Jing Zhang

For the first time, revealing MBene's DNA adsorbability. And based on its discrimination to single/double-stranded DNA and fluorescence quenching. then, a sensitive fluorescence biosensor for circulating tumor (ctDNA) detection is developed. To facilitate point-of-care testing (POCT) ctDNA, a paper-based microfluidic chip, and WeChat mini program is designed for user-friendly assay.

Abstract

The detection of circulating tumor DNA (ctDNA) in blood is significant for non-invasive cancer diagnosis and treatment monitoring. Herein, MBene nanosheets is synthesized and compared with MXene via Density Functional Theory (DFT) calculations and fluorescence kinetic evaluations, for first time, revealing MBene's exceptional DNA adsorbability and discrimination to single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA). Then, a sensitive fluorescence biosensor for ctDNA detection is developed, demonstrating impressive performance. To facilitate point-of-care testing (POCT) ctDNA, a paper-based microfluidic chip incorporated a delay area and a mixing channel is designed. The constricted-expanded structure channel optimization is guided by numerical simulations and experiments. A WeChat mini program named “ctDNA Detection” is designed for readout assay. Furthermore, cell and mice serum samples are analyzed, with Magnetic Bead@Graphene Oxide (MB@GO) and clutch probes for magnetic pre-enrichment. The results accuracy is confirmed by its consistency with standard qPCR results (AUC = 1). The successful detection of ctDNA in post-surgery mouse models underscored the biosensor's potential for cancer treatment monitoring. Thus, this research not only advanced the understanding of the MBene-DNA interaction in biosensing, but also can pave the way for novel applications in bioimaging and nanopore-based nucleic acid sequencing, leveraging the digital transformation of DNA base-MBene adsorption differences.

The work introduces a new way to improve the lasing performance of piezoelectric semiconductor materials and will expand the application of piezoelectric effects in flexible lasers and on-chip strain sensing.

Abstract

Nonlinear optics play an important role in laser technology, optical communication, integrated optics, and other fields. However, conventional two-photon lasing faces challenges such as high thresholds and large size, which hinder the miniaturization of lasers. In this study, the structure of single-crystal Au/Al₂O₃/CsPbBr₃ (ScAu/Al₂O₃/CPB) is constructed to achieve two-photon pumped frequency upconversion single-mode plasmonic lasing. The strong spatial confinement and near-field enhancement of surface plasmons in metals enable the plasmonic lasing mode output in a hybrid nanocavity, significantly reducing the lasing threshold. Additionally, by applying external mechanical strain, the resonant wavelength of the lasing mode is dynamically regulated, further reducing the threshold to 0.48 mJ cm⁻² based on piezo-electronic effect. These results provide an effective strategy for all-optical integration and the development of smaller, faster, and more efficient nanophotonics devices.

Food Safety and Monitoring

The frontispiece illustrates the digitalization of colorimetric sensor technologies in the food supply chain. Food packaging embedded with colorimetric QR codes, along with a floating screen displaying scanned data, enables real-time food quality assessment. This image highlights the transformative impact of combining digital tools with smart colorimetric sensors in enhancing safety and transparency in the food industry. More details can be found in article number 2404274 by Rona Chandrawati and co-workers.

Multifunctional photonic crystals with remarkable mechanochromic, thermochromic, solvatochromic, color/shape-recordable, self-healable, and adhesive functions have been fabricated by non-close-assembling silica particles into the unique commercially available 2-[[(Butylamino)carbonyl]oxy]ethyl acrylate with abundant stimuli-responsive and chemical/physical properties. These functions result in interesting emerging applications of photonic crystals, including multilayer optical filters, inkless printing, reconfigurable multicolor patterns, stretching-based anti-counterfeiting, etc.

Abstract

Fabricating photonic crystals (PCs) with dynamic multi-stimuli-responsive structural colors, recordable colors, and self-healable properties is significant for their emerging applications, yet remains a big challenge. Here, an all-in-one multifunctional PC (MFPC) film with outstanding mechanochromic, thermochromic, solvatochromic, color/shape-recordable, self-healable, and adhesive functions is designed and prepared by simply non-close-assembling silica particles into the unique 2-[[(Butylamino)carbonyl]oxy]ethyl acrylate (BCOEA) followed by photopolymerization. The success is mainly due to the rational combination of non-close-packing structures and BCOEA's characteristics, including its urethane groups with numerous sacrificial hydrogen bonds, temperature-dependent refractive index, swellable and deformable polymer network, as well as low glass-transition temperature. The MFPC's hue and color saturation can be reversibly and dynamically modulated by strain/pressure/solvents and temperature, respectively, thereby realizing visually and spectrally sensing these stimuli. More interestingly, the color-responsiveness combined with other functions endows MFPCs with fascinating emerging applications, including multilayer optical filters, inkless printing, reconfigurable multicolor patterns, stretching-based anti-counterfeiting, etc. This work offers a new perspective for designing next-generation smart photonic materials and will facilitate their all-round applications.

This work demonstrates an in situ reconfigurable “computing neuron” prototype with wafer-scale fabrication distinguished from a widespread collapsed integrator artificial neuron. The ambipolar nature can be further adapted to construct highly efficient soft-XOR-based neural networks.

Abstract

Brain neurons exhibit far more sophisticated and powerful information-processing capabilities than the simple integrators commonly modeled in neuromorphic computing. A biological neuron can in fact efficiently perform Boolean algebra, including linear nonseparable operations. Traditional logic circuits require more than a dozen transistors combined as NOT, AND, and OR gates to implement XOR. Lacking biological competency, artificial neural networks require multilayered solutions to exercise XOR operation. Here, it is shown that a single-transistor neuron, harnessing the intrinsic ambipolarity of graphene and ionic filamentary dynamics, can enable in situ reconfigurable multiple Boolean operations from linear separable to linear nonseparable in an ultra-compact design. By leveraging the spatiotemporal integration of inputs, bio-realistic spiking-dependent Boolean computation is fully realized, rivaling the efficiency of a human brain. Furthermore, a soft-XOR-based neural network via algorithm-hardware co-design, showcasing substantial performance improvement, is demonstrated. These results demonstrate how the artificial neuron, in the ultra-compact form of a single transistor, may function as a powerful platform for Boolean operations. These findings are anticipated to be a starting point for implementing more sophisticated computations at the individual transistor neuron level, leading to super-scalable neural networks for resource-efficient brain-inspired information processing.

In HSCs, PPNH-LQs trigger ascorbic acid oxidation and LOXL2 expression inhibition (Gear I). These effects impair processes of collagen I hydroxylation and enzyme-mediated crosslinking, leading to the impeded deposition and crosslinking of collagen I (Gear II). Consequently, the fibrotic biomechanical microenvironment can be remodeled and subsequently induce HSC quiescence, which facilitates the reversal of hepatic fibrosis (Gear III).

Abstract

Hepatic fibrosis progresses concomitantly with a variety of biomechanical alternations, especially increased liver stiffness. These biomechanical alterations have long been considered as pathological consequences. Recently, growing evidence proposes that these alternations result in the fibrotic biomechanical microenvironment, which drives the activation of hepatic stellate cells (HSCs). Here, an inorganic ascorbic acid-oxidase (AAO) mimicking nanozyme loaded with liquiritigenin (LQ) is developed to trigger remodeling of the fibrotic biomechanical microenvironment. The AAO mimicking nanozyme is able to consume intracellular ascorbic acid, thereby impeding collagen I deposition by reducing its availability. Simultaneously, LQ inhibits the transcription of lysyl oxidase like 2 (LOXL2), thus impeding collagen I crosslinking. Through its synergistic activities, the prepared nanosystem efficiently restores the fibrotic biomechanical microenvironment to a near-normal physiological condition, promoting the quiescence of HSCs and regression of fibrosis. This strategy of remodeling the fibrotic biomechanical microenvironment, akin to “pulling the rug out from under”, effectively treats hepatic fibrosis in mice, thereby highlighting the importance of tissue biomechanics and providing a potential approach to improve hepatic fibrosis treatment.

Hexagonal boron nitride (h-BN) bubbles induced using a UV laser beam are a promising system for hydrogen gas storage. These bubbles demonstrate high gravimetric storage capacity and internal pressure. In addition, h-BN bubbles exhibit long-term stability for more than 6 months after their creation.

Abstract

Hexagonal boron nitride (h-BN) bubbles are of significant interest to micro-scale hydrogen storage thanks to their ability to confine hydrogen gas molecules. Previous reports of h-BN bubble creation from grown h-BN films require electron beams under vacuum, making integrating with other experimental setups for hydrogen production impractical. Therefore, in this study, the formation of h-BN bubbles is demonstrated in a 20 nm h-BN film grown on a sapphire substrate with a 213 nm UV laser beam. Using atomic force microscopy, it is shown that longer illumination time induces larger h-BN bubbles up to 20 µm with higher density. It is also demonstrated that h-BN bubbles do not collapse for more than 6 months after their creation. The internal pressure and gravimetric storage capacity of h-BN bubbles are reported. A maximum internal pressure of 41 MPa and a gravimetric storage capacity of 6% are obtained. These findings show that h-BN bubbles can be a promising system for long-term hydrogen storage.

The study presents a comprehensive analysis of the optical nonlinear losses observed in multiple silicon-rich nitride (SRN) nano-waveguides. Free carrier absorption (FCA) is established as the cause of the nonlinear losses due to photo-induced carriers generated in the C-band. The dynamics of FCA is thoroughly investigated, and it is concluded that SRN defects are responsible for the observed nonlinear losses.

Abstract

Free carrier absorption (FCA) is established to be the cause of nonlinear losses in plasma-enhanced chemical vapor deposition (PECVD) silicon-rich nitride (SRN) waveguides. To validate this hypothesis, a photo-induced current is measured in SRN thin films with refractive indices varying between 2.5 and 3.15 when a C-band laser light is illuminating the SRN films at various powers, indicating the generation of free carriers. Furthermore, nonlinear loss dynamics is, for the first time, measured and characterized in detail in SRN waveguides by utilizing high peak power C-band complex shape optical pulses for estimation of free carrier generation (FCG) and free carrier recombination (FCR) lifetimes and their dynamics. Both FCG and FCR are found to decrease with an increase in the refractive index of SRN, and, specifically, the FCR lifetimes are found (92 ± 7) ns, (39 ± 3) ns, and (31 ± 2) ns for the SRN indices of 2.7, 3, and 3.15, respectively. Lastly, nonlinear losses in high refractive index SRN waveguides are demonstrated to be minimized and altogether avoided when the pulse duration reduced below the free carrier generation lifetime, thus providing a way of taking a full advantage of the large inherent SRN nonlinear properties.

This paper reports a promising 2D/3D anti-counterfeiting security system based on the physical unclonable self-wrinkling patterns, fluorescence, and shape memory behavior. 3D structures constructed based on the shape memory behavior can be utilized to encrypt these 2D information, enhancing the security level and weakening the cloneable risk of surface wrinkle and fluorescence for further.

Abstract

The issue of counterfeiting has always been a major challenge in today's society, putting forward high requirements for anti-counterfeiting technology. Here, a promising 2D/3D anti-counterfeiting security system is developed based on anthracene-functionalized poly(styrene-butadiene-styrene) (SBS-CAN), which possessed the physical unclonable self-wrinkling patterns, fluorescence, and shape memory behavior. By controlling the dimerization of anthracene groups with ultraviolet light and external pre-stretched operation, 2D information with surface wrinkle and fluorescence is achieved, allowing for the design of security systems based on actual needs. Furthermore, 3D structures constructed based on the shape memory behavior can further be utilized to encrypt these 2D information, enhancing the security level and weakening the cloneable risk of surface wrinkle and fluorescence for further. This programmable 2D/3D anti-counterfeiting system has multiple advantages over the commonly used fluorescent wrinkled tag or fluorescent shape memory label, providing an intelligent choice for high-security information carriers.

This review highlights the roles of micro- and nanoscale materials in cell engineering, demonstrating how they can be adaptively controlled to regulate cellular reprogramming and core cell-level functions.

Abstract

Customizable manufacturing of ex vivo cell engineering is driven by the need for innovations in the biomedical field and holds substantial potential for addressing current therapeutic challenges; but it is still only in its infancy. Micro- and nanoscale-engineered materials are increasingly used to control core cell-level functions in cellular engineering. By reprogramming or redirecting targeted cells for extremely precise functions, these advanced materials offer new possibilities. This influences the modularity of cell reprogramming and reengineering, making these materials part of versatile and emerging technologies. Here, the roles of micro- and nanoscale materials in cell engineering are highlighted, demonstrating how they can be adaptively controlled to regulate cellular reprogramming and core cell-level functions, including differentiation, proliferation, adhesion, user-defined gene expression, and epigenetic changes. The current reprogramming routes used to achieve pluripotency from somatic cells and the significant potential of induced pluripotent stem cell technology for translational biomedical research are covered. Recent advances in nonviral intracellular delivery modalities for cell reprogramming and their constraints are evaluated. This paper focuses on emerging physical and combinatorial approaches of intracellular delivery for cell engineering, revealing the capabilities and limitations of these routes. It is showcased how these programmable materials are continually being explored as customizable tools for inducing biophysical stimulation. Harnessing the power of micro- and nanoscale-engineered materials will be a step change in the design of cell engineering, producing a suite of powerful tools for addressing potential future challenges in therapeutic cell engineering.

2D materials are central to next-generation information technology. Exciting their bandgap with light has led to significant performance breakthroughs in 2D material sensors. This perspective covers the mechanisms, applications, and challenges of light-excited 2D material sensors, highlighting recent advancements and future directions.

Abstract

2D materials are highly regarded for their exceptional sensing application prospects, stemming from their distinctive atomic layer structure and exceptionally sensitive surfaces. Over the past decade, numerous high-performance 2D material sensors are extensively developed; however, challenges related to sensitivity, selectivity, and stability continue to impede their industrial advancement. The interaction between light and 2D materials has introduced unique properties, including absorption and emission characteristics, photoelectric effects, nonlinear optical effects, surface-enhanced Raman scattering, and light response enhancement. Consequently, exciting and adjusting the electronic structure and carrier concentration of 2D materials through light with specific wavelength ranges is an effective strategy for enhancing sensing performance. This strategy has yielded remarkable breakthroughs in applications such as photodetectors, semiconductor gas sensors, and fiber optic sensors. Moreover, it demonstrates extraordinary potential in emerging applications such as image sensors, flexible electronics, and biomedical sensors. However, the sensing mechanism, device structure design, and specific applications of 2D materials under light excitation remain unclear. This perspective endeavors to elucidate the intrinsic photophysical mechanisms between light-excited 2D materials and their target sensing analytes. Furthermore, it aims to explain the evolutionary pattern of sensing applications and provide novel insights and inspiration to advance this burgeoning field.

Flexible electronics are essential in various fields like wearables, healthcare, and environmental sensing due to their flexibility, lightweight construction, and low profile. These systems conform to diverse surfaces, enhancing or replacing bulky instruments in many applications. This study reviews key components of standalone flexible electronics, integration strategies, and recent advancements, emphasizing flexible hybrid and transformational electronics, and concludes with future research directions and challenges.

Abstract

Flexible electronics are integral in numerous domains such as wearables, healthcare, physiological monitoring, human–machine interface, and environmental sensing, owing to their inherent flexibility, stretchability, lightweight construction, and low profile. These systems seamlessly conform to curvilinear surfaces, including skin, organs, plants, robots, and marine species, facilitating optimal contact. This capability enables flexible electronic systems to enhance or even supplant the utilization of cumbersome instrumentation across a broad range of monitoring and actuation tasks. Consequently, significant progress has been realized in the development of flexible electronic systems. This study begins by examining the key components of standalone flexible electronic systems–sensors, front-end circuitry, data management, power management and actuators. The next section explores different integration strategies for flexible electronic systems as well as their recent advancements. Flexible hybrid electronics, which is currently the most widely used strategy, is first reviewed to assess their characteristics and applications. Subsequently, transformational electronics, which achieves compact and high-density system integration by leveraging heterogeneous integration of bare-die components, is highlighted as the next era of flexible electronic systems. Finally, the study concludes by suggesting future research directions and outlining critical considerations and challenges for developing and miniaturizing fully integrated standalone flexible electronic systems.

Nature, Published online: 09 October 2024; doi:10.1038/s41586-024-08041-4

A bio-inspired supramolecular material combines tiny amino acid sequences present in proteins with equally small segments of the plastic poly(vinylidene fluoride), yielding high-performance sustainable ferroelectric nanostructures with potential for future resorbable bioelectronics, ultra-low power devices, and large-scale information storage.

Nature Communications, Published online: 10 October 2024; doi:10.1038/s41467-024-53030-w

Confocal and super-resolution tools used for multiplexed fluorescence imaging often demand specialized equipment and software. Here, the authors present NanoPlex, a universal method for high-plex labeling while preserving cellular ultrastructure. The approach relies on engineered secondary nanobodies that allow the selective removal of fluorescence signals.

Nanomaterials are the most rapidly emerging technologies in infrared sensing and imaging. This review delves into the latest developments in nanomaterials, including 2D materials, nanowires, quantum dots and nanocomposites that significantly enhanced the performance of infrared photodetectors.

Abstract

Nanomaterials have superior electronic, optical, and mechanical properties making them highly suitable for a range of applications in optoelectronics, biomedical fields, and photonics. Nanomaterials-based IR detectors are rapidly growing due to enhanced sensitivity, wide spectral range, and device miniaturization compared to commercial photodetectors. This review paper focuses on the significant role of nanomaterials in infrared detection, an area critical for enhancing night vision and health monitoring technologies. The latest advancements in IR photodetectors that employ various nanomaterials and their hybrids are discussed. The manuscript covers the operational mechanisms, device designing, performance optimization strategies, and material challenges. This review aims to provide a comprehensive overview of the current developments in nanomaterial-based IR photodetectors and to identify key directions for future research and technological advancements.

The Ln-coordination polymers of [Eu_0.3Yb_0.7(pfbz)₂(phen)Cl] and [Tb_0.4Yb_0.6(pfbz)₂(phen)Cl] are prepared, with the former representing the first instance of a Ln-CP where the UCL of Eu³⁺ ions is visually observable.

Abstract

Achieving the up-conversion luminescence (UCL) centered around trivalent lanthanide (Ln³⁺) ions in coordination polymers (CPs) is extremely challenging. Herein, Yb³⁺-doped Ln-CPs of [Eu_1-xYb_x(pfbz)₂(phen)Cl] (x = 0.3, namely 3; x = 0.5, namely 4; x = 0.7; namely 5), and [Tb_1-xYb_x(pfbz)₂(phen)Cl] (x = 0.2, namely 6; x = 0.5, namely 7; x = 0.6, namely 8) are reported by doping Yb³⁺ into Ln-CPs of [Ln(pfbz)₂(phen)Cl] (Ln = Eu, 1; Ln = Tb, 2). Both 5 and 8 visually exhibit excellent cooperative sensitization UCL of Eu³⁺ and Tb³⁺ ions, while 5 represents the first instance of an Ln-CP where the UCL of Eu³⁺ ion is visually observable. Investigations into the UCL of these CPs reveal that the energy transfer is achieved through direct energy transfer from two individual Yb³⁺ ions, marking the first time such a mechanism has been employed in UCL in Eu/Tb-CPs.

Many modern detector systems require structured scintillators in combination with photo-detectors. This requirement can be fulfilled by 3D printing plastic scintillators which becomes more and more relevant. However, the resolution and surface quality of 1-photon-based 3D printing techniques are not sufficient for many applications. Therefore, the first multi-photon micro-printable scintillator is presented and its printing and scintillation capabilities are demonstrated.

Abstract

Plastic scintillators are inexpensive to manufacture and therefore a popular alternative to inorganic crystalline scintillators. For many applications, their advantages outweigh their lower light yield. Additionally, it is easier to structure plastic scintillators with well-developed processing techniques which is of growing relevance in modern applications. One technique to structure plastic material is 3D printing, with noteworthy recent advances in one-photon-based approaches. However, some applications require high spatial resolution and optically smooth surfaces, which can be achieved by multi-photon 3D laser micro-printing. One application example is the improvement of sensitivity of the Karlsruhe Tritium Neutrino (KATRIN) experiment. This improvement can be realized by printing a 3D scintillator structure as an active transverse energy filter directly onto the detector. Herein, the first two-photon printable plastic scintillator providing a printing resolution in the micrometer regime is presented. Using the benefits of two-photon grayscale lithography, optical-grade surfaces are achieved. The light output is estimated to be 930 photons MeV⁻¹. A prototype structure printed directly on a single-photon avalanche diode array is demonstrated.

Accurately identifying an upconversion-emitting phase in a multi-phase composite produced by lanthanide-induced phase change poses a challenge. Utilizing a single-particle-level upconversion imaging and DFT calculations, an unprecedented resolution in visualizing individual emitting and non-emitting regions within the composite has been achieved, thereby allowing to accurately assign Yb₂Mo₄O₁₅ as a sole upconversion-emitting phase in the MoO₃/Yb₂Mo₄O₁₅/NiMoO₄ micro-nano composite.

Abstract

The crystal structure and phase stability of a host lattice plays an important role in efficient upconversion phenomena. In stable hosts, lanthanides doping should not generally change the crystal structure of the host itself. But when phase of a system drastically changes after lanthanide doping resulting in multiple phases, accurate identification of upconverting phase remains a challenge. Herein, an attempt to synthesize lanthanide-doped NiMoO₄ by microwave hydrothermal method produced MoO₃/Yb₂Mo₄O₁₅/NiMoO₄ micro-nano composite upconversion phosphor. A combined approach of density functional theory (DFT) calculations and single-particle-level upconversion imaging has been employed to elucidate the phase stability of different phases and upconversion properties within the composite. Through single-particle-level imaging under 980 nm excitation, an unprecedented resolution in visualizing individual emitting and non-emitting regions within the composite has been achieved, thereby allowing to accurately assign the Yb₂Mo₄O₁₅ as a sole upconversion emitting phase in the composite. Result of the DFT calculation further shows that the Yb₂Mo₄O₁₅ phase is the most thermodynamically preferred over other lanthanide-doped phases in the composite. This comprehensive understanding not only advances the knowledge of upconversion emission from composite materials but also holds promise for tailoring optical properties of materials for various applications, including bioimaging, sensing, and photonics, where controlled light emission is crucial.

Disordered (chaotic) bismuth waveguides can be formed and structurally tuned by electromigration until their efficiency as TE devices is maximized. The stability of these structures is found to be uniquely high. Analysis of their Seebeck variance enables to probe the changes in the transmission of their conductance modes as their structures are changed and tuned for maximal performance.

Abstract

Junctions based on electronic ballistic waveguides, such as semiconductor nanowires or nanoribbons with transverse structural variations in the order of a large fraction of their Fermi wavelength, are suggested as highly efficient thermoelectric (TE) devices. Full harnessing of their potential requires a capability to either deterministically induce structural variations that tailor their transmission properties at the Fermi level or alternatively to form waveguides that are disordered (chaotic) but can be structurally modified continuously until favorable TE properties are achieved. Well-established methods to realize either of these routes do not exist. Here, disordered bismuth (Bi) waveguides are reported, which are both formed and structurally tuned by electromigration until their efficiency as TE devices is maximized. In accordance with theory, the conductance of the most efficient TE waveguides is in the sub quantum of conductance regime. The stability of these structures is found to be substantially higher than other actively studied devices such as single molecule junctions.

The use of a simple, in situ temperature marker of particle formation is demonstrated for the thermal decomposition of iron oleate. The marker reveals a relationship between the onset of particle formation, the concentration of surfactants, and the shape of the particles that corroborates a chemically activated burst nucleation. The marker is tested with multiple solvents, providing particle size and shape control.

Abstract

Thermal decomposition of iron oleate is a simple and widespread method for synthesizing monodispersed iron oxide nanoparticles (IONPs) with well-defined morphology. However, the complexity of the underlying mechanism makes this method rather sensitive to variations in experimental conditions, and the lack of simple techniques to monitor the reaction progress in situ usually results in poor reproducibility and time-consuming optimizations. Here, a simple, robust, and versatile in situ marker to monitor particle formation based on a sudden change in the temperature during reflux is reported. A linear relationship between the onset of particle formation and the concentration of surfactants is unveiled, corroborating a ‘chemically activated’ burst nucleation mechanism. Using this linear relationship as a guide, highly uniform spherical, cubic, and star-shaped particles between 12 and 30 nm can be obtained. This temperature marker and the derived linear relationship not only deepen the understanding of the reaction process, but also provide a powerful tool for the straightforward optimization of IONPs.

Through transmission electron microscopy and statistical image processing, Cu-atom locations in a Cu-doped SnTe rocksalt alloy are investigated to explain its ultralow lattice thermal conductivity for efficient thermoelectric energy production. This study offers atomic-scale insights for achieving more precise dopant engineering, leading to the accelerated development of functional thermoelectric materials.

Abstract

The development of functional thermoelectric materials requires direct evidence of dopants’ locations to rationally design the electronic and phononic structure of the host matrix. In this study, Cs-corrected scanning transmission electron microscopy and energy dispersive X-ray spectroscopy is employed at the atomic scale to identify Cu atoms’ locations in a Cu-doped SnTe thermoelectric alloy. It is revealed that Cu atoms in the rocksalt SnTe form solid solutions at both Sn and Te sites, contrary to their electronegativity order and the intentional Cu doping at Sn sites. Cu atoms are also located at the tetrahedral and crowdion sites of the face-centred cubic structure, with varying degrees of correlations. Such high flexibility of Cu atoms in the rocksalt SnTe offers diverse phonon-scattering mechanisms conducive to the ultra-low lattice thermal conductivity of singly Cu-doped SnTe. This study offers atomic-scale insights for achieving more precise dopant engineering, leading to the accelerated development of functional thermoelectric materials.

Advanced in situ biasing and atomic-scale imaging in an aberration-corrected scanning transmission electron microscope are employed to investigate and manipulate in real space local picometer-level structure variations and polarization in a prototype 2D vdW ferroelectrics InSe. Intralayer sliding within each Se–In–In–Se quadruple-layer is identified to be responsible for switchable out-of-plane polarization and ferroelectricity of InSe.

Abstract

Ferroelectric 2D van der Waals (vdW) layered materials are attracting increasing attention due to their potential applications in next-generation nanoelectronics and in-memory computing with polarization-dependent functionalities. Despite the critical role of polarization in governing ferroelectricity behaviors, its origin and relation with local structures in 2D vdW layered materials have not been fully elucidated so far. Here, intralayer sliding of approximately six degrees within each quadruple-layer of the prototype 2D vdW ferroelectrics InSe is directly observed and manipulated using sub-angstrom resolution imaging and in situ biasing in an aberration-corrected scanning transmission electron microscope. The in situ electric manipulation further indicates that the reversal of intralayer sliding can be achieved by altering the electric field direction. Density functional theory calculations reveal that the reversible picometer-level intralayer sliding is responsible for switchable out-of-plane polarization. The observation and manipulation of intralayer sliding demonstrate the structural origin of ferroelectricity in InSe and establish a dynamic structural variation model for future investigations on more 2D ferroelectric materials.

The design and synthesis of a bidentate photo-crosslinkable ligand for high-density photo-patterning of perovskite nanocrystals is reported. The incorporation of the photo-crosslinker to perovskite nanocrystals enables the creation of a high-density crosslinked film with high optical density of 1.1, at a film thickness of only 1.4 µm. Patterning via laser writing gave well-defined patterns with feature sizes of 20 µm.

Abstract

Perovskite nanocrystals (PNCs) are promising luminescent materials for electronic color displays due to their high luminescence efficiency, widely-tunable emission wavelengths, and narrow emission linewidth. Their application in emerging display technologies necessitates precise micron-scale patterning while maintaining good optical performance. Although photolithography is a well-established micro-patterning technique in the industry, conventional processes are incompatible with PNCs as the use of polar solvents can damage the ionic PNCs, causing severe luminescence quenching. Here, we report the rational design and synthesis of a new bidentate photo-crosslinkable ligand for the direct photo-patterning of PNCs. Each ligand contains two photosensitive acrylate groups and two carboxylate groups, and is introduced to the PNCs via an entropy-driven ligand exchange process. In a close-packed thin film, the acrylate ligands photo-polymerize and crosslink under ultraviolet light, rendering the PNCs insoluble in developing solvents. A high-density crosslinked PNC film with an optical density of 1.1 is attained at 1.4 µm thickness, surpassing industry requirements on the absorption coefficient. Micron-scale patterning is further demonstrated using direct laser writing, producing well-defined 20 µm features. This study thus offers an effective and versatile approach for micro-patterning PNCs, and may also be broadly applicable to other nanomaterial systems.

The interfacial stress transfer and fracture of a MoS₂/graphene vdW heterostructure are studied, through the lateral and vertical strain distributions in the vdW heterostructure revealed in-situ. This leads to the interfacial shear strength and interfacial fracture energy being estimated, and a failure criterion proposes to predict the failure mechanisms of similar vdW heterostructures with any lateral dimensions.

Abstract

Artificially stacking 2D materials (2DMs) into vdW heterostructures creates materials with properties not present in nature that offer great potential for various applications such as flexible electronics. Properties of such stacked structures are controlled largely by the interfacial interactions and the structural integrity of the 2DMs. In spite of their crucial roles, interfacial stress transfer and the failure mechanisms of the vdW heterostructures, particularly during deformation, have not been well addressed so far. In this work, the interfacial stress transfer and failure mechanisms of a MoS₂/graphene vdW heterostructure are studied, through the strain distributions both laterally in individual 2DMs and vertically across different 2DMs revealed in-situ. The fracture of the MoS₂ and the associated states of stress and strain are monitored experimentally. This enables various interfacial properties, such as the interfacial shear strength and interfacial fracture energy, to be estimated. Based only on the measured strength and interfacial properties of a single vdW heterostructure, a failure criterion is proposed to predict the failure mechanisms of similar vdW heterostructures with any lateral dimensions. This work provides an insight to the deformation micromechanics of vdW heterostructures that are of great value for their miniaturization and applications, especially in flexible electronics.