Inherent Structural Instability Research Articles

Stabilised pathway and its anti-oxygen/glucose deprived activity about ligustilide, as a pharmacodynamic marker for Angelica sinensis (Oliv) Diles or Ligusticum chuanxiong Hort

The inherent structural instability and very low bioavailability of ligustilide (Lig) lead to the limited application of the clinical neuroprotection. We developed a stabilised method for Lig, which involved a chemical synthesis between cyclopropylamine and the active phthalides extract included Lig from Angelica sinensis (Oliv) Diles or Ligusticum chuanxiong Hort, which generated correspond phthalide derivatives by nucleophilic additive and substituted reaction. During this process, four phthalide derivatives have been obtained and two compounds (3 and 4) stands out as an unprecedented dimeric phthalide entity. This research has meticulously delineated the stabilised pathway and polymerisation mechanics of Lig or its derivatives, an oxygen/glucose deprived PC12 cells experiment model utilised to screen the anti-stroke activity of this isolated Lig derivatives and the results supported this chemical transformation could achieve the stabilised goal of Lig and improved its anti-oxygen/glucose deprived activity.

Spatial Structure of Electron Interactions in High-entropy Oxide Nanoparticles for Active Electrocatalysis of Carbon Dioxide Reduction.

High-entropy oxides (HEOs) exhibit distinctive catalytic properties owing to their diverse elemental compositions, garnering considerable attention across various applications. However, the preparation of HEO nanoparticles with different spatial structures remains challenging due to their inherent structural instability. Herein, ultrasmall high-entropy oxide nanoparticles (less than 5nm) with different spatial structures are synthesized on carbon supports via the rapid thermal shock treatment. The low-symmetry HEO, BiSbInCdSn-O4, demonstrates exceptional performance for electrocatalytic carbon dioxide reaction (eCO2RR), including a lower overpotential, high Faraday efficiency across a wide electrochemical range (-0.3 to -1.6V), and sustained stability for over100h. In the membrane electrode assembly electrolyzer, BiSbInCdSn-O4 achieves a current density of 350mAcm-2 while maintaining good stability for 24h. Both experimental observations and theoretical calculations reveal that the electron donor-acceptor interactions between bismuth and indium sites in BiSbInCdSn-O4 enable the electron delocalization to facilitate the efficient adsorption of CO2 and hydrogenation reactions. Thus, the energy barrier of the rate-determining step is reduced to enhance the electrocatalytic activity and stability. This study elucidates that the spatial structure of metal sites in HEOs is able to regulate CO2 adsorption status for eCO2RR, paving the way for the rational design of efficient HEO catalysts.

Enzymatic interlocking aptamer-micelles for enhanced cellular internalization and nucleus-targeted cancer phototherapy

Multifunctional micelles that permit both diagnosis and treatment present enormous advantage and potential for precision medicine. However, the inherent complexities and structural instability of these systems often cause unsatisfactory targeting and therapeutic performances. Herein, by ingenious design of a 2,5-bis(2-thienyl)pyrrole (SNS) modifier to covalently link with AS1411 aptamer and lipid segment, a simple strategy is proposed for one-step enzymatic preparation of interlocked aptamer-micelle (IApM) under bio-friendly conditions. The interlocked poly(SNS) skeleton in IApM can not only stabilize the micelle structure but also enhance near-infrared (NIR) absorption ability, thus further enhancing cellular internalization and photothermal therapy. In addition, the multivalent AS1411 aptamers tethered in the hydrophilic shell can simultaneously increase the specific binding affinity of DNA micelles and induce nucleus-targeted accumulation for DNA damage-triggered apoptosis. This DNA micelle achieves “best of both worlds” with enhanced biostability for cellular internalization and improved NIR photothermal conversion efficiency for nucleus-targeted therapy, which provides a promising formulation strategy for precision cancer treatment.

Analyzing the Doping Mechanism of High-Valence Element in Ni-Rich Cathode Materials

Layered cathode materials, LiMO2 (M=Ni, Co,Mn, or Al), with a high nickel content are promising cathode materials owing to their near-theoretical specific capacity. However, the inherent chemical and structural instabilities of Ni-rich cathodes lead to several problems, including rapid capacity fading, thermal instability, gas evolution, and safety concerns.1 Introducing additional elements into Ni-rich cathodes is an essential strategy for addressing the instability of the cathode material. Conventionally, this doping strategy considers only the incorporation of additional elements into the bulk structure of the cathode in terms of fortifying the crystal structure.2 However, high-valence elements are likely to be insoluble in the crystal structure, resulting in accumulation along the interparticle boundaries.3 Herein, a new mechanism for doping high-valence elements into Ni-rich cathodes and their effects on the morphology and crystal structure are investigated by calcining LiNiO2 (LNO) and X-doped LNO cathodes (X=Al, Nb, Ta, and Mo) at various temperatures. Operando X-ray diffraction analysis reveals that the temperature at which the content of Li-X-O compounds declines is higher for the dopants with high oxidation states, reinforcing segregation at the grain boundary. Thus, the highly aligned microstructure and high crystallinity of the LNO cathode are maintained over a wide calcination temperature range after doping with high-valence elements, enhancing the electrochemical performance.

In Situ Synthesis of CsPbX3/Polyacrylonitrile Nanofibers with Water-Stability and Color-Tunability for Anti-Counterfeiting and LEDs.

Inorganic CsPbX3 (X = Cl, Br, I) perovskite quantum dots (PQDs) have attracted widespread attention due to their excellent optical properties and extensive application prospects. However, their inherent structural instability significantly hinders their practical application despite their outstanding optical performance. To enhance stability, an in situ electrospinning strategy was used to synthesize CsPbX3/polyacrylonitrile composite nanofibers. By optimizing process parameters (e.g., halide ratio, electrospinning voltage, and heat treatment temperature), all-inorganic CsPbX3 PQDs have been successfully grown in a polyacrylonitrile (PAN) matrix. During the electrospinning process, the rapid solidification of electrospun fibers not only effectively constrained the formation of large-sized PQDs but also provided effective physical protection for PQDs, resulting in the improvement in the water stability of PQDs by minimizing external environmental interference. Even after storage in water for over 100 days, the PQDs maintained approximately 93.5% of their photoluminescence intensity. Through the adjustment of halogen elements, the as-obtained composite nanofibers exhibited color-tunable luminescence in the visible light region, and based on this, a series of multicolor anti-counterfeiting patterns were fabricated. Additionally, benefiting from the excellent water stability and optical performance, the CsPbBr3/PAN composite film was combined with red-emitting K2SiF6:Mn4+ (KSF) on a blue LED (460 nm), producing a stable and efficient WLED device with a color temperature of around 6000 K and CIE coordinates of (0.318, 0.322). These results provide a general approach to synthesizing PQDs/polymer nanocomposites with excellent water stability and multicolor emission, thereby promoting their practical applications in multifunctional optoelectronic devices and advanced anti-counterfeiting.

Mo Doping to Modify Lattice and Morphology of the LiNi0.9Co0.05Mn0.05O2 Cathode toward High-Efficient Lithium-Ion Storage.

The Ni-rich Co-poor layered cathode (LiNixCoyMn1-x-yO2, x ≥ 0.9) is a candidate for the next-generation lithium-ion batteries due to its high specific capacity and low cost. However, the inherent structural instability and slow kinetics of Li+ migration hinder their large-scale application. Mo doping is proposed to enhance the crystal structure stability of LiNi0.9Co0.05Mn0.05O2 and to ensure the preservation of the spherical secondary particles after the cycle. The characterization results indicate that Mo doping not only significantly relieves the lattice strain accompanied by H2 → H3 phase transition but also alleviates particle stress accumulation to avoid pulverization. The Mo-modification allows the generation of uniform fine primary particulates and further agglomeration into the smooth secondary particles to inhibit electrolyte penetration. Hence, the Mo-modified sample NCM90-1%Mo displays an excellent capacity retention of 85.9% after 200 cycles at 0.5 C current density, which is 23.8% higher than that of the pristine NCM90. In addition, with the expansion of the Li slab to accelerate Li+ diffusion and the fine primary particles to shorten the Li+ pathway, the NCM90-1%Mo sample exhibits a high discharge capacity of 150 mAh g-1 at 5 C current density. This work provides a new thought for the design and construction of high-capacity cathode materials for the next-generation lithium-ion batteries.

Assembly and catalytic activity of short prion-inspired peptides.

Enzymes play a crucial role in biochemical reactions, but their inherent structural instability limits their performance in industrial processes. In contrast, amyloid structures, known for their exceptional stability, are emerging as promising candidates for synthetic catalysis. This article explores the development of metal-decorated nanozymes formed by short peptides, inspired by prion-like domains. We detail the rational design of synthetic short Tyrosine-rich peptide sequences, focusing on their self-assembly into stable amyloid structures and their metallization with biologically relevant divalent metal cations, such as Cu2+, Ni2+, Co2+ and Zn2+. The provided experimental framework offers a step-by-step guide for researchers interested in exploring the catalytic potential of metal-decorated peptides. By bridging the gap between amyloid structures and catalytic function, these hybrid molecules open new avenues for developing novel metalloenzymes with potential applications in diverse chemical reactions.

Operando High-Temperature X-Ray Absorption Spectroscopy of LiNiO2 Cathode Material during Synthesis

The increasing demand for higher energy density in batteries for automotive applications has led to a trend toward increasing the Ni content in layered oxide cathode materials to increase their reversible capacity. However, LiNiO2, which has the highest Ni content, shows a faster capacity drop during charge-discharge cycling, which is attributed to its inherent structural instability in both the pristine and delithiated states. Therefore, to address the former issue and to better understand the appropriate synthesis conditions for LiNiO2, we have studied the changes in the local structure of LiNiO2 during the synthesis process using operando analysis techniques. Recently, high temperature in situ X-ray diffraction during LiNiO2 synthesis was reported by Bianchini [1] and Weber [2], which confirmed the loss of lithium and oxygen and the migration of Ni to Li layers above 700 °C. To further understand the mechanism of Li/Ni mixing and oxygen loss, operando high-temperature X-ray absorption spectroscopy (XAS) was performed during the synthesis of LiNiO2 to clarify the electrical structure of Ni at high temperatures. Pre-heated Li x NiO2 (x = 0.76, 1.01, 1.26, and 1.51) precursors were prepared by heating LiOH·H2O and Ni(OH)2 at 480 °C for 24 h in air. The precursor was pelletized and set in a quartz sample holder. Operando high-temperature Ni K-edge XAS spectra of the precursor were obtained at BL9A and BL12C in Photon Factory (PF), High Energy Accelerator Research Organization (KEK) by a transmission mode. The operando spectra of all samples except Li/Ni = 0.76 revealed a clear edge shift to the lower energy side corresponding to nickel reduction above 700 °C. The Li/Ni = 0.76 sample has a lithium-deficient composition and Ni is not oxidized to Ni3+ below 700 °C, so the Li/Ni = 0.76 sample has almost no Ni K-edge energy shift above 700 °C. These results suggest that Ni in LiNiO2 is reduced above 700 °C even in an oxygen atmosphere, regardless of whether the Li/Ni ratio is greater than 1. The Ni reduction above 700 °C is probably the cause of the Li/Ni mixture.Reference[1] M. Bianchini, J. Janek, et al., Angew. Chem., Int. Ed., 58, 10434 (2019).[2] R. Weber, J. R. Dahn, et al., J. Electrochem. Soc., 167, 100501 (2020).

Capacity Fading Mechanism of Ni-Rich Cathode Materials Focusing on Particle Interior

With the prevalence of electric vehicles, Ni-rich layered cathodes have been extensively developed to increase the energy density of Li-ion batteries (LIBs). However, cathodes with a high Ni content suffer from inherent structural and chemical instabilities, which lead to rapid capacity fading and thermal instability.1 The degradation of Ni-rich cathode materials is largely caused by the high proportion of reactive Ni4+ combined with the mechanical instability originated from microcracks. This unstable Ni4+ can be readily reduced to Ni2+ by parasitic reactions with the electrolyte concurrently with oxygen release, forming a NiO-like rocksalt impurity phase.2 This phase increases the charge-transfer resistance and thus deteriorates the electrochemical performance of Ni-rich cathodes. As the degradation mainly occurs at the surface of cathode by deleterious electrolyte attack, the rate of degradation is significantly determined by the area exposed to the electrolyte. For cathodes with low Ni contents of ≤60%, the cathode−electrolyte interphase is only limited to the exterior surface of cathode particles in which microcracks are not severe; thus, the decrease in the cycling stability of cathodes is directly proportional only to their Ni4+ fraction. However, as the Ni content in the cathode increases above 60%, the extent of microcracks rapidly increases owing to the buildup of anisotropic strain induced by abrupt lattice volume changes during the H2−H3 phase transition.2 The resultant microcracks in Ni-rich cathode particles can create channels through which the electrolyte infiltrates into the particle interior, thereby increasing the surface area exposed to the electrolyte attack. Janek et al. reported that the specific surface area of 0.2 m2 g−1 for pristine LixNi0.8Co0.1Mn0.1O2 cathode increased to ∼1.4 m2 g−1 when charged to 4.2 V (vs Li/Li+) owing to crack formation.3 This increased surface area further accelerated the rate of capacity fading for Ni-rich cathodes (especially Ni fraction ≥90%), as not only the particle exteriors but also the interiors were exposed to deleterious electrolyte attack and were thus also passivated by NiO-like impurity phases caused by surface degradation.In this study, we performed comparative post-mortem analyses of Li[Ni0.8Co0.1Mn0.1]O2 (NCM811) and Li[Ni0.90Co0.05Mn0.05]O2 (NCM90) cathodes after long-term cycling to elucidate the degradation mechanism of Ni-rich cathodes, focusing on the particle interior. Furthermore, we demonstrated correlations between the degradation of cathodes and the resultant changes in electrochemical properties (e.g., ionic and electrical conductivities). This systematic approach enables us to identify the mechanism by which cathode degradation deteriorates the electrochemical performance, which we expect to lead to breakthroughs in developing Ni-rich cathodes appropriate for EV applications. Reference s : [1] H.-J. Noh, S. Youn, C. S. Yoon, Y.-K. Sun, J. Power Sources, 2013, 233, 121.[2] H.-H. Ryu, K.-J. Park, C. S. Yoon, Y.-K. Sun, Chem. Mater. 2018, 30, 1155.[3] E. Trevisanello, R. Ruess, G. Conforto, F. H. Richter, J. Janek, Adv. Energy Mater. 2021, 11, 2003400.

K(NH4)Zn2(PO4)2: a Beryllium-Free Sr2Be2B2O7 Derivative with Enhanced Interlayer Connectivity.

A novel zinc phosphate derivative of Sr2Be2B2O7 (SBBO), K(NH4)Zn2(PO4)2 (KNZP), featuring [Zn2P2O8]∞2- double layers akin to the [Be2B2O7]∞4- layers in SBBO, was successfully synthesized via a moderate hydrothermal method. Through the substitution of BeO4 and BO3 with ZnO4 and PO4, the issue of toxicity has been effectively resolved, while the enhanced interlayer interactions facilitated by covalent and hydrogen bonding in KNZP overcome the inherent structural instability. Notably, KNZP exhibits a wide transparent window and a moderate second-harmonic generation (SHG) intensity, reaching 0.7 times that of KH2PO4 (KDP), rendering it type-I phase-matchable, indicating that it is a promising UV nonlinear optical (NLO) material.

Metal-Ion Intercalation Mechanisms in Vanadium Pentoxide and Its New Perspectives.

The investigation into intercalation mechanisms in vanadium pentoxide has garnered significant attention within the realm of research, primarily propelled by its remarkable theoretical capacity for energy storage. This comprehensive review delves into the latest advancements that have enriched our understanding of these intricate mechanisms. Notwithstanding its exceptional storage capacity, the compound grapples with challenges arising from inherent structural instability. Researchers are actively exploring avenues for improving electrodes, with a focus on innovative structures and the meticulous fine-tuning of particle properties. Within the scope of this review, we engage in a detailed discussion on the mechanistic intricacies involved in ion intercalation within the framework of vanadium pentoxide. Additionally, we explore recent breakthroughs in understanding its intercalation properties, aiming to refine the material's structure and morphology. These refinements are anticipated to pave the way for significantly enhanced performance in various energy storage applications.

Construction of cobalt hexacyanoferrate multivoid nanoframes as efficient aqueous aluminum ion batteries

In the search for innovative materials for aqueous Al-ion batteries, Prussian blue analogs (PBAs) have drawn significant attention due to their open-framework structures. Yet, PBAs face challenges like restricted capacity and rapid capacity deterioration, primarily stemming from the scarcity of redox sites and their inherent structural instability. In the current research, a synthesis of Fe–Co PBA multivoid nanoframe structures was achieved through straightforward co-precipitation techniques, aimed at optimizing Al-ion storage. Key to enhancing their performance was the modulation of the hydrothermal self-assembly reaction duration. As a result of this modulation, a morphological transition from nanocubes to multivoid nanoframes became evident, leading to the exposure of a higher number of active sites. This morphological transition also minimized the effects of volumetric shifts during the electrochemical charge/discharge cycles. Performance analysis indicated that the Fe–Co PBA multivoid nanoframes demonstrated a stable specific capacity, reaching 43 mAh g⁻¹ over 2000 cycles at 0.5 A g⁻¹ . Impressively, even under the more demanding current density of 1 A g⁻¹ , the specific capacity remained a substantial 36 mAh g⁻¹ after the same number of cycles. Comprehensive ex situ evaluations further underscored the predominant charge storage mechanisms, highlighting the reversible redox activities of the involved transition metals, coupled with the insertion/extraction dynamics of Al³ ⁺ ions.

In-depth theoretical study on the structures of betaine-1,2-propanediol based deep eutectic solvents

Deep eutectic solvents (DESs) have been arousing more and more attention because they meet the important standard of new green solvents, and have been widely used in chemistry. However, the further commercialization is limited by the inherent structural instability and high viscosity. An in-depth understanding of the atomic-level structure and the interactions between hydrogen bond acceptors (HBA) and hydrogen bond donors (HBD) is conducive to better exploring the stability and properties of DESs. In this work, density functional theory (DFT) and molecular dynamics (MD) simulation were used to study the structure and properties of DESs synthesized by betaine and 1,2-propanediol with different molar ratios (1:3 to 1:6). It is confirmed that the relationship between betaine and 1,2-propanediol is essential for the formation of DESs with a reasonable number of hydrogen bonds. In-depth analysis of these hydrogen bonds based on the quantum theory of atoms in molecules shows that they belong to “weak to medium” category. It is mainly the electrostatic interaction between the oxygen atoms of betaine and hydrogen atoms from hydroxyl groups of 1,2-propanediol. In addition, the simulation results showed that the increase of 1,2-propanediol content weakens the hydrogen bond between betaine and 1,2-propanediol, and strengthens the hydrogen bond between 1,2-propanediol molecules. The viscosity of DESs is mainly dependent on the interaction between betaine and 1,2-propanediol. The changes in intramolecular interactions of DESs illustrate that HBD molecules such as 1,2-propanediol play a critical role in the development of application-specific DESs.

Printable and Free-Standing Silicon-Based Anode for Current Collector-Free Lithium-Ion Batteries.

The evolution of Li-ion rechargeable batteries has driven a demand for systems exceeding the energy density and shape diversity of conventional lithium-ion batteries. Silicon (Si)-based materials, suitable for high-energy-density applications, have been restricted in practical use due to their inherent structural instability and poor conductivities upon electrochemical cycling. Here, we propose a fully printable and free-standing anode, composed of hollow SiOx/C (H-SiOx/C) composite material and an MXene conductive binder, exhibiting high specific capacity, structural reliability, and superior ionic conductivity without any current collector. The hollow structure of H-SiOx/C accommodates volume changes during cycling, while the MXene binder forms a three-dimensional interconnected conducting structure for maintaining the structural integrity of electrodes without a current collector. Furthermore, the printability and free-standing nature of the H-SiOx/C/MXene anode are validated in both coin-type full cell and heart-shaped pouch cell configurations through a straightforward stencil printing technique. This work establishes a foundation for advanced Si-based anodes, enhancing performance and design flexibility and potentially contributing to practical printable battery systems.

Comprehensive Approach about Time-Relevant Degradation of Ni-Rich Cathode Materials for Electric Vehicles

With the prevalence of electric vehicles, Ni-rich layered cathodes have been extensively developed to increase the energy density of Li-ion batteries (LIBs). However, cathodes with a high Ni content suffer from inherent structural and chemical instabilities, which lead to rapid capacity fading and thermal instability.1 In particular, the rapid capacity fading of Ni-rich layered cathodes is largely caused by microcracking and the resultant microstructural instability.2 In addition to microcracking, the time during which highly reactive Ni4+ ions are exposed to the electrolyte when the cathode is in a highly charged state also affects the deterioration of the cathode. Although the exposure time is not significant for cathodes with Ni contents of <60%, the calendar aging test of Ni-rich cathodes reveals that the exposure time, especially at high SoCs, critically affects the degradation of these high-Ni cathodes, as the internal surfaces of the particles are also exposed to the electrolyte via the microcracks.3 The exposure time is particularly pertinent for electric vehicle (EV) LIBs, as they remain stationary for long periods in the highly charged state and are operated intermittently. Consequently, the upper SoC limit of EV LIBs is commonly limited to ≈85%, but this limits the driving range and increases the cost of the batteries. Therefore, a holistic approach considering real-use behavior, as well as the properties of the material itself, is needed to overcome the limitations of Ni-rich cathodes.Here, 1 mol% B doping of a core–shell concentration gradient (CSG) Li[Ni0.88Co0.10Al0.02]O2 cathode (CSG-NCA88) is shown to dramatically alter the microstructure of the cathode and effectively protect the particle interior from parasitic electrolyte attack. The B-doped CSG-NCA88 cathode, CSG-NCAB87, maintains its original microstructure even after holding for 500 h in the fully charged state, whereas irreversible structural damage occurs in the pristine CSG-NCA88 cathode during the prolonged electrolyte exposure. The long-term cycling results confirm that the capacity retention of the cathodes is determined by the electrolyte exposure time at a high SoC and that microstructural modification can effectively suppress the time-dependent degradation from electrolyte attack. The proposed CSG-NCAB87 cathode can be utilized at full capacity without restricting the SoC, thus realizing the development of economical high-energy-density LIBs. Reference s : [1] H.-J. Noh, S. Youn, C. S. Yoon, Y.-K. Sun, J. Power Sources, 2013, 233, 121.[2] H.-H. Ryu, K.-J. Park, C. S. Yoon, Y.-K. Sun, Chem. Mater. 2018, 30, 1155.[3] H.-H. Ryu, G.-T. Park, C. S. Yoon, Y.-K. Sun, Small, 2018, 14, 1803179.

Simultaneous B/W dual coating on ultra-high nickel single crystal cathode material for lithium-ion batteries

The ultra-high nickel LiNixCoyMn1-x-yO2 (x > 0.9) cathode material is a prime candidate for powering next-generation electric vehicles. However, its inherent structural instability and complicated interface side-reactions limit its commercialization. Here, the LiNi0.92Co0.04Mn0.04O2 single-crystal cathode material with an average particle size of 1.69 μm is prepared via a simple temperature fluctuation method combined with B and W surface modification. As-formed surface Li–B–O and Li2WO4 lithium ion conductors can successfully enhance the discharge capacity of single crystal LiNi0.92Co0.04Mn0.04O2 from 219.9 to 226.5 mAh g−1 by facilitating lithium ion diffusion. At 4.5 V, the B and W surface modification significantly enhances the cycle retention from 71.8% to 87.1% at 1 C after 100 cycles due to the construction of a uniform boron-rich cathode/electrolyte interface (CEI) layer. The specific composition of the as-formed CEI film is clearly identified. The analysis results of B and W modifications show that the presence of boron-rich CEI and Li2WO4 coating layer protects the particles from electrolyte erosion under high voltage and enhances lithium-ion diffusion on the particle surface. Therefore, the chemical states of Ni within the particle for B- and W-modified samples are distributed more homogeneously after long cycling.

Chalcogen-Peierls Transition: Single-Crystal-to-Single-Crystal Transition from a Two-Dimensional to a One-Dimensional Network of Chalcogen Bonds at Low Temperature

Abstract Due to inherent structural instability, low-dimensional materials often undergo the Peierls transition upon cooling, which is suppressed by an increase in dimensionality of their solid-state electronic structures using secondary bonding interactions such as chalcogen bonds (ChB). We revealed here that ChB themselves have an inherent structural instability when a chalcogen atom participates in simultaneous formation of two ChB, demonstrating for the first time a Peierls-like transition (chalcogen-Peierls transition) of ChB-based organic solids upon cooling. Thus, a lattice dimerization occurs at 220–230 K that changes the two-dimensional ChB network into an accumulated one-dimensional ribbon network in the tetracyanoquinodimethane fused with two [1,2,5]thiadiazoles (1). Negative cooperativity of two ChB formation is weakened on the Se atom due to greater polarizability. Thus, the selenadiazole analogues (2 and 3) undergo a similar chalcogen-Peierls transition at lower temperatures, such as at 160–170 K and at 110–120 K, respectively, depending on the number of Se atom incorporated (one or two, respectively).

Surface Lattice Modulation through Chemical Delithiation toward a Stable Nickel-Rich Layered Oxide Cathode

Nickel-rich layered oxides (NLOs) are considered as one of the most promising cathode materials for next-generation high-energy lithium-ion batteries (LIBs), yet their practical applications are currently challenged by the unsatisfactory cyclability and reliability owing to their inherent interfacial and structural instability. Herein, we demonstrate an approach to reverse the unstable nature of NLOs through surface solid reaction, by which the reconstructed surface lattice turns stable and robust against both side reactions and chemophysical breakdown, resulting in improved cycling performance. Specifically, conformal La(OH)3 nanoshells are built with their thicknesses controlled at nanometer accuracy, which act as a Li+ capturer and induce controlled reaction with the NLO surface lattices, thereby transforming the particle crust into an epitaxial layer with localized Ni/Li disordering, where lithium deficiency and nickel stabilization are both achieved by transforming oxidative Ni3+ into stable Ni2+. An optimized balance between surface stabilization and charge transfer is demonstrated by a representative NLO material, namely, LiNi0.83Co0.07Mn0.1O2, whose surface engineering leads to a highly improved capacity retention and excellent rate capability with a strong capability to inhibit the crack of NLO particles. Our study highlights the importance of surface chemistry in determining chemical and structural behaviors and paves a research avenue in controlling the surface lattice for the stabilization of NLOs toward reliable high-energy LIBs.

Alloying engineering for thermoelectric performance enhancement in p-type skutterudites with synergistic carrier concentration optimization and thermal conductivity reduction

The enhancements in thermoelectric (TE) performances of p-type skutterudites are usually limited due to the relatively low Seebeck coefficients owing to the higher carrier concentration and more impurity phases induced by inherent structural instability of a Fe-based skutterudite. As shown in this study, alloying engineering of Ni doping at Fe sites in a p-type CeFe_3.8Co_0.2Sb₁₂ skutterudite can not only reduce the impurity phases with high thermal conductivity but also regulate the carrier concentration, and thus significantly increase the Seebeck coefficient. The thermal conductivity was largely suppressed due to the enhanced point defect phonon scattering and decreased hole concentration. As a result, a TE figure of merit <i>ZT</i> of the CeFe_3.5Ni_0.3Co_0.2Sb₁₂ sample reached 0.8, which is approximately 50% higher than that of a Ni-free sample. Appropriate Ni doping can maintain a high <i>ZT</i> at a high temperature by controlling the reduction in a band gap. Therefore, a high average <i>ZT</i> close to 0.8 at 650–800 K for CeFe_3.5Ni_0.3Co_0.2Sb₁₂ was obtained, which was comparable to or even higher than those of the reported Ce-filled Fe-based skutterudites due to the synergistic optimization of electrical and thermal performances. This study provides a strategy to synergistically optimize electrical–thermal performances of the p-type skutterudites by alloying engineering.

Glucose and pH responsive fluorescence detection system based on simple synthesis of silicon-coated perovskite quantum dots

Perovskite quantum dots (PQDs) are extremely unstable in ambient air due to their inherent structural instability, which limits the wide application of PQDs. In this work, silicon-coated CsPbBr3 PQDs (CsPbBr3@SiO2) was synthesized via a simple method. The SiO2 coating effectively isolated PQDs from water and oxygen in the environment, which were the main elements that destroyed the structure stability of PQDs. The synthesized CsPbBr3@SiO2 can be stored in water for more than 2 months and posessed wonderful dispersibility in aqueous solution. The fluorescence intensity remained unchanged within 7 days and only decreased by 11.9 % within 2 months. We found that CsPbBr3@SiO2 was extremely sensitive to environmental pH, and the fluorescence intensity decreased with the reduction of pH. In addition, an excellent linear relationship with pH value in the range of 1.0 ∼ 5.0 was achieved. As we all known that glucose can be catalyzed by glucose oxidase to produce gluconic acid and hydrogen peroxide, in which a good deal of protons were produced and the pH was gradually lowered. Since CsPbBr3@SiO2 was stable to water and oxygen, and sensitive to ambient pH, we applied CsPbBr3@SiO2 to the detection of glucose. CsPbBr3@SiO2 showed fantastic selectivity and sensitivity to glucose, and the detection limit can even reach 18.5 μM. Furthermore, CsPbBr3@SiO2 was successfully applied to the detection of glucose in the human serum with satisfactory performance.