Recently, anionic‐redox‐based materials have shown promising electrochemical performance as cathode materials for sodium‐ion batteries. However, one of the limiting factors in the development of ...oxygen‐redox‐based electrodes is their low operating voltage. In this study, the operating voltage of oxygen‐redox‐based electrodes is raised by incorporating nickel into P2‐type Na2/3Zn0.3Mn0.7O2 in such a way that the zinc is partially substituted by nickel. As designed, the resulting P2‐type Na2/3(Ni0.5Zn0.5)0.3Mn0.7O2 electrode exhibits an average operating voltage of 3.5 V and retains 95% of its initial capacity after 200 cycles in the voltage range of 2.3–4.6 V at 0.1C (26 mA g−1). Operando X‐ray diffraction analysis reveals the reversible phase transition: P2 to OP4 phase on charge and recovery to the P2 phase on discharge. Moreover, ex situ X‐ray absorption near edge structure and X‐ray photoelectron spectroscopy studies reveal that the capacity is generated by the combination of Ni2+/Ni4+ and O2−/O1− redox pairs, which is supported by first‐principles calculations. It is thought that this kind of high voltage redox species combined with oxygen redox could be an interesting approach to further increase energy density of cathode materials for not only sodium‐based rechargeable batteries, but other alkali‐ion battery systems.
Herein, the fabrication of a cathode that achieves a high operating voltage via Ni substitution in P2‐Na2/3(Ni0.5Zn0.5)0.3Mn0.7O2. The cathode delivers outstanding electrochemical performance as well as structural stability for prolonged cycling.
Cathode materials are usually active in the range of 2–4.3 V, but the decomposition of the electrolytic salt above 4 V versus Na+/Na is common. Arguably, the greatest concern is the formation of HF ...after the reaction of the salts with water molecules, which are present as an impurity in the electrolyte. This HF ceaselessly attacks the active materials and gradually causes the failure of the electrode via electric isolation of the active materials. In this study, a bioinspired β‐NaCaPO4 nanolayer is reported on a P2‐type layered Na2/3Ni1/3Mn2/3O2 cathode material. The coating layers successfully scavenge HF and H2O, and excellent capacity retention is achieved with the β‐NaCaPO4‐coated Na2/3Ni1/3Mn2/3O2 electrode. This retention is possible because a less acidic environment is produced in the Na cells during prolonged cycling. The intrinsic stability of the coating layer also assists in delaying the exothermic decomposition reaction of the desodiated electrodes. Formation and reaction mechanisms are suggested for the coating layers responsible for the excellent electrode performance. The suggested technology is promising for use with cathode materials in rechargeable sodium batteries to mitigate the effects of acidic conditions in Na cells.
A bio‐inspired β‐NaCaPO4 surface layer is applied to Na2/3Ni1/3Mn2/3O2, and the coated material dramatically improves the electrochemical and thermal properties. The β‐NaCaPO4 surface layer retards the particle separation and exfoliation which is the main cause of failure for long‐term cycling. The layer scavenges the generated HF, which would otherwise ceaselessly attack the active materials.
Ambient stability of colloidal nanocrystal quantum dots (QDs) is imperative for low-cost, high-efficiency QD photovoltaics. We synthesized air-stable, ultrasmall PbS QDs with diameter (D) down to 1.5 ...nm, and found an abrupt transition at D ≈ 4 nm in the air stability as the QD size was varied from 1.5 to 7.5 nm. X-ray photoemission spectroscopy measurements and density functional theory calculations reveal that the stability transition is closely associated with the shape transition of oleate-capped QDs from octahedron to cuboctahedron, driven by steric hindrance and thus size-dependent surface energy of oleate-passivated Pb-rich QD facets. This microscopic understanding of the surface chemistry on ultrasmall QDs, up to a few nanometers, should be very useful for precisely and accurately controlling physicochemical properties of colloidal QDs such as doping polarity, carrier mobility, air stability, and hot-carrier dynamics for solar cell applications.
Recent developments in the Internet of Things (IoT) technology provide an unprecedented opportunity for personalized services. To take advantage of this great potential, consumers are willing to ...provide their personal information at the risk of privacy breach. This paper examines factors affecting the willingness to provide privacy information based on the privacy calculus theory in several IoT services; healthcare, smart home and smart transportation. The proposed model is estimated using survey data collected from 154 people who know the concept of IoT. The results indicate that people do not pay much attention to perceived privacy risk when providing privacy information for a better personalized service. However, in healthcare service, where perceived privacy risk is high, people are not willing to provide their personal information despite the lower expected value from incomplete personalization. Analysis of privacy behavior in the context of IoT services provides implications for and insight into the tradeoff decision between perceived privacy risk and willingness to provide personal information.
•Perceived benefit has an effect on the willingness to provide privacy information.•Some network externality factors have a significant effect on perceived benefit.•Perceived privacy risk does not matter when providing privacy information.•Despite the lower expected value from non-personalization, risk matters in healthcare.
Interaction between dipoles often emerges intriguing physical phenomena, such as exchange bias in the magnetic heterostructures and magnetoelectric effect in multiferroics, which lead to advances in ...multifunctional heterostructures. However, the defect‐dipole tends to be considered the undesired to deteriorate the electronic functionality. Here, deterministic switching between the ferroelectric and the pinched states by exploiting a new substrate of cubic perovskite, BaZrO3 is reported, which boosts the square‐tensile‐strain to BaTiO3 and promotes four‐variants in‐plane spontaneous polarization with oxygen vacancy creation. First‐principles calculations propose a complex of an oxygen vacancy and two Ti3+ ions coins a charge‐neutral defect‐dipole. Cooperative control of the defect‐dipole and the spontaneous polarization reveals ternary in‐plane polar states characterized by biased/pinched hysteresis loops. Furthermore, it is experimentally demonstrated that three electrically controlled polar‐ordering states lead to switchable and nonvolatile dielectric states for application of nondestructive electro‐dielectric memory. This discovery opens a new route to develop functional materials via manipulating defect‐dipoles and offers a novel platform to advance heteroepitaxy beyond the prevalent perovskite substrates.
A new cubic perovskite substrate BaZrO3 promotes an innovative ferroelectric state and functionality in heteroepitaxial BaTiO3 film through applications of square tensile strain. The isotropic strain induces intriguing four‐variants polar domains of in‐plane spontaneous polarization. Cooperation between the built‐in local point defect‐dipole and the four‐variants polar domains enables the reversible control of ternary polar states.
The well‐known ferromagnetic oxide, NiFe2O4, was studied as a potential candidate for room‐temperature Type II magnetoelectrics. A spin canting as one of the essential requirements for Type II ...multiferroics was induced by breaking the stoichiometry, that is, intentionally subtracting Fe ions. We observed that Fe ions were first subtracted exclusively from the tetrahedral sites, leading to an increase in the magnetoelectric coupling owing to an increasing degree of spin canting. The enhancement in the magnetoelectric coupling culminated beyond the subtraction level of ~30 at.%, at which Fe ions started to be removed from the octahedral sites. Alongside, we observed that the subtraction of Fe ions gives rise to a ferroelectricity due to the formation of defect complexes that establish an internal bias field.
Wet chemical synthesis of covalent III‐V colloidal quantum dots (CQDs) has been challenging because of uncontrolled surfaces and a poor understanding of surface–ligand interactions. We report a ...simple acid‐free approach to synthesize highly crystalline indium phosphide CQDs in the unique tetrahedral shape by using tris(dimethylamino) phosphine and indium trichloride as the phosphorus and indium precursors, dissolved in oleylamine. Our chemical analyses indicate that both the oleylamine and chloride ligands participate in the stabilization of tetrahedral‐shaped InP CQDs covered with cation‐rich (111) facets. Based on density functional theory calculations, we propose that fractional dangling electrons of the In‐rich (111) surface could be completely passivated by three halide and one primary amine ligands per the (2×2) surface unit, satisfying the 8‐electron rule. This halide–amine co‐passivation strategy will benefit the synthesis of stable III‐V CQDs with controlled surfaces.
InP colloidal tetrahedral nanocrystals were synthesized through a simple acid‐free approach using tris(dimethylamino) phosphine and indium trichloride dissolved in oleylamine. Their formation was attributed to the unique stabilization of the In‐rich (111) facets by co‐passivation with halide and primary amine.
Recent advances in 3D culture systems have led to the generation of brain organoids that resemble different human brain regions; however, a 3D organoid model of the midbrain containing functional ...midbrain dopaminergic (mDA) neurons has not been reported. We developed a method to differentiate human pluripotent stem cells into a large multicellular organoid-like structure that contains distinct layers of neuronal cells expressing characteristic markers of human midbrain. Importantly, we detected electrically active and functionally mature mDA neurons and dopamine production in our 3D midbrain-like organoids (MLOs). In contrast to human mDA neurons generated using 2D methods or MLOs generated from mouse embryonic stem cells, our human MLOs produced neuromelanin-like granules that were structurally similar to those isolated from human substantia nigra tissues. Thus our MLOs bearing features of the human midbrain may provide a tractable in vitro system to study the human midbrain and its related diseases.
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•Self-organizing midbrain-like organoids (hMLOs) develop from hPSCs in 3D culture•hMLOs, but not mouse MLOs or human cerebral organoids, produce neuromelanin•hMLOs secrete dopamine (DA) and neurons within the hMLOs form functional synapses•Neurons within hMLOs exhibit SNpc DA neuron-like electrophysiological properties
Jo et al. report a method for generating human midbrain-like organoids (hMLOs) from hPSCs in 3D culture. The hMLOs contain distinct layers of neuronal cells expressing human midbrain markers, such as neuromelanin, are electrically active, form functional synapses, and produce dopamine, suggesting that they may be useful for studying human midbrain.
Chronic hyperglycemia is the primary risk factor for the development of complications in diabetes mellitus (DM); however, it is believed that frequent or large glucose fluctuations may independently ...contribute to diabetes-related complications. Postprandial spikes in blood glucose, as well as hypoglycemic events, are blamed for increased cardiovascular events in DM. Glycemic variability (GV) includes both of these events; hence, minimizing GV can prevent future cardiovascular events. Correcting GV emerges as a target to be pursued in clinical practice to safely reduce the mean blood glucose and to determine its direct effects on vascular complications in diabetes. Modern diabetes management modalities, including glucagon-related peptide-1-based therapy, newer insulins, modern insulin pumps and bariatric surgery, significantly reduce GV. However, defining GV remains a challenge primarily due to the difficulty of measuring it and the lack of consensus regarding the optimal approach for its management. The purpose of this manuscript was not only to review the most recent evidence on GV but also to help readers better understand the available measurement options and how the various definitions relate differently to the development of diabetic complications.
Bioelectronic implants delivering electrical stimulation offer an attractive alternative to traditional pharmaceuticals in electrotherapy. However, achieving simple, rapid, and cost‐effective ...personalization of these implants for customized treatment in unique clinical and physical scenarios presents a substantial challenge. This challenge is further compounded by the need to ensure safety and minimal invasiveness, requiring essential attributes such as flexibility, biocompatibility, lightness, biodegradability, and wireless stimulation capability. Here, a flexible, biodegradable bioelectronic paper with homogeneously distributed wireless stimulation functionality for simple personalization of bioelectronic implants is introduced. The bioelectronic paper synergistically combines i) lead‐free magnetoelectric nanoparticles (MENs) that facilitate electrical stimulation in response to external magnetic field and ii) flexible and biodegradable nanofibers (NFs) that enable localization of MENs for high‐selectivity stimulation, oxygen/nutrient permeation, cell orientation modulation, and biodegradation rate control. The effectiveness of wireless electrical stimulation in vitro through enhanced neuronal differentiation of neuron‐like PC12 cells and the controllability of their microstructural orientation are shown. Also, scalability, design flexibility, and rapid customizability of the bioelectronic paper are shown by creating various 3D macrostructures using simple paper crafting techniques such as cutting and folding. This platform holds promise for simple and rapid personalization of temporary bioelectronic implants for minimally invasive wireless stimulation therapies.
A flexible, biodegradable bioelectronic paper featuring homogeneously distributed wireless stimulation functionality is presented. This paper synergistically combines lead‐free magnetoelectric nanoparticles for external magnetic field‐induced electrical stimulation and flexible, biodegradable nanofibers for high‐selectivity stimulation, oxygen/nutrient permeation, cell orientation modulation, and biodegradation rate control. Scalability, design flexibility, and rapid customizability are demonstrated through simple paper crafting techniques such as origami and kirigami.
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