Jing Zhang

This study presents a novel strategy for highly sensitive pressure sensors using a composite film with curved 3D carbon nanotube structures. Enhanced sensitivity results from microdome structure contact and percolation network changes, demonstrating potential for wearable health monitoring and real-time pressure sensing.

Abstract

Soft pressure sensors based on 3D microstructures exhibit high sensitivity in the low-pressure range, which is crucial for various wearable and soft touch applications. However, it is still a challenge to manufacture soft pressure sensors with sufficient sensitivity under small mechanical stimuli for wearable applications. This work presents a novel strategy for extremely sensitive pressure sensors based on the composite film with local changes in curved 3D carbon nanotube (CNT) structure via expandable microspheres. The sensitivity is significantly enhanced by the synergetic effects of heterogeneous contact of the microdome structure and changes of percolation network within the curved 3D CNT structure. The finite-element method simulation is used to comprehend the relationships between the sensitivity and mechanical/electrical behavior of microdome structure under the applied pressure. The sensor shows an excellent sensitivity (571.64 kPa⁻¹) with fast response time (85 ms), great repeatability, and long-term stability. Using the developed sensor, a wireless wearable health monitoring system to avoid carpel tunnel syndrome is built, and a multi-array pressure sensor for realizing a variety of movements in real-time is demonstrated.

An artificial sensory neural network system that combines a digital−analog bimodal memristor with a 5 × 5 tactile sensing array based on piezoresistive sensors can achieve the integration of tactile sensing, information storage, and neuromorphic computing and further recognize handwritten patterns of different letters with high accuracy of 94.44% under assistance of supervised learning.

Abstract

Memristor with digital and analog bipolar bimodal resistive switching offers a promising opportunity for the information-processing component. However, it still remains a huge challenge that the memristor enables bimodal digital and analog types and fabrication of artificial sensory neural network system. Here, a proposed CsPbBr₃-based memristor demonstrates a high ON/OFF ratio (>10³), long retention (>10⁴ s), stable endurance (100 cycles), and multilevel resistance memory, which acts as an artificial synapse to realize fundamental biological synaptic functions and neuromorphic computing based on controllable resistance modulation. Moreover, a 5 × 5 spinosum-structured piezoresistive sensor array (sensitivity of 22.4 kPa⁻¹, durability of 1.5 × 10⁴ cycles, and fast response time of 2.43 ms) is constructed as a tactile sensory receptor to transform mechanical stimuli into electrical signals, which can be further processed by the CsPbBr₃-based memristor with synaptic plasticity. More importantly, this artificial sensory neural network system combined the artificial synapse with 5 × 5 tactile sensing array based on piezoresistive sensors can recognize the handwritten patterns of different letters with high accuracy of 94.44% under assistance of supervised learning. Consequently, the digital−analog bimodal memristor would demonstrate potential application in human–machine interaction, prosthetics, and artificial intelligence.

A ferroelectric gating photodetector is developed with a ReS₂/WSe₂ vdW heterojunction-channel. This device effectively detects a wide range of light wavelengths, including broadband light exceeding 1300 nm and expandable up to 2700 nm. The successful detection is attributed to the staggered type-II bandgap alignment, which results in an interlayer gap of 0.46 eV. By controlling the polarity of the P(VDF-TrFE) ferroelectric dipole for a specific wavelength, both high photoresponsivity (>6.9 × 10³ A W⁻¹) and low dark current (<0.26 nA) is simultaneously achieved across a broad range of wavelengths.

Abstract

The potential for various future industrial applications has made broadband photodetectors beyond visible light an area of great interest. Although most 2D van-der-Waals (vdW) semiconductors have a relatively large energy bandgap (>1.2 eV), which limits their use in short-wave infrared detection, they have recently been considered as a replacement for ternary alloys in high-performance photodetectors due to their strong light-matter interaction. In this study, a ferroelectric gating ReS₂/WSe₂ vdW heterojunction-channel photodetector is presented that successfully achieves broadband light detection (>1300 nm, expandable up to 2700 nm). The staggered type-II bandgap alignment creates an interlayer gap of 0.46 eV between the valence band maximum (VB_MAX) of WSe₂ and the conduction band minimum (CB_MIN) of ReS₂. Especially, the control of poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) ferroelectric dipole polarity for a specific wavelength allows a high photoresponsivity of up to 6.9 × 10³ A W⁻¹ and a low dark current below 0.26 nA under the laser illumination with a wavelength of 405 nm in P-up mode. The achieved high photoresponsivity, low dark current, and full-range near infrared (NIR) detection capability open the door for next-generation photodetectors beyond traditional ternary alloy photodetectors.

Nature Communications, Published online: 07 September 2023; doi:10.1038/s41467-023-41313-7

Many phototransistors are multi-component systems with inorganic materials or involve faradaic processes that can be irreversible. Using a single photoactive polymer, Druet et al. report a reversible, water-compatible n-type photoelectrochemical transistor with potentiometric photodetection and current modulation.

Nature, Published online: 06 September 2023; doi:10.1038/s41586-023-06404-x

Stacks of van der Waals superconductor heterostructures comprising many layers and several blocks of two-dimensional materials have been grown in a highly controllable manner at a wafer scale using a high-to-low temperature strategy.

Two-dimensional semiconducting transition metal dichalcogenides (TMDs) have attracted significant interest due to their unique optoelectronic properties. More often, these materials are enclosed inside a dielectric layer that can work as an insulator for field-effect transistors. The insulating layer is typically grown with atomic layer deposition (ALD). Here, we study the effects on bare and hBN-covered monolayer MoS2 and WSe2 flakes with ALD TiO2 films. Our results reveal a significant shift and decrease in intensity in photoluminescence and Raman signals of the monolayer TMDs. Further analysis suggests that these changes are caused by chemical doping, strain, and dielectric screening after the ALD. Our study not only sheds light on the impact of ALD on the properties of TMDs, but also indicates ALD can be an alternative method to engineer the doping, strain and dielectric environment for potential optoelectronics and photonics applications.

Low-dimensional materials used as polarization-sensitive components in polarized photodetection and imaging are comprehensively reviewed. From the view of the constitutive relation, polarized photodetectors based on LDMs can be creatively divided into three categories. Based on this, the state-of-the-art works are reorganized, summarized, and analyzed, and perspectives on the future opportunities and challenges are also discussed.

Abstract

The vector characteristics of light and the vectorial transformations during its transmission lay a foundation for polarized photodetection of objects, which broadens the applications of related detectors in complex environments. With the breakthrough of low-dimensional materials (LDMs) in optics and electronics over the past few years, the combination of these novel LDMs and traditional working modes is expected to bring new development opportunities in this field. Here, the state-of-the-art progress of LDMs, as polarization-sensitive components in polarized photodetection and even the imaging, is the main focus, with emphasis on the relationship between traditional working principle of polarized photodetectors (PPs) and photoresponse mechanisms of LDMs. Particularly, from the view of constitutive equations, the existing works are reorganized, reclassified, and reviewed. Perspectives on the opportunities and challenges are also discussed. It is hoped that this work can provide a more general overview in the use of LDMs in this field, sorting out the way of related devices for “more than Moore” or even the “beyond Moore” research.

Nature Nanotechnology, Published online: 04 September 2023; doi:10.1038/s41565-023-01484-2

A free-standing two-dimensional sheet composed solely of Mo atoms shows metallic character, with an electrical conductivity of ~940 S m−1.

Here, a new strategy for controllable growth of large-scale monolayer, 2H-stacking, and 3R-stacking bilayer transition metal dichalcogenides is developed, by modulating the resolidified chalcogen precursors supply kinetics. Noteworthy, the 3R-stacking bilayer tungsten disulfide (WS₂) exhibits better electrical performance compared to 2H-stacking bilayer WS₂, due to the difference of stacking-order-dependent surface potentials.

Abstract

Bilayer semiconductors have attracted much attention due to their stacking-order-dependent properties. However, as both 3R- and 2H-stacking are energetically stable at high temperatures, most of the high-temperature grown bilayer materials have random 3R- or 2H-stacking orders, leading to non-uniformity in optical and electrical properties. Here, a chemical vapor deposition method is developed to grow bilayer semiconductors with controlled stacking order by modulating the resolidified chalcogen precursors supply kinetics. Taking tungsten disulfide (WS₂) as an example, pure 3R-stacking (100%) and 2H-stacking dominated (87.6%) bilayer WS₂ are grown by using this method and both show high structural and optical quality and good uniformity. Importantly, the bilayer 3R-stacking WS₂ shows higher field effect mobility than 2H-stacking samples, due to the difference in stacking order-dependent surface potentials. This method is universal for growing other bilayer semiconductors with controlled stacking orders including molybdenum disulfide and tungsten diselenide, paving the way to exploit stacking-order-dependent properties of these family of emerging bilayer materials.

Carbon dots (CDs) are one type of fluorescent nanomaterial with excellent optical properties. Organosilicon is widely used in various fields including optics and biology, which can be used as precursors for CD synthesis and matrix materials for compounding with CDs. The preparation methods, formation mechanism, properties, and versatile applications of functional CDs derived from organosilicon are thoroughly discussed.

Abstract

Carbon dots (CDs) are a newly discovered type of fluorescent material that has gained significant attention due to their exceptional optical properties, biocompatibility, and other remarkable characteristics. However, single CDs have some drawbacks such as self-quenching, low quantum yield (QY), and poor stability. To address these issues, researchers have turned to organosilicon, which is known for its green, economical, and abundant properties. Organosilicon is widely used in various fields including optics, electronics, and biology. By utilizing organosilicon as a synthetic precursor, the biocompatibility, QY, and resistance to self-quenching of CDs can be improved. Meanwhile, the combination of organosilicon with CDs enables the functionalization of CDs, which significantly expands their original application scenarios. This paper comprehensively analyzes organosilicon in two main categories: precursors for CD synthesis and matrix materials for compounding with CDs. The role of organosilicon in these categories is thoroughly reviewed. In addition, the paper presents various applications of organosilicon compounded CDs, including detection and sensing, anti-counterfeiting, optoelectronic applications, and biological applications. Finally, the paper briefly discusses current development challenges and future directions in the field.

Surface functionalization enables assembly and covalent attachment of stimuli-responsive “microgels” to a substrate through wettability interactions and direct polymerization, respectively. This process enables the scalable fabrication of fixed microgel arrays, with dynamic optofluidic microlensing functionality and future applications in soft robotics and 3D cell culture. Microgel chemistry and geometry can be tuned, simultaneously, to produce structures with desired adaptive properties.

Abstract

Hydrogels have emerged as prototypical stimuli-responsive materials with potential applications in soft robotics, microfluidics, tissue engineering, and adaptive optics. To leverage the full potential of these materials, fabrication techniques capable of simultaneous control of microstructure, device architecture, and interfacial stability, that is, adhesion of hydrogel components to support substrates, are needed. A universal strategy for the microfabrication of hydrogel-based devices with robust substrate adhesion amenable to use in liquid environments would enable numerous applications. This manuscript reports a general approach for the facile production of covalently attached, ordered arrays of microscale hydrogels (microgels) on silicone supports. Specifically, silicone-based templates are used to: i) drive mechanical assembly of prepolymer droplets into well-defined geometries and morphologies, and ii) present appropriate conjugation moieties to fix gels in place during photoinitiated crosslinking via a “graft from” polymerization scheme. Automated processing enabled rapid microgel array production for characterization, testing, and application. Furthermore, the stimuli-responsive microlensing properties of these arrays, via contractile modulated refractive index, are demonstrated. This process is directly applicable to the fabrication of adaptive optofluidic systems and can be further applied to advanced functional systems such as soft actuators and robotics, and 3D cell culture technologies.

Nature Communications, Published online: 02 September 2023; doi:10.1038/s41467-023-40997-1

Over the last few years, several van der Waals materials have been found that retain magnetic ordering down to monolayer thickness. These materials provide a simple platform for studying the magnetism in reduced dimensions. Here, Zhong et al study the thickness dependence of magnetic ordering in Cr2Te3, and find a crossover from Stoner to Heisenberg-type magnetism as thicknesses are reduced.

Nature Chemistry, Published online: 31 August 2023; doi:10.1038/s41557-023-01311-0

Two-dimensional hybrid perovskites have gained substantial interest recently due to their controllable optoelectronic properties; however precise control over layer thickness has been synthetically challenging. Now a crystal growth method is shown to achieve high-quality single crystals of organic semiconductor-incorporated perovskites with control over their thickness and length through judicious solvent choice, affording precisely tuned optoelectronic properties.

Nature Electronics, Published online: 31 August 2023; doi:10.1038/s41928-023-01018-7

A platform that integrates a ferroelectric gate and two-dimensional heterostructure of tungsten diselenide and tin diselenide can operate in various gating modes, demonstrating typical transistor, steep-slope transistor and synaptic behaviours.

A surfactant-free liquid-phase synthetic route for high-quality 2D tellurium based on ultrasonication-assisted exfoliation of metastable 1T'-MoTe₂ is reported. The as-grown 2D tellurium nanosheets exhibit excellent single crystallinity and clean surface. 2D tellurium-based field-effect transistors show ultrahigh hole mobility exceeding 1000 cm² V^-1 s^-1 at room temperature and exceptional chemical and operational stability in both solid- and liquid-state gating devices.

Abstract

Elemental 2D materials (E2DMs) have been attracting considerable attention owing to their chemical simplicity and excellent/exotic properties. However, the lack of robust chemical synthetic methods seriously limits their potential. Here, a surfactant-free liquid-phase synthesis of high-quality 2D tellurium is reported based on ultrasonication-assisted exfoliation of metastable 1T'-MoTe₂. The as-grown 2D tellurium nanosheets exhibit excellent single crystallinity, ideal 2D morphology, surfactant-free surface, and negligible 1D by-products. Furthermore, a unique growth mechanism based on the atomic escape of Te atoms from metastable transition metal dichalcogenides and guided 2D growth in the liquid phase is proposed and verified. 2D tellurium-based field-effect transistors show ultrahigh hole mobility exceeding 1000 cm² V⁻¹ s⁻¹ at room temperature attributing to the high crystallinity and surfactant-free surface, and exceptional chemical and operational stability using both solid-state dielectric and liquid-state electrical double layer. The facile ultrasonication-assisted synthesis of high-quality 2D tellurium paves the way for further exploration of E2DMs and expands the scope of liquid-phase exfoliation (LPE) methodology toward the controlled wet-chemical synthesis of functional nanomaterials.

In the CDW phase of a nonmagnetic Dirac-semimetal, LaAgSb₂, a large planar Hall signal is detected, which changes sign above the CDW transitions and remains finite even at room temperature. First principle calculations reveal the emergence of an unusual chiral metallic phase with broken inversion symmetry and finite Berry curvature in the CDW regime.

Abstract

The presence of electron correlations in a system with topological order can lead to exotic ground states. Considering single crystals of LaAgSb₂ which has a square net crystal structure, one finds multiple charge density wave transitions (CDW) as the temperature is lowered. Large planar Hall (PHE) signals are found in the CDW phase, which are still finite in the high-temperature phase though they change sign. Optimizing the structure within first-principles calculations, one finds an unusual chiral metallic phase. This is because as the temperature is lowered, the separation between the Ag/Sb atoms on different layers decreases, leading to stronger repulsions between electrons associated with atoms on different layers. This leads to successive layers sliding with respect to each other, thereby stabilizing a chiral structure in which inversion symmetry is also broken. The large Berry curvature associated with the low-temperature structure explains the low-temperature PHE. At high temperature, the PHE arises from the changes induced in the anisotropic Dirac cone in presence of a magnetic field. This work represents a route toward detecting and understanding the mechanism in a correlation-driven topological transition through electron transport measurements, complemented by ab-initio electronic structure calculations.

A dual-gate synaptic transistor, integrating nonvolatile ferroelectric polarization and interface charge trapping/de-trapping memory, is proposed to fulfill the bi-directional dynamic modulation on synaptic plasticity, where the conversion between excitatory and inhibitory plasticity is manipulated by two different approaches. Moreover, the back-gate voltage significantly controls the conductance range, therefore improving the visual recognition precision.

Abstract

The dynamic modulation of the plasticity of artificial neuromorphic devices facilitates a wide range of neuromorphic functions. However, integrating diverse plasticity modulation techniques into a single device presents a challenge due to limitations in the device structure design. Here, a multiterminal artificial synaptic device capable of bi-directional modulation on its plasticity is proposed. Significantly, the conversion of inhibitory and excitatory synaptic plasticity can be achieved not only by modifying the polarity of the presynaptic voltage spike but also by exchanging its input terminal between top and bottom gate while maintaining the same presynaptic stimuli. This unique bi-directional modulation of synaptic plasticity has been attributed to two distinct physical mechanisms: nonvolatile ferroelectric polarization and interface charge trap-induced memory characteristics. Additionally, the effective dynamic modulation of the synaptic behaviors is quantified under different back-gate bias and verified in the constructed neural network perceptron. Further, a visual simulation demonstrates the enhanced clarity and precision of edge recognition through the back-gate modulation in the artificial synapses. This study provides a strategy to fulfill diversified modulation on synaptic plasticity in ferroelectric-gated transistors, thereby prompting efficient and controllable neuromorphic visual systems.

A wearable integrated self-powered electroluminescent display device (W-ELD) that integrates MXene/silicone-based triboelectric nanogenerator and electroluminescent (EL) device based on a shared MXene electrode is developed for information encryption. When dripping conductive solution, the W-ELD based on coplanar “中國”-patterned electrode can reveal the hidden encryption information through self-powered EL emission for real-time visualized information interaction.

Abstract

Anti-counterfeiting and visual optical information encryption/decryption technology have attracted widespread attention in the field of information security. Luminescent encryption technologies still face a huge challenge in external high voltage power supply, complex architecture, and expensive decryption equipment, which hinder their broad applications. Herein, a wearable integrated self-powered electroluminescent (EL) display device (W-ELD) that consists of MXene/Silicone-based triboelectric nanogenerator (MS-TENG) and EL device based on a shared MXene electrode is developed for patterned display and information encryption. The W-ELD features an all-in-one MXene electrode with excellent flexibility and high conductivity of 0.6 kΩ sq⁻¹, which is shared by both MS-TENG and EL devices. The MS-TENG demonstrates excellent output performances (output power of 0.9 Wm⁻²) and high stability and durability (10⁴ cycles), which can directly light up the flexible patterned EL device. More importantly, when dripping conductive electrolyte solution, the W-ELD based on “中國”-patterned MXene electrode can precisely reveal the encryption information through self-powered EL emission for real-time visualized information interaction. Consequently, the all-in-one MXene electrode-based W-ELD that integrates both MS-TENG and EL device demonstrates exceptional patterned EL-based information encryption features, which offers a potential prospect in wearable self-powered optoelectronic devices, flexible displays, and encryption technology.

This memristor, fabricated using a low-cost solution process, can modulate its conductance positively and negatively by utilizing specific intensities of red light (630 nm), namely 11.8 and 0.9 mW cm⁻². Consequently, the memristor achieves both excitatory and inhibitory synaptic properties through all-optical control. Additionally, the memristor exhibits significant advantages in image memory and stabilization.

Abstract

Image stabilization is a crucial field in machine vision, aiming to eliminate image blurring or distortion caused by the camera or object jitter. However, traditional image stabilization techniques often suffer from the drawbacks of requiring complex equipment or extensive computing resources, resulting in inefficiencies. In contrast, the human retina performs a highly efficient all-in-one system, encompassing the detection and processing of light stimuli. In this study, an all-optically controlled retinomorphic memristor based on the Cs_xFA_yMA_1-x-yPb(I_zBr_1-z)₃ is proposed, which integrates perception, storage, and processing functions. This memristor exhibits significant advantages in image stabilization. It is capable of positively and negatively modulating its conductance using specific intensities (11.8 and 0.9 mW cm⁻², respectively) of red light (630 nm). To demonstrate the effectiveness of the proposed approach, handwritten digit recognition simulations are conducted. The application of specific light stimuli effectively highlights the characteristics of blurred images. The processed images are then fed into a conductance-mapped neural network for rapid recognition. Remarkably, the recognition rates of the processed images reach 83.5% after 19 000 iterations, surpassing the performance of blurred images (only 56.2% after 19 000 iterations). These results highlight the immense potential of retinomorphic memristors as the hardware foundation for next-generation image stabilization systems.

By using a magnetostrictive/ferroelectric laminated structure, magnetic field-induced biaxial strain could be efficiently transferred to piezotronic devices. The charge carrier transport and corresponding drain current of the piezotronic devices can be directly modulated by either the applied magnetic field or external strain. The device exhibits high sensitivity with on/off ratio of 1700% and a gauge factor as high as 2.3 × 10⁴.

Abstract

Piezotronics is the coupling effect of the piezoelectric and semiconductor properties; however, the piezoelectric constant of the piezoelectric semiconductor is relatively small while the ferroelectric materials with large piezoelectric constant typically possess weak semiconductor properties, thus limiting the effective coupling coefficient of the piezotronic materials and devices. Here, a piezotronics and magnetic dual-gated ferroelectric semiconductor transistor (PM-FEST) is fabricated by Terfenol-D, aluminum oxide (Al₂O₃), and ferroelectric semiconductor α-In₂Se₃, which has a large piezoelectric coefficient, room-temperature ferroelectricity, and dipole locking. The charge carrier transport and corresponding drain current of the PM-FEST can be directly modulated by either the applied magnetic field or external strain. At a low magnetic field (<200 mT), the maximum current on/off ratio of α-In₂Se₃ based PM-FEST is as high as 1700%. Compared with traditional piezotronic devices, the PM-FEST demonstrates a higher gauge factor (2.3 × 10⁴) than that of the piezoelectric semiconductors. This work provides a possibility of realizing magnetism-modulated electronics in semiconductors by exploiting the coupling of piezotronics and magnetostriction.

An advanced neuroinflammation-on-a-chip system is developed, employing a nano-biosensing approach to replicate the human neurovascular unit in vitro. The model comprises parallel microchannels housing human vascular endothelial cells, astrocytes, and neurons. Here, inflammation is induced using lipopolysaccharide, while proinflammatory cytokines are quantitatively detected by incorporating aptamer-functionalized reduced graphene oxide.

Abstract

The human neurovascular system is a complex network of blood vessels and brain cells that is essential to the proper functioning of the brain. Researchers have become increasingly interested in the system for developing drugs to treat neuroinflammation. Currently, creating neurovascular models begins with animal models, followed by testing on humans in clinical trials. However, the high number of medication failures that pass through animal testing indicates that animal models do not always reflect the outcome of human clinical trials. To overcome the challenges of the issues with animal models, a neurovascular-unit-on-a-chip system is developed to accurately replicate the in vivo human neurovascular microenvironment. By replicating the human neurovascular unit, a more accurate representation of human physiology can be achieved compared to animal models. The ability to detect proinflammatory cytokines in situ and monitor physiological changes can provide an invaluable tool for evaluating the efficacy and safety of drugs. Using nanosized graphene oxide for in situ detection of inflammatory responses is an innovative approach that can advance the field of neuroinflammation research. Overall, the developed neuroinflammation-on-a-chip system has the potential to provide a more efficient and effective method for developing drugs for treating neurodegenerative diseases and other central nervous system diseases.

A security label capable of dual information encoding for reflection and fluorescence states is established based on polymer-stabilized blue phase, which is achieved by photonic band gap tuning of patterned polymerization and emission transition of fluorescent molecules during UV irradiation, respectively.

Abstract

Anticounterfeit labels with multiple information-carrying functions serve a critical role in boosting security and minimizing counterfeit-related losses, whose development remains challenging. Here, a security label with the ability to encode information in reflective and fluorescent sates is fabricated from light-emitting polymer-stabilized blue phase (LE-PSBP) liquid crystals (LCs). The LE-PSBP with temperature-dependent reflective color can be encoded with information by UV irradiation through photomasks. On the other hand, introduction of a fluorescent molecule, which can be easily photocyclized upon UV irradiation, enables the convenient encoding of fluorescent information without impacting the reflective information. As an illustration, a security label with distinct information in reflective and fluorescent states is demonstrated. Such innovative security labels have tremendous potential to provide a platform for multi-information encoding to enhance the protection level in anticounterfeiting technology.

Nature Nanotechnology, Published online: 31 August 2023; doi:10.1038/s41565-023-01482-4

This Review analyses the mechanisms of light extraction from perovskite light-emitting diodes and suggests new approaches towards ultrahigh electroluminescence efficiencies.

The fusion of inkjet printing and soft lithography techniques is employed to obtain differently shaped light emitting motifs made out of phosphor inks. The potential of this approach is depicted by processing a self-standing photoluminescent quick response code whose emission is both polarized and directionally beamed.

Abstract

Herein a versatile and scalable method to prepare periodically corrugated nanophosphor surface patterns displaying strongly polarized and directional visible light emission is demonstrated. A combination of inkjet printing and soft lithography techniques is employed to obtain arbitrarily shaped light emitting motifs. Such predesigned luminescent drawings, in which the polarization and angular properties of the emitted light are determined and finely tuned through the surface relief, can be used as anti-counterfeiting labels, as these two specific optical features provide additional means to identify any unauthorized or forged copy of the protected item. The potential of this approach is exemplified by processing a self-standing photoluminescent quick response code whose emission is both polarized and directionally beamed. Physical insight of the mechanism behind the directional out-coupled photoluminescence observed is provided by finite-difference time-domain calculations.

Visible light-triggered phosphorescent carbon dots with record-breaking lifetime of 2.1 s through rational design of hydrogen bonding interactions are demonstrated, offering enormous potential in anti-counterfeiting security and advanced optical information storage.

Abstract

Room temperature phosphorescence (RTP) has emerged as an interesting but rare phenomenon with multiple potential applications in anti-counterfeiting, optoelectronic devices, and biosensing. Nevertheless, the pursuit of ultralong lifetimes of RTP under visible light excitation presents a significant challenge. Here, new phosphorescent materials that can be excited by visible light with record-long lifetimes are demonstrated, realized through embedding nitrogen doped carbon dots (N-CDs) into a poly(vinyl alcohol) (PVA) film. The RTP lifetime of the N-CDs@PVA film is remarkably extended to 2.1 s excited by 420 nm, representing the highest recorded value for visible light-excited phosphorescent materials. Theoretical and experimental studies reveal that the robust hydrogen bonding interactions can effectively reduce the non-radiative decay rate and radiative transition rate of triplet excitons, thus dramatically prolong the phosphorescence lifetime. Notably, the RTP emission of N-CDs@PVA film can also be activated by easily accessible low-power white-light-emitting diode. More significantly, the practical applications of the N-CDs@PVA film in state-of-the-art anti-counterfeiting security and optical information storage domains are further demonstrated. This research offers exciting opportunities for utilizing visible light-activated ultralong-lived RTP systems in a wide range of promising applications.

This study presents a novel electrochemical dopamine sensor consisting of three-dimensional graphene oxide- incorporated metallic polymer nanopillar arrays (GOMPON). Owing to excellent sensing capability, the dopamine release from living neurons is detectable on the GOMPON in a label-free and non-invasive manner. This technology offers exceptional sensitivity, enabling the evaluation of functionality and maturity of dopaminergic neurons.

Abstract

Stem-cell-based therapeutics have shown immense potential in treating various diseases that are currently incurable. In particular, partial recovery of Parkinson's disease, which occurs due to massive loss or abnormal functionality of dopaminergic (DAnergic) neurons, through the engraftment of stem-cell-derived neurons ex vivo is reported. However, precise assessment of the functionality and maturity of DAnergic neurons is still challenging for their enhanced clinical efficacy. Here, a novel conductive cell cultivation platform, a graphene oxide (GO)-incorporated metallic polymer nanopillar array (GOMPON), that can electrochemically detect dopamine (DA) exocytosis from living DAnergic neurons, is reported. In the cell-free configuration, the linear range is 0.5–100 µm, with a limit of detection of 33.4 nm. Owing to its excellent biocompatibility, a model DAnergic neuron (SH-SY5Y cell) can be cultivated and differentiated on the platform while their DA release can be quantitatively measured in a real-time and nondestructive manner. Finally, it is showed that the functionality of the DAnergic neurons derived from stem cells can be precisely assessed via electrochemical detection of their DA exocytosis. The developed GOMPON is highly promising for a wide range of applications, including real-time monitoring of stem cell differentiation into neuronal lineages, evaluating differentiation protocols, and finding practical stem cell therapies.

Nature, Published online: 30 August 2023; doi:10.1038/s41586-023-06281-4

Er3+ is implanted into CaWO4, a material with non-polar site symmetry free of background rare earth ions, to realize reduced optical spectral diffusion in nanophotonic devices, representing a step towards making telecom band quantum repeater networks with single ions.

Nature, Published online: 30 August 2023; doi:10.1038/s41586-023-06295-y

A study describes the development of a miniaturized hydrogel-based soft power source capable of modulating the activity of networks of neuronal cells without the need for metal electrodes.

Superlattice Films

Work function difference induces spontaneous charge donation and band bending at the interfaces of superlattices, which causes optimization effects of modulation doping and energy filtering, leading to remarkably enhanced thermoelectric performances. This optimizing strategy is successfully elucidated in 1T′-MoTe₂/Bi₂Te₃ superlattice films. Meanwhile, the rational manipulation of interfacial band bending via tuning the Te/Bi flux ratio further promotes thermoelectric performances. More details can be found in article number 2300745 by Hang Zhang, Qingjie Zhang, Wei Liu, Xinfeng Tang, and co-workers.

Nature Materials, Published online: 29 August 2023; doi:10.1038/s41563-023-01642-w

Using the van der Waals crystal Sb2O3 as a buffer layer enables the growth of high-κ dielectrics on two-dimensional materials via atomic layer deposition.