Jing Zhang

Abstract

The artificial nervous system proves the great potential for the emulation of complex neural signal transduction. However, a more bionic system design for bio-signal transduction still lags behind that of physical signals, and relies on additional external sources. Here, we present a zero-voltage-writing artificial nervous system (ZANS) that integrates a bio-source-sensing device (BSSD) for ion-based sensing and power generation with a hafnium-zirconium oxide-ferroelectric tunnel junction (HZO-FTJ) for the continuously adjustable resistance state. The BSSD can use ion bio-source as both perception and energy source, and then output voltage signals varied with the change of ion concentrations to the HZO-FTJ, which completes the zero-voltage-writing neuromorphic bio-signal modulation. In view of in-/ex-vivo biocompatibility, we show the precise muscle control of a rabbit leg by integrating the ZANS with a flexible nerve stimulation electrode. The independence on external source enhances the application potential of ZANS in robotics and prosthetics.

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Nature Chemistry, Published online: 17 May 2024; doi:10.1038/s41557-024-01525-w

Liquid droplets form in cells to concentrate specific biomolecules (while excluding others) in order to perform specific functions. The molecular mechanisms that determine whether different macromolecules undergo co-partitioning or exclusion has so far remained elusive. Now, two studies uncover key principles underlying this selectivity.

Silicon-based avalanche photodetectors (APDs) have emerged as crucial devices in imaging and optical communication systems. For challenges such as silicon bandgap, high operating voltage, and large noise, an innovative approach to fabricate highly sensitive multilayer graphene/epitaxial silicon near-infrared (NIR) APDs is introduced. This study also offers the opportunity to develop CMOS-compatible room temperature NIR image sensors and signal receivers.

Abstract

2D materials and their heterostructures exhibit considerable potential in the development of avalanche photodetectors (APDs) with high gain, response, and signal-to-noise ratio. These materials hold promise in addressing inherent technical challenges associated with APDs, such as low light absorption coefficient, elevated noise current, and substantial power consumption due to high bias resulting in only moderate current gain. In this work, a macro-assembled graphene nanofilm (nMAG)/epitaxial silicon (epi-Si) vertical heterostructure photodetector with a responsivity of 0.38 A W⁻¹ and a response time of 1.4 µs is reported. The photodetectors use high-quality nMAG as the absorption layer and a lightly-doped epi-Si layer as the multiplication region under the avalanche mode to provide a high responsivity (2.51 mA W⁻¹) and detectivity (2.67 × 10⁹ Jones) at 1550 nm, which can achieve high-resolution imaging. In addition, the APD displays a weak noise level and an avalanche gain of M = 1123. It can work with relatively low avalanche turn-on voltages and achieve self-quenching by switching from illumination to dark during avalanche multiplication, with a real-time data transfer rate of 38 Mbps in near-infrared light communication data links. The proposed structure enables the fabrication of high-performance APDs in the infrared range using complementary-metal-oxide-semiconductor (CMOS)-compatible processes.

This article presents the distinct thickness-related properties of boron nitride nanosheets (BNNSs), encompassing Raman signatures, unique adsorption behavior, mechanical properties, thermal conductivity, and thermal expansion coefficients. It delves into the mechanisms governing thickness effects and explores BNNS applications in surface-enhanced Raman spectroscopy, metal-enhanced fluorescence, and thermal management.

Abstract

Owing to its exceptional properties and wide-ranging potential applications from aerospace to medicine, hexagonal boron nitride (h-BN) has garnered considerable attention over the past decades. Boron nitride nanosheets (BNNSs), atomically thin h-BN, not only inherit most of the outstanding properties of h-BN but also exhibit superior characteristics compared to their bulk counterpart due to their reduced thickness, such as special adsorption behaviors and enhanced thermal conductivity. Furthermore, BNNSs display distinct thickness-dependent properties from graphene and other 2D materials, such as unique mechanical response under indentation. This feature article provides an overview of the thickness-related special properties of BNNSs, primarily derived from mechanically exfoliated h-BN single crystals. These properties span various domains, including Raman signatures, molecule adsorption-induced conformational changes, mechanical properties, thermal conductivity, and thermal expansion coefficients. Moreover, the feature article explores the underlying mechanisms governing these atomic-scale thickness effects. Leveraging their unique properties, the feature article investigates diverse applications of BNNSs, encompassing surface-enhanced Raman spectroscopy, metal-enhanced fluorescence, and isotropic thermal management.

Abstract

Deterministic integration of phase-pure Ruddlesden-Popper (RP) perovskites has great significance for realizing functional optoelectronic devices. However, precise fabrications of artificial perovskite heterostructures with pristine interfaces and rational design over electronic structure configurations remain a challenge. Here, the controllable synthesis of large-area ultrathin single-crystalline RP perovskite nanosheets and the deterministic fabrication of arbitrary 2D vertical perovskite heterostructures are reported. The 2D heterostructures exhibit intriguing dual-peak emission phenomenon and dual-band photoresponse characteristic. Importantly, the interlayer energy transfer behaviors from wide-bandgap component (WBC) to narrow-bandgap component (NBC) modulated by comprising quantum wells are thoroughly revealed. Functional nanoscale photodetectors are further constructed based on the 2D heterostructures. Moreover, by combining the modulated dual-band photoresponse characteristic with double-beam irradiation modes, and introducing an encryption algorithm mechanism, a light communication system with high security and reliability is achieved. This work can greatly promote the developments of heterogeneous integration technologies of 2D perovskites, and could provide a competitive candidate for advanced integrated optoelectronics.

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Abstract

Electronic skin (e-skin), a skin-like wearable electronic device, holds great promise in the fields of telemedicine and personalized healthcare because of its good flexibility, biocompatibility, skin conformability, and sensing performance. E-skin can monitor various health indicators of the human body in real time and over the long term, including physical indicators (exercise, respiration, blood pressure, etc.) and chemical indicators (saliva, sweat, urine, etc.). In recent years, the development of various materials, analysis, and manufacturing technologies has promoted significant development of e-skin, laying the foundation for the application of next-generation wearable medical technologies and devices. Herein, we discuss the properties required for e-skin health monitoring devices to achieve long-term and precise monitoring and summarize several detectable indicators in the health monitoring field. Subsequently, the applications of integrated e-skin health monitoring systems are reviewed. Finally, current challenges and future development directions in this field are discussed. This review is expected to generate great interest and inspiration for the development and improvement of e-skin and health monitoring systems.

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Nature Nanotechnology, Published online: 17 May 2024; doi:10.1038/s41565-024-01664-8

A single monolayer semiconductor integrated into a plasmonic tunnel junction exhibits electroluminescence with photon energies that exceed the excitation electron potential. This phenomenon is shown to be indirectly triggered by inelastically tunnelling electrons.

In this review, it is described how methods from materials science are being used to understand and control the behavior of biological cells in elastic and structured environments. This field currently moves from single cells to cell collectives and organoids, and from 2D to 3D environments. Special emphasis is placed on the role of mathematical modeling.

Abstract

With the advent of mechanobiology, cell shape and forces have emerged as essential elements of cell behavior and fate, in addition to biochemical factors such as growth factors. Cell shape and forces are intrinsically linked to the physical properties of the environment. Extracellular stiffness guides migration of single cells and collectives as well as differentiation and developmental processes. In confined environments, cell division patterns are altered, cell death or extrusion might be initiated, and other modes of cell migration become possible. Tools from materials science such as adhesive micropatterning of soft elastic substrates or direct laser writing of 3D scaffolds have been established to control and quantify cell shape and forces in structured environments. Herein, a review is given on recent experimental and modeling advances in this field, which currently moves from single cells to cell collectives and tissue. A very exciting avenue is the combination of organoids with structured environments, because this will allow one to achieve organotypic function in a controlled setting well suited for long-term and high-throughput culture.

Mechanical Metamaterials

In article number 2301133, Martin Wegener, Martin Bastmeyer, Motomu Tanaka, and co-workers design and manufacture microstructured bio-metamaterials based on an elastic photoresist and two-photon laser printing. The differential responses of human mesenchymal stem cells, both on the cellular level and the sub-cellular level, correlate with the calculated effective elastic properties of the bio-metamaterials, suggesting the potential of bio-metamaterials towards mechanical regulation of cells by the arrangement of unit cells.

Mesenchymal stem cells experience and respond to the effective elastic properties of three types of metamaterials made from an elastomer-like photoresist manufactured by two-photon laser printing both on the cellular and the subcellular level. These findings suggest the potential of “bio-metamaterials” toward mechanical regulation of cell behavior by the design of unit cells without changing the base material.

Abstract

Cell behaviors significantly depend on the elastic properties of the microenvironments, which are distinct from commonly used polymer-based substrates. Artificial elastic materials called metamaterials offer large freedom to adjust their effective elastic properties as experienced by cells, provided (i) the metamaterial unit cell is sufficiently small compared to the biological cell size and (ii) the metamaterial is sufficiently soft to deform by the active cell contraction. Thus, metamaterials targeting bio-applications (bio-metamaterials) appear as a promising path toward the mechanical control of stem cells. Herein, human mesenchymal stem cells (hMSCs) are cultured on three different types of planar periodic elastic metamaterials. To fulfill the above two key requirements, microstructured bio-metamaterials have been designed and manufactured based on a silicon elastomer-like photoresist and two-photon laser printing. In addition to the conventional morphometric and immunocytochemical analysis, the traction force that hMSCs exert on metamaterials are inferred by converting the measured displacement-vector fields into force-vector fields. The differential responses of hMSCs, both on the cellular level and the sub-cellular level, correlate with the calculated effective elastic properties of the bio-metamaterials, suggesting the potential of bio-metamaterials toward mechanical regulation of cell behaviors by the arrangement of unit cells.

Vertical-structure devices offer distinct advantages in terms of integration feasibility, efficiency and stability. However, poor out-of-plane carrier transport in layered 2D perovskite hampers vertical-structure X-ray detection performance. Layered CsPb₂Br₅ single crystals, grown with ligand-assisted methods, achieve excellent out-of-plane µτ product. The resulting vertical-structure X-ray detectors demonstrate a sensitivity of 8865.6 µC Gyair⁻¹ cm⁻² and good imaging performance.

Abstract

The emerging 2D layered perovskites have promising optoelectronic properties, good intrinsic stability and reduced ion migration, making them effective for detecting X-ray radiation. However, their application is constrained by poor out-of-plane carrier transport. In this study, inch-sized high-quality CsPb₂Br₅ layered single crystals (SCs) are developed using an organic ligand-assisted solution process. By modifying the surface energy, the anisotropy of crystal growth is conquered, resulting in CsPb₂Br₅ SCs with sufficient thickness for X-ray detection. Importantly, this modification significantly enhanced the crystal quality as the grown CsPb₂Br₅ SCs exhibited longer photoluminescence lifetime and smaller trap density. Notably, the CsPb₂Br₅ SCs demonstrate unprecedented out-of-plane carrier transport, achieving a high carrier mobility-lifetime product of 2.53 × 10⁻² cm²V⁻¹. This can be attributed to the small interlayer distance and the strong interlayer force of Cs─Br bonding. Furthermore, CsPb₂Br₅ SCs possess other intriguing attributes for X-ray detection, including high bulk resistivity and outstanding thermal stability. These advantageous properties enable high-performance vertical-structure X-ray detection with a superior sensitivity of up to 8865.6 µC Gy_air ⁻¹cm⁻² and a low detectable dose rate of 12.7 nGy_airs⁻¹. Additionally, CsPb₂Br₅ SCs exhibit high spatial resolution in X-ray imaging and exceptional thermal stability, making them promising candidates for nondestructive determination.

Large-area continuous thin films of metastable trigonal Cr₂S₃ are grown by ultralow gas-flow governed dynamic transport methods. The anisotropic SHG response of as-prepared Cr₂S₃ demonstrated effective second-order nonlinearity of 48.0 pm V⁻¹, in which sulfur vacancies and dangling bonds could break the surface central-symmetry and contribute nonlinear optical polarizabilities, providing a new understanding of SHG for nonlayered 2D materials.

Abstract

As for nonlayered 2D polymorphic materials, especially for Cr-based chalcogenides, large-area thin film growth with phase control is considered the most important synthesis challenge for magnetic, electronic, and optoelectronic devices. However, the synthesis methods of large continuous thin films for nonlayered 2D materials are still limited and rarely reported, also for the phase control growth, which is inhibited by isotropic 3D growth and similar Gibbs free energy for different phases. Herein, enhanced mass transport chemical vapor deposition is established to achieve the control synthesis of trigonal Cr₂S₃ thin films, in which the stable boundary layer supplies the continuous reaction species and tunes the reaction kinetics. The trigonal phase formation is confirmed by atomic structure characterization, optical absorption and piezoelectric measurements, demonstrating unique physical properties different from rhombohedral phase. The trigonal Cr₂S₃ thin films show obvious layer independent and dissimilar angle-resolved harmonic generation, indicating the surface broken symmetry that can be understood by the combination of negligible piezoelectric response for bulk. The work presents the large-area synthesized strategy by the modification of mass transport for nonlayered 2D materials with new phase formation and establishes the surface symmetry breaking dominated SHG mechanism for future nonlinear optical materials.

Electrochemical analysis is a highly sensitive, cost-effective, and rapidly advancing technique with broad applicability. Its integration with diverse signal modes like light, magnetic, and thermal offers biosensors with enhanced capabilities. By combining multi-modes/signals, detection accuracy improves dramatically, reducing false positives or negatives.

Abstract

Electrochemical (EC) analysis has emerged as a high-sensitivity, reliable, cost-effective, and rapidly evolving technique that has garnered significant attention across diverse domains. Furthermore, EC-based techniques hold great potential for miniaturization and integration. The integration of EC techniques with diverse mode/signal (such as light, magnetic, and thermal signals, etc.) provides unique opportunities for biosensors to acquire more information through a single sensing platform. By coupling multiple signals or processing them logically, the detection accuracy can be further improved, and the probability of false positives or negatives can be minimized. In this review, a thorough analysis of multi- mode/signal sensors in the field of EC sensing is conducted, along with their integration with various sensing techniques (e.g., fluorescence, photothermal, colorimetry, microfluidic, etc.). The aim is to delve into the latest advances, potential applications, as well as challenges in multi-mode/signal biosensors, where the utilization of multiple sensing modalities helps enhance accuracy, sensitivity, and selectivity. This review provides new insight into the synergistic effects of integrating EC sensing with other techniques, aiming to shed light on the near-future developments in EC-integrated multi-mode/signal biosensors.

Abstract

Two-dimensional (2D) Janus Transition Metal Dichalcogenides (TMDs) have attracted much interest due to their exciting quantum properties arising from their unique two-faced structure, broken-mirror symmetry, and consequent colossal polarisation field within the monolayer. While efforts have been made to achieve high-quality Janus monolayers, the existing methods rely on highly energetic processes that introduce unwanted grain-boundary and point defects with still unexplored effects on the material's structural and excitonic properties Through High-resolution scanning transmission electron microscopy (HRSTEM), density functional theory (DFT), and optical spectroscopy measurements; this work introduces the most encountered and energetically stable point defects. It establishes their impact on the material's optical properties. HRSTEM studies show that the most energetically stable point defects are single (V_S  and V_Se ) and double chalcogen vacancy (V_S −V_Se ), interstitial defects (M_i), and metal impurities (M_W) and establish their structural characteristics. DFT further establishes their formation energies and related localized bands within the forbidden band. Cryogenic excitonic studies on h-BN-encapsulated Janus monolayers offer a clear correlation between these structural defects and observed emission features, which closely align with the results of the theory. The overall results introduce the defect genome of Janus TMDs as an essential guideline for assessing their structural quality and device properties.

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Abstract

Two-dimensional (2D) polarization materials have emerged as promising candidates for meeting the demands of device miniaturization, attributed to their unique electronic configurations and transport characteristics. Although the existing inherent and sliding mechanisms have been increasingly investigated in recent years, strategies for inducing 2D polarization with innovative mechanisms remain rare. In this study, we introduce a novel 2D Janus state by modulating the puckered structure. Combining scanning probe microscopy, transmission electron microscopy, and density functional theory calculations, we realized force-triggered out-of-plane and in-plane dipoles with distorted smaller warping in GeSe. The Janus state is preserved after removing the external mechanical perturbation, which could be switched by modulating the sliding direction. Our work offers a versatile method to break the space inversion symmetry in a 2D system to trigger polarization in the atomic scale, which may open an innovative insight into configuring novel 2D polarization materials.

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Nature Nanotechnology, Published online: 15 May 2024; doi:10.1038/s41565-024-01672-8

FRETfluors—nanostructures with Cy3 and Cy5 dyes and a DNA scaffold—are used to generate distinct spectroscopic signals from different configurations and mixtures of mRNA, dsDNA and proteins in an anti-Brownian electrokinetic trap for single-molecule multiplexed sensing.

Abstract

The quantity of sensor nodes within current computing systems is rapidly increasing in tandem with the sensing data. The presence of a bottleneck in data transmission between the sensors, computing, and memory units obstructs the system's efficiency and speed. To minimize the latency of data transmission between units, novel in-memory and in-sensor computing architectures are proposed as alternatives to the conventional von Neumann architecture, aiming for data-intensive sensing and computing applications. The integration of two-dimensional (2D) materials and 2D ferroelectric materials has been expected to build these novel sensing and computing architectures due to the dangling-bond-free surface, ultra-fast polarization flipping and ultra-low power consumption of the 2D ferroelectrics. Here, we review the recent progress of 2D ferroelectric devices for in-sensing and in-memory neuromorphic computing. Experimental and theoretical progresses on 2D ferroelectric devices, including passive ferroelectrics-integrated 2D devices and active ferroelectrics-integrated 2D devices, are reviewed followed by the integration of perception, memory, and computing application. Notably, 2D ferroelectric devices have been used to simulate synaptic weights, neuronal model functions, and neural networks for image processing. As an emerging device configuration, 2D ferroelectric devices have the potential to expand into the sensor-memory and computing integration application field, leading to new possibilities for modern electronics.

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Abstract

Achieving thermochromic afterglow (TCAG) in a single material for advanced information encryption remains a significant challenge. Herein, TCAG in carbon dots (CDs)-inked paper (CDs@Paper) was achieved by tuning the temperature-dependent dual-mode afterglow of room-temperature phosphorescence (RTP) and thermally activated delayed fluorescence (TADF). The CDs were synthesized through thermal treatment of levofloxacin in melting boric acid with post-purification via dialysis. CDs@Paper exhibited TCAG and excitation-dependent afterglow color properties. The TCAG of CDs@Paper exhibited dynamic color changes from blue at high temperatures to yellow at low temperatures by adjusting the proportion of the temperature-dependent TADF and phosphorescence. Notably, two-photon afterglow in CDs-based afterglow materials and time-dependent two-photon afterglow colors were achieved for the first time. Moreover, leveraging the opposite emission responses of phosphorescence and TADF to temperature, CDs@Paper demonstrated TCAG with temperature-sensing capabilities across a wide temperature range. Furthermore, a CDs@Paper-based 3D code containing color and temperature information was successfully developed for advanced dynamic information encryption.

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Abstract

Intracranial implants for diagnosis and treatment of brain diseases have been developed over the past few decades. However, the platform of conventional implantable devices still relies on invasive probes and bulky sensors in conjunction with large-area craniotomy and provides only limited biometric information. Here, we report an implantable multi-modal sensor array that can be injected through a small hole in the skull and inherently spread out for conformal contact with the cortical surface. The injectable sensor array, composed of graphene multi-channel electrodes for neural recording and electrical stimulation and MoS₂-based sensors for monitoring intracranial temperature and pressure, was designed based on a mesh structure whose elastic restoring force enables the contracted device to spread out. We demonstrated that the sensor array injected into a rabbit's head can detect epileptic discharges on the surface of the cortex and mitigate it by electrical stimulation while monitoring both intracranial temperature and pressure. This method provides good potential for implanting a variety of functional devices via minimally invasive surgery.

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High-quality transition metal dichalcogenide (TMD) thin films can be synthesized using a two-step approach where a solid transition metal precursor layer is converted in a chalcogen-containing atmosphere to a TMD. Herein, a critical review of this method, demonstrating its versatility and outlining key features, applications, and outlook on this method's impact in the TMD synthesis community is given.

Abstract

The widely studied class of two-dimensional (2D) materials known as transition metal dichalcogenides (TMDs) are now well-poised to be employed in real-world applications ranging from electronic logic and memory devices to gas and biological sensors. Several scalable thin film synthesis techniques have demonstrated nanoscale control of TMD material thickness, morphology, structure, and chemistry and correlated these properties with high-performing, application-specific device metrics. In this review, the particularly versatile two-step conversion (2SC) method of TMD film synthesis is highlighted. The 2SC technique relies on deposition of a solid metal or metal oxide precursor material, followed by a reaction with a chalcogen vapor at an elevated temperature, converting the precursor film to a crystalline TMD. Herein, the variables at each step of the 2SC process including the impact of the precursor film material and deposition technique, the influence of gas composition and temperature during conversion, as well as other factors controlling high-quality 2D TMD synthesis are considered. The specific advantages of the 2SC approach including deposition on diverse substrates, low-temperature processing, orientation control, and heterostructure synthesis, among others, are featured. Finally, emergent opportunities that take advantage of the 2SC approach are discussed to include next-generation electronics, sensing, and optoelectronic devices, as well as catalysis for energy-related applications.

As shown, macroscale superlubricity with high pressure on engineering steel is enabled by partially oxidized violet phosphorus nanosheets (oVP) in poly alpha olefin (PAO) oil. The outstanding tribological performance (coefficient of friction: 0.0064) and load-bearing capacity (interfacial maximal stress: 810 MPa) are mainly attributed to a reliable chemical tribofilm formed on on steel surface with the catalyzation effect of oVP.

Abstract

As a novel cross-structured 2D material, violet phosphorus (VP) promises to further develop the dynamic performance, energy efficiency, and service lifetime of mechanical components owing to its high strength and toughness, large carrier mobility, wide bandgap, and good friction-reducing properties. In this work, the partially oxidized violet phosphorus nanosheets (oVP) are synthesized and employed as the lubricating additives in the poly alpha olefin (PAO) oil environment with less oleic acid (OA) improver, which can trigger the macroscale superlubricity on the diamond-like carbon (DLC) film deposited steel surface at high loading pressures (>800 MPa) and sliding speeds (>0.1 m s⁻¹). The friction coefficient (COF) of the steel-DLC tribopair lubricated by the oVP-PAO oil can reduce down to 0.0064 with little wear. At the high-pressure sliding interface, the force-thermal coupling action during the running-in process promotes the cleavage and recombination of oVP nanosheets and OA molecules to form a reliable chemical adsorption tribofilm mainly composed of phosphorus oxides and amorphous carbon, which prevents the original asperities from direct contact and provides an ultralow shear strength. These findings suggest a new method to achieve macroscale oil-based high-pressure superlubricity for engineering steel through the lubrication and catalyzation effects of oVP.

Through the self-leveling and self-evaporative properties of gelatin solution, nano-scale flexible transparent films are obtained. Leveraging its adhesive properties with a mixture of liquid metal, wet-adhesive flexible electronic devices are fabricated, enabling rapid adhesion in moist environments in vivo and improving the accuracy and stability of implanted monitoring.

Abstract

Implantable flexible electronic has attracted significant research interest in various fields. However, it still faces the challenge of simultaneously achieving tight adhesion to tissues in a mildly wet environment and possessing excellent biocompatibility to reduce immune rejection reactions after implantation. Here, a degradable wet-adhesive flexible electronic device based on liquid metal and ultrathin gelatin film is developed. The ultrathin gelatin film forms numerous hydrogen bonds with tissue in a slightly humid environment, rapidly constructing a wet-adhesive interface without damaging tissue structure. Inkjet printing is utilized to pattern the mixture of liquid metal and PVP on the surface of the ultrathin gelatin to create flexible patch. With the excellent conductivity of liquid metal, low toxicity, and similarity to natural tissue components of gelatin, flexible patch exhibits outstanding biocompatibility and fatigue resistance. It can be implanted in the body for up to 6 weeks, retaining monitoring capabilities and resisting 1 000 000 cycles of bending fatigue. This study provides a novel strategy for the future development of implantable flexible electronics.

Metal halide perovskite single crystals (MHP SCs) have attracted much attention due to their dramatically enhanced optoelectronic properties and improved stability compared with their polycrystalline counterparts. The recent advancements in MHP SC-based light-emitting diodes, potential strategies for further device performance improvement and future application prospects in electrically pumped lasers are discussed in this review.

Abstract

Metal halide perovskite single crystals (MHP SCs) have attracted extensive attention due to their superior properties, such as higher carrier mobility, longer carrier diffusion length, and better stability than their polycrystalline counterparts. In particular, the suppression of ion migration and Auger recombination endows MHP SCs with excellent electroluminescence (EL) properties, thus holding great potential for highly efficient and stable light-emitting devices. In this review, general overview of MHP crystal structures are begin, and highlight the merits of MHP SCs in terms of outstanding optoelectronic properties and high stability. Then, appropriate growth methods of high-quality, thickness-controlled MHP SCs for EL device applications are systematically summarized. Subsequently, recent advancements in developing MHP SC-based perovskite light-emitting diodes (PeLEDs) are discussed, and the effective strategies to further enhance the device performance are reviewed. Moreover, the potential application of MHP SCs for electrically pumped lasers is highlighted. Finally, the review is concluded with a detailed account of the current challenges and a perspective on the key approaches and opportunities on the optimization of SC growth, the improvement of device performance and the integration of SC-based optoelectronic devices.

This study assesses the potential of layered 2D materials for gas sensing using second harmonic generation (SHG). It focuses on the adsorption behaviors of oxygen, ammonia, and water vapor on WS₂ surfaces. By applying the simplified bond hyperpolarizability model, it confirms physical adsorption and explores competitive interactions between gases, aligning with Langmuir's model and theoretical predictions from density functional theory.

Abstract

While understanding the competitive adsorption behavior of gas sensor is important, it is yet to be unraveled. Especially for the influence of water molecules to the gas adsorbed on 2D materials. This study explores the potential of layered 2D materials as a candidate material for gas sensing, employing non-destructive measurement, and second harmonic generation (SHG). The investigation focuses on analyzing oxygen, ammonia, and water vapor adsorbed on a WS₂ surface by studying the evolutions in electric dipole and electric field. Leveraging the simplified bond hyperpolarizability model (SBHM), a foundation is established for gas sensors utilizing high-quality 2D materials. This approach facilitates the detection of material modifications in response to environmental influences, including the inevitable water molecules. The obtained hyperpolarizability from SBHM exhibits remarkable consistency with Langmuir's adsorption model, confirming the physical adsorption in the system. In addition, the competitive effects between gases are explored by comparing experimental results with theoretical predictions based on Boltzmann distribution and density functional theory (DFT) calculations. This highlights the effectiveness of SHG and SBHM in studying gas adsorption on layered van der Waals materials.

2D flexible magnets hold great promise in flexible spintronics. By employing an aged precursor, 2D chromium selenide with internal voids can be synthesized. The unique structure induces ferrimagnetism and a small Young's modulus. This work offers avenues for obtaining 2D magnets with desired mechanical properties, paving the way for future flexible spintronics.

Abstract

2D magnetic materials with distinct mechanical properties are of great importance for flexible spintronics. However, synthesizing 2D magnets with atomic thickness is challenging and their mechanical properties remain largely unexplored. Here, the growth of a ferrimagnetic 2D Cr₉Se₁₃ with anomalous elasticity is reported by an aged-precursor-assisted method. The obtained 2D Cr₉Se₁₃ exhibits an out-of-plane ferrimagnetic order with a coercivity larger than those of conventional magnetic materials. Noteworthy, it presents decent breaking strength and a Young's modulus of 52 ± 8 GPa that is among the smallest of the 2D family. This exceptional elasticity is attributed to the unique internal voids in Cr₉Se₁₃, as evidenced by the formed edge dislocations under strain. This work not only offers a facile method to synthesize 2D magnets but also develops avenues for obtaining 2D materials with desired mechanical properties, paving the way for future flexible spintronics.

Recent advances in poly(N-isopropylacrylamide) and its copolymers, with a specific focus on their structural and compositional features in the area of sensor and biosensor applications from 2016 until now are comprehensively summarized here.

Abstract

Stimuli-responsive polymers have received increasing attention for various applications due to their ability to adapt physical and chemical properties in response to external environmental stimuli. In this regard, poly(N-isopropylacrylamide) (PNIPAM) is the most extensively studied stimuli-responsive polymer and, consequently has been prominently featured in (bio)-sensor development, adaptive coating technology, drug delivery, wound healing, tissue regeneration, artificial actuator design, sensor technology, responsive coatings, and soft robotics. This success can be mainly attributed to the accessible and versatile nature of the PNIPAM platform, thus allowing the synthesis of a wide variety of copolymer architectures, topologies and compositions. Within this review, the structural and compositional features of PNIPAM-based materials in sensor and biosensor applications are discussed with a focus on the literature from 2016 until now. The reader is provided with the current state of the art regarding PNIPAM-based sensor development and their molecular design. Finally, the challenges ahead in the successful implementation of PNIPAM-based sensors are highlighted, as well as the opportunities in the rational design of improved PNIPAM-based sensors. Altogether, this review provides comprehensive insights into the exciting and rapidly expanding field of PNIPAM-based sensing systems, which will benefit the chemical, pharmaceutical, textile, and biotech industries is believed.

Various synthesis techniques on how to subtly incorporate rare earth/transition metals into various matrices in the NIR are reviewed, followed by a discussion of strategies to improve the excitation absorption and emission efficiency of NIR materials. Finally, functionalization strategies and their applications are presented. As such it provides a valuable overview of the field.

Abstract

The spotlight has shifted to near-infrared (NIR) luminescent materials emitting beyond 1000 nm, with growing interest due to their unique characteristics. The ability of NIR-II emission (1000–1700 nm) to penetrate deeply and transmit independently positions these NIR luminescent materials for applications in optical-communication devices, bioimaging, and photodetectors. The combination of rare earth metals/transition metals with a variety of matrix materials provides a new platform for creating new chemical and physical properties for materials science and device applications. In this review, the recent advancements in NIR emission activated by rare earth and transition metal ions are summarized and their role in applications spanning bioimaging, sensing, and optoelectronics is illustrated. It started with various synthesis techniques and explored how rare earths/transition metals can be skillfully incorporated into various matrixes, thereby endowing them with unique characteristics. The discussion to strategies of enhancing excitation absorption and emission efficiency, spotlighting innovations like dye sensitization and surface plasmon resonance effects is then extended. Subsequently, a significant focus is placed on functionalization strategies and their applications. Finally, a comprehensive analysis of the challenges and proposed strategies for rare earth/transition metal ion-doped near-infrared luminescent materials, summarizing the insights of each section is provided.