“Bio-switch Chip” Based on Nanostructured Conducting Polymer and Entrapped Enzyme

We report a switchable biochip strategy where enzymes were entrapped in conducting polymer layers and the enzymatic reaction of the entrapped enzymes was controlled in real-time via electrical stimuli on the polymer layers. This device is named here as a “bio-switch chip” (BSC). We fabricated BSC structures using polypyrrole (Ppy) with entrapped glucose oxidase (GOx) and demonstrated the switching of glucose oxidation reaction in real-time. We found that the introduction of a negative bias voltage on the BSC structure resulted in the enhanced glucose oxidation reaction by more than 20 times than that without a bias voltage. Moreover, because the BSC structures could be fabricated on specific regions, we could control the enzymatic reaction on specific regions. In view of the fact that enzymes enable very useful and versatile biochemical reactions, the ability to control the enzymatic reactions via conventional electrical signals could open up various applications in the area of biochips and other biochemical industries

Direct Visualization of Lithium Polysulfides and Their Suppression in Liquid Electrolyte

Understanding of lithium polysulfide (Li-PS) formation and the shuttle phenomenon is essential for practical application of the lithium/sulfur (Li/S) cell, which has superior theoretical specific energy (2600 Wh/kg). However, it suffers from the lack of direct observation on behaviors of soluble Li-PS in liquid electrolytes. Using in situ graphene liquid cell electron microscopy, we have visualized formation and diffusion of Li-PS simultaneous with morphological and phase evolutions of sulfur nanoparticles during lithiation. We found that the morphological changes and Li-PS diffusion are retarded by ionic liquid (IL) addition into electrolyte. Chronoamperometric shuttle current measurement confirms that IL addition lowers the experimental diffusion coefficient of Li-PS by 2 orders of magnitude relative to that in IL-free electrolyte and thus suppresses the Li-PS shuttle current, which accounts for better cyclability and Coulombic efficiency of the Li/S cell. This study provides significant insights into electrolyte design to inhibit the polysulfide shuttle phenomenon

Direct Visualization of Lithium Polysulfides and Their Suppression in Liquid Electrolyte

Understanding of lithium polysulfide (Li-PS) formation and the shuttle phenomenon is essential for practical application of the lithium/sulfur (Li/S) cell, which has superior theoretical specific energy (2600 Wh/kg). However, it suffers from the lack of direct observation on behaviors of soluble Li-PS in liquid electrolytes. Using in situ graphene liquid cell electron microscopy, we have visualized formation and diffusion of Li-PS simultaneous with morphological and phase evolutions of sulfur nanoparticles during lithiation. We found that the morphological changes and Li-PS diffusion are retarded by ionic liquid (IL) addition into electrolyte. Chronoamperometric shuttle current measurement confirms that IL addition lowers the experimental diffusion coefficient of Li-PS by 2 orders of magnitude relative to that in IL-free electrolyte and thus suppresses the Li-PS shuttle current, which accounts for better cyclability and Coulombic efficiency of the Li/S cell. This study provides significant insights into electrolyte design to inhibit the polysulfide shuttle phenomenon

Direct Visualization of Lithium Polysulfides and Their Suppression in Liquid Electrolyte

Understanding of lithium polysulfide (Li-PS) formation and the shuttle phenomenon is essential for practical application of the lithium/sulfur (Li/S) cell, which has superior theoretical specific energy (2600 Wh/kg). However, it suffers from the lack of direct observation on behaviors of soluble Li-PS in liquid electrolytes. Using in situ graphene liquid cell electron microscopy, we have visualized formation and diffusion of Li-PS simultaneous with morphological and phase evolutions of sulfur nanoparticles during lithiation. We found that the morphological changes and Li-PS diffusion are retarded by ionic liquid (IL) addition into electrolyte. Chronoamperometric shuttle current measurement confirms that IL addition lowers the experimental diffusion coefficient of Li-PS by 2 orders of magnitude relative to that in IL-free electrolyte and thus suppresses the Li-PS shuttle current, which accounts for better cyclability and Coulombic efficiency of the Li/S cell. This study provides significant insights into electrolyte design to inhibit the polysulfide shuttle phenomenon

Controlling Surface Structure and Primary Particle Size to Enhance Performance and Reduce Gas Evolution in Lithium- and Manganese-Rich Layered Oxide Cathodes

Practical application of lithium- and manganese-rich layered oxide cathodes has been hindered despite their high performance and low cost owing to high gas evolution accompanying capacity loss even in a conservative voltage window. Here, we control the surface structure and primary particle size of lithium- and manganese-rich layered oxide cathodes not only to enhance the electrochemical performance but also to reduce gas evolution. Sulfur-coated Fm3̅m/R3̅m double reduced surface layers and Mo doping dramatically reduce gas evolution, which entails the improvement of electrochemical performance. With the optimization, we prove that it is competitive enough to conventional high-nickel cathodes in the aspects of gas evolution as well as electrochemical performance in the conservative voltage window of 2.5–4.4 V. Our findings provide invaluable insights on the improvement of electrochemical performance and gas evolution properties in lithium- and manganese-rich layered oxide cathodes

Direct Visualization of Lithium Polysulfides and Their Suppression in Liquid Electrolyte

Understanding of lithium polysulfide (Li-PS) formation and the shuttle phenomenon is essential for practical application of the lithium/sulfur (Li/S) cell, which has superior theoretical specific energy (2600 Wh/kg). However, it suffers from the lack of direct observation on behaviors of soluble Li-PS in liquid electrolytes. Using in situ graphene liquid cell electron microscopy, we have visualized formation and diffusion of Li-PS simultaneous with morphological and phase evolutions of sulfur nanoparticles during lithiation. We found that the morphological changes and Li-PS diffusion are retarded by ionic liquid (IL) addition into electrolyte. Chronoamperometric shuttle current measurement confirms that IL addition lowers the experimental diffusion coefficient of Li-PS by 2 orders of magnitude relative to that in IL-free electrolyte and thus suppresses the Li-PS shuttle current, which accounts for better cyclability and Coulombic efficiency of the Li/S cell. This study provides significant insights into electrolyte design to inhibit the polysulfide shuttle phenomenon

Microscopic Insight into Tin Nanoparticle Magnesiation

Here, we demonstrate the magnesiation mechanism of Sn nanoparticles by performing liquid-phase electron microscopy. We discover that the sluggish Mg-ion diffusion into Sn involves the formation of the intermediate metastable phase besides an equilibrium Mg2Sn phase. The large stress likely from the interface between Sn and MgxSn leads to amorphous Mg2+xSn formation with Mg2+ overinsertion. Formation of Mg­(OH)2 on MgxSn impedes Mg2+ insertion into Sn, leading to rapid capacity fading of a Mg–Sn cell. The study provides important insights into the reaction dynamics of a Sn electrode for a rechargeable Mg-ion battery

Bioelectrical Nose Platform Using Odorant-Binding Protein as a Molecular Transporter Mimicking Human Mucosa for Direct Gas Sensing

Recently, various bioelectronic nose devices based on human receptors were developed for mimicking a human olfactory system. However, such bioelectronic nose devices could operate in an aqueous solution, and it was often very difficult to detect insoluble gas odorants. Here, we report a portable bioelectronic nose platform utilizing a receptor protein-based bioelectronic nose device as a sensor and odorant-binding protein (OBP) as a transporter for insoluble gas molecules in a solution, mimicking the functionality of human mucosa. Our bioelectronic nose platform based on I7 receptor exhibited dose-dependent responses to octanal gas in real time. Furthermore, the bioelectronic platforms with OBP exhibited the sensor sensitivity improved by ∼100% compared with those without OBP. We also demonstrated the detection of odorant gas from real orange juice and found that the electrical responses of the devices with OBP were much larger than those without OBP. Since our bioelectronic nose platform allows us to directly detect gas-phase odorant molecules including a rather insoluble species, it could be a powerful tool for versatile applications and basic research based on a bioelectronic nose

Morphological Evolution Induced through a Heterojunction of W‑Decorated NiO Nanoigloos: Synergistic Effect on High-Performance Gas Sensors

Morphological evolution accompanying a surface roughening and preferred orientation is an effective way to realize a high-performance gas sensor because of its significant potential as a chemical catalyst through chemical potentials and atomic energy states. In this work, we investigated a heterojunction of double-side-W-decorated NiO nanoigloos fabricated through radio frequency sputtering and a soft-template method. Interestingly, a morphological evolution characterized by a pyramidal rough surface and the preferred orientation of the (111) plane was observed upon decorating the bare NiO nanoigloos with W. The underlying mechanism of the morphological evolution was precisely demonstrated based on the van der Drift competitive growth model originating from the oxygen transport and chemical strain in the lattice. The gas sensing properties of W-decorated NiO show an excellent NO2 response and selectivity when compared to other gases. In addition, high response stability was evaluated under interference gas and humidity conditions. The synergistic effects on the sensing performance were interpreted on the basis of the morphological evolution of W-decorated NiO nanoigloos