2D MXene–TiO2 Core–Shell Nanosheets as a Data-Storage Medium in Memory Devices

MXenes, an emerging class of 2D transition metal carbides and nitrides with the general formula M_n+1X_nT_x (n = 1–4), have potential for application as floating gates in memory devices because of their intrinsic properties of a 2D structure, high density-of-states, and high work function. In this study, a series of MXene–TiO₂ core–shell nanosheets are synthesized by deterministic control of the surface oxidation of MXene. The floating gate (multilayer MXene) and tunneling layer (TiO₂) in a nano-floating-gate transistor memory (NFGTM) device are prepared simultaneously by a facile, low-cost, and water-based process. The memory performance is optimized via adjustment of the thickness of the oxidation layer formed on the MXene surface. The fabricated MXene NFGTMs exhibit excellent nonvolatile memory characteristics, including a large memory window (>35.2 V), high programming/erasing current ratio (≈10⁶), low off-current (<1 pA), long retention (>10⁴ s), and cyclic endurance (300 cycles). Furthermore, synaptic functions, including the excitatory postsynaptic current/inhibitory postsynaptic current, paired-pulse facilitation, and synaptic plasticity (long-term potentiation/depression), are successfully emulated using the MXene NFGTMs. The successful control of MXene oxidation and its application to NFGTMs are expected to inspire the application of MXene as a data-storage medium in future memory devices.     

3D Co-Doping α-Ni(OH)2 Nanosheets for Ultrastable,High-Rate Ni-Zn Battery

The α-Ni(OH)₂ is regarded as one promising cathode for aqueous nickel-zinc batteries due to its high theoretical capacity of ≈480 mAh g⁻¹, its practical deployment however suffers from the poor stability in strong alkaline solution, intrinsic low electrical conductivity as well as the retarded ionic diffusion. Herein, a 3D (three dimensional) macroporous α-Ni(OH)₂ nanosheets with Co doping is designed through a facile and easily scalable electroless plating combined with electrodeposition strategy. The unique micrometer-sized 3D pores come from Ni substrate and rich voids between Co-doping α-Ni(OH)₂ nanosheets can synergistically afford facile, interconnected ionic diffusion channels, sufficient free space for accommodating its volume changes during cycling; meanwhile, the Co-doping can stabilize the structural robustness of the α-Ni(OH)₂ in the alkaline electrolyte during cycling. Thus, the 3D α-Ni(OH)₂ shows a high capacity of 284 mAh g⁻¹ at 0.5 mA cm⁻² with an excellent retention of 78% even at 15 mA cm⁻², and more than 2000 stable cycles at 6 mA cm⁻², as well as the robust cycling upon various flexible batteries. This work provides a simple and efficient pathway to enhance the electrochemical performance of Ni-Zn batteries through improving ionic transport kinetics and stabilizing crystal structure of cathodes.     

Bandgap Tunable Oxynitride LaNb2O7–xNx Nanosheets

Bandgap tunable lanthanum niobium oxynitride [LaNb₂O_7-xN_x]^(1+x)− nanosheet is prepared by the delamination of a Ruddlesden−Popper phase perovskite oxynitride via ion−exchange and two−step intercalation processes. The lanthanum niobium oxynitride nanosheets have a homogeneous thickness of 1.6 nm and exhibit a variety of chromatic colors depending on the nitridation temperature of the parent-layered oxynitride. The bandgap energy of the nanosheets is determined by ultraviolet photoemission spectroscopy, Mott–Schottky, and photoelectrochemical measurements and is found to be tunable in the range of 2.03–2.63 eV. Furthermore, the oxide/oxynitride superlattice structures are fabricated by face−to−face stacking of 2D crystals using oxynitride [LaNb₂O_7-xN_x]^(1+x)− and oxide [Ca₂Nb₃O₁₀]⁻ nanosheets as building blocks. Moreover, the superlattices-like restacked oxynitride/oxide nanosheets hybrid exhibits unique proton conductivity and dielectric properties strongly influenced by the oxynitride nanosheets and enhanced photocatalytic activity under visible light irradiation.     

Pseudogap,Fermi arc,and Peierls-insulating phase induced by 3D–2D crossover in monolayer VSe2

Nano Research - One of important challenges in condensed-matter physics is to realize new quantum states of matter by manipulating the dimensionality of materials, as represented by the discovery...     

Ultrabroadband Photodetectors up to 10.6 µm Based on 2D Fe3O4 Nanosheets

The ultrabroadband spectrum detection from ultraviolet (UV) to long-wavelength infrared (LWIR) is promising for diversified optoelectronic applications of imaging, sensing, and communication. However, the current LWIR-detecting devices suffer from low photoresponsivity, high cost, and cryogenic environment. Herein, a high-performance ultrabroadband photodetector is demonstrated with detecting range from UV to LWIR based on air-stable nonlayered ultrathin Fe₃O₄ nanosheets synthesized via a space-confined chemical vapor deposition (CVD) method. Ultrahigh photoresponsivity (R) of 561.2 A W⁻¹, external quantum efficiency (EQE) of 6.6 × 10³%, and detectivity (D*) of 7.42 × 10⁸ Jones are achieved at the wavelength of 10.6 µm. The multimechanism synergistic effect of photoconductive effect and bolometric effect demonstrates the high sensitivity for light with any light intensities. The outstanding device performance and complementary mixing photoresponse mechanisms open up new potential applications of nonlayered 2D materials for future infrared optoelectronic devices.     

Ultrathin 2D Metal–Organic Framework Nanosheets In situ Interpenetrated by Functional CNTs for Hybrid Energy Storage Device

The controllable construction of two-dimensional(2D)metal–organic framework(MOF)nanosheets with favorable electrochemical performances is greatly challenging for energy storage.Here,we design an in situ induced growth strategy to construct the ultrathin carboxylated carbon nanotubes(C-CNTs)interpenetrated nickel MOF(Ni-MOF/C-CNTs)nanosheets.The deliberate thickness and specific surface area of novel 2D hybrid nanosheets can be effectively tuned via finely controlling C-CNTs involvement.Due to the unique microstructure,the integrated 2D hybrid nanosheets are endowed with plentiful electroactive sites to promote the electrochemical performances greatly.The prepared Ni-MOF/C-CNTs nanosheets exhibit superior specific capacity of 680 C g^−1 at 1 A g^−1 and good capacity retention.The assembled hybrid device demonstrated the maximum energy density of 44.4 Wh kg^−1 at a power density of 440 W kg^−1.Our novel strategy to construct ultrathin 2D MOF with unique properties can be extended to synthesize various MOF-based functional materials for diverse applications.     

Multiband Superconductors Close to a 3D–2D Electronic Topological Transition

Within the two-band model of superconductivity, we study the dependence of the critical temperature T _c and of the isotope exponent α in the proximity to an electronic topological transition (ETT). The ETT is associated with a 3D–2D crossover of the Fermi surface of one of the two bands: the σ subband of the diborides. Our results agree with the observed dependence of T _c on Mg content in A $_{1-x}{\rm Mg}_x{\rm B}_2$ (A?=?Al or Sc), where an enhancement of T _c can be interpreted as due to the proximity to a ‘shape resonance.’ Moreover we have calculated a possible variation of the isotope effect on the superconducting critical temperature by tuning the chemical potential.     

Stereopsis-Inspired 3D Visual Imaging System Based on 2D Ruddlesden–Popper Perovskite

Stereopsis is of great important functions for humans to perceive and interact with the world. To realize the function of stereoscopic imaging, optoelectronic sensors shall possess good photoresponsive performance, multidirectional sensing, and 3D building capabilities. However, the current imaging sensors are mainly focused on 2D imaging, limiting their practical application scenarios. In this study, a stereopsis-inspired flexible 3D visual imaging system (VIS) based on 2D Ruddlesden–Popper perovskite is demonstrated. The 3D-VIS consists of 800 device units, each of which demonstrates excellent photoresponse performance, mechanical characteristics, and environmental stability. In addition to the capability of detecting 2D reflective images, the 3D-VIS realizes the function of detecting the depth of field and fusing object projections of two directions to invert the 3D image by utilizing voxels to rebuild the spatial structure of the object. In the future, the 3D-VIS will have broad application prospects in medical imaging, virtual reality, industrial automation, and other fields.     

Photoinduced Defect Engineering: Enhanced Photothermal Catalytic Performance of 2D Black In2O3−x Nanosheets with Bifunctional Oxygen Vacancies

Photothermal CO₂ reduction technology has attracted tremendous interest as a solution for the greenhouse effect and energy crisis, and thereby it plays a critical role in solving environmental problems and generating economic benefits. In₂O_3−x has emerged as a potential photothermal catalyst for CO₂ conversion into CO via the light-driven reverse water gas shift reaction. However, it is still a challenge to modulate the structural and electronic characteristics of In₂O₃ to enhance photothermocatalytic activity synergistically. In this work, a novel route to activate inert In(OH)₃ into 2D black In₂O_3−x nanosheets via photoinduced defect engineering is proposed. Theoretical calculations and experimental results verify the existence of bifunctional oxygen vacancies in the 2D black In₂O_3−x nanosheets host, which enhances light harvesting and chemical adsorption of CO₂ molecules dramatically, achieving 103.21 mmol g_cat⁻¹ h⁻¹ with near-unity selectivity for CO generation and meanwhile excellent stability. This study reveals an exciting phenomenon that light is an ideal external stimulus on the layered In₂O₃ system, and its electronic structure can be adjusted efficiently through photoinduced defect engineering; it can be anticipated that this synthesis strategy can be extended to wider application fields.     

Optical,thermal and radiation shielding properties of B2O3–NaF–PbO–BaO–La2O3 glasses

Journal of Materials Science: Materials in Electronics - The&nbsp;techniques&nbsp;of&nbsp;melt-quenching have been used to generate 53B2O3—2NaF—27PbO – $$(20-x)$$...     

Boosting Li–O2 Battery Performance via Coupling of P–N Site-Rich N,P Co-Doped Graphene-Like Carbon Nanosheets with Nano-CePO4

Development of efficient and robust cathode catalysts is critical for the commercialization of Li-O₂ batteries (LOBs). Herein, a well-designed CePO₄@N-P-CNSs cathode catalyst for LOBs via coupling P-N site-rich N, P co-doped graphene-like carbon nanosheets (N-P-CNSs) with nano-CePO₄ via a novel “in situ derivation” coupling strategy by in situ transforming the P atoms of P-C sites in N-P-CNSs to CePO₄ is reported. The CePO₄@N-P-CNSs exhibit superior bifunctional ORR/OER activity relative to commercial Pt/C-RuO₂ with an overall overpotential of 0.64 V (vs RHE). Moreover, the LOB with CePO₄@N-P-CNSs as the cathode catalyst delivers a low charge overpotential of 0.67 V (vs Li/Li⁺), high discharge capacity of 29774 mAh g⁻¹ at 100 mA g⁻¹ and long cycling stability of 415 cycles, respectively. The remarkably enhanced LOB performance is attributable to the in situ derived CePO₄ nanoparticles and the P-N sites in N-P-CNSs, which facilitate increased bifunctional ORR/OER activity, promote the rapid and effective decomposition of Li₂O₂ and inhibit the formation of Li₂CO₃. This work may provide new inspiration for designing efficient, durable, and cost-effective cathode catalysts for LOBs.     

Sm3+-doped La2O3–Al2O3–SiO2-glasses: structure, fluorescence and thermal expansion

This paper reports on the effect of the chemical composition on the glass structure, the coefficients of thermal expansion and the fluorescence properties of Sm³⁺-doped La₂O₃–Al₂O₃–SiO₂-glasses. The silica concentration was varied between 50 and 70 mol% and the La₂O₃:Al₂O₃ ratio between 50:50 and 30:70. The glass formation and the densities are evaluated and FTIR reflectance spectra, coefficients of thermal expansion and fluorescence lifetimes are determined. It is shown that high SiO₂ concentrations and low La₂O₃:Al₂O₃ ratios result in relatively high fluorescence lifetime (2.19 ms, ⁴G_5/2) and low coefficients of thermal expansion (4.6 × 10^?6/K). The coefficients of thermal expansion and the fluorescence lifetimes show a linear dependency on the ratio LaO_3/2/(AlO_3/2 + SiO₂).     

Characterization of SiO2–Na2O–Fe2O 3–CaO–P2O 5–B 2O 3 glass ceramics

Bioactivity and magnetic properties were investigated in glass and glass ceramics based on the SiO₂–Na₂O–Fe₂O₃–CaO–P₂O₅–B₂O₃ system to find their suitability as thermoseed for hyperthermia treatment of cancer. The effect of change in compositions on bioactivity was examined in simulated body fluids. The glass ceramic samples exhibit Na₃CaSi₃O₈ and Na_3-XFe_XPO₄ phases. After dipping the glass ceramic samples in simulated body fluids silica hydrogel first forms, followed by an amorphous calcium phosphate layer. Magnetic and microwave resonance experiments further demonstrate the potential of these glass ceramics for possible use in hyperthermia.     

Anchoring and Catalytic Effects of rGO Supported VS2 Nanosheets Enable High-Performance Li–Organosulfur Battery

As a high-energy-density cathode material, organosulfur has great potential for lithium batteries. However, their practical application is plagued by electronic/ionic insulation and sluggish redox kinetics. Hence, our strategy is to design a self-weaving, freestanding host material by introducing reduced graphene oxide–supported VS₂ nanosheets (VS₂-rGO) and carbon nanotubes (CNTs) for lithium–phenyl tetrasulfide (Li–PTS) batteries. Unique host materials not only provide physicochemical confinement of active materials to boost the utilization but also catalyze the conversion of active materials to accelerate redox kinetics. Therefore, Li–PTS cell based on the 3D VS₂-rGO-CNTs (VSGC) host material shows excellent cyclability, with a slow capacity decay rate of 0.08% per cycle over 500 cycles at 0.5 C, and a high areal capacity of 3.1 mAh cm⁻² with the PTS loading of 7.2 mg cm⁻². More importantly, the potential for practical applications is highlighted by the flexible pouch cell with a high areal capacity (4.1 mAh cm⁻²) and a low electrolyte/PTS ratio (3.5 µL mg⁻¹). This work sheds light on elevating the electrochemical performance of Li–organosulfur batteries through the effective catalytic and adsorbed host material.     

Performance of Pt–C,Cr_7C_3–Cr_3C_2, Cr_3C_2–C,and Ru–C Fixed Points for Thermocouple Calibrations Above 1600 ^{\circ }C

A series of high-temperature fixed points (HTFPs) Pt–C (1738 \(^{\circ }\mathrm {C}), \text {Cr}_{7}\text {C}_{3}{-\text {Cr}}_{3}\text {C}_{2}\,(1742\,^{\circ } \mathrm{C}), \text {Cr}_{3}\text {C}_{2}{-\text {C}}\,(1826\,^{\circ }\mathrm{C})\) , and Ru-C (1953 \(^{\circ }\text {C}\) ) have been constructed at the National Physical Laboratory (NPL) and the Laboratoire National de métrologie et d’Essais and Conservatoire national des arts et métiers (LNE-Cnam). These are required for the calibration of high-temperature thermocouples in the framework of work package 6 of the European Metrology Research Programme IND01 project “HiTeMS.” The goal of this work package is to establish a European capability that can determine low-uncertainty reference functions of non-standard high-temperature thermocouples. For reference functions to be widely applicable, measurements must be performed by more than one institute and preferably by more than one method. Due to the high price of the ingot materials, miniature HTFP cells are used. NPL and LNE-Cnam constructed their HTFP cells with different designs; these are described here, together with the performance of the cells using both radiation thermometry and thermocouples. The melting temperature of the Ru–C cells (for thermocouple calibrations) was determined using radiation thermometry at both NPL and LNE-Cnam, and the two results are compared. The suitability of the cells for calibration of W–Re and Rh–Ir thermocouples is evaluated, and some results are presented. Some discussion is given regarding the materials challenges when calibrating Rh–Ir thermocouples up to 2000 \(^{\circ }\) C.     

Electrical conductivity studies of Bi2O3–Li2O–ZnO–B2O3 glasses

Ac conductivity measurements and its analysis has been performed on xBi₂O₃–(65?x)Li₂O–20ZnO–15B₂O₃ (0 ≤ x ≤ 20) glasses in the temperature range 30–300 °C and a frequency range of 100 Hz to 1 MHz. The dc conductivity increased and the activation energy decreased with lithium content. The frequency dependent conductivity has been analyzed employing conductivity and modulus formalisms. The onset of conductivity relaxation shifts towards higher frequencies with temperature. The Almond–West conductivity formalism is used to explain the scaling behavior, and the relaxation mechanism is independent of temperature.