Jing Zhang

This paper reports a high-security solution for anti-counterfeiting using hierarchical pattern with perfect combination of micro self-wrinkle and nano phase-separation as physical unclonable function labels (PUFs). A high security intelligent anti-counterfeiting authentication system is constructed by utilizing micro-nano information database of hierarchical PUF labels, combined with the advanced artificial intelligence machine learning model LPLA.

Abstract

With the increasing demand for information security, current anti-counterfeiting methods not only suffer from issues such as low information density and vulnerability to forgery, but also inherently involve a trade-off between information capacity and readout methods. This paper reports a high-security solution using hierarchical pattern with perfect combination of micro self-wrinkle and nano phase-separation as physical unclonable function (PUF) labels, which is generated through self-organization of anthracene-functionalized poly(styrene-block-butadiene-block-styrene) (SBS-CAN) under UV exposure. The double-layer morphologies formed by the wrinkle and phase separation are adjustable, independent, and stable. The obtained hierarchical PUF labels exhibit random and unique features similar to the minutiae of fingerprints at both micro and nano scales, ensuring a well-balanced bit uniformity (>0.492), high uniqueness (>0.496), and outstanding reliability (>96%). As a consequence of the multi-layered combination of morphologies, the designed PUF label possesses an information density about 10¹⁰ times higher than that of human fingerprints. The PUF labels can be quickly obtained through simple visual scanning and exhibit sufficient security. To cope with various application environments, the advanced authentication pipeline designed LPLA guarantees robust label recognition capability in real-world scenarios. A practical integrated anti-counterfeiting authentication system is developed by combining hierarchical PUF labels and authentication pipeline.

This work presents a novel 2D ferromagnetic semiconducting material with an unprecedented Curie temperature (T _c) of 230 K, over four times higher than previous records for 2D magnetic semiconductors. Such a high T _c arises from the synergy between in-plane and out-of-plane superexchange interactions, and puts forward a novel concept of regulating properties in the vertical dimension for 2D materials.

Abstract

2D magnetic semiconductors exhibit great potential for next-generation spintronics, but realizing their full capabilities has been hindered by the low Curie temperatures (T _c) below 50 K observed in current materials. Here, a new mechanism to substantially enhance the T _c of 2D semiconducting materials through incorporating both in-plane and out-of-plane superexchange interactions enabled by structural design is demonstrated. Specifically, monolayer Cr₂Se₃ is synthesized with a five-layer Se–Cr–Se–Cr–Se atomic structure using molecular beam epitaxy (MBE). This unique structure not only possesses optimized in-plane superexchange interaction but also incorporates out-of-plane Cr–Se–Cr couplings. Scanning tunneling spectroscopy (STS) and angular-resolved photoemission spectroscopy (ARPES) confirm its semiconducting nature. Remarkably, the ferromagnetic phase transition observed by ARPES and Magnetic Force Microscopy (MFM) indicated that its T _c is up to 230 K. This not only establishes a new record for T _c in 2D ferromagnetic semiconductor materials but also introduces a novel approach to modulating materials' properties by manipulating the vertical dimension in 2D materials.

The progress was summarized in the flexible electronics empowered by the two-dimensional materials, including electronic skins (for sweat and temperature sensors), gas sensors, touch pads, nanogenerators for mechanical energy collection, flexible supercapacitors and batteries, transistors and logic circuits, as well as memristors for neuromorphic computing. The readers may collect the stat-of-the-art research on graphene and MXene based flexible electronics.

Abstract

Flexible electronics has emerged as a continuously growing field of study. Two-dimensional (2D) materials often act as conductors and electrodes in electronic devices, holding significant promise in the design of high-performance, flexible electronics. Numerous studies have focused on harnessing the potential of these materials for the development of such devices. However, to date, the incorporation of 2D materials in flexible electronics has rarely been summarized or reviewed. Consequently, there is an urgent need to develop comprehensive reviews for rapid updates on this evolving landscape. This review covers progress in complex material architectures based on 2D materials, including interfaces, heterostructures, and 2D/polymer composites. Additionally, it explores flexible and wearable energy storage and conversion, display and touch technologies, and biomedical applications, together with integrated design solutions. Although the pursuit of high-performance and high-sensitivity instruments remains a primary objective, the integrated design of flexible electronics with 2D materials also warrants consideration. By combining multiple functionalities into a singular device, augmented by machine learning and algorithms, we can potentially surpass the performance of existing wearable technologies. Finally, we briefly discuss the future trajectory of this burgeoning field. This review discusses the recent advancements in flexible sensors made from 2D materials and their applications in integrated architecture and device design.

Nature, Published online: 05 June 2024; doi:10.1038/s41586-024-07482-1

Direct visualization of oxygen vacancies and self-doped ligand holes reveals the role of ligand oxygen in La3Ni2O7−δ and provides further understanding of superconducting nickelate materials.

Nature, Published online: 05 June 2024; doi:10.1038/s41586-024-07517-7

Nascent transcription in genes and enhancers genome-wide at the single-cell level is quantified using global run-on and sequencing (GRO–seq) with click chemistry.

Nature, Published online: 05 June 2024; doi:10.1038/s41586-024-07513-x

The spontaneous formation of magnesium-intercalated gallium nitride superlattices by the interstitial intercalation of two-dimensional magnesium results in considerable compressive strain perpendicular to the layers, leading to enhanced hole transport.

Relying on the intramolecular energy transfer and ultraviolet LED top-pumping technology, a relative gain of 11.6 dB cm⁻¹ at near-infrared 1535 nm wavelength can be achieved in complex Er(DBTTA)₃(DBFDPO)-doped polymer waveguides. The upconversion luminescence of Er³⁺ ions and thermal damage to the polymer waveguide caused by the high power density of laser pumping can be effectively reduced.

Abstract

A near-infrared luminescent complex Er(DBTTA)₃(DBFDPO) [where DBTTA = dibenzotetrathienoacene; DBFDPO = 4,6-bis (diphenylphosphoryl) dibenzofuran] is synthesized. Based on the intramolecular energy transfer between organic ligands and Er³⁺ ions, optical gains at 1535 nm are demonstrated in Er(DBTTA)₃(DBFDPO)-doped polymer waveguides under the excitation of light-emitting diodes (LEDs) instead of laser pumping. Relative gains of 6.4, 8.2, and 10.6 dB are obtained in 1 cm long waveguides with cross-sectional dimensions of 6 × 4, 4 × 4, and 2 × 3 µm² respectively, using the vertical top-pumping mode of a 365 nm LED with 462 mW. Incorporating an ≈100 nm thick aluminum reflector grown under the lower cladding, enhanced the optical gain to 11.6 dB cm⁻¹ in a waveguide with a cross-section of 4 × 4 µm², and an internal gain of ≈7.4 dB cm⁻¹ is achieved. By relying on the intramolecular energy transfer and LED top-pumping technology, the upconversion luminescence of Er³⁺ ions and thermal damage to polymer waveguides caused by the high power density of laser pumping can be effectively reduced. The complex Er(DBTTA)₃(DBFDPO)-doped polymer can be spin-coated on different types of waveguides to compensate for optical losses at 1.5 µm and is expected to have a critical role in planar photonic integration.

SnO₂/LaOCl nanofibers with a built-in electric field is designed to achieve efficient catalysis for electrochemical carbon dioxide reduction reaction for the first time. They exhibit remarkably high C1 Faradaic efficiency (FE) of 100% and 90.1% of FE_HCOOH in H-cell, as well as the current density of almost 400 mA cm⁻² at −2.31 V and FE_HCOOH of 83.4% in flow-cell.

Abstract

Constructing a built-in interfacial electric field (BIEF) is an effective approach to enhance the electrocatalysts performance, but it has been rarely demonstrated for electrochemical carbon dioxide reduction reaction (CO₂RR) to date. Herein, for the first time, SnO₂/LaOCl nanofibers (NFs) with BIEF is created by electrospinning, exhibiting a high Faradaic efficiency (FE) of 100% C₁ product (CO and HCOOH) at −0.9–−1.1 V versus reversible hydrogen electrode (RHE) and a maximum FE_HCOOH of 90.1% at −1.2 V_RHE in H-cell, superior to the commercial SnO₂ nanoparticles (NPs) and LaOCl NFs. SnO₂/LaOCl NFs also exhibit outstanding stability, maintaining negligible activity degradation even after 10 h of electrolysis. Moreover, their current density and FE_HCOOH are almost 400 mA cm⁻² at −2.31 V and 83.4% in flow-cell. The satisfactory CO₂RR performance of SnO₂/LaOCl NFs with BIEF can be ascribed to tight interface of coupling SnO₂ NPs and LaOCl NFs, which can induce charge redistribution, rich active sites, enhanced CO₂ adsorption, as well as optimized Gibbs free energy of *OCHO. The work reveals that the BIEF will trigger interfacial accumulation and stability enhancement effects in promoting CO₂RR activity and stability of SnO₂-based materials, providing a novel approach to develop stable and efficient CO₂RR electrocatalysts.

Nature Materials, Published online: 04 June 2024; doi:10.1038/s41563-024-01896-y

Precision laser irradiation of liquid-crystal polymer networks with dynamic bonds enables reversible phase patterning to create multi-stimuli responsive materials towards wearable devices and information encryption.

Elastic-Plastic Fully π-Conjugated Polymers (FπCPs) are prepared via side-chain internal plasticization for deep-blue flexible polymer light-emitting diods (PLEDs). Elastic-plastic FπCPs films present an excellent energy dissipation capacity (maximum fracture strain of 34.6%) and outstanding ultra-deep-blue emission (photoluminescence quantum yield of 56.38%). PLEDs based on stretchable films display a stable and efficient ultra-deep-blue emission, slightly depended on strains and cycling deformation.

Abstract

Emerging intrinsically flexible fully π-conjugated polymers (FπCPs) are a promising functional material for flexible optoelectronics, attributed to their potential interchain interpenetration and entanglement. However, the challenge remains in obtaining elastic–plastic FπCPs with intrinsic robust optoelectronic property and excellent long-term and cycling deformation stability simultaneously for applications in deep-blue flexible polymer light-emitting diodes (PLEDs). This study, demonstrates a series of elastic-plastic FπCPs (P1–P4) with an excellent energy dissipation capacity via side-chain internal plasticization for the ultra-deep-blue flexible PLEDs. First, the freestanding P1 film exhibited a maximum fracture strain of 34.6%. More interestingly, the elastic behavior is observed with a low strain (≤10%), and the stretched film with a high deformation (>10%) attributed to plastic processing revealed the robust capacity to realize energy absorption and release. The elastic–plastic P1 film exhibits outstanding ultra-deep-blue emission, with an efficiency of 56.38%. Subsequently, efficient PLEDs are fabricated with an ultra-deep-blue emission of CIE (0.16, 0.04) and a maximum external quantum efficiency of 1.73%. Finally, stable and efficient ultra-deep-blue electroluminescence are obtained from PLEDs based on stretchable films with different strains and cycling deformations, suggesting excellent elastic–plastic behavior and deformation stability for flexible electronics.

Nature Chemistry, Published online: 04 June 2024; doi:10.1038/s41557-024-01545-6

Chemical probes that selectively react with histidine could afford functional insight for those located in vital protein regions, but the moderate nucleophilicity of histidine and interference from other residues pose challenges. A singlet oxygen and chemical probe relay labelling approach demonstrates high selectivity, enabling comprehensive histidine profiling and providing crucial functional insights.

Nature Communications, Published online: 03 June 2024; doi:10.1038/s41467-024-48980-0

Bioadhesive materials and patches are promising alternatives to surgical sutures and staples but many existing bioadhesives do not meet the functional requirements of current surgical procedures. Here the authors present a tissue adhesive, stretchable and rapid photo-projection compatible translational patch material which is able to deliver therapeutics.

Nature Synthesis, Published online: 04 June 2024; doi:10.1038/s44160-024-00562-0

A van der Waals epitaxial strategy is reported for growing intrinsic quantum dots (QDs) by modulating interfacial couplings on van der Waals surfaces. This method overcomes lattice mismatch constraints and produces versatile III–V and IV–VI QDs with controllable morphologies, broadening near-infrared photoresponse in InSb QDs/MoS2 by efficient interlayer charge transfer.

Nature Communications, Published online: 03 June 2024; doi:10.1038/s41467-024-48521-9

This study explores alternative stable states in microbial communities. Focusing on a respiratory tract community of 6 species, the authors identified four distinct stable states that are predicted to be driven by cooperative growth. The findings contrast with the common association between competitive interactions and multistability in microbial communities.

Borophene, a monolayer of boron atoms, emerges as a promising material for energy storage devices. This review comprehensively explores borophene's synthesis techniques, tunable properties, and potential applications in lithium-ion batteries, supercapacitors, and other battery systems. Its exceptional capacities, ionic conductivities, and structural stabilities make borophene a prime candidate for next-generation energy storage technologies.

Abstract

Monolayer boron nanosheet, commonly known as borophene, has garnered significant attention in recent years due to its unique structural, electronic, mechanical, and thermal properties. This review paper provides a comprehensive overview of the advancements in the synthetic strategies, tunable properties, and prospective applications of borophene, specifically focusing on its potential in energy storage devices. The review begins by discussing the various synthesis techniques for borophene, including molecular beam epitaxy (MBE), chemical vapor deposition (CVD), and chemical methods, such as ultrasonic exfoliation and thermal decomposition of boron-containing precursors. The tunable properties of borophene, including its electronic, mechanical, and thermal characteristics, are extensively reviewed, with discussions on its bandgap engineering, plasmonic behavior, and thermal conductivity. Moreover, the potential applications of borophene in energy storage devices, particularly as anode materials in metal-ion batteries and supercapacitors, along with its prospects in other energy storage systems, such as sodium-oxygen batteries, are succinctly, discussed. Hence, this review provides valuable insights into the synthesis, properties, and applications of borophene, offering much-desired guidance for further research and development in this promising area of nanomaterials science.

This paper encapsulates the review's focus on recent advances in strain engineering of 2D layered materials like graphene, h-BN, TMDs, and BP. It outlines the methods, effects on properties, and potential applications in devices, providing a roadmap for further research.

Abstract

This review explores the growing interest in 2D layered materials, such as graphene, h-BN, transition metal dichalcogenides (TMDs), and black phosphorus (BP), with a specific focus on recent advances in strain engineering. Both experimental and theoretical results are delved into, highlighting the potential of strain to modulate physical properties, thereby enhancing device performance. Various strain engineering methods are summarized, and the impact of strain on the electrical, optical, magnetic, thermal, and valleytronic properties of 2D materials is thoroughly examined. Finally, the review concludes by addressing potential applications and challenges in utilizing strain engineering for functional devices, offering valuable insights for further research and applications in optoelectronics, thermionics, and spintronics.

Information can be encoded onto a fluorescent polymer via facile ultraviolet light exposure. The inscriptions can be written as a single color or in a polychromic format. The polymer can then be removed from the substrate as a freestanding, flexible, transparent film. When exposed to certain wavelengths, the written information becomes visible, especially if aided by the appropriate filter.

Abstract

A poly(para)phenylene conjugated polymer is developed to store information via a quick and facile optical writing method. After exposure to UV light, co-fluorescence (films with two or more written emission colors –, i.e., “double-on”) and “on-off” states are written into the flexible polymer films. The hidden information is invisible under ambient lighting and can only be read with an appropriate light source, optical filter, and/or magnifier, thus providing a level of security for information encoded into the films. The physical and chemical mechanisms are discussed responsible for the rapid fluorescence changes that occur under UV exposure and demonstrate microscale multi-colored artwork and hidden QR codes written into pliable and freestanding films. Depending on the preparation, the written patterns remained easily visible and stable after exposure to water and to ambient levels of UV background radiation.

This work has systematically reviewed the emerging 2D MXenes in terms of their physical and chemical properties and thoroughly discussed the multi-interfacial engineering on MXenes encompassing termination regulation, polymerization modification, heteroatom doping and defects manipulation for energy storage and harvesting. The significant achievements of the state-of-the-art MXene-based platforms for power sources and self-powered wearable devices are comprehensively outlined.

Abstract

Self-powered wearable devices with integrated energy supply module and sensitive sensors have significantly blossomed for continuous monitoring of human activity and the surrounding environment in healthcare sectors. The emerging of MXene-based materials has brought research upsurge in the fields of energy and electronics, owing to their excellent electrochemical performance, large surface area, superior mechanical performance, and tunable interfacial properties, where their performance can be further boosted via multi-interface engineering. Herein, a comprehensive review of recent progress in MXenes for self-powered wearable devices is discussed from the aspects of multi-interface engineering. The fundamental properties of MXenes including electronic, mechanical, optical, and thermal characteristics are discussed in detail. Different from previous review works on MXenes, multi-interface engineering of MXenes from termination regulation to surface modification and their impact on the performance of materials and energy storage/conversion devices are summarized. Based on the interfacial manipulation strategies, potential applications of MXene-based self-powered wearable devices are outlined. Finally, proposals and perspectives are provided on the current challenges and future directions in MXene-based self-powered wearable devices.

This review provides perspectives on the chemical intercalation of layered materials. The characteristics of the different intercalation methods and their chemical mechanisms are discussed. The properties and applications of intercalation compounds are discussed. Finally, brief insights into the challenges and future opportunities for the chemical intercalation of layered materials are provided.

Abstract

The intercalation of layered materials offers a flexible approach for tailoring their structures and generating unexpected properties. This review provides perspectives on the chemical intercalation of layered materials, including graphite/graphene, transition metal dichalcogenides, MXenes, and some particular materials. The characteristics of the different intercalation methods and their chemical mechanisms are discussed. The influence of intercalation on the structural changes of the host materials and the structural change how to affect the intrinsic properties of the intercalation compounds are discussed. Furthermore, a perspective on the applications of intercalation compounds in fields such as energy conversion and storage, catalysis, smart devices, biomedical applications, and environmental remediation is provided. Finally, brief insights into the challenges and future opportunities for the chemical intercalation of layered materials are provided.

The article presents the development of fibre-based photodetectors using rolled graphene layers and perovskites, achieving high external responsivity (∼22 kAW^-1 at 488 nm) and fast response times (∼9 ms). These photodetectors maintain performance after 30 wash cycles (∼72% photocurrent), suitable for wearable applications.

Abstract

The integration of optoelectronic devices, such as transistors and photodetectors (PDs), into wearables and textiles is of great interest for applications such as healthcare and physiological monitoring. These require flexible/wearable systems adaptable to body motions, thus materials conformable to non-planar surfaces, and able to maintain performance under mechanical distortions. Here, fibre PDs are prepared by combining rolled graphene layers and photoactive perovskites. Conductive fibres (~500 Ωcm^-1) are made by rolling single-layer graphene (SLG) around silica fibres, followed by deposition of a dielectric layer (Al₂O₃ and parylene C), another rolled SLG as a channel, and perovskite as photoactive component. The resulting gate-tunable PD has a response time~9ms, with an external responsivity~22kAW^-1 at 488nm for a 1V bias. The external responsivity is two orders of magnitude higher, and the response time one order of magnitude faster, than state-of-the-art wearable fibre-based PDs. Under bending at 4mm radius, up to~80% photocurrent is maintained. Washability tests show~72% of initial photocurrent after 30 cycles, promising for wearable applications.

3D Printed Electronic Skin

3D-printed electronic skin, mimicking human sensitivity, advances wearable technology and human–machine interfaces. In article number 2313575, Akhilesh K. Gaharwar and co-workers show that its nanoengineering enables multifunctional capabilities, paving new paths in robotics and personal devices with motion, touch, and temperature detection features.

A novel family of cell manipulators is presented, which are deformable by optical tweezers and rely on their elasticity to hold single, nonadherent cells. The structures, prepared with multiphoton polymerization, provide high spatial and temporal control over the manipulation of the cells enabling single cell movement with 6° of freedom and cell–cell interactions.

Abstract

Precisely controlled manipulation of nonadherent single cells is often a pre-requisite for their detailed investigation. Optical trapping provides a versatile means for positioning cells with submicrometer precision or measuring forces with femto-Newton resolution. A variant of the technique, called indirect optical trapping, enables single-cell manipulation with no photodamage and superior spatial control and stability by relying on optically trapped microtools biochemically bound to the cell. High-resolution 3D lithography enables to prepare such cell manipulators with any predefined shape, greatly extending the number of achievable manipulation tasks. Here, it is presented for the first time a novel family of cell manipulators that are deformable by optical tweezers and rely on their elasticity to hold cells. This provides a more straightforward approach to indirect optical trapping by avoiding biochemical functionalization for cell attachment, and consequently by enabling the manipulated cells to be released at any time. Using the photoresist Ormocomp, the deformations achievable with optical forces in the tens of pN range and present three modes of single-cell manipulation as examples to showcase the possible applications such soft microrobotic tools can offer are characterized. The applications describe here include cell collection, 3D cell imaging, and spatially and temporally controlled cell–cell interaction.

Immunochromatographic Diagnosis

In article number 2310014, Chaoguang Wang, Chongwen Wang, Bing Gu, and co-workers show that 4-mercaptophenylboronic acid-modified two-dimensional film-like magnetic SERS tag (GFe–DAu–D/M) exhibits universal capture ability and superior SERS activity for immunochromatographic diagnosis of three important bacteria in real clinical specimens. The GFe–DAu–D/M-based immunochromatography method could be served as a promising candidate for application in the clinical and POCT fields for the rapid and sensitive monitoring of multiple pathogens.

The free-standing titanium dioxide film can be transferred to carbon cloth (TiO₂-CC) to form a highly sensitive flexible electrochemical sensor. The TiO₂-CC electrochemical sensor can be integrated into a smart diaper to detect the trace amount of dopamine or an integrated skin-interfaced patch with microfluidic sampling and wireless transmission units for real-time detection of the sweat tyrosine and paracetamol concentration.

Abstract

The concentration of dopamine (DA) and tyrosine (Tyr) reflects the condition of patients with Parkinson's disease, whereas moderate paracetamol (PA) can help relieve their pain. Therefore, real-time measurements of these bioanalytes have important clinical implications for patients with Parkinson's disease. However, previous sensors suffer from either limited sensitivity or complex fabrication and integration processes. This work introduces a simple and cost-effective method to prepare high-quality, flexible titanium dioxide (TiO₂) thin films with highly reactive (001)-facets. The as-fabricated TiO₂ film supported by a carbon cloth electrode (i.e., TiO₂–CC) allows excellent electrochemical specificity and sensitivity to DA (1.390 µA µM⁻¹ cm⁻²), Tyr (0.126 µA µM⁻¹ cm⁻²), and PA (0.0841 µA µM⁻¹ cm⁻²). More importantly, accurate DA concentration in varied pH conditions can be obtained by decoupling them within a single differential pulse voltammetry measurement without additional sensing units. The TiO₂–CC electrochemical sensor can be integrated into a smart diaper to detect the trace amount of DA or an integrated skin-interfaced patch with microfluidic sampling and wireless transmission units for real-time detection of the sweat Try and PA concentration. The wearable sensor based on TiO₂–CC prepared by facile manufacturing methods holds great potential in the daily health monitoring and care of patients with neurological disorders.

A hierarchical structure integrating nano-scale protrusions on micro-scale protuberances is achieved on Ni-free Ti-based bulk metallic glasses via a two-step thermoplastic forming technique. The patterned materials preserve advantageous mechanical properties and biocompatibility from the as-cast materials. However, the surface features change the cell morphology. Besides implant applications, this work realizes a strategy for studying cell behavior on rigid ordered surfaces.

Abstract

Ni-free Ti-based bulk metallic glasses (BMGs) are exciting materials for biomedical applications because of their outstanding biocompatibility and advantageous mechanical properties. The glassy nature of BMGs allows them to be shaped and patterned via thermoplastic forming (TPF). This work demonstrates the versatility of the TPF technique to create micro- and nano-patterns and hierarchical structures on Ti₄₀Zr₁₀Cu₃₄Pd₁₄Sn₂ BMG. Particularly, a hierarchical structure fabricated by a two-step TPF process integrates 400 nm hexagonal close-packed protrusions on 2.5 µm square protuberances while preserving the advantageous mechanical properties from the as-cast material state. The correlations between thermal history, structure, and mechanical properties are explored. Regarding biocompatibility, Ti₄₀Zr₁₀Cu₃₄Pd₁₄Sn₂ BMGs with four surface topographies (flat, micro-patterned, nano-patterned, and hierarchical-structured surfaces) are investigated using Saos-2 cell lines. Alamar Blue assay and live/dead analysis show that all tested surfaces have good cell proliferation and viability. Patterned surfaces are observed to promote the formation of longer filopodia on the edge of the cytoskeleton, leading to star-shaped and dendritic cell morphologies compared with the flat surface. In addition to potential implant applications, TPF-patterned Ti-BMGs enable a high level of order and design flexibility on the surface topography, expanding the available toolbox for studying cell behavior on rigid and ordered surfaces.

A series of heterojunction phototransistors (HPTs) based on Ruddlesden–Popper phase layered perovskites (RPLPs) with different organic spacers are developed. The 2-thiophenethylammonium-RPLP- and p-fluorophenylethylammonium-RPLP-based HPTs show ultrasensitive performance with ultra-high photoresponsivity. These HPTs work well as optoelectronic synapses. Systematically studies on the structure-property relationship of organic spacers/RPLPs provides valuable guidance for the further development of perovskite materials and their optoelectronic applications.

Abstract

2D Ruddlesden–Popper phase layered perovskites (RPLPs) hold great promise for optoelectronic applications. In this study, a series of high-performance heterojunction phototransistors (HPTs) based on RPLPs with different organic spacer cations (namely butylammonium (BA⁺), cyclohexylammonium (CyHA⁺), phenethylammonium (PEA⁺), p-fluorophenylethylammonium (p-F-PEA⁺), and 2-thiophenethylammonium (2-ThEA⁺)) are fabricated successfully, in which high-mobility organic semiconductor 2,7-dioctyl[1]benzothieno[3,2-b]benzothiophene is adopted to form type II heterojunction channels with RPLPs. The 2-ThEA⁺-RPLP-based HPTs show the highest photosensitivity of 3.18 × 10⁷ and the best detectivity of 9.00 × 10¹⁸ Jones, while the p-F-PEA⁺-RPLP-based ones exhibit the highest photoresponsivity of 5.51 × 10⁶ A W⁻¹ and external quantum efficiency of 1.32 × 10⁹%, all of which are among the highest reported values to date. These heterojunction systems also mimicked several optically controllable fundamental characteristics of biological synapses, including excitatory postsynaptic current, paired-pulse facilitation, and the transition from short-term memory to long-term memory states. The device based on 2-ThEA⁺-RPLP film shows an ultra-high PPF index of 234%. Moreover, spacer engineering brought fine-tuned thin film microstructures and efficient charge transport/transfer, which contributes to the superior photodetection performance and synaptic functions of these RPLP-based HPTs. In-depth structure-property correlations between the organic spacer cations/RPLPs and thin film microstructure/device performance are systematically investigated.

High-quality hexagonal/hexagonal β-NaYF₄:Yb,Tm/Cs₄PbBr₆ core/shell nanocrystals are successfully synthesized owing to their similar crystal structures. The core/shell nanocrystals exhibit narrow-band green emission centered at 524 nm under 980 nm excitation through a Förster resonance energy transfer process with a high efficiency of 58.33%. Further, the core/shell structure leads to excellent water and thermal cycling stability of Cs₄PbBr₆.

Abstract

Synthesis of upconversion nanoparticles (UCNPs)-metal halide perovskites (MHPs) heterostructure is garnered immense attentions due to their unparalleled photophysical properties. However, the obvious difference in their structural forms makes it a huge challenge. Herein, hexagonal β-NaYF₄ and hexagonal Cs₄PbBr₆ are filtrated to construct the UCNP/MHP heterostructural luminescent material. The similarity in their crystal structures facilitate the heteroepitaxial growth of Cs₄PbBr₆ on the surface of β-NaYF₄ NPs, leading to the formation of high-quality β-NaYF₄:Yb,Tm/Cs₄PbBr₆ core/shell nanocrystals (NCs). Interestingly, this heterostructure endows the core/shell NCs with typically narrow-band green emission centered at 524 nm under 980 nm excitation, which should be attributed to the Förster resonance energy transfer (FRET) from Tm³⁺ to Cs₄PbBr₆. It is noteworthy that the FRET efficiency of β-NaYF₄:Yb,Tm/Cs₄PbBr₆ core/shell NCs (58.33%) is much higher than that of the physically mixed sample (1.84%). In addition, the reduced defect density, lattice anchoring effect, as well as diluted ionic bonding proportion induced by the core/shell structure further increase the excellent water-resistance and thermal cycling stability of Cs₄PbBr₆. These findings open up a new way to construct UCNP/MHP heterostructure with better multi-code luminescence performance and stability and promote its wide optoelectronic applications.

A practical sensory interface for glucose detection is prepared through nanopatterned auto-fluorescent polymer brushes decorated with phenylboronic acid receptors. These glucose-responsive luminescent polymer brushes, which are capable of translating conformational transitions triggered by pH variations and binding events into fluorescent readouts without the need for fluorescent dyes, hold potential for medical and bioelectronic applications such as the fabrication of miniaturized sensors, micro- or nanofluidic devices, and biochips, and offer advantages such as the higher density of reaction sites and much smaller sample volume.

Abstract

Designing smart (bio)interfaces with the capability to sense and react to changes in local environments offers intriguing possibilities for new surface-based sensing devices and technologies. Polymer brushes make ideal materials to design such adaptive and responsive interfaces given their large variety of functional and structural possibilities as well as their outstanding abilities to respond to physical, chemical, and biological stimuli. Herein, a practical sensory interface for glucose detection based on auto-fluorescent polymer brushes decorated with phenylboronic acid (PBA) receptors is presented. The glucose-responsive luminescent surfaces, which are capable of translating conformational transitions triggered by pH variations and binding events into fluorescent readouts without the need for fluorescent dyes, are grown from both nanopatterned and non-patterned substrates. Two-photon laser scanning confocal microscopy and atomic force microscopy (AFM) analyses reveal the relationship between the brush conformation and glucose concentration and confirm that the phenylboronic acid functionalized brushes can bind glucose over a range of physiologically relevant concentrations in a reversible manner. The combination of auto-fluorescent polymer brushes with synthetic receptors presents a promising avenue for designing innovative and robust sensing systems, which are essential for various biomedical applications, among other uses.