Highly Selective and Reversible Detection of Simulated Breath Hydrogen Sulfide Using Fe-Doped CuO Hollow Spheres: Enhanced Surface Redox Reaction by Multi-Valent Catalysts

The precise and reversible detection of hydrogen sulfide (H2 S) at high humidity condition, a malodorous and harmful volatile sulfur compound, is essential for the self-assessment of oral diseases, halitosis, and asthma. However, the selective and reversible detection of trace concentrations of H2 S (≈0.1 ppm) in high humidity conditions (exhaled breath) is challenging because of irreversible H2 S adsorption/desorption at the surface of chemiresistors. The study reports the synthesis of Fe-doped CuO hollow spheres as H2 S gas-sensing materials via spray pyrolysis. 4 at.% of Fe-doped CuO hollow spheres exhibit high selectivity (response ratio ≥ 34.4) over interference gas (ethanol, 1 ppm) and reversible sensing characteristics (100% recovery) to 0.1 ppm of H2 S under high humidity (relative humidity 80%) at 175 °C. The effect of multi-valent transition metal ion doping into CuO on sensor reversibility is confirmed through the enhancement of recovery kinetics by doping 4 at.% of Ti- or Nb ions into CuO sensors. Mechanistic details of these excellent H2 S sensing characteristics are also investigated by analyzing the redox reactions and the catalytic activity change of the Fe-doped CuO sensing materials. The selective and reversible detection of H2 S using the Fe-doped CuO sensor suggested in this work opens a new possibility for halitosis self-monitoring.

Scalable Dry Process for Fabricating a Na Superionic Conductor-Type Solid Electrolyte Sheet

The cost reduction and mass production of oxide-based solid electrolytes are critical for the commercialization of all-solid-state batteries. In this study, an environmentally friendly, low-cost, and high-density oxide-based Na superionic conductor-type solid electrolyte sheet was fabricated via a dry process without the use of any solvent. The polytetrafluoroethylene (PTFE), used as a binder, was transformed into thin thread-like structures via shear force, resulting in a flexible solid electrolyte sheet. The solid electrolyte powder quantity was limited to 50 wt % for fabricating a uniform green sheet via the wet process. However, when the dry process was employed for green sheet fabrication, the solid electrolyte powder quantity could be increased to values exceeding 95 wt %. Therefore, the green sheets produced by using the dry process demonstrated a higher density than those fabricated by using the wet process. The binder content and particle size affected the ionic conductivity of a solid electrolyte sheet fabricated via a dry process. The sheet obtained via the blending of 3 wt % PTFE binder with a solid electrolyte powder, finely ground using a planetary ball mill, which exhibited the highest total ionic conductivity of 1.03 mS cm-1.

Synthesis of Iron Sulfide Nanocrystals Encapsulated in Highly Porous Carbon-Coated CNT Microsphere as Anode Materials for Sodium-Ion Batteries

Highly porous carbon materials with a rationally designed pore structure can be utilized as reservoirs for metal or nonmetal components. The use of small-sized metal or metal compound nanoparticles, completely encapsulated by carbon materials, has attracted significant attention as an effective approach to enhancing sodium ion storage properties. These materials have the ability to mitigate structural collapse caused by volume expansion during the charging process, enable short ion transport length, and prevent polysulfide elution. In this study, a concept of highly porous carbon-coated carbon nanotube (CNT) porous microspheres, which serve as excellent reservoir materials is suggested and a porous microsphere is developed by encapsulating iron sulfide nanocrystals within the highly porous carbon-coated CNTs using a sulfidation process. Furthermore, various sulfidation processes to determine the optimal method for achieving complete encapsulation are investigated by comparing the morphologies of diverse iron sulfide-carbon composites. The fully encapsulated structure, combined with the porous carbon, provides ample space to accommodate the significant volume changes during cycling. As a result, the porous iron sulfide-carbon-CNT composite microspheres exhibited outstanding cycling stability (293 mA h g-1 over 600 cycles at 1 A g-1 ) and remarkable rate capability (100 mA h g-1 at 5 A g-1 ).

Synergistic Integration of Machine Learning with Microstructure/Composition-Designed SnO2 and WO3 Breath Sensors

A high-performance semiconductor metal oxide gas sensing strategy is proposed for efficient sensor-based disease prediction by integrating a machine learning methodology with complementary sensor arrays composed of SnO2- and WO3-based sensors. The six sensors, including SnO2- and WO3-based sensors and neural network algorithms, were used to measure gas mixtures. The six constituent sensors were subjected to acetone and hydrogen environments to monitor the effect of diet and/or irritable bowel syndrome (IBS) under the interference of ethanol. The SnO2- and WO3-based sensors suffer from poor discrimination ability if sensors (a single sensor or multiple sensors) within the same group (SnO2- or WO3-based) are separately applied, even when deep learning is applied to enhance the sensing operation. However, hybrid integration is proven to be effective in discerning acetone from hydrogen even in a two-sensor configuration through the synergistic contribution of supervised learning, i.e., neural network approaches involving deep neural networks (DNNs) and convolutional neural networks (CNNs). DNN-based numeric data and CNN-based image data can be exploited for discriminating acetone and hydrogen, with the aim of predicting the status of an exercise-driven diet and IBS. The ramifications of the proposed hybrid sensor combinations and machine learning for the high-performance breath sensor domain are discussed.

Compartment Syndrome following Intramedullary Nail Fixation in Closed Tibial Shaft Fractures

Introduction

Compartment syndrome complicating intramedullary nailing of closed tibia fractures has been described as early as the 1980s, but currently remains less described in literature compared to compartment syndrome directly following trauma. This study aims to review this potentially disabling complication and highlight the importance of timely diagnosis and management of compartment syndrome following fracture fixation, not just after fracture itself, via a review of three cases.

Material and methods

A retrospective study of a series of three cases was conducted. The type of fracture, wait time to fixation, surgery duration, reaming, size of nail implant used, tourniquet time, and surgical technique were recorded. Time to diagnosis of compartment syndrome, compartment pressure if available, extent of muscle necrosis, reconstructive procedures performed, and post-operative complications were analysed.

Results

The three cases following high-energy trauma from road traffic accidents presented from January to May 2010. Compartment syndrome was diagnosed clinically for all cases, between one to six days post-operatively and supported by elevated compartment pressure measurements in two of the three cases.

Conclusion

This study advocates thorough clinical monitoring and maintaining strong clinical suspicion of compartment syndrome in patients even after intramedullary nail fixation of tibial shaft fractures to achieve timely limb-salvaging intervention. While intercompartmental pressure can be used to aid in diagnosis, we do not advise using it in isolation to diagnose compartment syndrome. Tendon transfer improves functional mobility and provides a good result in patients with severe muscle damage, while skin grafting sufficient in patients with minimal muscle damage.

Hollow porous carbon nanospheres containing polar cobalt sulfide (Co9S8) nanocrystals as electrocatalytic interlayers for the reutilization of polysulfide in lithium-sulfur batteries

HYPOTHESIS

The introduction of functional interlayers for efficient anchoring of lithium polysulfides has received significant attention worldwide.

EXPERIMENTS

A facile wet-chemical method was adopted to obtain hollow porous carbon nanospheres (HPCNSs) impregnated with metallic and polar cobalt sulfide (Co₉S₈) nanocrystals (abbreviated as "Co₉S₈@HPCNS"). The prepared nanocrystals were employed as electrocatalytic interlayers via separator coating for the efficient capture and reutilization of polysulfide species in Li-S batteries. The HPCNSs were synthesized via the polymerization method followed by carbonization and template removal. The Co₉S₈ nanocrystals were impregnated inside the HPCNSs, followed by heat treatment in a reducing atmosphere.

FINDINGS

The porous structure of the CNS enables the efficient percolation of the electrolyte, in addition to accommodating unwanted volume fluctuations during redox processes. Furthermore, the metallic Co₉S₈ nanocrystals improve the electronic conductivity and enhance the polarity of the CNS towards the polysulfide. Correspondingly, the Li-S cells featuring Co₉S₈@HPCNS as electrocatalytic interlayers and regular sulfur (S) electrodes display improved electrochemical performance such as reasonable rate performance and prolonged cycling stability at different current rates (0.1, 0.5, and 1.0 C). Therefore, we anticipate that the rational design strategy proposed herein will provide significant insights into the synthesis of advanced materials for various energy storage applications.

Controllable Synthesis of Carbon Yolk-Shell Microsphere and Application of Metal Compound-Carbon Yolk-Shell as Effective Anode Material for Alkali-Ion Batteries

Recently, nanostructured carbon materials, such as hollow-, yolk-, and core-shell-configuration, have attracted attention in various fields owing to their unique physical and chemical properties. Among them, yolk-shell structured carbon is considered as a noteworthy material for energy storage due to its fast electron transfer, structural robustness, and plentiful active reaction sites. However, the difficulty of the synthesis for controllable carbon yolk-shell has been raised as a limitation. In this study, novel synthesis strategy of nanostructured carbon yolk-shell microspheres that enable to control morphology and size of the yolk part is proposed for the first time. To apply in the appropriate field, cobalt compounds-carbon yolk-shell composites are applied as the anode of alkali-ion batteries and exhibit superior electrochemical performances to those of core-shell structures owing to their unique structural merits. Co₃ O₄ -C hollow yolk-shell as a lithium-ion battery anode exhibits a long cycling lifetime (619 mA h g^-1 for 400 cycles at 2 A g^-1 ) and excellent rate capability (286 mA h g^-1 at 10 A g^-1 ). The discharge capacities of CoSe₂ -C hollow yolk-shell as sodium- and potassium-ion battery anodes at the 200th cycle are 311 mA h g^-1 at 0.5 A g^-1 and 268 mA h g^-1 at 0.2 A g^-1 , respectively.

Achieving Cycling Stability in Anode of Lithium-Ion Batteries with Silicon-Embedded Titanium Oxynitride Microsphere

Surface coating approaches for silicon (Si) have demonstrated potential for use as anodes in lithium-ion batteries (LIBs) to address the large volume change and low conductivity of Si. However, the practical application of these approaches remains a challenge because they do not effectively accommodate the pulverization of Si during cycling or require complex processes. Herein, Si-embedded titanium oxynitride (Si-TiON) was proposed and successfully fabricated using a spray-drying process. TiON can be uniformly coated on the Si surface via self-assembly, which can enhance the Si utilization and electrode stability. This is because TiON exhibits high mechanical strength and electrical conductivity, allowing it to act as a rigid and electrically conductive matrix. As a result, the Si-TiON electrodes delivered an initial reversible capacity of 1663 mA h g^-1 with remarkably enhanced capacity retention and rate performance.

A Novel High-Performance TiO2-x /TiO1-y Ny Coating Material for Silicon Anode in Lithium-Ion Batteries

Protective surface coatings on Si anodes are promising for improving the electrochemical performance of lithium-ion batteries (LIBs). Nevertheless, most coating materials have severe issues, including low initial coulombic efficiency, structural fracture, morphology control, and complicated synthetic processing. In this study, a multifunctional TiO_{2- x} /TiO_{1- y} N_y (TTN) formed via a facile and scalable synthetic process is applied as a coating material for Si anodes. A thin layer of amorphous TiO₂ is uniformly coated onto Si nanoparticles by a simple sol-gel method and then converted into a two phase TiO_{2- x} /TiO_{1- y} N_y via nitridation. The lithiated TiO_2-x provides high ionic and electrical conductivity, while TiO_1-y N_y can improve mechanical strength that alleviates volume change of Si to address capacity fading issue. Owing to these synergetic advantages, TiO_{2- x} /TiO_{1- y} N_y -coated Si (Si@TTN) exhibits excellent electrochemical properties, including a high charge capacity of 1650 mA h g^-1 at 0.1 A g^-1 and 84% capacity retention after 100 cycles at 1 A g^-1 . Moreover, a significantly enhanced rate performance can be achieved at a high current density. This investigation presents a facile and effective coating material to use as the high-capacity silicon anode in the emerging Si anode technology in LIBs.

Morphological and Electrochemical Properties of ZnMn2O4 Nanopowders and Their Aggregated Microspheres Prepared by Simple Spray Drying Process

Phase-pure ZnMn₂O₄ nanopowders and their aggregated microsphere powders for use as anode material in lithium-ion batteries were obtained by a simple spray drying process using zinc and manganese salts as precursors, followed by citric acid post-annealing at different temperatures. X-ray diffraction (XRD) analysis indicated that phase-pure ZnMn₂O₄ powders were obtained even at a low post-annealing temperature of 400 °C. The post-annealed powders were transformed into nanopowders by simple milling process, using agate mortar. The mean particle sizes of the ZnMn₂O₄ powders post-treated at 600 and 800 °C were found to be 43 and 85 nm, respectively, as determined by TEM observation. To provide practical utilization, the nanopowders were transformed into aggregated microspheres consisting of ZnMn₂O₄ nanoparticles by a second spray drying process. Based on the systematic analysis, the optimum post-annealing temperature required to obtain ZnMn₂O₄ nanopowders with high capacity and good cycle performance was found to be 800 °C. Moreover, aggregated ZnMn₂O₄ microsphere showed improved cycle stability. The discharge capacities of the aggregated microsphere consisting of ZnMn₂O₄ nanoparticles post-treated at 800 °C were 1235, 821, and 687 mA h g⁻¹ for the 1st, 2nd, and 100th cycles at a high current density of 2.0 A g⁻¹, respectively. The capacity retention measured after the second cycle was 84%.

Carbon-Coated Three-Dimensional MXene/Iron Selenide Ball with Core-Shell Structure for High-Performance Potassium-Ion Batteries

Two-dimensional (2D) MXenes are promising as electrode materials for energy storage, owing to their high electronic conductivity and low diffusion barrier. Unfortunately, similar to most 2D materials, MXene nanosheets easily restack during the electrode preparation, which degrades the electrochemical performance of MXene-based materials. A novel synthetic strategy is proposed for converting MXene into restacking-inhibited three-dimensional (3D) balls coated with iron selenides and carbon. This strategy involves the preparation of Fe₂O₃@carbon/MXene microspheres via a facile ultrasonic spray pyrolysis and subsequent selenization process. Such 3D structuring effectively prevents interlayer restacking, increases the surface area, and accelerates ion transport, while maintaining the attractive properties of MXene. Furthermore, combining iron selenides and carbon with 3D MXene balls offers many more sites for ion storage and enhances the structural robustness of the composite balls. The resultant 3D structured microspheres exhibit a high reversible capacity of 410 mAh g^-1 after 200 cycles at 0.1 A g^-1 in potassium-ion batteries, corresponding to the capacity retention of 97% as calculated based on 100 cycles. Even at a high current density of 5.0 A g^-1, the composite exhibits a discharge capacity of 169 mAh g^-1.

Magnetic Control and Real-Time Monitoring of Stem Cell Differentiation by the Ligand Nanoassembly

Native extracellular matrix (ECM) exhibits dynamic change in the ligand position. Herein, the ECM-emulating control and real-time monitoring of stem cell differentiation are demonstrated by ligand nanoassembly. The density of gold nanoassembly presenting cell-adhesive Arg-Gly-Asp (RGD) ligand on Fe₃ O₄ (magnetite) nanoparticle in nanostructures flexibly grafted to material is changed while keeping macroscale ligand density invariant. The ligand nanoassembly on the Fe₃ O₄ can be magnetically attracted to mediate rising and falling ligand movements via linker stretching and compression, respectively. High ligand nanoassembly density stimulates integrin ligation to activate the mechanosensing-assisted stem cell differentiation, which is monitored via in situ real-time electrochemical sensing. Magnetic control of rising and falling ligand movements hinders and promotes the adhesion-mediated mechanotransduction and differentiation of stem cells, respectively. These rising and falling ligand states yield the difference in the farthest distance (≈34.6 nm) of the RGD from material surface, thereby dynamically mimicking static long and short flexible linkers, which hinder and promote cell adhesion, respectively. Design of cytocompatible ligand nanoassemblies can be made with combinations of dimensions, shapes, and biomimetic ligands for remotely regulating stem cells for offering novel methodologies to advance regenerative therapies.

Boosting the Electrochemical Performance of V2 O3 by Anchoring on Carbon Nanotube Microspheres with Macrovoids for Ultrafast and Long-Life Aqueous Zinc-Ion Batteries

Zinc-ion batteries (ZIBs) are next-generation energy storage systems with high safety and environmental friendliness because they can be operated in aqueous systems. However, the search for electrode materials with ideal nanostructures and compositions for aqueous ZIBs is in progress. Herein, the synthesis of porous microspheres, consisting of V₂ O₃ anchored on entangled carbon nanotubes (p-V₂ O₃ -CNT) and their application as cathode for ZIBs is reported. From various analyses, it is revealed that V₂ O₃ phase disappears after the initial charge process, and Zn_{3+ x} (OH)_{2+3 x} V_{2- x} O_{7-3 x} ∙2H₂ O and zinc vanadate (Zn_y VO_z ) phases undergo zinc-ion intercalation/deintercalation processes from the second cycle. Additionally, the electrochemical performances of p-V₂ O₃ -CNT, V₂ O₃ -CNT (without macrovoids), and porous V₂ O₃ (without CNTs) microspheres are compared to determine the effects of nanostructures and conductive carbonaceous matrix on the zinc-ion storage performance. p-V₂ O₃ -CNT exhibits a high reversible capacity of 237 mA h g^-1 after 5000 cycles at 10 A g^-1 . Furthermore, a reversible capacity of 211 mA h g^-1 is obtained at an extremely high current density of 50 A g^-1 . The macrovoids in V₂ O₃ nanostructure effectively alleviate the volume changes during cycling, and the entangled CNTs with high electrical conductivity assist in achieving fast electrochemical kinetics.

Yolk-Shell-Structured Nanospheres with Goat Pupil-Like S-Doped SnSe Yolk and Hollow Carbon-Shell Configuration as Anode Material for Sodium-Ion Storage

Rationally nanostructured electrode materials exhibit excellent sodium-ion storage performance. In particular, yolk-shell configurations of metal chalcogenide@void@C are introduced in various synthetic strategies for use as superior anode materials. Herein, yolk-shell-structured nanospheres, with goat pupil-like configuration of S-doped SnSe yolks and hollow carbon shells, are synthesized by salt-infiltration and a simple post-treatment procedure. Impressively, the co-infiltration of thiourea and selenium oxide enables the doping of sulfur into SnSe (SnSeS) and carbon shells, as well as the formation of a goat pupil-like yolk-shell architecture. High-reactivity thiourea-derived H₂ S gas forms nanocrystals inside the carbon nanospheres. The nanocrystals act as seeds for the crystal growth of SnSeS through Ostwald ripening. The unique yolk-shell structure and composition with a heterointerface provide not only structural stability but also fast electrode reaction kinetics during repeated cycling. The SnSeS@C electrode shows an excellent cycle life (186 mA h g^-1 for 1000 cycles at 0.5 A g^-1 ) and rate capability (112 mA h g^-1 at 5.0 A g^-1 ).

Remote Control of Time-Regulated Stretching of Ligand-Presenting Nanocoils In Situ Regulates the Cyclic Adhesion and Differentiation of Stem Cells

Native extracellular matrix (ECM) can exhibit cyclic nanoscale stretching and shrinking of ligands to regulate complex cell-material interactions. Designing materials that allow cyclic control of changes in intrinsic ligand-presenting nanostructures in situ can emulate ECM dynamicity to regulate cellular adhesion. Unprecedented remote control of rapid, cyclic, and mechanical stretching ("ON") and shrinking ("OFF") of cell-adhesive RGD ligand-presenting magnetic nanocoils on a material surface in five repeated cycles are reported, thereby independently increasing and decreasing ligand pitch in nanocoils, respectively, without modulating ligand-presenting surface area per nanocoil. It is demonstrated that cyclic switching "ON" (ligand nanostretching) facilitates time-regulated integrin ligation, focal adhesion, spreading, YAP/TAZ mechanosensing, and differentiation of viable stem cells, both in vitro and in vivo. Fluorescence resonance energy transfer (FRET) imaging reveals magnetic switching "ON" (stretching) and "OFF" (shrinking) of the nanocoils inside animals. Versatile tuning of physical dimensions and elements of nanocoils by regulating electrodeposition conditions is also demonstrated. The study sheds novel insight into designing materials with connected ligand nanostructures that exhibit nanocoil-specific nano-spaced declustering, which is ineffective in nanowires, to facilitate cell adhesion. This unprecedented, independent, remote, and cytocompatible control of ligand nanopitch is promising for regulating the mechanosensing-mediated differentiation of stem cells in vivo.

Highly Selective Detection of Benzene and Discrimination of Volatile Aromatic Compounds Using Oxide Chemiresistors with Tunable Rh-TiO2 Catalytic Overlayers

Volatile aromatic compounds are major air pollutants, and their health impacts should be assessed accurately based on the concentration and composition of gas mixtures. Herein, novel bilayer sensors consisting of a SnO2 sensing layer and three different xRh-TiO2 catalytic overlayers (x = 0.5, 1, and 2 wt%) are designed for the new functionalities such as the selective detection, discrimination, and analysis of benzene, toluene, and p-xylene. The 2Rh-TiO2/SnO2 bilayer sensor shows a high selectivity and response toward ppm- and sub-ppm-levels of benzene over a wide range of sensing temperatures (325-425 °C). An array of 0.5Rh-, 1Rh-, and 2Rh-TiO2/SnO2 sensors exhibits discrimination and composition analyses of aromatic compounds. The conversion of gases into more active species at moderate catalytic activation and the complete oxidation of gases into non-reactive forms by excessive catalytic promotion are proposed as the reasons behind the enhancement and suppression of analyte gases, respectively. Analysis using proton transfer reaction-quadrupole mass spectrometer (PTR-QMS) is performed to verify the above proposals. Although the sensing characteristics exhibit mild moisture interference, bilayer sensors with systematic and tailored control of gas selectivity and response provide new pathways for monitoring aromatic air pollutants and evaluating their health impacts.

MOF-Derived CoSe2@N-Doped Carbon Matrix Confined in Hollow Mesoporous Carbon Nanospheres as High-Performance Anodes for Potassium-Ion Batteries

In this work, a novel vacuum-assisted strategy is proposed to homogenously form Metal-organic frameworks within hollow mesoporous carbon nanospheres (HMCSs) via a solid-state reaction. The method is applied to synthesize an ultrafine CoSe2 nanocrystal@N-doped carbon matrix confined within HMCSs (denoted as CoSe2@NC/HMCS) for use as advanced anodes in high-performance potassium-ion batteries (KIBs). The approach involves a solvent-free thermal treatment to form a Co-based zeolitic imidazolate framework (ZIF-67) within the HMCS templates under vacuum conditions and the subsequent selenization. Thermal treatment under vacuum facilitates the infiltration of the cobalt precursor and organic linker into the HMCS and simultaneously transforms them into stable ZIF-67 particles without any solvents. During the subsequent selenization process, the "dual confinement system", composed of both the N-doped carbon matrix derived from the organic linker and the small-sized pores of HMCS, can effectively suppress the overgrowth of CoSe2 nanocrystals. Thus, the resulting uniquely structured composite exhibits a stable cycling performance (442 mAh g-1 at 0.1 A g-1 after 120 cycles) and excellent rate capability (263 mAh g-1 at 2.0 A g-1) as the anode material for KIBs.

Encapsulation of Se into Hierarchically Porous Carbon Microspheres with Optimized Pore Structure for Advanced Na-Se and K-Se Batteries

Sodium-selenium (Na-Se) and potassium-selenium (K-Se) batteries have emerged as promising energy storage systems with high energy density and low cost. However, major issues such as huge Se volume changes, polyselenide shuttling, and low Se loading need to be overcome. Although many strategies have been developed to resolve these issues, the relationship between the carbon host pore structure and electrochemical performance of Se has not been studied extensively. Here, the effect of the carbon host pore structure on the electrochemical performance of Na-Se and K-Se batteries is investigated. N, S-co-doped hierarchically porous carbon microspheres with different pore structures that can incorporate a large amount of amorphous Se (∼60 wt %) are synthesized by spray pyrolysis and subsequent chemical activation at different temperatures. By optimizing the amount of micropore volume and micropore-to-mesopore ratio, high reversible capacity and cycling stability are achieved for the Se cathode. The optimized cathode delivers a reversible capacity of 445 mA h g^-1 after 400 cycles at 0.5C for Na-Se batteries and 436 mA h g^-1 after 120 cycles at 0.2C for K-Se batteries. This study marks the importance of developing conductive carbon matrices with delicately designed pore structures for advanced alkali metal-chalcogen battery systems.

Porous SnO2/C Nanofiber Anodes and LiFePO4/C Nanofiber Cathodes with a Wrinkle Structure for Stretchable Lithium Polymer Batteries with High Electrochemical Performance

Stretchable lithium batteries have attracted considerable attention as components in future electronic devices, such as wearable devices, sensors, and body-attachment healthcare devices. However, several challenges still exist in the bid to obtain excellent electrochemical properties for stretchable batteries. Here, a unique stretchable lithium full-cell battery is designed using 1D nanofiber active materials, stretchable gel polymer electrolyte, and wrinkle structure electrodes. A SnO2/C nanofiber anode and a LiFePO4/C nanofiber cathode introduce meso- and micropores for lithium-ion diffusion and electrolyte penetration. The stretchable full-cell consists of an elastic poly(dimethylsiloxane) (PDMS) wrapping film, SnO2/C and LiFePO4/C nanofiber electrodes with a wrinkle structure fixed on the PDMS wrapping film by an adhesive polymer, and a gel polymer electrolyte. The specific capacity of the stretchable full-battery is maintained at 128.3 mAh g-1 (capacity retention of 92%) even after a 30% strain, as compared with 136.8 mAh g-1 before strain. The energy densities are 458.8 Wh kg-1 in the released state and 423.4 Wh kg-1 in the stretched state (based on the electrode), respectively. The high capacity and stability in the stretched state demonstrate the potential of the stretchable battery to overcome its limitations.

Golden Bristlegrass-Like Hierarchical Graphene Nanofibers Entangled with N-Doped CNTs Containing CoSe2 Nanocrystals at Each Node as Anodes for High-Rate Sodium-Ion Batteries

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 H₂ Se 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.

Conversion Reaction Mechanism of Ultrafine Bimetallic Co-Fe Selenides Embedded in Hollow Mesoporous Carbon Nanospheres and Their Excellent K-Ion Storage Performance

Potassium-ion batteries (KIBs) are considered as promising alternatives to lithium-ion batteries owing to the abundance and affordability of potassium. However, the development of suitable electrode materials that can stably store large-sized K ions remains a challenge. This study proposes a facile impregnation method for synthesizing ultrafine cobalt-iron bimetallic selenides embedded in hollow mesoporous carbon nanospheres (HMCSs) as superior anodes for KIBs. This involves loading metal precursors into HMCS templates using a repeated "drop and drying" process followed by selenization at various temperatures, facilitating not only the preparation of bimetallic selenide/carbon composites but also controlling their structures. HMCSs serve as structural skeletons, conductive templates, and vehicles to restrain the overgrowth of bimetallic selenide particles during thermal treatment. Various analysis strategies are employed to investigate the charge-discharge mechanism of the new bimetallic selenide anodes. This unique-structured composite exhibits a high discharge capacity (485 mA h g^-1 at 0.1 A g^-1 after 200 cycles) and enhanced rate capability (272 mA h g^-1 at 2.0 A g^-1 ) as a promising anode material for KIBs. Furthermore, the electrochemical properties of various nanostructures, from hollow to frog egg-like structures, obtained by adjusting the selenization temperature, are compared.

Hierarchically Well-Developed Porous Graphene Nanofibers Comprising N-Doped Graphitic C-Coated Cobalt Oxide Hollow Nanospheres As Anodes for High-Rate Li-Ion Batteries

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.

Amorphous iron oxide-selenite composite microspheres with a yolk-shell structure as highly efficient anode materials for lithium-ion batteries

Yolk-shell structured transition metal compounds have intrinsic structural advantages as anode materials and have been synthesized in a highly crystalline form. Thus, development of a synthesis process for a yolk-shell structure with an amorphous state, that displays high structural stability and fast ionic diffusion, is a notable research subject, with wide applications in fields such as energy storage. Herein, a novel approach for synthesizing amorphous materials with a yolk-shell structure using several facile phase transformation processes is presented. Crystalline iron oxide microspheres with a yolk-shell structure were formed by oxidation of the spray-dried product at 400 °C. Using the pitch/tetrahydrofuran solution infiltration method, pitch-infiltrated iron oxide was selenized at 350 °C to form a crystalline iron selenide-C composite. The following partial oxidation process at 375 °C produced a yolk-shell structured amorphous iron oxide-selenite composite. The amorphous characteristics, the yolk-shell structure, and the formation of a heterostructured interface from iron selenite during the initial cycle contributed to high electrochemical kinetic properties and excellent cycling performance of the iron oxide-selenite composite. The amorphous iron oxide-iron selenite yolk-shell microspheres exhibited enhanced reversible capacities, cycling stability, and remarkable electrochemical kinetic properties when compared to crystalline iron oxide.

Enhanced Li-ion storage performance of novel tube-in-tube structured nanofibers with hollow metal oxide nanospheres covered with a graphitic carbon layer

One-dimensional (1D) nanofibers constructed with structurally stable nano-architecture and highly conductive carbon components can be employed to develop enhanced anodic materials for lithium-ion batteries. However, achieving an intricate combination of well-designed 1D-nanostructural materials and conductive carbon components for excellent lithium-ion storage capacity is a key challenge. In this study, novel and unique tube-in-tube structured nanofibers consisting of hollow metal oxide (CoFe₂O₄) nanospheres covered with a graphitic carbon (GC) layer were feasibly and successfully synthesized. A facile pitch solution infiltration method was applied to provide electrical conductivity in the tube-in-tube structure. Generally, mesophase pitch with liquid characteristics uniformly infiltrates the porous nanocrystals and transforms into graphitic layers around metallic CoFe₂ alloys during the reduction process. The oxidation process that follows produces the hollow CoFe₂O₄ nanosphere by the nanoscale Kirkendall effect and the GC layer by selective decomposition of amorphous carbon layers. Hollow CoFe₂O₄ nanospheres comprising tube-in-tube structured nanofibers and GC layers are formed by pitch-derived carbon; these have improved structural stability and electrical conductivity resulting in excellent cycling and characteristics. Tube-in-tube structured nanofibers consisting of hollow CoFe₂O₄@GC nanospheres showed excellent long-cycle performance (682 mA h g^-1 for the 1400th cycle at a high current density of 3.0 A g^-1) and excellent rate capability (355 mA h g^-1) even at an extremely high current density of 50 A g^-1.

A New Strategy for Detecting Plant Hormone Ethylene Using Oxide Semiconductor Chemiresistors: Exceptional Gas Selectivity and Response Tailored by Nanoscale Cr2O3 Catalytic Overlayer

A highly selective and sensitive detection of the plant hormone ethylene, particularly at low concentrations, is essential for controlling the growth, development, and senescence of plants, as well as for ripening of fruits. However, this remains challenging because of the non-polarity and low reactivity of ethylene. Herein, a strategy for detecting ethylene at a sub-ppm-level is proposed by using oxide semiconductor chemiresistors with a nanoscale oxide catalytic overlayer. The SnO2 sensor coated with the nanoscale catalytic Cr2O3 overlayer exhibits rapid sensing kinetics, good stability, and an unprecedentedly high ethylene selectivity with exceptional gas response (R a/R g - 1, where R a represents the resistance in air and R g represents the resistance in gas) of 16.8 at an ethylene concentration of 2.5 ppm at 350 °C. The sensing mechanism underlying the ultraselective and highly sensitive ethylene detection in the unique bilayer sensor is systematically investigated with regard to the location, configuration, and thickness of the catalytic Cr2O3 overlayer. The mechanism involves the effective catalytic oxidation of interfering gases into less- or non-reactive species, without limiting the analyte gas transport. The sensor exhibits a promising potential for achieving a precise quantitative assessment of the ripening of five different fruits.

Hierarchical Tubular-Structured MoSe2 Nanosheets/N-Doped Carbon Nanocomposite with Enhanced Sodium Storage Properties

Intimately coupled carbon/molybdenum-based hierarchical nanostructures are promising anodes for high-performance sodium-ion batteries owing to the combined effects of the two components and their robust structural stability. Mo-polydopamine (PDA) complexes are appealing precursors for the preparation of various Mo-based nanostructures containing N-doped carbon (NC). A facile method for the fabrication of hierarchical tubular nanocomposites with intimately coupled MoSe₂ and NC nanosheets has been developed, which involves the preparation of Mo-PDA hybrid nanotubes through a chemical route followed by two heat treatments. The strong coupling between Mo anions and the catechol groups in dopamine not only restricts the crystallite size but also inhibits agglomeration during selenization, resulting in few-layered MoSe₂ nanosheets embedded in hierarchical NC substrates. The as-synthesized nanotube composites are constructed by assembling primary MoSe₂ /NC nanosheets. This unique structure not only increases the number of active sites but also shortens the diffusion length of ions and enhances the electronic conductivity of electrode materials. The as-synthesized hierarchical MoSe₂ /NC nanotubes deliver a high capacity of 429 mAh g^-1 at 1 A g^-1 after the 150th cycle when used as anodes in sodium-ion batteries. Furthermore, at a high current density of 10 A g^-1 , a high discharge capacity of 236 mAh g^-1 is achieved.

Biotransformation of methane into methanol by methanotrophs immobilized on coconut coir

This study aimed to establish a unique approach for the production of methanol from methane (CH₄) in the presence of paraffin oil mediated by methanotrophs immobilized on coconut coir (CC). Immobilization of different methanotrophs through covalent method increased the immobilization yield and relative efficiency for methanol production to 48.6% and 96.8%, respectively. In the presence of paraffin oil, methanol production was 1.6-fold higher by Methylocystis bryophila than by control. Compared to free cells, whole cells immobilized on CC showed higher stability for methanol production. Under repeated batch conditions, cumulative methanol production by immobilized cells and free cells, after eight cycles of reuse, was 52.9 and 30.9 mmol/L, respectively. This study effectively demonstrated the beneficial influence of lignocellulosic biowaste CC as support for immobilization of methanotrophs and paraffin oil on bioconversion of CH₄ to methanol.

Structural combination of polar hollow microspheres and hierarchical N-doped carbon nanotubes for high-performance Li-S batteries

Hierarchical structured materials constructed with conductive carbon materials have been extensively studied as S host materials for Li-S batteries. However, their outwardly developed hierarchical structures, which do not contain structures or materials to inhibit polysulfide dissolution, lead to the dissipation of dissolved polysulfides and poor dispersion properties during the slurry-making process, which results in non-uniformity in the cathodes. Herein, an assembly of polar materials (hollow structured SiO2 microspheres) and electrically conductive hierarchical N-doped bamboo-like carbon nanotubes (b-NCNTs) is designed as an efficient S host material for minimizing the dissolution of polysulfides during Li-S battery operations. Highly aligned and packed b-NCNTs are grown in hollow structured SiO2 microspheres. The SiO2 layer coated on the surface of the hollow CoFe2O4 microspheres plays a key role in the synthesis of easily dispersible hierarchical b-NCNTs microspheres (b-NCNTs@SiO2). The S-loaded b-NCNTs@SiO2 electrodes show better cycling stability than S-loaded b-NCNTs electrodes. The polysulfide trapping of the polar SiO2 layer and the well-developed b-NCNTs minimize the dissolution of polysulfides during cycling. In addition, the introduction of electronegative N atoms into the b-NCNTs lattice enhances their polysulfide trapping ability. The S-loaded b-NCNTs@SiO2 electrodes exhibit stable discharge capacities of >771 mA h g-1 over 195 cycles at a current density of 0.5 C and a high reversible capacity of 486 mA h g-1 even at a high current density of 5.0 C.

Investigation of Binary Metal (Ni, Co) Selenite as Li-Ion Battery Anode Materials and Their Conversion Reaction Mechanism with Li Ions

Highly efficient anode materials with novel compositions for Li-ion batteries are actively being researched. Multicomponent metal selenite is a promising candidate, capable of improving their electrochemical performance through the formation of metal oxide and selenide heterostructure nanocrystals during the first cycle. Here, the binary nickel-cobalt selenite derived from Ni-Co Prussian blue analogs (PBA) is chosen as the first target material: the Ni-Co PBA are selenized and partially oxidized in sequence, yielding (NiCo)SeO₃ phase with a small amount of metal selenate. The conversion mechanism of (NiCo)SeO₃ for Li-ion storage is studied by cyclic voltammetry, in situ X-ray diffraction, ex situ X-ray photoelectron spectroscopy, in situ electrochemical impedance spectroscopy, and ex situ transmission electron microscopy. The reversible reaction mechanism of (NiCo)SeO₃ with the Li ions is described by the reaction: NiO + CoO + xSeO₂ + (1 - x)Se + (4x + 6)Li⁺ + (4x + 6)e^- ↔ Ni + Co + (2x + 2)Li₂ O + Li₂ Se. To enhance electrochemical properties, polydopamine-derived carbon is uniformly coated on (NiCo)SeO₃ , resulting in excellent cycling and rate performances for Li-ion storage. The discharge capacity of C-coated (NiCo)SeO₃ is 680 mAh g^-1 for the 1500th cycle when cycled at a current density of 5 A g^-1 .

Advances in the synthesis and design of nanostructured materials by aerosol spray processes for efficient energy storage

The increasing demand for energy storage has motivated the search for highly efficient electrode materials for use in rechargeable batteries with enhanced energy density and longer cycle life. One of the most promising strategies for achieving improved battery performance is altering the architecture of nanostructured materials employed as electrode materials in the energy storage field. Among numerous synthetic methods suggested for the fabrication of nanostructured materials, aerosol spray techniques such as spray pyrolysis, spray drying, and flame spray pyrolysis are reliable, as they are facile, cost-effective, and continuous processes that enable the synthesis of nanostructured electrode materials with desired morphologies and compositions with controlled stoichiometry. The post-treatment of spray-processed powders enables the fabrication of oxide, sulfide, and selenide nanostructures hybridized with carbonaceous materials including amorphous carbon, reduced graphene oxide, carbon nanotubes, etc. In this article, recent progress in the synthesis of nanostructured electrode materials by spray processes and their general formation mechanisms are discussed in detail. A brief introduction to the working principles of each spray process is given first, and synthetic strategies for the design of electrode materials for lithium-ion, sodium-ion, lithium-sulfur, lithium-selenium, and lithium-oxygen batteries are discussed along with some examples. This analysis sheds light on the synthesis of nanostructured materials by spray processes and paves the way toward the design of other novel and advanced nanostructured materials for high performance electrodes in rechargeable batteries of the future.

Metal Oxide Gas Sensors with Au Nanocluster Catalytic Overlayer: Toward Tuning Gas Selectivity and Response Using a Novel Bilayer Sensor Design

Noble metals or oxide catalysts have traditionally been loaded or doped to enhance the gas sensing properties of oxide semiconductor chemiresistors. However, the selective detection of various chemicals for a wide range of new applications remains a challenging problem. In this paper, we propose a novel bilayer design with an oxide chemiresistor sensing layer and nanoscale catalytic Au overlayer to provide high controllability for gas sensing characteristics. The Au nanocluster overlayer significantly enhances the methylbenzene response of a SnO₂ thick film sensor by reforming gases into more reactive species and suppresses the responses to reactive interference gases through oxidative filtering, leading to excellent selectivity to methylbenzene. Gas sensing characteristics can be tuned by controlling the morphology, amount, and number density of Au nanoclusters through the variation in the Au coating thickness (0.5-3 nm) and thermal annealing conditions (0.5-4 h at 550 °C). Furthermore, the general validity of the proposed Au-coated bilayer sensor design was confirmed through the enhancement of response and selectivity toward methylbenzenes by coating Au nanoclusters onto ZnO and Co₃O₄ sensors. The sensing mechanism, advantages, and potential applications of bilayer sensors are discussed from the perspective of the separation of sensing and catalytic reactions, as well as the reforming and oxidation of analyte gases in association with the configuration of the sensing layer and Au catalytic overlayer.

Synthesis Process of CoSeO3 Microspheres for Unordinary Li-ion Storage Performances and Mechanism of Their Conversion Reaction with Li ions

Multicomponent materials with various double cations have been studied as anode materials of lithium-ion batteries (LIBs). Heterostructures formed by coupling different-bandgap nanocrystals enhance the surface reaction kinetics and facilitate charge transport because of the internal electric field at the heterointerface. Accordingly, metal selenites can be considered efficient anode materials of LIBs because they transform into metal selenide and oxide nanocrystals in the first cycle. However, few studies have reported synthesis of uniquely structured metal selenite microspheres. Herein, synthesis of high-porosity CoSeO₃ microspheres is reported. Through one-pot oxidation at 400 °C, CoSe_x -C microspheres formed by spray pyrolysis transform into CoSeO₃ microspheres showing unordinary cycling and rate performances. The conversion mechanism of CoSeO₃ microspheres for lithium-ion storage is systematically studied by cyclic voltammetry, in situ X-ray diffraction and electrochemical impedance spectroscopy, and transmission electron microscopy. The reversible reaction mechanism of the CoSeO₃ phase from the second cycle onward is evaluated as CoO + xSeO₂ + (1 - x)Se + 4(x + 1)Li⁺ + 4( x + 1)e^- ↔ Co + (2x + 1)Li₂ O + Li₂ Se. The CoSeO₃ microspheres show a high reversible capacity of 709 mA h g^-1 for the 1400th cycle at a current density of 3 A g^-1 and a high reversible capacity of 526 mA h g^-1 even at an extremely high current density of 30 A g^-1 .

The effect of ILs as co-salts in electrolytes for high voltage supercapacitors

Ionic liquids (ILs) which have electrical stability are attractive materials to enhance the potential window of electrolyte. According to the potential window is extended, available voltage for supercapacitor is broaden. In this study, the addition of ILs which is 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIBF4) and 1-ethyl-3-methylimidazolium bis(trifluoromethylesulfonyl) imide (EMITFSI) as co-salts, to a supercapacitor electrolyte increases the ionic conductivity and stability of it due to inhibition of electrolyte decomposition. As a result, the electrochemical stability potential windows (ESPWs) of supercapacitor is improved and the supercapacitor exhibited increased cycling stability. The loss of specific capacitance upon addition of 7 wt% EMIBF4 or EMITFSI to the electrolyte was 2.5% and 8.7%, respectively, after 10,000 cycles at 3.5 V, compared to the specific capacitance of the initial discharge.

Coral-Like Yolk-Shell-Structured Nickel Oxide/Carbon Composite Microspheres for High-Performance Li-Ion Storage Anodes

In this study, coral-like yolk-shell-structured NiO/C composite microspheres (denoted as CYS-NiO/C) were prepared using spray pyrolysis. The unique yolk-shell structure was characterized, and the formation mechanism of the structure was proposed. Both the phase separation of the polyvinylpyrrolidone and polystyrene (PS) colloidal solution and the decomposition of the size-controlled PS nanobeads in the droplet played crucial roles in the formation of the unique coral-like yolk-shell structure. The CYS-NiO/C microspheres delivered a reversible discharge capacity of 991 mAh g^-1 after 500 cycles at the current density of 1.0 A g^-1. The discharge capacity of the CYS-NiO/C microspheres after the 1000th cycle at the current density of 2.0 A g^-1 was 635 mAh g^-1, and the capacity retention measured from the second cycle was 91%. The final discharge capacities of the CYS-NiO/C microspheres at the current densities of 0.5, 1.5, 3.0, 5.0, 7.0, and 10.0 A g^-1 were 753, 648, 560, 490, 440, and 389 mAh g^-1, respectively. The synergetic effect of the coral-like yolk-shell structure with well-defined interconnected mesopores and highly conductive carbon resulted in the excellent Li⁺-ion storage properties of the CYS-NiO/C microspheres.

Yolk-shell-structured microspheres composed of N-doped-carbon-coated NiMoO4 hollow nanospheres as superior performance anode materials for lithium-ion batteries

Novel yolk-shell-structured microspheres consisting of N-doped-carbon-coated metal-oxide hollow nanospheres are designed as efficient anode materials for lithium-ion batteries and synthesized via a spray pyrolysis process. A NiMoO4 yolk-shell architecture formed via spray pyrolysis is transformed into equally structured NiSe2-MoSe2 composite microspheres. Because of the complementary effect between the Ni and Mo components that prevents severe crystal growth during selenization, NiSe2-MoSe2 nanocrystals are uniformly distributed over the yolk-shell structure. Then, the yolk-shell-structured NiSe2-MoSe2 microspheres are oxidized, which yields microspheres composed of NiMoO4 hollow nanospheres by nanoscale Kirkendall diffusion. Uniform coating with polydopamine and a subsequent carbonization process produce uniquely structured microspheres consisting of N-doped-carbon-coated NiMoO4 hollow nanospheres. The discharge capacity of the yolk-shell-structured NiMoO4-C composite microspheres for the 500th cycle at a current density of 3.0 A g-1 is 862 mA h g-1. In addition, the NiMoO4-C composite microspheres show a high reversible capacity of 757 mA h g-1 even at an extremely high current density of 10 A g-1. The synergetic effect between the hollow nanospheres comprising the yolk-shell structure and the N-doped carbon coating layer results in the excellent lithium-ion storage performance of the NiMoO4-C composite microspheres.

A Salt-Templated Strategy toward Hollow Iron Selenides-Graphitic Carbon Composite Microspheres with Interconnected Multicavities as High-Performance Anode Materials for Sodium-Ion Batteries

In this work, a facile salt-templated approach is developed for the preparation of hollow FeSe₂ /graphitic carbon composite microspheres as sodium-ion battery anodes; these are composed of interconnected multicavities and an enclosed surface in-plane embedded with uniform hollow FeSe₂ nanoparticles. As the precursor, Fe₂ O₃ /carbon microspheres containing NaCl nanocrystals are obtained using one-pot ultrasonic spray pyrolysis in which inexpensive NaCl and dextrin are used as a porogen and carbon source, respectively, enabling mass production of the composites. During post-treatment, Fe₂ O₃ nanoparticles in the composites transform into hollow FeSe₂ nanospheres via the Kirkendall effect. These rational structures provide numerous conductive channels to facilitate ion/electron transport and enhance the capacitive contribution. Moreover, the synergistic effect between the hollow cavities within FeSe₂ and the outstanding mechanical strength of the porous carbon matrix can effectively accommodate the large volume changes during cycling. Correspondingly, the composite microsphere exhibits high discharge capacity of 510 mA h g^-1 after 200 cycles at 0.2 A g^-1 with capacity retention of 88% when calculated from the second cycle. Even at a high current density of 5.0 A g^-1 , a high discharge capacity of 417 mA h g^-1 can be achieved.

Rattle-type porous Sn/C composite fibers with uniformly distributed nanovoids containing metallic Sn nanoparticles for high-performance anode materials in lithium-ion batteries

Rattle-type porous Sn/carbon (Sn/C) composite fibers with uniformly distributed nanovoids containing metallic Sn nanoparticles in void space surrounded by C walls (denoted as RT-Sn@C porous fiber) were prepared by electrospinning and subsequent facile heat-treatment. Highly concentrated polystyrene nanobeads used as a sacrificial template played a key role in the synthesis of the unique structured RT-Sn@C porous fiber. The RT-Sn@C porous fiber exhibited excellent long-term cycling and rate performances. The discharge capacity of the RT-Sn@C porous fiber at the 1000^th cycle was 675 mA h g^-1 at a high current density of 3.0 A g^-1. The RT-Sn@C porous fiber had final discharge capacities of 991, 924, 890, 848, 784, 717, 679, and 614 mA h g^-1 at current densities of 0.1, 0.2, 0.3, 0.5, 1.0, 2.0, 3.0, 5.0, and 10.0 A g^-1, respectively. The numerous void spaces, surrounding a Sn nanoparticle as the rattle-type particle, and the surrounding C could efficiently accommodate the volume changes of the Sn nanoparticles, improve the electrical conductivity, and enable efficient penetration of the liquid electrolyte into the structure.

Quorum sensing inhibitors as antipathogens: biotechnological applications

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.

Three-dimensionally ordered mesoporous multicomponent (Ni, Mo) metal oxide/N-doped carbon composite with superior Li-ion storage performance

Among the various nanostructures, porous materials with controlled pore structures have been widely used for designing transition metal-based anode materials for lithium-ion batteries, because they provide good access to electrolyte and can effectively accommodate stress arising from volume changes. In particular, ternary transition metal oxide materials containing nanovoids, arranged with high degree of periodicity, are ideal for enhancing lithium-ion storage capability. In this study, we provide a method using spray pyrolysis for the synthesis of mesoporous multicomponent metal oxide microspheres containing Ni and Mo components and N-doped carbon, in which three-dimensionally ordered 40 nm-sized mesopores are interconnected. During the synthesis, polystyrene nanobeads are used as a sacrificial template and are readily eliminated via thermal decomposition. Increased concentrations of polystyrene nanobeads enables the formation of open channels throughout the microspheres. When employed as a lithium-ion battery anode, the mesoporous multicomponent metal oxide microspheres containing Ni and Mo components and N-doped carbon exhibit high reversible capacity, good cycling stability, and excellent rate performance. After 1000 cycles, the microspheres deliver a discharge capacity of 693 mA h g^-1 at a current density of 1.0 A g^-1.

Lithium-ion storage performances of sunflower-like and nano-sized hollow SnO2 spheres by spray pyrolysis and the nanoscale Kirkendall effect

Nanostructured metal selenides with a variety of morphologies are crucial for fabricating porous, hollow metal-oxide nanomaterials by nanoscale Kirkendall diffusion. Herein, SnSe-SnO2 composite powders and SnSe nanospheres were synthesized via one-pot spray pyrolysis by optimizing the concentration of the Se precursor in the spray solution; these were then used to fabricate sunflower-like SnO2 and hollow SnO2 nanospheres, respectively, via nanoscale Kirkendall diffusion. Post-treatment of the SnSe-decorated SnO2 under air produced sunflower-like SnO2, in which ray and disk florets consisting of hollow nanoplates and dense nanospheres, respectively, were present. The mean diameter of the homogeneous hollow SnO2 nanospheres was 150 nm. The hollow morphology shortens the diffusion length, increasing the contact area between the electrolyte and voids and buffering large volume changes during repeated cycling. As anode materials for lithium-ion batteries, the hollow SnO2 nanospheres showed excellent cycling and rate performances. The discharge capacity of the hollow SnO2 nanospheres, after 500 cycles from 0.001 V to 3.0 V, was 1043 mA h g-1, at a current density of 3.0 A g-1. The hollow SnO2 nanospheres showed a high reversible capacity of 638 mA h g-1, even at current density as high as 10 A g-1.

Design and synthesis of interconnected hierarchically porous anatase titanium dioxide nanofibers as high-rate and long-cycle-life anodes for lithium-ion batteries

We suggest an efficient and simple synthetic strategy to prepare interconnected hierarchically porous anatase TiO2 (IHP-A-TiO2) nanofibers by two synergetic effects: phase separation between polymers and relative humidity control during electrospinning. The macro channels formed by polystyrene decomposition were interconnected by numerous mesopores that were formed by evaporation of infiltrated water vapor in the structure. The resulting IHP-A-TiO2 nanofibers showed better Li+ ion storage performances than the TiO2 materials reported in the literature. The discharge capacity of IHP-A-TiO2 nanofibers for the 3000th cycle at 1.0 A g-1 and corresponding coulombic efficiency from the 20th cycle onward were 142 mA h g-1 and >99.0%, respectively. Well-interconnected, ultrafine TiO2 nanocrystals within the nanofiber showed structural stability during cycling and facilitated facile charge transfer at the electrode-electrolyte interface.

Three-dimensional porous microspheres comprising hollow Fe2O3 nanorods/CNT building blocks with superior electrochemical performance for lithium ion batteries

It is highly desirable to develop anode materials with rational architectures for lithium ion batteries to achieve high-performance electrochemical properties. In this study, three-dimensional porous composite microspheres comprising hollow Fe2O3 nanorods/carbon nanotube (CNT) building blocks are successfully constructed by direct deposition and further thermal transformation of beta-FeOOH nanorods on CNT porous microspheres. The CNT porous microsphere, which is prepared by a spray pyrolysis, provides ample sites for the direct growth of beta-FeOOH nanorods. During the further oxidation process, the beta-FeOOH nanorods are transformed into hollow Fe2O3 nanorods as a result of dehydroxylation and lattice shrinkage, resulting in the formation of hollow Fe2O3 nanorods/CNT porous microspheres. Such a hierarchical structure of composite microspheres not only facilitates electrolyte accessibility but also offers conductive networks for electrons during electrochemical reactions. Accordingly, the electrodes exhibit a high discharge capacity of 1307 mA h g-1 after 300 cycles at a current density of 1 A g-1; this is associated with an excellent capacity retention of 84%, which is calculated from the initial cycle. In addition, the composite delivers a discharge capacity of 703 mA h g-1 at a current density of 15 A g-1.

MOF-Templated N-Doped Carbon-Coated CoSe2 Nanorods Supported on Porous CNT Microspheres with Excellent Sodium-Ion Storage and Electrocatalytic Properties

Three-dimensional (3D) porous microspheres composed of CoSe₂@N-doped carbon nanorod-deposited carbon nanotube (CNT) building blocks (CoSe₂@NC-NR/CNT) can be successfully synthesized using CNT/Co-based metal-organic framework (ZIF-67) porous microspheres as a precursor. This strategy involves the homogeneous coating of ZIF-67 polyhedrons onto porous CNT microspheres prepared by spray pyrolysis and further selenization of the composites under an Ar/H₂ atmosphere. During the selenization process, the ZIF-67 polyhedrons on the CNT backbone are transformed into N-doped carbon-coated CoSe₂ nanorods by a directional recrystallization process, resulting in a homogeneous deposition of CoSe₂@NC nanorods on the porous CNT microspheres. Such a unique structure of CoSe₂@NC-NR/CNT microspheres facilitates the transport of ions, electrons, and mass and provides a conductive pathway for electrons during electrochemical reactions. Correspondingly, the composite exhibits a superior dual functionality as both an electrocatalyst for the hydrogen evolution reaction (HER) and an electrode for sodium-ion batteries (SIBs). The CoSe₂@NC-NR/CNT microspheres exhibit a small Tafel slope (49.8 mV dec^-1) and a superior stability for HER. Furthermore, the composite delivers a high discharge capacity of 555 mA h g^-1 after 100 cycles at a current density of 0.2 A g^-1 and a good rate capability for SIBs.

Metal-Organic-Framework-Derived N-Doped Hierarchically Porous Carbon Polyhedrons Anchored on Crumpled Graphene Balls as Efficient Selenium Hosts for High-Performance Lithium-Selenium Batteries

Developing carbon scaffolds showing rational pore structures as cathode hosts is essential for achieving superior electrochemical performances of lithium-selenium (Li-Se) batteries. Hierarchically porous N-doped carbon polyhedrons anchored on crumpled graphene balls (NPC/CGBs) are synthesized by carbonizing a zeolitic imidazolate framework-8 (ZIF-8)/CGB composite precursor, producing an unprecedented effective host matrix for high-performance Li-Se batteries. Mesoporous CGBs obtained by one-pot spray pyrolysis are used as a highly conductive matrix for uniform polyhedral ZIF-8 growth. During carbonization, ZIF-8 polyhedrons on mesoporous CGBs are converted into N-doped carbon polyhedrons showing abundant micropores, forming a high-surface-area, high-pore-volume hierarchically porous NPC/CGB composite whose small unique pores effectively confine Se during melt diffusion, thereby providing conductive electron pathways. Thus, the integrated NPC/CGB-Se composite ensures high Se utilization originating from complete electrochemical reactions between Se and Li ions. The NPC/CGB-Se composite cathode exhibits high discharge capacities (998 and 462 mA h g^-1 at the 1st and 1000th cycles, respectively, at a 0.5 C current density), good capacity retention (68%, calculated from the 3rd cycle), and excellent rate capability. A discharge capacity of 409 mA h g^-1 is achieved even at an extremely high (15.0 C) current density.