ions participate in the electrochemical reaction in the transpassive region. It is worth noting that the present work also provides a simple and cost-effective way for the synthesis of copper sulfides (Cu2S and CuS) through electrochemical processes.