Materials Today最新文献

Two-dimensional (2D) van der Waals (vdW) heterostructures offer new platforms for exploring novel physics and diverse applications ranging from electronics and photonics to optoelectronics at the nanoscale. The studies to date have largely focused on transition-metal dichalcogenides (TMDCs) based samples prepared by mechanical exfoliation method, therefore it is of significant interests to study high-quality vdW heterostructures using novel materials prepared by a versatile method. Here, we report a two-step vapor phase growth process for the creation of high-quality vdW heterostructures based on perovskites and TMDCs, such as 2D Cs₃Bi₂I₉/MoSe₂, with a large lattice mismatch. Supported by experimental and theoretical investigations, we discover that the Cs₃Bi₂I₉/MoSe₂ vdW heterostructure possesses hybrid band alignments consisting of type-I and type-II heterojunctions because of the existence of defect energy levels in Cs₃Bi₂I₉. More importantly, we demonstrate that the type-II heterojunction in the Cs₃Bi₂I₉/MoSe₂ vdW heterostructure not only shows a higher interlayer exciton density, but also exhibits a longer interlayer exciton lifetime than traditional 2D TMDCs based type-II heterostructures. We attribute this phenomenon to the reduced overlap of electron and hole wavefunctions caused by the large lattice mismatch. Our work demonstrates that it is possible to directly grow high-quality vdW heterostructures based on entirely different materials which provide promising platforms for exploring novel physics and cutting-edge applications, such as optoelectronics, valleytronics, and high-temperature superfluidity.

Colloid science has classically concerned itself with the investigation of the properties of dispersed phases in a bulk medium. This has led to the development of a rich amount of chemistry, physics, and engineering that have facilitated the evolution and maturation of this field. One of the many developments made over the last 30 years is the introduction of particles that are heterogeneous in chemistry and shape. These heterogeneities can introduce behaviors that are not achievable in homogeneous systems and that are specific to the type and class of nonuniformity. This has led to the development of numerous technologies, two of which are Janus micromotors and solid surfactants. This review aims to familiarize the reader with the field of heterogeneous particles. We begin with an overview of various synthetic methods to produce colloidal particles that are heterogeneous in chemistry and shape. We then discuss their use as solid surfactants and autonomous micromotors. We then close by summarizing and providing a future perspective on the field.

Realizing an electrode that can stably monitor biosignals after multiple exposures to sweat is challenging. Utilizing a Janus electrode, which is composed of a stack of ultrathin hydrophobic microporous Au membrane and water-durable hydrophilic nanofiber layers, asymmetric wettability can be realized and maintained for 7 days. Thus, it can create spontaneous unidirectional sweat transport from the skin surface, ensuring that the skin-electrode interface remains dry, especially during sweating. The ultrathin hydrophobic membrane facilitates self-adhesion with an adhesion energy of 59.2 µJ cm⁻², which creates a high conformal contact to the skin and self-adhering to the hydrophilic nanofibers. The hydrophilic nanofibers exhibit excellent durability even after continuous immersion in water for up to 1 month. Additionally, a thin translucent polyvinyl alcohol nanofibers frame assists the Janus electrode in achieving highly conformable attachment to both dry and sweaty skin. The Janus electrode also exhibits excellent breathability and high mechanical stability owing to its porous structure and fine thickness. With these properties, the Janus electrode can monitor an electrocardiogram signal after dynamic activities, including physical exercise, waking up, desk work, meals, and going out for 6 days, while maintaining a stable signal-to-noise ratio of ∼ 18.8 dB.

While cellulose-based stretchable hydrogels have been extensively explored in recent years, all-cellulose hydrogels continue to face the limitation of low stretchability (less than 250 %). Herein, for the first time, we fabricate an all-cellulose hydrogel with ultrahigh stretchability that can exceed 40000 % strain. By ring opening reaction on cellulose anhydroglucose unit rings, secondary hydroxyls are converted to primary hydroxyls, enabling enhanced chain flexibility, and facilitating the formation of abundant hydrogen bonds. As a result, the obtained hydrogel displays remarkable characteristics, including record-high stretchability (44200 %), rapid self-healing property (within seconds), and the unique ability to form cellulose fiber. With simple drawing, a smooth and flexible cellulose fiber can be obtained, demonstrating good processability and a high tensile strength of 226 MPa. Furthermore, the all-cellulose hydrogel can function as a human motion sensor and electrocardiogram electrode for monitoring physiological signals. This simple yet highly effective method will not only propel the advancement of ultrastretchable all-cellulose hydrogels but also create new possibilities for wearable device applications.

As ideal and smart stimuli-responsive materials for soft actuators, artificial muscles, etc., liquid crystalline elastomers (LCEs) can respond to external stimuli, including heat, light, electricity, magnetism, humidity, etc., and make corresponding deformations. Among these external stimuli, magnetic stimulus is featured by remote and contactless control, fast, precise, extremely strong penetration, safe, easy tunability, and so on. By doping magnetic nanoparticles into LCEs, their actuation and motion can be triggered by magnetic fields or forces untetheredly, remotely, and highly precisely. Therefore, the magnetic nanoparticles endow LCEs with magneto-responsiveness, opening doors to LCEs for many unique potential uses, such as magnetic read-out, magnetic valves, magnetic switches, and so on. This review summarizes recent advances in magneto-responsive LCE nanocomposites. Their fabrication is comprehensively discussed. New properties of magneto-responsive LCEs brought by magnetic nanoparticles are also thoroughly reviewed. Their promising applications are subsequently summarized and explored.

The enhanced compositional flexibility of complex concentrated materials, which can incorporate multiple-principal elements, provides the opportunity to explore a wider range of compositions and unconventional properties in multifunctional materials. Complex concentrated oxides (CCOs) have demonstrated attractive functionalities in energy storage and catalysis applications, motivating the expansion of the boundaries of CCOs with accessible compositions and unique properties. However, the development and utilization of CCOs, especially in large-scale applications at high temperatures, pose significant challenges due to limited design strategies and fabrication techniques. To address these challenges, we develop a new complex concentrated alloy (CCA) AlCrTiVNi₅ screened from the valve metal group. Our approach has yielded a thermally grown (TG-)CCO that has not been previously reported, which demonstrates unique thermomechanical properties, including high thermodynamic stability, low thermal expansion, high fracture tolerance, and an excellent combination of strength and ductility. These initial findings are expected to offer fresh perspectives on designing and developing advanced materials that boast exceptional functionality and versatility.

Based on the “ion-confined transport” strategy, supercapacitor-diodes and switchable supercapacitors as new ion-type devices have emerged with promising applications in fields such as smart grids, energy storage chips, ionic logic circuits, and neuromorphic computing. In this review, we first clarify the mechanisms of “ion-confined transport” strategies including pore confinement, interfacial confinement and field-effect confinement, and then comprehensively summarize the development of supercapacitor-diodes and switchable supercapacitors. Subsequently, building upon the physical principles of ion-confined transport in supercapacitors, the inevitable emergence of two new types of ion-type devices, supercapacitor-memristors and supercapacitor-chips, are predicted. Finally, open issues for novel supercapacitors with ion-confined transport properties are proposed, as well as their potential applications in multifunctional energy storage, next-generation information technology, and especially integrated energy electronics.

Co-free Ni-rich single crystal LiNi_xMn_1-xO₂ (x ≥ 0.6) (denoted as SCNM) have been actively studied as a candidate cathode for high energy density and low-cost lithium-ion batteries (LIBs). However, their practical use in LIBs is significantly hindered by their poor chemo-mechanical stability and short cycle life. Herein, we show much improved structural stability and cycle life by bulk and surface modifications of SCNM. We show strong evidence that bulk Ti-doping and gradient Nb-doping are effective in stabilizing lattice oxygen and suppressing detrimental phase transformations, while LiTi_2-xNb_x(PO₄)₃ (LTNP) surface coating protects SCNM from reacting with liquid electrolyte and promotes formation of thin and robust interphase layers. As a result, LTNP-modified SCNM achieves an excellent electrochemical performance with 87.2% capacity retention after 100 cycles at high voltage of 4.4 V. This work demonstrates a new approach to stabilize lattice oxygen of Co-free and Ni-rich cathodes and their interfaces with liquid electrolytes, thus contributing to the development of high-energy–density LIBs.

Two-dimensional (2D) transition metal carbide and nitride (MXenes) and 2D transition metal borides are analogs to MXenes and are given the name MBenes. MXenes and MBenes are important 2D nanomaterials with diverse potential in various research domains of physics and chemistry. MBenes offer high conductivity, flexibility, and mechanical properties, attracting attention for energy storage applications such as mono/divalent batteries and supercapacitors. Both theoretical and experimental results confirmed the exciting potential of MBene for energy storage applications. MBenes have demonstrated a broad range of fascinating characteristics and have been extensively researched for their potential uses in energy storage and conversion devices. It is reasonable to anticipate that MBenes will have a bright future. The investigation of MBenes, on the other hand, is still in its early stages, and there are a great deal of expected features and applications that are being investigated. This review aims to provide an overview of recent advancements not only in energy storage applications but also in various other aspects, including synthetic methods, morphological and structural characteristics, and other associated properties of MBene. Finally, this critical review ends with the promising prospects, challenges, and opportunities in MBene advancements.

The outstanding emission of halide perovskites make them ideal candidates for white emission light-emitting diodes (LEDs) for lighting applications. However, many perovskites contain toxic or scarce elements and have unsatisfactory stability. Here, we report a target-driven approach, based on active learning (AL) techniques, to discover halide perovskites suitable for commercial LED applications. Based on the similarity between halide and oxide perovskites, a model trained on an oxide perovskite dataset plus six AL-selected halide perovskites exhibited excellent performance for photoluminescence quantum yield (PLQY) predictions of oxide and halide perovskites. The model proposed a strong relationship between ionic radii and PLQY, postulated to be due to the self-trap excitons derived from the Jahn-Teller deformation. A novel halide perovskite phosphor, Cs₄Zn(Bi_0.85Sb_0.15)₂Cl₁₂:0.01Mn, was designed and synthesized with the aid of the model. It exhibited an 88 % PLQY and outstanding thermal and luminescent stability. A simple white LED was fabricated from this material, exemplifying its commercial potential. This study demonstrates how machine learning techniques can accelerate discovery of next-generation phosphors for high performance single emitter-based white-light emitting devices.