Roll-to-roll production of 30-inch graphene films for transparent electrodes

Is Low Polydispersity Always Beneficial? Exploring the Impact of Size Polydispersity on the Microstructure and Rheological Properties of Graphene Oxide

Graphene oxide (GO) is a promising material widely utilized in advanced materials engineering, such as in the development of soft robotics, sensors, and flexible devices. Considering that GOs are often processed using solution-based methods, a comprehensive understanding of the fundamental characteristics of GO in dispersion states becomes crucial given their significant influence on the ultimate properties of the device. GOs inherently exhibit polydispersity in solution, which plays a critical role in determining the mechanical behavior and flowability. However, research in the domain of 2D colloids concerning the effects of GO's polydispersity on its rheological properties and microstructure is relatively scant. Consequently, gaining a comprehensive understanding of how GO's polydispersity affects these critical aspects remains a pressing concern. In this study, we aim to investigate the dispersions and structure of GOs and clarify the effect of polydispersity on the rheological properties and yielding behavior. Using a rheometer, polarized optical microscopy, and small-angle X-ray scattering, we found that higher polydispersity in the same average size leads to overall improved rheological properties and higher flowability during yielding. Thus, our study can be beneficial in the employment of polydispersity in the processing of GO such as 3D printing and fiber spinning.

Graphene-enabled laser lift-off for ultrathin displays

Laser lift-off (LLO) of ultrathin polyimide (PI) films is important in the manufacturing of ultrathin displays. However, conventional LLO technologies face challenges in separating the ultrathin PI films without causing mechanical and electrical damage to integrated devices. Here, we propose a graphene-enabled laser lift-off (GLLO) method to address the challenges. The GLLO method is developed by integrating chemical vapor deposition (CVD)-grown graphene at the interface between a transparent carrier and an ultrathin PI film, exhibiting improved processability and lift-off quality. In particular, the GLLO method significantly mitigates plastic deformation of the PI film and minimizes carbonaceous residues remaining on the carrier. The role of graphene is attributed to three factors: enhancement of interfacial UV absorption, lateral heat diffusion, and adhesion reduction, and experimentations and numerical simulations verify the mechanism. Finally, it is demonstrated that the GLLO method separates ultrathin organic light-emitting diode (OLED) devices without compromising performance. We believe that this work will pave the way for utilizing CVD graphene in various laser-based manufacturing applications.

Optimization of Magnetic Behaviors of Au-NP-Decorated MWCNTs and Reduced Graphene Oxide for Biomedical Applications

Optimization of electronic/magnetic behaviors of chemically decorated diamagnetic noble-metal gold nanoparticles (Au-NPs ≈5 at. %) on multiwalled carbon nanotubes (MWCNTs) and reduced graphene oxide (r-GO) is studied for future uses of optoelectronic/magnetic and biomedical applications. The changes between Au 4f5/2 and Au 4f7/2 ≈ 3.7 eV in X-ray photoelectron spectroscopy and 1.1 (±0.3) eV shifts in the C K-edge in X-ray absorption near edge structure spectroscopy confirm that the reduced form of Au0 was present in the Au-NP-decorated nanocomposites. The potential difference (ΔV) is built due to charge creations at the interface of r-GO/MWCNTs and Au-NPs and shifts in the Fermi level (ΔE F) due to electronic transfer effects, and as a result, the work functions are reduced from 3.2 eV (MWCNTs) to 3.0 eV (MWCNTs:Au-NPs) and 3.1 (r-GO) to 2.8 eV (r-GO:Au-NPS), respectively. Negligible remanence/coercivity in MWCNTs/r-GO (/Au-NPs) with blocking temperature ≈300 K in MWCNTs:Au-NPs accounted for the existence of diamagnetic Au-NPs in these nanocomposites, which implies a superparamagnetic nature. These results furnish the evidence about the optimization of magnetic behaviors of r-GO/MWCNTs (/Au-NPs) that may possibly be altered as a novel contrast agent for clinical magnetic resonance imaging, drug delivery, and hyperthermia applications.

Laser-Assisted Photo-Thermal Reaction for Ultrafast Synthesis of Single-Walled Carbon Nanotube/Copper Nanoparticles Hybrid Films as Flexible Electrodes

The hybridization of single-walled carbon nanotubes (SWCNTs) and Cu nanoparticles offers a promising strategy for creating highly conductive and mechanically stable fillers for flexible printed electronics. In this study, we report the ultrafast synthesis of SWCNT/Cu hybrid nanostructures and the fabrication of flexible electrodes under ambient conditions through a laser-induced photo-thermal reaction. Thermal energy generated from the nonradiative relaxation of the π-plasmon resonance of SWCNTs was utilized to reduce the Cu-complex (known as a metal-organic decomposition ink) into Cu nanoparticles. We systematically investigated the effects of SWCNT concentration and output laser power on the structural and electrical properties of the SWCNT/Cu hybrid electrodes. The SWCNT/Cu electrodes achieved a minimum electrical resistivity of 46 μohm·cm, comparable to that of the metal-based printed electrodes. Mechanical bending tests demonstrated that the SWCNT/Cu electrodes were highly stable and durable, with no significant deformation observed even after 1000 bending cycles. Additionally, the electrodes showed rapid temperature increases and stable Joule heating performance, reaching temperatures of nearly 80 °C at an applied voltage of less than 3.5 V.

Ultrafast 2D Nanosheet Assembly via Spontaneous Spreading Phenomenon

In 2D materials, a key engineering challenge is the mass production of large-area thin films without sacrificing their uniform 2D nature and unique properties. Here, it is demonstrated that a simple fluid phenomenon of water/alcohol solvents can become a sophisticated tool for self-assembly and designing organized structures of 2D nanosheets on a water surface. In situ, surface characterizations show that water/alcohol droplets of 2D nanosheets with cationic surfactants exhibit spontaneous spreading of large uniform monolayers within 10 s. Facile transfer of the monolayers onto solid or flexible substrates results in high-quality mono- and multilayer films with high coverages (>95%) and homogeneous electronic/optical properties. This spontaneous spreading is quite general and can be applied to various 2D nanosheets, including metal oxides, graphene oxide, h-BN, MoS2, and transition metal carbides, enabling on-demand smart manufacture of large-size (>4 inchϕ) 2D nanofilms and free-standing membranes.

A Polymeric Two-in-One Electron Transport Layer and Transparent Electrode for Efficient Indoor All-Organic Solar Cells

Transparent electrodes (TEs) are vital in optoelectronic devices, enabling the interaction of light and charges. While indium tin oxide (ITO) has traditionally served as a benchmark TE, its high cost prompts the exploration of alternatives to optimize electrode characteristics and improve device efficiencies. Conducting polymers, which combine polymer advantages with metal-like conductivity, emerge as a promising solution for TEs. This work introduces a two-in-one electron transport layer (ETL) and TE based on films of polyethylenimine ethoxylated (PEIE)-modified poly(benzodifurandione) (PBFDO). These PEIE-modified PBFDO layers exhibit a unique combination of properties, including low sheet resistance (130 Ω sq-1), low work function (4.2 eV), and high optical transparency (>85% in the UV-vis-NIR range). In contrast to commonly used poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), the doping level of PBFDO remains unaffected by the PEIE treatment, as verified through UV-vis-NIR absorption and X-ray photoelectron spectroscopy measurements. When employed as a two-in-one ETL/TE in organic solar cells, the PEIE-modified PBFDO electrode exhibits performance comparable to conventional ITO electrodes. Moreover, this work demonstrates all-organic solar cells with record-high power conversion efficiencies of >15.1% under indoor lighting conditions. These findings hold promise for the development of fully printed, all-organic optoelectronic devices.

Transferrable CsPbBr3 Perovskite Single-Crystalline Films for Visible-Wavelength Photodetectors

In this study, we propose large-scale CsPbBr3 (CPB) single-crystalline films (SCFs) grown by a one-step vapor-phase epitaxy (VPE) method for application in optoelectronic devices. After optimizing the transport speed of the precursor and cooling rate, we obtained continuous CPB films with a lateral size exceeding 2 cm2, and the thickness could be controlled from several micrometers to hundreds of nanometers. Crystallography and optoelectronic characterization proved the excellent crystallinity and very low trap density (2.14 × 1011) of the SCFs. Furthermore, we demonstrate a transfer-assembly strategy for fabricating perovskite SCF-based heterostructures for visible photodetectors. The high-quality SCF films in the active layer suppress the leakage current, leading to a low dark current of 5 × 10-10 A at -0.6 V. Therefore, the self-biased photodetector based on the vertical CsPbBr3 SCF-SnO2 heterostructure showed a high responsivity of 1.9 A/W, a detectivity of 4.65 × 1012 Jones, and a large on/off ratio of 4.63 × 103 under a 1 mW/cm2 450 nm light illumination. Our study not only demonstrates the excellent performance of single-crystalline perovskite-based photodiodes but also provides a universal assembly method for the integration of monocrystalline perovskite films in optoelectronic devices.

Gels/Hydrogels in Different Devices/Instruments-A Review

Owing to their physical and chemical properties and stimuli-responsive nature, gels and hydrogels play vital roles in diverse application fields. The three-dimensional polymeric network structure of hydrogels is considered an alternative to many materials, such as conductors, ordinary films, constituent components of machines and robots, etc. The most recent applications of gels are in different devices like sensors, actuators, flexible screens, touch panels, flexible storage, solar cells, batteries, and electronic skin. This review article addresses the devices where gels are used, the progress of research, the working mechanisms of hydrogels in those devices, and future prospects. Preparation methods are also important for obtaining a suitable hydrogel. This review discusses different methods of hydrogel preparation from the respective raw materials. Moreover, the mechanism by which gels act as a part of electronic devices is described.

Chemiresistive Gas Sensing using Graphene-Metal Oxide Hybrids

Chemiresistive sensing lies in its ability to provide fast, accurate, and reliable detection of various gases in a cost-effective and non-invasive manner. In this context, graphene-functionalized metal oxides play crucial role in hydrogen gas sensing. However, a cost-effective, defect-free, and large production schemes of graphene-based sensors are required for industrial applications. This review focuses on graphene-functionalized metal oxide nanostructures designed for gaseous molecules detection, mainly hydrogen gas sensing applications. For the convenience of the reader and to understand the role of graphene-metal oxide hybrids (GMOH) in gas sensing activities, a brief overview of the properties and synthesis routes of graphene and GMOH have been reported in this paper. Metal oxides play an essential role in the GMOH construct for hydrogen gas sensing. Therefore, various metal oxides-decorated GMOH constructs are detailed in this review as gas sensing platforms, particularly for hydrogen detection. Finally, specific directions for future research works and challenges ahead in designing highly selective and sensitive hydrogen gas sensors have been highlighted. As illustrated in this review, understanding of the metal oxides-decorated GMOH constructs is expected to guide ones in developing emerging hybrid nanomaterials that are suitable for hydrogen gas sensing applications.

Fast adaptive focusing confocal Raman microscopy for large-area two-dimensional materials

Large-area two-dimensional (2D) materials possess significant potential in the development of next generation semiconductor due to their unique physicochemical properties. Confocal Raman spectroscopy (CRM), a typical 2D material characterization method, has a limited effective measurement area owing to the restricted focus depth of the system and the less-than-ideal level of the substrate. We propose fast adaptive focusing confocal Raman microscopy (FAFCRM) to realize real-time focusing detection for large-area 2D materials. By observing spot changes on the charge coupled device (CCD) caused by placing an aperture in front of the CCD, the methodology gives a focusing resolution up to 100 nm per 60 μm without axial scanning. A graphene was measured over 25.6 mm × 25.6 mm area on focus through all the scanning. The research results provide new perspectives for non-destructive characterization of 2D materials at the inch level.

Polymer-Assisted Graphite Exfoliation: Advancing Nanostructure Preparation and Multifunctional Composites

Exfoliated graphite (ExG) embedded in a polymeric matrix represents an accessible, cost-effective, and sustainable method for generating nanosized graphite-based polymer composites with multifunctional properties. This review article analyzes diverse methods currently used to exfoliate graphite into graphite nanoplatelets, few-layer graphene, and polymer-assisted graphene. It also explores engineered methods for small-scale pilot production of polymer nanocomposites. It highlights the chemistry involved during the graphite intercalation and exfoliation process, particularly emphasizing the interfacial interactions related to steric repulsion forces, van der Waals forces, hydrogen bonds, π-π stacking, and covalent bonds. These interactions promote the dispersion and stabilization of the graphite derivative structures in polymeric matrices. Finally, it compares the enhanced properties of nanocomposites, such as increased thermal and electrical conductivity and electromagnetic interference (EMI) shielding applications, with those of neat polymer materials.

Recent Advances in Transparent Electrodes and Their Multimodal Sensing Applications

This review examines the recent advancements in transparent electrodes and their crucial role in multimodal sensing technologies. Transparent electrodes, notable for their optical transparency and electrical conductivity, are revolutionizing sensors by enabling the simultaneous detection of diverse physical, chemical, and biological signals. Materials like graphene, carbon nanotubes, and conductive polymers, which offer a balance between optical transparency, electrical conductivity, and mechanical flexibility, are at the forefront of this development. These electrodes are integral in various applications, from healthcare to solar cell technologies, enhancing sensor performance in complex environments. The paper addresses challenges in applying these electrodes, such as the need for mechanical flexibility, high optoelectronic performance, and biocompatibility. It explores new materials and innovative techniques to overcome these hurdles, aiming to broaden the capabilities of multimodal sensing devices. The review provides a comparative analysis of different transparent electrode materials, discussing their applications and the ongoing development of novel electrode systems for multimodal sensing. This exploration offers insights into future advancements in transparent electrodes, highlighting their transformative potential in bioelectronics and multimodal sensing technologies.

Graphene-skinned alumina fiber fabricated through metalloid-catalytic graphene CVD growth on nonmetallic substrate and its mass production

Graphene growth on widely used dielectrics/insulators via chemical vapor deposition (CVD) is a strategy toward transfer-free applications of CVD graphene for the realization of advanced composite materials. Here, we develop graphene-skinned alumina fibers/fabrics (GAFs/GAFFs) through graphene CVD growth on commercial alumina fibers/fabrics (AFs/AFFs). We reveal a vapor-surface-solid growth model on a non-metallic substrate, which is distinct from the well-established vapor-solid model on conventional non-catalytic non-metallic substrates, but bears a closer resemblance to that observed on catalytic metallic substrates. The metalloid-catalytic growth of graphene on AFs/AFFs resulted in reduced growth temperature (~200 °C lower) and accelerated growth rate (~3.4 times faster) compared to that obtained on a representative non-metallic counterpart, quartz fiber. The fabricated GAFF features a wide-range tunable electrical conductivity (1-15000 Ω sq-1), high tensile strength (>1.5 GPa), lightweight, flexibility, and a hierarchical macrostructure. These attributes are inherited from both graphene and AFF, making GAFF promising for various applications including electrical heating and electromagnetic interference shielding. Beyond laboratory level preparation, the stable mass production of large-scale GAFF has been achieved through a home-made roll-to-roll system with capacity of 468-93600 m2/year depending on product specifications, providing foundations for the subsequent industrialization of this material, enabling its widespread adoption in various industries.

Graphene-Enhanced UV-C LEDs

Light-emitting diodes in the UV-C spectral range (UV-C LEDs) can potentially replace bulky and toxic mercury lamps in a wide range of applications including sterilization and water purification. Several obstacles still limit the efficiencies of UV-C LEDs. Devices in flip-chip geometry suffer from a huge difference in the work functions between the p-AlGaN and high-reflective Al mirrors, whereas the absence of UV-C transparent current spreading layers limits the development of UV-C LEDs in standard geometry. Here it is demonstrated that transfer-free graphene implemented directly onto the p-AlGaN top layer by a plasma enhanced chemical vapor deposition approach enables highly efficient 275 nm UV-C LEDs in both, flip-chip and standard geometry. In flip-chip geometry, the graphene acts as a contact interlayer between the Al-mirror and the p-AlGaN enabling an external quantum efficiency (EQE) of 9.5% and a wall-plug efficiency (WPE) of 5.5% at 8 V. Graphene combined with a ≈1 nm NiOx support layer allows a turn-on voltage <5 V. In standard geometry graphene acts as a current spreading layer on a length scale up to 1 mm. These top-emitting devices exhibit a EQE of 2.1% at 8.7 V and a WPE of 1.1%.

Amino-functionalized graphene oxide affects bacteria-phage interactions in aquatic environments

The widespread use of graphene family nanomaterials (GFNs) in mass production has resulted in their release into the atmosphere, soil and water environment through various processes. Among these, the water environment is particularly affected by GFN pollution. Our previous study has demonstrated the impact of graphene oxide (GO) on bacteria-phage interactions in natural systems. However, the effects of amino-functionalized GO with a positive charge on bacteria-phage interactions in aquatic environments remain unclear. In the present study, we found that amino-functionalized graphene oxide (AGO) (0.05 mg/mL) inhibited the growth of Pseudomonas aeruginosa Y12. Furthermore, treating P. aeruginosa Y12 and phage with AGO (0.05 mg/mL) led to a reduced ratio of phage to bacteria, indicating that AGO can inhibit phage infection of bacteria. Additionally, the acidic environment exacerbated this effect by promoting electrostatic adsorption between the positively charged AGO and the negatively charged phage. Finally, a field water body intervention experiment showed that the richness and diversity of bacterial communities in six water samples changed due to AGO exposure, as revealed by Illumina analysis based on the bacterial 16S rRNA gene. These findings offer valuable insights into the environmental impacts of GFNs.

Carbon Corrosion Induced by Surface Defects Accelerates Degradation of Platinum/Graphene Catalysts in Oxygen Reduction Reaction

Graphene supported electrocatalysts have demonstrated remarkable catalytic performance for oxygen reduction reaction (ORR). However, their durability and cycling performance are greatly limited by Oswald ripening of platinum (Pt) and graphene support corrosion. Moreover, comprehensive studies on the mechanisms of catalysts degradation under 0.6-1.6 V versus RHE (Reversible Hydrogen Electrode) is still lacking. Herein, degradation mechanisms triggered by different defects on graphene supports are investigated by two cycling protocols. In the start-up/shutdown cycling (1.0-1.6 V vs. RHE), carbon oxidation reaction (COR) leads to shedding or swarm-like aggregation of Pt nanoparticles (NPs). Theoretical simulation results show that the expansion of vacancy defects promotes reaction kinetics of the decisive step in COR, reducing its reaction overpotential. While under the load cycling (0.6-1.0 V vs. RHE), oxygen containing defects lead to an elevated content of Pt in its oxidation state which intensifies Oswald ripening of Pt. The presence of vacancy defects can enhance the transfer of electrons from graphene to the Pt surface, reducing the d-band center of Pt and making it more difficult for the oxidation state of platinum to form in the cycling. This work will provide comprehensive understanding on Pt/Graphene catalysts degradation mechanisms.

Graphene-Perovskite Fibre Photodetectors

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.

The Rise of Xene Hybrids

Xenes, mono-elemental atomic sheets, exhibit Dirac/Dirac-like quantum behavior. When interfaced with other 2D materials such as boron nitride, transition metal dichalcogenides, and metal carbides/nitrides/carbonitrides, it enables them with unique physicochemical properties, including structural stability, desirable bandgap, efficient charge carrier injection, flexibility/breaking stress, thermal conductivity, chemical reactivity, catalytic efficiency, molecular adsorption, and wettability. For example, BN acts as an anti-oxidative shield, MoS2 injects electrons upon laser excitation, and MXene provides mechanical flexibility. Beyond precise compositional modulations, stacking sequences, and inter-layer coupling controlled by parameters, achieving scalability and reproducibility in hybridization is crucial for implementing these quantum materials in consumer applications. However, realizing the full potential of these hybrid materials faces challenges such as air gaps, uneven interfaces, and the formation of defects and functional groups. Advanced synthesis techniques, a deep understanding of quantum behaviors, precise control over interfacial interactions, and awareness of cross-correlations among these factors are essential. Xene-based hybrids show immense promise for groundbreaking applications in quantum computing, flexible electronics, energy storage, and catalysis. In this timely perspective, recent discoveries of novel Xenes and their hybrids are highlighted, emphasizing correlations among synthetic parameters, structure, properties, and applications. It is anticipated that these insights will revolutionize diverse industries and technologies.

Site-Selective Synthesis of Bilayer Graphene on Cu Substrates Using Titanium as a Carbon Diffusion Barrier

Chemical vapor deposition (CVD) is a widely used method for graphene synthesis, but it struggles to produce large-area uniform bilayer graphene (BLG). This study introduces a novel approach to meet the demands of large-scale integrated circuit applications, challenging the conventional reliance on uniform BLG over extensive areas. We developed a unique method involving the direct growth of bilayer graphene arrays (BLGA) on Cu foil substrates using patterned titanium (Ti) as a diffusion barrier. The use of the Ti layer can effectively control carbon atom diffusion through the Cu foil without altering the growth conditions or compromising the graphene quality, thereby showcasing its versatility. The approach allows for targeted BLG growth and achieved a yield of 100% for a 10 × 10 BLG units array. Then a 10 × 10 BLG memristor array was fabricated, and a yield of 96% was achieved. The performances of these devices show good uniformity, evidenced by the set voltages concentrated around 4 V, and a high resistance state (HRS) to low resistance state (LRS) ratio predominantly around 107, reflecting the spatial uniformity of the prepared BLGA. This study provides insight into the BLG growth mechanism and opens new possibilities for BLG-based electronics.

Emerging Advances around Nanofluidic Transport and Mass Separation under Confinement in Atomically Thin Nanoporous Graphene

Membrane separation stands as an environmentally friendly, high permeance and selectivity, low energy demand process that deserves scientific investigation and industrialization. To address intensive demand, seeking appropriate membrane materials to surpass trade-off between permeability and selectivity and improve stability is on the schedule. 2D materials offer transformational opportunities and a revolutionary platform for researching membrane separation process. Especially, the atomically thin graphene with controllable porosity and structure, as well as unique properties, is widely considered as a candidate for membrane materials aiming to provide extreme stability, exponentially large selectivity combined with high permeability. Currently, it has shown promising opportunities to develop separation membranes to tackle bottlenecks of traditional membranes, and it has been of great interest for tremendously versatile applications such as separation, energy harvesting, and sensing. In this review, starting from transport mechanisms of separation, the material selection bank is narrowed down to nanoporous graphene. The study presents an enlightening overview of very recent developments in the preparation of atomically thin nanoporous graphene and correlates surface properties of such 2D nanoporous materials to their performance in critical separation applications. Finally, challenges related to modulation and manufacturing as well as potential avenues for performance improvements are also pointed out.

Recent advances in graphene-based electroanalytical devices for healthcare applications

Graphene, with its outstanding mechanical, electrical, and biocompatible properties, stands out as an emerging nanomaterial for healthcare applications, especially in building electroanalytical biodevices. With the rising prevalence of chronic diseases and infectious diseases, such as the COVID-19 pandemic, the demand for point-of-care testing and remote patient monitoring has never been greater. Owing to their portability, ease of manufacturing, scalability, and rapid and sensitive response, electroanalytical devices excel in these settings for improved healthcare accessibility, especially in resource-limited settings. The development of different synthesis methods yielding large-scale graphene and its derivatives with controllable properties, compatible with device manufacturing - from lithography to various printing methods - and tunable electrical, chemical, and electrochemical properties make it an attractive candidate for electroanalytical devices. This review article sheds light on how graphene-based devices can be transformative in addressing pressing healthcare needs, ranging from the fundamental understanding of biology in in vivo and ex vivo studies to early disease detection and management using in vitro assays and wearable devices. In particular, the article provides a special focus on (i) synthesis and functionalization techniques, emphasizing their suitability for scalable integration into devices, (ii) various transduction methods to design diverse electroanalytical device architectures, (iii) a myriad of applications using devices based on graphene, its derivatives, and hybrids with other nanomaterials, and (iv) emerging technologies at the intersection of device engineering and advanced data analytics. Finally, some of the major hurdles that graphene biodevices face for translation into clinical applications are discussed.

Carbon carrier-based rapid Joule heating technology: a review on the preparation and applications of functional nanomaterials

Compared to conventional heating techniques, the carbon carrier-based rapid Joule heating (CJH) method is a new class of technologies that offer significantly higher heating rates and ultra-high temperatures. Over the past few decades, CJH technology has spawned several techniques with similar principles for different application scenarios, including ultra-fast high temperature sintering (UHS), carbon thermal shock (CTS), and flash Joule heating (FJH), which have been widely used in material preparation research studies. Functional nanomaterials are a popular direction of research today, mainly including nanometallic materials, nanosilica materials, nanoceramic materials and nanocarbon materials. These materials exhibit unique physical, chemical, and biological properties, including a high specific surface area, strength, thermal stability, and biocompatibility, making them ideal for diverse applications across various fields. The CJH method is a remarkable approach to producing functional nanomaterials that has attracted attention for its significant advantages. This paper aims to delve into the fundamental principles of CJH and elucidate the efficient preparation of functional nanomaterials with superior properties using this technique. The paper is organized into three sections, each dedicated to introducing the process and characteristics of CJH technology for the preparation of three distinct material types: carbon-based nanomaterials, inorganic non-metallic materials, and metallic materials. We discuss the distinctions and merits of the CJH method compared to alternative techniques in the preparation of these materials, along with a thorough examination of their properties. Furthermore, the potential applications of these materials are highlighted. In conclusion, this paper concludes with a discussion on the future research trends and development prospects of CJH technology.

Graphene via Microwave Expansion of Graphite Followed by Cryo-Quenching and its Application in Electrostatic Droplet Switching

Monoelemental atomic sheets (Xenes) and other 2D materials offer record electronic mobility, high thermal conductivity, excellent Young's moduli, optical transparency, and flexural capability, revolutionizing ultrasensitive devices and enhancing performance. The ideal synthesis of these quantum materials should be facile, fast, scalable, reproducible, and green. Microwave expansion followed by cryoquenching (MECQ) leverages thermal stress in graphite to produce high-purity graphene within minutes. MECQ synthesis of graphene is reported at 640 and 800 W for 10 min, followed by liquid nitrogen quenching for 5 and 90 min of sonication. Microscopic and spectroscopic analyses confirmed the chemical identity and phase purity of monolayers and few-layered graphene sheets (200-12 µm). Higher microwave power yields thinner layers with enhanced purity. Molecular dynamics simulations and DFT calculations support the exfoliation under these conditions. Electrostatic droplet switching is demonstrated using MECQ-synthesized graphene, observing electrorolling of a mercury droplet on a BN/graphene interface at voltages above 20 V. This technique can inspire the synthesis of other 2D materials with high purity and enable new applications.

Advancing Nanoelectronics Applications: Progress in Non-van der Waals 2D Materials

Extending the inventory of two-dimensional (2D) materials remains highly desirable, given their excellent properties and wide applications. Current studies on 2D materials mainly focus on the van der Waals (vdW) materials since the discovery of graphene, where properties of atomically thin layers have been found to be distinct from their bulk counterparts. Beyond vdW materials, there are abundant non-vdW materials that can also be thinned down to 2D forms, which are still in their early stage of exploration. In this review, we focus on the downscaling of non-vdW materials into 2D forms to enrich the 2D materials family. This underexplored group of 2D materials could show potential promise in many areas such as electronics, optics, and magnetics, as has happened in the vdW 2D materials. Hereby, we will focus our discussion on their electronic properties and applications of them. We aim to motivate and inspire fellow researchers in the 2D materials community to contribute to the development of 2D materials beyond the widely studied vdW layered materials for electronic device applications. We also give our insights into the challenges and opportunities to guide researchers who are desirous of working in this promising research area.

Germanium and Tin Precursors for Chalcogenide Materials Containing N-Alkoxy Thioamide Ligands

This study describes the synthesis of germanium and tin complexes Ge(mdpaS)2 (1), Ge(edpaS)2 (2), Ge(bdpaS)2 (3), Ge(empaS)2 (4), Sn(mdpaS)2 (5), Sn(edpaS)2 (6), Sn(bdpaS)2 (7), and Sn(empaS)2 (8) (mdpaSH = (Z)-N-methoxy-2,2-dimethylpropanimidothioic acid; edpaSH = (Z)-N-ethoxy-2,2-dimethylpropanimidothioic acid; bdpaSH = (Z)-N-(tert-butoxy)-2,2-dimethylpropanimidothioic acid; empaSH = (Z)-N-ethoxy-2-methylpropanimidothioic acid), using newly designed N-alkoxy thioamide ligands as precursors for metal chalcogenide materials. All complexes were characterized using various analytical techniques, and the single-crystal structures of complexes 5 and 7 revealed a distorted seesaw geometry in the monomeric SnL2 form. Thermogravimetric (TG) curves showed differences between Ge compounds, which exhibited single-step weight losses, and Sn compounds, which exhibited multistep weight losses. As a result, we suggest that the synthesized complexes 1-8 are potential precursors for group IV metal chalcogenide materials.

Understanding epitaxial growth of two-dimensional materials and their homostructures

The exceptional physical properties of two-dimensional (2D) van der Waals (vdW) materials have been extensively researched, driving advances in material synthesis. Epitaxial growth, a prominent synthesis strategy, enables the production of large-area, high-quality 2D films compatible with advanced integrated circuits. Typical 2D single crystals, such as graphene, transition metal dichalcogenides and hexagonal boron nitride, have been epitaxially grown at a wafer scale. A systematic summary is required to offer strategic guidance for the epitaxy of emerging 2D materials. Here we focus on the epitaxy methodologies for 2D vdW materials in two directions: the growth of in-plane single-crystal monolayers and the fabrication of out-of-plane homostructures. We first discuss nucleation control of a single domain and orientation control over multiple domains to achieve large-scale single-crystal monolayers. We analyse the defect levels and measures of crystalline quality of typical 2D vdW materials with various epitaxial growth techniques. We then outline technical routes for the growth of homogeneous multilayers and twisted homostructures. We further summarize the current strategies to guide future efforts in optimizing on-demand fabrication of 2D vdW materials, as well as subsequent device manufacturing for their industrial applications.

A review on synthesis, properties, and biomedical applications of graphene quantum dots (GQDs)

A new type of 0-dimensional carbon-based materials called graphene quantum dots (GQDs) is gaining significant attention as a non-toxic and eco-friendly nanomaterial. GQDs are nanomaterials composed of sp2hybridized carbon domains and functional groups, with their lateral size less than 10 nm. The unique and exceptional physical, chemical, and optical properties arising from the combination of graphene structure and quantum confinement effect due to their nano-size make GQDs more intriguing than other nanomaterials. Particularly, the low toxicity and high solubility derived from the carbon core and abundant edge functional groups offer significant advantages for the application of GQDs in the biomedical field. In this review, we summarize various synthetic methods for preparing GQDs and important factors influencing the physical, chemical, optical, and biological properties of GQDs. Furthermore, the recent application of GQDs in the biomedical field, including biosensor, bioimaging, drug delivery, and therapeutics are discussed. Through this, we provide a brief insight on the tremendous potential of GQDs in biomedical applications and the challenges that need to be overcome in the future.

Borophene: Synthesis, Chemistry, and Electronic Properties

As a neighbor of carbon in the periodic table, boron exhibits versatile structural and electronic configurations, with its allotropes predicted to possess intriguing structures and properties. Since the experimental realization of two-dimensional (2D) boron sheets (borophene) on Ag(111) substrates in 2015, the experimental study of the realization and characteristics of borophene has drawn increasing interest. In this review, we summarize the synthesis and properties of borophene, which are mainly based on experimental results. First, the synthesis of borophene on different substrates, as well as borophane and bilayer borophene, featuring unique phases and properties, are discussed. Next, the chemistry of borophene, such as oxidation, hydrogenation, and its integration into heterostructures with other materials, is summarized. We also mention a few works focused on the physical properties of borophene, specifically its electronic properties. Lastly, the brief outlook addresses challenges toward practical applications of borophene and possible solutions.

Multispecies-coadsorption-induced rapid preparation of graphene glass fiber fabric and applications in flexible pressure sensor

Direct chemical vapor deposition (CVD) growth of graphene on dielectric/insulating materials is a promising strategy for subsequent transfer-free applications of graphene. However, graphene growth on noncatalytic substrates is faced with thorny issues, especially the limited growth rate, which severely hinders mass production and practical applications. Herein, graphene glass fiber fabric (GGFF) is developed by graphene CVD growth on glass fiber fabric. Dichloromethane is applied as a carbon precursor to accelerate graphene growth, which has a low decomposition energy barrier, and more importantly, the produced high-electronegativity Cl radical can enhance adsorption of active carbon species by Cl-CH2 coadsorption and facilitate H detachment from graphene edges. Consequently, the growth rate is increased by ~3 orders of magnitude and carbon utilization by ~960-fold, compared with conventional methane precursor. The advantageous hierarchical conductive configuration of lightweight, flexible GGFF makes it an ultrasensitive pressure sensor for human motion and physiological monitoring, such as pulse and vocal signals.

Transfer of 2D Films: From Imperfection to Perfection

Atomically thin 2D films and their van der Waals heterostructures have demonstrated immense potential for breakthroughs and innovations in science and technology. Integrating 2D films into electronics and optoelectronics devices and their applications in electronics and optoelectronics can lead to improve device efficiencies and tunability. Consequently, there has been steady progress in large-area 2D films for both front- and back-end technologies, with a keen interest in optimizing different growth and synthetic techniques. Parallelly, a significant amount of attention has been directed toward efficient transfer techniques of 2D films on different substrates. Current methods for synthesizing 2D films often involve high-temperature synthesis, precursors, and growth stimulants with highly chemical reactivity. This limitation hinders the widespread applications of 2D films. As a result, reports concerning transfer strategies of 2D films from bare substrates to target substrates have proliferated, showcasing varying degrees of cleanliness, surface damage, and material uniformity. This review aims to evaluate, discuss, and provide an overview of the most advanced transfer methods to date, encompassing wet, dry, and quasi-dry transfer methods. The processes, mechanisms, and pros and cons of each transfer method are critically summarized. Furthermore, we discuss the feasibility of these 2D film transfer methods, concerning their applications in devices and various technology platforms.

Reproductive toxicity perspectives of nanoparticles: an update

INTRODUCTION

The rapid development of nanotechnologies with their widespread prosperities has advanced concerns regarding potential health hazards of the Nanoparticles.

RESULTS

Nanoparticles are currently present in several consumer products, including medications, food, textiles, sports equipment, and electrical components. Despite the advantages of Nanoparticles, their potential toxicity has negative impact on human health, particularly on reproductive health.

CONCLUSIONS

The impact of various NPs on reproductive system function is yet to be determined. Additional research is required to study the potential toxicity of various Nanoparticles on reproductive health. The primary objective of this review is to unravel the toxic effects of different Nanoparticles on the human reproductive functions and recent investigations on the reproductive toxicity of Nanoparticles both in vitro and in vivo.

Establishment of a steroid binding assay for goldfish membrane progesterone receptor (mPR) by coupling with graphene quantum dots (GQDs)

A homogeneous assay was developed to evaluate ligands that target the membrane progesterone receptor alpha (mPRα) of goldfish. This was achieved by employing graphene quantum dots (GQDs), a type of semiconductor nanoparticle conjugated to the goldfish mPRα. When progesterone-BSA-fluorescein isothiocyanate (P4-BSA-FITC) was combined with the other agents, fluorescence was observed through Förster resonance energy transfer (FRET). However, this fluorescence was quenched by binding between the ligand and receptor. This established method demonstrated the ligand selectivity of the mPRα protein. Then, the methylotrophic yeast Pichia pastoris was used to express the goldfish mPRα (GmPRα) protein. The recombinant purified GmPRα protein was coupled with graphene quantum dots (GQDs) to generate GQD-conjugated goldfish mPRα (GQD-GmPRα). Fluorescence at a wavelength of 520 nm was observed through FRET upon the combination of P4-BSA-FITC and subsequent activation by ultraviolet (UV) light. Adding free P4 to the reaction mixture resulted in a decrease in fluorescence intensity at a wavelength of 520 nm. The fluorescence was reduced by the administration of GmPRα ligands but not by steroids that do not interact with GmPRα. The findings indicated that the interaction between the ligand and receptor led to the formation of a complex involving GQD-GmPRα and P4-BSA-FITC. The interaction between the compounds and GQD-GmPRα was additionally validated by a binding experiment that employed the radiolabeled natural ligand [3H]-17α,20β-dihydroxy-4-pregnen-3-one. We established a ligand-binding assay for the fish membrane progesterone receptor that is applicable for screening compounds.

2D Memory Selectors with Giant Nonlinearity Enabled by Van der Waals Heterostructures

The integration of one-selector-one-resistor crossbar arrays requires the selectors featured with high nonlinearity and bipolarity to prevent leakage currents and any crosstalk among distinct cells. However, a selector with sufficient nonlinearity especially in the frame of device miniaturization remains scarce, restricting the advance of high-density storage devices. Herein, a high-performance memory selector is reported by constructing a graphene/hBN/WSe2 heterostructure. Within the temperature range of 300-80 K, the nonlinearity of this selector varies from ≈103 - ≈104 under forward bias, and increases from ≈300 - ≈105 under reverse bias, the highest reported nonlinearity among 2D selectors. This improvement is ascribed to direct tunneling at low bias and Fowler-Nordheim tunneling at high bias. The tunneling current versus voltage curves exhibit excellent bipolarity behavior because of the comparable hole and electron tunneling barriers, and the charge transport polarity can be effectively tuned from N-type or P-type to bipolar by simply changing source-drain bias. In addition, the conceptual memory selector exhibits no sign of deterioration after 70 000 switching cycles, paving the way for assembling 2D selectors into modern memory devices.

Large-Area Flexible Carbon Nanofilms with Synergistically Enhanced Transmittance and Conductivity Prepared by Reorganizing Single-Walled Carbon Nanotube Networks

Large-area flexible transparent conductive films (TCFs) are highly desired for future electronic devices. Nanocarbon TCFs are one of the most promising candidates, but some of their properties are mutually restricted. Here, a novel carbon nanotube network reorganization (CNNR) strategy, that is, the facet-driven CNNR (FD-CNNR) technique, is presented to overcome this intractable contradiction. The FD-CNNR technique introduces an interaction between single-walled carbon nanotube (SWNT) and Cu─-O. Based on the unique FD-CNNR mechanism, large-area flexible reorganized carbon nanofilms (RNC-TCFs) are designed and fabricated with A3-size and even meter-length, including reorganized SWNT (RSWNT) films and graphene and RSWNT (G-RSWNT) hybrid films. Synergistic improvement in strength, transmittance, and conductivity of flexible RNC-TCFs is achieved. The G-RSWNT TCF shows sheet resistance as low as 69 Ω sq-1 at 86% transmittance, FOM value of 35, and Young's modulus of ≈45 MPa. The high strength enables RNC-TCFs to be freestanding on water and easily transferred to any target substrate without contamination. A4-size flexible smart window is fabricated, which manifests controllable dimming and fog removal. The FD-CNNR technique can be extended to large-area or even large-scale fabrication of TCFs and can provide new insights into the design of TCFs and other functional films.

Facile synthesis of nanostructured Ni/NiO/N-doped graphene electrocatalysts for enhanced oxygen evolution reaction

Electrocatalysts containing a Ni/NiO/N-doped graphene interface have been synthesised using the ligand-assisted chemical vapor deposition technique. NiO nanoparticles were used as the substrate to grow N-doped graphene by decomposing vapours of benzene and N-containing ligands. The method was demonstrated with two nitrogen-containing ligands, namely dipyrazino[2,3-f:2',3'-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile (L) and melamine (M). The structure and composition of the as-synthesized composites were characterized by XRD, Raman spectroscopy, SEM, TEM and XPS. The composite prepared using the ligand L had NiO sandwiched between Ni and N-doped graphene and showed an overpotential of 292 mV at 10 mA cm-2 and a Tafel slope of 45.41 mV dec-1 for the OER, which is comparable to the existing noble metal catalysts. The composite prepared using the ligand M had Ni encapsulated by N-doped graphene without NiO. It showed an overpotential of 390 mV at 10 mA cm-2 and a Tafel slope of 78.9 mV dec-1. The ligand-assisted CVD route demonstrates a facile route to control the microstructure of the electrocatalysts.

Enhancing modulation performance by design of hybrid plasmonic optical modulator integrating multi-layer graphene and TiO2on silicon waveguides

A novel way to enhance modulation performance is through the design of a hybrid plasmonic optical modulator that integrates multi-layer graphene and TiO2on silicon waveguides. In this article, a design is presented of a proposed modulator based on the use of the two-dimensional finite difference eigenmode solver, the three-dimensional eigenmode expansion solver, and the CHARGE solver. Leveraging inherent graphene properties and utilizing the subwavelength confinement capabilities of hybrid plasmonic waveguides (HPWs), we achieved a modulator design that is both compact and highly efficient. The electrical bandwidthf3dBis at 460.42 GHz and it reduces energy consumption to 12.17 fJ/bit with a modulator that functions at a wavelength of 1.55μm. According to our simulation results, our innovation was the optimization of the third dielectric layer's thickness, setting the stage to achieve greater modulation depths. This synergy between graphene and HPWs not only augments subwavelength confinement, but also optimizes light-graphene interaction, culminating in a markedly enhanced modulation efficiency. As a result, our modulator presents a high extinction ratio and minimized insertion loss. Furthermore, it exhibits polarization insensitivity and a greater bandwidth. Our work sets a new benchmark in optical communication systems, emphasizing the potential for the next generation of chip-scale with high-efficiency optical modulators that significantly outpace conventional graphene-based designs.

Ultrathin and Deformable Graphene Etch Mask for Fabrication of 3D Microstructures

Three-dimensional (3D) microfabrication techniques play a crucial role across various research fields. These techniques enable the creation of functional 3D structures on the microscale, unlocking possibilities for diverse applications. However, conventional fabrication methods have limits in producing complex 3D structures, which require numerous fabrication steps that increase the costs. Graphene is an atomically thin material known for its deformability and impermeability to small gases and molecules, including reactive gases like XeF2. These features make graphene a potential candidate as an etch mask for 3D microfabrication. Here, we report the fabrication of various 3D microstructures using graphene etch masks directly grown and patterned on a Si substrate. The patterned graphene deforms and wraps the etched structures, allowing for the fabrication of complicated 3D microstructures, such as mushroom-like and step-like microstructures. As a practical demonstration of the graphene etch mask, we fabricate an omniphobic surface of reentrant 3D structures on a Si substrate. Our work provides a method for fabricating complex 3D microstructures using a graphene etch mask, contributing to advancements in etching and fabrication processes.

Electrochemical-repaired porous graphene membranes for precise ion-ion separation

The preparation of atom-thick porous lattice hosting Å-scale pores is attractive to achieve a large ion-ion selectivity in combination with a large ion flux. Graphene film is an ideal selective layer for this if high-precision pores can be incorporated, however, it is challenging to avoid larger non-selective pores at the tail-end of the pore size distribution which reduces ion-ion selectivity. Herein, we develop a strategy to overcome this challenge using an electrochemical repair strategy that successfully masks larger pores in large-area graphene. 10-nm-thick electropolymerized conjugated microporous polymer (CMP) layer is successfully deposited on graphene, thanks to a strong π-π interaction in these two materials. While the CMP layer itself is not selective, it effectively masks graphene pores, leading to a large Li+/Mg2+ selectivity from zero-dimensional pores reaching 300 with a high Li+ ion permeation rate surpassing the performance of reported materials for ion-ion separation. Overall, this scalable repair strategy enables the fabrication of monolayer graphene membranes with customizable pore sizes, limiting the contribution of nonselective pores, and offering graphene membranes a versatile platform for a broad spectrum of challenging separations.

Clean Transfer of Two-Dimensional Materials: A Comprehensive Review

The growth of two-dimensional (2D) materials through chemical vapor deposition (CVD) has sparked a growing interest among both the industrial and academic communities. The interest stems from several key advantages associated with CVD, including high yield, high quality, and high tunability. In order to harness the application potentials of 2D materials, it is often necessary to transfer them from their growth substrates to their desired target substrates. However, conventional transfer methods introduce contamination that can adversely affect the quality and properties of the transferred 2D materials, thus limiting their overall application performance. This review presents a comprehensive summary of the current clean transfer methods for 2D materials with a specific focus on the understanding of interaction between supporting layers and 2D materials. The review encompasses various aspects, including clean transfer methods, post-transfer cleaning techniques, and cleanliness assessment. Furthermore, it analyzes and compares the advances and limitations of these clean transfer techniques. Finally, the review highlights the primary challenges associated with current clean transfer methods and provides an outlook on future prospects.

Toward the Production of Super Graphene

The quality requirements of graphene depend on the applications. Some have a high tolerance for graphene quality and even require some defects, while others require graphene as perfect as possible to achieve good performance. So far, synthesis of large-area graphene films by chemical vapor deposition of carbon precursors on metal substrates, especially on Cu, remains the main way to produce high-quality graphene, which has been significantly developed in the past 15 years. However, although many prototypes are demonstrated, their performance is still more or less far from the theoretical property limit of graphene. This review focuses on how to make super graphene, namely graphene with a perfect structure and free of contaminations. More specially, this study focuses on graphene synthesis on Cu substrates. Typical defects in graphene are first discussed together with the formation mechanisms and how they are characterized normally, followed with a brief review of graphene properties and the effects of defects. Then, the synthesis progress of super graphene from the aspects of substrate, grain size, wrinkles, contamination, adlayers, and point defects are reviewed. Graphene transfer is briefly discussed as well. Finally, the challenges to make super graphene are discussed and a strategy is proposed.

Toward Clean 2D Materials and Devices: Recent Progress in Transfer and Cleaning Methods

Two-dimensional (2D) materials have tremendous potential to revolutionize the field of electronics and photonics. Unlocking such potential, however, is hampered by the presence of contaminants that usually impede the performance of 2D materials in devices. This perspective provides an overview of recent efforts to develop clean 2D materials and devices. It begins by discussing conventional and recently developed wet and dry transfer techniques and their effectiveness in maintaining material "cleanliness". Multi-scale methodologies for assessing the cleanliness of 2D material surfaces and interfaces are then reviewed. Finally, recent advances in passive and active cleaning strategies are presented, including the unique self-cleaning mechanism, thermal annealing, and mechanical treatment that rely on self-cleaning in essence. The crucial role of interface wetting in these methods is emphasized, and it is hoped that this understanding can inspire further extension and innovation of efficient transfer and cleaning of 2D materials for practical applications.

Recent trends in the transfer of graphene films

Recent years have witnessed advances in chemical vapor deposition growth of graphene films on metal foils with fine scalability and thickness controllability. However, challenges for obtaining wrinkle-free, defect-free and large-area uniformity remain to be tackled. In addition, the real commercial applications of graphene films still require industrially compatible transfer techniques with reliable performance of transferred graphene, excellent production capacity, and suitable cost. Transferred graphene films, particularly with a large area, still suffer from the presence of transfer-related cracks, wrinkles and contaminants, which would strongly deteriorate the quality and uniformity of transferred graphene films. Potential applications of graphene films include moisture barrier films, transparent conductive films, electromagnetic shielding films, and optical communications; such applications call different requirements for the performance of transferred graphene, which, in turn, determine the suitable transfer techniques. Besides the reliable transfer process, automatic machines should be well developed for the future batch transfer of graphene films, ensuring the repeatability and scalability. This mini-review provides a summary of recent advances in the transfer of graphene films and offers a perspective for future directions of transfer techniques that are compatible for industrial batch transfer.

The Future of Graphene: Preparation from Biomass Waste and Sports Applications

At present, the main raw material for producing graphene is graphite ore. However, researchers actively seek alternative resources due to their high cost and environmental problems. Biomass waste has attracted much attention due to its carbon-rich structure and renewability, emerging as a potential raw material for graphene production to be used in sports equipment. However, further progress is required on the quality of graphene produced from waste biomass. This paper, therefore, summarizes the properties, structures, and production processes of graphene and its derivatives, as well as the inherent advantages of biomass waste-derived graphene. Finally, this paper reviews graphene's importance and application prospects in sports since this wonder material has made sports equipment available with high-strength and lightweight quality. Moreover, its outstanding thermal and electrical conductivity is exploited to prepare wearable sensors to collect more accurate sports data, thus helping to improve athletes' training levels and competitive performance. Although the large-scale production of biomass waste-derived graphene has yet to be realized, it is expected that its application will expand to various other fields due to the associated low cost and environmental friendliness of the preparation technique.

On the mechanism of piezoresistance in nanocrystalline graphite

Strain sensors are sensitive to mechanical deformations and enable the detection of strain also within integrated electronics. For flexible displays, the use of a seamlessly integrated strain sensor would be beneficial, and graphene is already in use as a transparent and flexible conductor. However, graphene intrinsically lacks a strong response, and only by engineering defects, such as grain boundaries, one can induce piezoresistivity. Nanocrystalline graphene (NCG), a derivative form of graphene, exhibits a high density of defects in the form of grain boundaries. It holds an advantage over graphene in easily achieving wafer-scale growth with controlled thickness. In this study, we explore the piezoresistivity in thin films of nanocrystalline graphite. Simultaneous measurements of sheet resistance and externally applied strain on NCG placed on polyethylene terephthalate (PET) substrates provide intriguing insights into the underlying mechanism. Raman measurements, in conjunction with strain applied to NCG grown on flexible glass, indicate that the strain is concentrated at the grain boundaries for smaller strain values. For larger strains, mechanisms such as grain rotation and the formation of nanocracks might contribute to the piezoresistive behavior in nanocrystalline graphene.

Thermal transport in a defective pillared graphene network: insights from equilibrium molecular dynamics simulation

Graphene-based hybrid nanostructures have great potential to be ideal candidates for developing tailored thermal transport materials. In this study, we perform equilibrium molecular dynamics simulations employing the Green-Kubo method to investigate the influence of topological defects in three-dimensional pillared graphene networks. Similar to single-layer graphene and carbon nanotubes, the thermal conductivity (k) of pillared graphene systems exhibits a strong correlation with the system size (L), following a power-law relation k ∼ Lα, where α ranges from 0.12 to 0.15. Our results indicate that the vacancy defects significantly reduce thermal conductivity in pillared graphene systems compared to Stone-Wales defects. We observe that, beyond defect concentration, the location of the defects also plays a crucial role in determining thermal conductivity. We further analyze the phonon vibrational spectrum and the phonon participation ratio to obtain more insight into the thermal transport in the defective pillared graphene network. In most scenarios, longitudinal and flexural acoustic phonons experience significant localization within the 15-45 THz frequency range in the defective pillared graphene system.

New Carbon Materials for Multifunctional Soft Electronics

Soft electronics are garnering significant attention due to their wide-ranging applications in artificial skin, health monitoring, human-machine interaction, artificial intelligence, and the Internet of Things. Various soft physical sensors such as mechanical sensors, temperature sensors, and humidity sensors are the fundamental building blocks for soft electronics. While the fast growth and widespread utilization of electronic devices have elevated life quality, the consequential electromagnetic interference (EMI) and radiation pose potential threats to device precision and human health. Another substantial concern pertains to overheating issues that occur during prolonged operation. Therefore, the design of multifunctional soft electronics exhibiting excellent capabilities in sensing, EMI shielding, and thermal management is of paramount importance. Because of the prominent advantages in chemical stability, electrical and thermal conductivity, and easy functionalization, new carbon materials including carbon nanotubes, graphene and its derivatives, graphdiyne, and sustainable natural-biomass-derived carbon are particularly promising candidates for multifunctional soft electronics. This review summarizes the latest advancements in multifunctional soft electronics based on new carbon materials across a range of performance aspects, mainly focusing on the structure or composite design, and fabrication method on the physical signals monitoring, EMI shielding, and thermal management. Furthermore, the device integration strategies and corresponding intriguing applications are highlighted. Finally, this review presents prospects aimed at overcoming current barriers and advancing the development of state-of-the-art multifunctional soft electronics.

Float-stacked graphene-PMMA laminate

Semi-infinite single-atom-thick graphene is an ideal reinforcing material that can simultaneously improve the mechanical, electrical, and thermal properties of matrix. Here, we present a float-stacking strategy to accurately align the monolayer graphene reinforcement in polymer matrix. We float graphene-poly(methylmethacrylate) (PMMA) membrane (GPM) at the water-air interface, and wind-up layer-by-layer by roller. During the stacking process, the inherent water meniscus continuously induces web tension of the GPM, suppressing wrinkle and folding generation. Moreover, rolling-up and hot-rolling mill process above the glass transition temperature of PMMA induces conformal contact between each layer. This allows for pre-tension of the composite, maximizing its reinforcing efficiency. The number and spacing of the embedded graphene fillers are precisely controlled. Notably, we accurately align 100 layers of monolayer graphene in a PMMA matrix with the same intervals to achieve a specific strength of about 118.5 MPa g-1 cm3, which is higher than that of lightweight Al alloy, and a thermal conductivity of about 4.00 W m-1 K-1, which is increased by about 2,000 %, compared to the PMMA film.

Metal-insulator transition effect on Graphene/VO[Formula: see text] heterostructure via temperature-dependent Raman spectroscopy and resistivity measurement

High-quality VO[Formula: see text] films were fabricated on top of c-Al[Formula: see text]O[Formula: see text] substrates using Reactive Bias Target Ion Beam Deposition (RBTIBD) and the studies of graphene/VO[Formula: see text] heterostructure were conducted. Graphene layers were placed on top of [Formula: see text] 50 and [Formula: see text] 100 nm VO[Formula: see text]. The graphene layers were introduced using mechanical exfoliate and CVD graphene wet-transfer method to prevent the worsening crystallinity of VO[Formula: see text], to avoid the strain effect from lattice mismatch and to study how VO[Formula: see text] can affect the graphene layer. Slight increases in graphene/VO[Formula: see text] T[Formula: see text] compared to pure VO[Formula: see text] by [Formula: see text] 1.9 [Formula: see text]C and [Formula: see text] 3.8 [Formula: see text]C for CVD graphene on 100 and 50 nm VO[Formula: see text], respectively, were observed in temperature-dependent resistivity measurements. As the strain effect from lattice mismatch was minimized in our samples, the increase in T[Formula: see text] may originate from a large difference in the thermal conductivity between graphene and VO[Formula: see text]. Temperature-dependent Raman spectroscopy measurements were also performed on all samples, and the G-peak splitting into two peaks, G[Formula: see text] and G[Formula: see text], were observed on graphene/VO[Formula: see text] (100 nm) samples. The G-peak splitting is a reversible process and may originates from in-plane asymmetric tensile strain applied under the graphene layer due to the VO[Formula: see text] phase transition mechanism. The 2D-peak measurements also show large blue-shifts around 13 cm[Formula: see text] at room temperature and slightly red-shifts trend as temperature increases for 100 nm VO[Formula: see text] samples. Other electronic interactions between graphene and VO[Formula: see text] are expected as evidenced by 2D-peak characteristic observed in Raman measurements. These findings may provide a better understanding of graphene/VO[Formula: see text] and introduce some new applications that utilize the controllable structural properties of graphene via the VO[Formula: see text] phase transition.

Simulation and experimental evaluation of laser-induced graphene on the cellulose and lignin substrates

In this article, the formation of laser-induced graphene on the two natural polymers, cellulose, and lignin, as precursors was investigated with molecular dynamics simulations and some experiments. These eco-friendly polymers provide significant industrial advantages due to their low cost, biodegradability, and recyclable aspects. It was discovered during the simulation that LIG has numerous defects and a porous structure. Carbon monoxide, H2, and water vapor are gases released by cellulose and lignin substrates. H2O and CO are released when the polymer transforms into an amorphous structure. Later on, as the amorphous structure changes into an ordered graphitic structure, H2 is released continuously. Since cellulose monomer has a higher mass proportion of oxygen (49%) than lignin monomer (29%), it emits more CO. The LIG structure contains many 5- and 7-carbon rings, which cause the structure to have bends and undulations that go out of the plane. In addition, to verify the molecular dynamics simulation results with experimental tests, we used a carbon dioxide laser to transform filter paper, as a cellulose material, and coconut shell, as a lignin material, into graphene. Surprisingly, empirical experiments confirmed the simulation results.

A Review on Recent Trends and Future Developments in Electrochemical Sensing

Electrochemical methods and devices have ignited prodigious interest for sensing and monitoring. The greatest challenge for science is far from meeting the expectations of consumers. Electrodes made of two-dimensional (2D) materials such as graphene, metal-organic frameworks, MXene, and transition metal dichalcogenides as well as alternative electrochemical sensing methods offer potential to improve selectivity, sensitivity, detection limit, and response time. Moreover, these advancements have accelerated the development of wearable and point-of-care electrochemical sensors, opening new possibilities and pathways for their applications. This Review presents a critical discussion of the recent developments and trends in electrochemical sensing.