Despite their high theoretical specific capacity (1675 mA h g−1), the practical application of Li–S batteries remains limited because the capacity rapidly degrades through severe dissolution of ...lithium polysulfide and the rate capability is low because of the low electronic conductivity of sulfur. This paper describes novel hierarchical yolk–shell microspheres comprising 1D bamboo‐like N‐doped carbon nanotubes (CNTs) encapsulating Co nanoparticles (Co@BNCNTs YS microspheres) as efficient cathode hosts for Li–S batteries. The microspheres are produced via a two‐step process that involves generation of the microsphere followed by N‐doped CNTs growth. The hierarchical yolk–shell structure enables efficient sulfur loading and mitigates the dissolution of lithium polysulfides, and metallic Co and N doping improves the chemical affinity of the microspheres with sulfur species. Accordingly, a Co@BNCNTs YS microsphere‐based cathode containing 64 wt% sulfur exhibits a high discharge capacity of 700.2 mA h g−1 after 400 cycles at a current density of 1 C (based on the mass of sulfur); this corresponds to a good capacity retention of 76% and capacity fading rate of 0.06% per cycle with an excellent rate performance (752 mA h g−1 at 2.0 C) when applied as cathode hosts for Li–S batteries.
Hierarchical yolk–shell microspheres comprising 1D bamboo‐like N‐doped carbon nanotubes (CNTs) encapsulating Co nanocrystals are first introduced as efficient cathode hosts for Li–S batteries. The synergetic effect of the presence of the N‐doped CNTs with Co nanocrystals and the hierarchical structure of yolk‐shell microspheres is responsible for the superior performances as the cathode hosts for Li–S batteries.
A novel anode material for sodium‐ion batteries consisting of 3D graphene microspheres divided into several tens of uniform nanospheres coated with few‐layered MoS2 by a one‐pot spray pyrolysis ...process is prepared. The first discharge/charge capacities of the composite microspheres are 797 and 573 mA h g−1 at a current density of 0.2 A g−1. The 600th discharge capacity of the composite microspheres at a current density of 1.5 A g−1 is 322 mA h g−1. The Coulombic efficiency during the 600 cycles is as high as 99.98%. The outstanding Na ion storage properties of the 3D MoS2–graphene composite microspheres may be attributed to the reduced stacking of the MoS2 layers and to the 3D structure of the porous graphene microspheres. The reduced stacking of the MoS2 layers relaxes the strain and lowers the barrier for Na+ insertion. The empty nanospheres of the graphene offer voids for volume expansion and pathways for fast electron transfer during repeated cycling.
3D MoS2–graphene composite microspheres consisting of multiple nanospheres are prepared by a one‐pot spray pyrolysis process with high scale‐up potential. The 3D MoS2–graphene composite microspheres show high reversible capacity and long cycle stability as anode materials for sodium‐ion batteries. The facile and continuous synthesis of 3D graphene‐based composite microspheres could be applied to the potential materials for various fields including energy storage.
Porous FeS nanofibers with numerous nanovoids for use as anode materials for sodium-ion batteries were prepared by electrospinning and subsequent sulfidation. The post-treatment of the as-spun ...Fe（acac）3-polyacrylonitrile composite nanofibers in an air atmosphere yielded hollow Fe2O3 nanofibers due to Ostwald ripening. The ultrafine Fe2O3 nanocrystals formed at the center of the fiber diffused toward the outside of the fiber via Ostwald ripening. On sulfidation, the Fe2O3 hollow nanofibers were transformed into porous FeS nanofibers, which contained numerous nanovoids. The formation of porosity in the FeS nanofibers was driven by nanoscale Kirkendall diffusion. The porous FeS nanofibers were very structurally stable and had superior sodium-ion storage properties compared with the hollow Fe2O3 nanofibers. The discharge capacities of the porous FeS nanofibers for the Ist and 150th cycles at a current density of 500 mA.g-1 were 561 and 592 mA.h-g-1, respectively. The FeS nanofibers had final discharge capacities of 456, 437, 413, 394, 380, and 353 mA-h.g-1 at current densities of 0.2, 0.5, 1.0, 2.0, 3.0, and 5.0 A.g-1, respectively.
Uniquely structured CoSe2–carbon nanotube (CNT) composite microspheres with optimized morphology for the hydrogen‐evolution reaction (HER) are prepared by spray pyrolysis and subsequent selenization. ...The ultrafine CoSe2 nanocrystals uniformly decorate the entire macroporous CNT backbone in CoSe2–CNT composite microspheres. The macroporous CNT backbone strongly improves the electrocatalytic activity of CoSe2 by improving the electrical conductivity and minimizing the growth of CoSe2 nanocrystals during the synthesis process. In addition, the macroporous structure resulting from the CNT backbone improves the electrocatalytic activity of the CoSe2–CNT microspheres by increasing the removal rate of generated H2 and minimizing the polarization of the electrode during HER. The CoSe2–CNT composite microspheres demonstrate excellent catalytic activity for HER in an acidic medium (10 mA cm−2 at an overpotential of ≈174 mV). The bare CoSe2 powders exhibit moderate HER activity, with an overpotential of 226 mV at 10 mA cm−2. The Tafel slopes for the CoSe2–CNT composite and bare CoSe2 powders are 37.8 and 58.9 mV dec−1, respectively. The CoSe2–CNT composite microspheres have a slightly larger Tafel slope than that of commercial carbon‐supported platinum nanoparticles, which is 30.2 mV dec–1.
Macroporous CoSe2–carbon nanotube (CNT) composite microspheres demonstrating excellent electrocatalytic activity for hydrogen‐evolution reaction are prepared by a simple two‐step process based on spray pyrolysis. The macroporous CNT backbone strongly improves the electrocatalytic activity of CoSe2 by improving the electrical conductivity and minimizing the growth of CoSe2 nanocrystals. The Tafel slopes of the CoSe2–CNT composite is 37.8 mV dec–1.
Golden bristlegrass‐like unique nanostructures comprising reduced graphene oxide (rGO) matrixed nanofibers entangled with bamboo‐like N‐doped carbon nanotubes (CNTs) containing CoSe2 nanocrystals at ...each node (denoted as N‐CNT/rGO/CoSe2 NF) are designed as anodes for high‐rate sodium‐ion batteries (SIBs). Bamboo‐like N‐doped CNTs (N‐CNTs) are successfully generated on the rGO matrixed nanofiber surface, between rGO sheets and mesopores, and interconnected chemically with homogeneously distributed rGO sheets. The defects in the N‐CNTs formed by a simple etching process allow the complete phase conversion of Co into CoSe2 through the efficient penetration of H2Se gas inside the CNT walls. The N‐CNTs bridge the vertical defects for electron transfer in the rGO sheet layers and increase the distance between the rGO sheets during cycles. The discharge capacity of N‐CNT/rGO/CoSe2 NF after the 10 000th cycle at an extremely high current density of 10 A g−1 is 264 mA h g−1, and the capacity retention measured at the 100th cycle is 89%. N‐CNT/rGO/CoSe2 NF has final discharge capacities of 395, 363, 328, 304, 283, 263, 246, 223, 197, 171, and 151 mA h g−1 at current densities of 1, 2, 4, 6, 8, 10, 12, 14, 16, 18, and 20 A g−1, respectively.
As high‐performance anodes for sodium‐ion batteries, golden bristlegrass‐like graphene nanofibers entangled with N‐doped CNTs containing CoSe2 nanocrystals are designed and synthesized. The synthesized unique nanostructure exhibits high cycling and rate performances even at extremely high current densities. The synergistic effect of the golden bristlegrass‐like unique structure and the N‐doped CNTs/graphene composite results in efficient anode materials for sodium‐ion batteries.
The mechanisms through which microbes communicate using signal molecules has inspired a great deal of research. Microbes use this exchange of information, known as quorum sensing (QS), to initiate ...and perpetuate infectious diseases in eukaryotic organisms, evading the eukaryotic defense system by multiplying and expressing their pathogenicity through QS regulation. The major issue to arise from such networks is increased bacterial resistance to antibiotics, resulting from QS-dependent mediation of the formation of biofilm, the induction of efflux pumps, and the production of antibiotics. QS inhibitors (QSIs) of diverse origins have been shown to act as potential antipathogens. In this review, we focus on the use of QSIs to counter diseases in humans as well as plants and animals of economic importance. We also discuss the challenges encountered in the potential applications of QSIs.
•Quorum sensing (QS) mediated pathogenicity in aquaculture, plants, and humans•QS inhibitors (QSIs) as antipathogens•Bioetchnological applications of QSIs•Field trials of QSIs in treating plants, water and humans
Adipose tissue derived mesenchymal stem/stromal cell (ASC)-derived extracellular vesicles (EV) have been reported to be beneficial against dextran sulfate sodium (DSS)-induced colitis in mice. ...However, the underlying mechanisms have not been fully elucidated. We hypothesize that the tumor necrosis factor-α-stimulated gene/protein 6 (TSG-6) in EVs is a key factor influencing the alleviation of colitis symptoms. DSS-induced colitis mice (C57BL/6, male, Naïve = 6, Sham = 8, PBS = 8 EV = 8, CTL-EV = 8, TSG-6 depleted EV = 8) were intraperitoneally administered EVs (100 ug/mice) on day 1, 3, and 5; colon tissues were collected on day 10 for histopathological, RT-qPCR, western blot and immunofluorescence analyses. In mice injected with EV, inflammation was alleviated. Indeed, EVs regulated the levels of pro- and anti-inflammatory cytokines, such as TNF-α, IL-1β, IFN-γ, IL-6, and IL-10 in inflamed colons. However, when injected with TSG-6 depleted EV, the degree of inflammatory relief was reduced. Furthermore, TSG-6 in EVs plays a key role in increasing regulatory T cells (Tregs) and polarizing macrophage from M1 to M2 in the colon. In conclusion, this study shows that TSG-6 in EVs is a major factor in the relief of DSS-induced colitis, by increasing the number of Tregs and macrophage polarization from M1 to M2 in the colon.
•Cross-linked (CL) laccase-metal hybrid nanoflower (NF) was prepared.•The catalytic efficiency of CL-NF laccase was 2.2-fold higher than that of free laccase.•CL-NF laccase showed 2.6-fold higher ...oxidation potential than free laccase towards phenolic compounds.•Under repeated batch conditions, it retained high decolorization efficiency for synthetic dyes.
Herein, we report the preparation of a cross-linked protein-metal hybrid nanoflower (NF) system for laccase immobilization. The immobilized laccase showed effective encapsulation yield and activity recovery of 78.1% and 204%, respectively. The catalytic efficiency (kcatVmax−1) of cross-linked NF (CL-NF) was 2.2-fold more than that of free laccase. The CL-NF also exhibited significantly higher stability towards pH and temperature changes. It exhibited excellent storage stability and tolerance towards solvents and inhibitors as compared with the free enzyme. After 10 cycles of reuses, the NF and CL-NF laccase showed 41.2% and 92.3% residual activity, respectively. The CL-NF showed high oxidation potential, 265% that of the free enzyme, towards phenolic compounds. The CL-NF laccase retained the residual decolorization efficiency of up to 84.6% for synthetic dyes under repeated batch conditions of 10 cycles. These results suggested that the preparation of CL-NF is an effective approach to enhance the enzymatic properties and has great potential in many industrial applications.
A new mechanism for the transformation of nanostructured metal selenides into uniquely structured metal oxides via the Kirkendall effect, which results from the different diffusion rates of metal and ...Se ions and O2 gas, is proposed. SnSe nanoplates are selected as the first target material and transformed into SnO2 hollow nanoplates by the Kirkendall effect. SnSe‐C composite powder, in which SnSe nanoplates are attached or stuck to amorphous carbon microspheres, transforms into several tens of SnO2 hollow nanoplates by a thermal oxidation process under an air atmosphere. Core–shell‐structured SnSe‐SnSe2@SnO2, SnSe2@SnO2, Se‐SnSe2@SnO2, and Se@SnO2 and yolk–shell‐structured Se@void@SnO2 intermediates are formed step‐by‐step during the oxidation of the SnSe nanoplates. The uniquely structured SnO2 hollow nanoplates have superior cycling and rate performance for Li‐ion storage. Additionally, their discharge capacities at the 2nd and 600th cycles are 598 and 500 mA h g‐1, respectively, and the corresponding capacity retention measured from the 2nd cycle is as high as 84%.
A new mechanism for the transformation of nanostructured metal selenides into uniquely structured metal oxides via the Kirkendall effect is proposed. SnSe nanoplates are selected as the first target material and transformed into SnO2 hollow nanoplates by the Kirkendall effect. The uniquely structured SnO2 hollow nanoplates have superior cycling and rate performance for Li‐ion storage.
Hierarchically well‐developed porous graphene nanofibers comprising N‐doped graphitic C (NGC)‐coated cobalt oxide hollow nanospheres are introduced as anodes for high‐rate Li‐ion batteries. For this, ...three strategies, comprising the Kirkendall effect, metal–organic frameworks, and compositing with highly conductive C, are applied to the 1D architecture. In particular, NGC layers are coated on cobalt oxide hollow nanospheres as a primary transport path of electrons followed by graphene‐nanonetwork‐constituting nanofibers as a continuous and secondary electron transport path. Superior cycling performance is achieved, as the unique nanostructure delivers a discharge capacity of 823 mAh g−1 after 500 cycles at 3.0 A g−1 with a low decay rate of 0.092% per cycle. The rate capability is also noteworthy as the structure exhibits high discharge capacities of 1035, 929, 847, 787, 747, 703, 672, 650, 625, 610, 570, 537, 475, 422, 294, and 222 mAh g−1 at current densities of 0.5, 1.5, 3, 5, 7, 10, 12, 15, 18, 20, 25, 30, 40, 50, 80, and 100 A g−1, respectively. In view of the highly efficient Li+ ion/electron diffusion and high structural stability, the present nanostructuring strategy has a huge potential in opening new frontiers for high‐rate and long‐lived stable energy storage systems.
Hierarchically well‐developed porous graphene nanofibers comprising N‐doped graphitic C‐coated cobalt oxide hollow nanospheres are introduced as anodes for high‐rate Li‐ion batteries. In view of the highly efficient Li+ ion/electron diffusion and high structural stability, the unique nanostructuring strategy has a huge potential in opening new frontiers for high‐rate and long‐lived stable energy storage systems.
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