Dry mechanochemical route to nanocomposites containing multi-layer graphene

Traditional von Neumann architecture-based devices are limited by the memory wall, hindering the development of next-generation artificial intelligence. Controlling proton transport to achieve hydrogenation in monolayer graphene resulting in the reversible and controllable nature of their memristive behavior has attracted significant interest for neuromorphic applications. However, multilayer graphene is impermeable to protons and most ions, which severely restricts the development of graphene-based neuromorphic devices in practice. To address this challenge, we developed a three-terminal artificial synapse based on stacked graphene nanosheets induced by an organic nano carbon source (ONCS). The device achieves co-regulated proton transport and hydrogenation through the gate-source voltage (VGS) and source-drain voltage (VDS), enabling dual-stimulus memristive effects (gate stimulus and source-drain stimulus). It successfully mimics essential synaptic functions, including short-term depression (STD), long-term depression (LTD), and paired-pulse depression (PPD) with intensity-dependent and pulse number-sensitive responses. This work resolves the ion-electron co-regulation challenge in multilayer graphene for next-generation AI computing.

Laser-induced graphene (LIG) is widely utilized in flexible sensors because of its simple fabrication and low cost. However, transferring LIG to PDMS results in insufficient conductivity and high overall device resistance, which limits its application in high-sensitivity signal detection. Liquid metal (LM), characterized by high conductivity and low resistance, offers a promising pathway to enhance the sensing performance of LIG. This study proposes a hierarchical composite structure that adopts the liquid metal/polydimethylsiloxane (LP) composite strategy to prepare liquid metal graphene flexible sensors (LM-LIGFS). By adopting this composite strategy, the resistance of the pure LIG flexible sensor has been reduced by approximately 50%, significantly enhancing sensitivity. Furthermore, the composite sensor demonstrates excellent dynamic response capabilities under various pressures, frequencies, and grip strengths, featuring both rapid response times (loading: 0.138 s/unloading: 0.234 s) and high stability (over 9000 s of repetitive bending). Additionally, the sensor possesses superior waterproof properties and generates distinct responses at different underwater depths. Finally, the potential of the LM-LIG flexible sensor in correcting human breaststroke movements was demonstrated. These attributes make the LM-LIG sensor a low-cost and green solution for wearable electronics.

We report insights into the reversible electrochemical intercalation of ionic liquids into multilayer graphene (MLG) using attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy. The studied device is comprised of an MLG/alumina membrane/copper stack, where the nanoporous alumina membrane is filled with ionic liquid [DEME+][TFSI-], forming a compact electrochemical cell. Upon application of a positive voltage, [TFSI-] anions intercalate into the interlayer regions of the MLG, despite the anion's diameter (0.9 nm) being nearly 3 times the typical graphene interlayer spacing (0.355 nm). Pronounced spectral changes accompany this poorly understood intercalation. We observe a blue-shift of up to 21.2 cm-1 in several [TFSI-] vibrational modes, attributed to mechanical compression within the confined graphene layers and/or ion-ion interactions. Additionally, an infrared peak emerges at 1384 cm-1, corresponding to the symmetric bending mode of methyl (-CH3) groups, whose appearance suggests that symmetry breaking within the confined electrochemical environment activates otherwise forbidden transitions in the [DEME+] cation. These findings reveal the nanoscale structural and electronic perturbations induced by ionic liquid intercalation, identifying spectroscopic signatures to track intercalation dynamics in layered materials. Raman shifts observed in the graphene indicate doping levels on the order of 1021 cm-1, corresponding to a roughly 100-fold increase in free carrier concentration, thus providing evidence consistent with intercalation. However, these observations challenge our previous interpretation of the complete intercalation of ionic liquids into graphene. We additionally used density-functional tight-binding (DFTB) simulations to qualitatively determine the behavior of the [TFSI-] anion sandwiched between two graphene sheets for different separation distances from 7 to 10 Å with a 0.5 Å increment. The resulting frequency shifts at smaller separation distances exhibit qualitative agreement with experimental observations, and in the case of greater separation, the peak shifts diminish and plateau, transitioning toward the bulk anion.

The fractional quantum Hall effect at half-filled Landau levels provides a promising route to unusual topological phases that may host non-Abelian excitations, but these states are often fragile and difficult to control experimentally. Here, we report the observation of a cascade of even-denominator fractional quantum Hall states at fillings ν = -5/2, -7/2, -9/2, -11/2 and -13/2, alongside numerous odd-denominator states in mixed-stacked pentalayer graphene-a system characterized by intertwined quadratic and cubic band dispersions. These even-denominator states emerge from two distinct intra-zeroth Landau levels and exhibit displacement-field tunability. At half fillings, continuous quantum phase transitions between even-denominator states, magnetic Bloch states, and composite Fermi liquids are clearly identified upon tuning external fields. Numerical calculations support possible Moore-Read type pairing for even-denominator states, although direct probes of their exchange statistics remain important for future experiments. These results establish mixed-stacked graphene as a versatile platform for tunable correlated topological phases.

Although graphene is promising for a variety of practical applications, its practical implementation in a high-temperature environment is hindered by its intrinsic thermal instability and weak interfacial adhesion to most substrates, such as metals and oxides. Various strategies have been explored to solve these issues; however, achieving robust stability and adhesion remains a challenge. This study suggests a nitrogen-doped amorphous carbon (a-C:N) thin film interface on graphene to significantly enhance the thermal stability and interfacial adhesion. It investigates the effect of the a-C:N layer on the thermal stability of the graphene crystal structure and electrical performance. This study evaluates the origin of adhesion enhancement to the oxide substrates and metal electrodes. As an example of a demonstration, a transparent high-temperature electrical heater utilizing a multilayer graphene with an a-C:N interface layer as the heating source is presented. The heater exhibited long-term stability during 1000 heating cycles to 400 °C, without device failure or resistance increase. This result provides insights into the interfacial engineering of graphene, not only for thermal environments but also for various electronic devices.

Exploiting atomic-precision metal nanoclusters as an electrochemical sensor for environmental detection is a significant application in the field of cluster chemistry. However, the development of cluster-based sensors is still in its infancy. Herein, we successfully fabricate a three-layer KBE-CS/Au25@MLG/GC electrode (KBE = kidney bean enzyme, CS = chitosan, MLG = multilayer graphene, GC = glassy carbon), in which Au25@MLG and CS serve to adsorb and protect the plant esterase of KBE, respectively. The optimized Au25-based sensor demonstrates an excellent linear relationship between the mass concentration of profenofos (lgC) and the inhibition rate (Inh %) within the range of 1∼2000µg/L with a detection limit of 0.137µg/L. Furthermore, this biosensor presents excellent reproducibility, anti-interference, and stability for the detection of profenofos in real samples. This study paves an avenue to construct a cluster-based detection platform with high performance in electrochemical sensing, facilitating the practical application of metal nanoclusters in pesticide detection.

The structural evolution of multilayer graphene grown at 275 °C by hot-wire in plasma–very high frequency plasma-enhanced chemical vapor deposition was investigated as a function of Ni catalyst pre-annealing temperature. Raman spectroscopy reveals temperature-dependent variations in the D, G, and 2D bands, reflecting changes in defect density, inter-defect spacing, and stacking coherence induced by catalyst thermal treatment. A non-monotonic evolution of disorder is observed, with the highest defect density occurring at 300 °C, which is attributed to partial catalyst restructuring and enhanced nucleation activity. At higher pre-annealing temperatures, progressive grain stabilization promotes partial recovery of the lateral crystallite size while preserving the multilayer growth regime. The estimated defect density (∼1011 cm−2) indicates nanocrystalline graphene composed of interconnected sp2 domains. Optical transmittance measurements show a systematic increase in visible transparency with increasing catalyst annealing temperature, reaching a maximum at 450 °C, consistent with reduced structural disorder and improved interlayer ordering. These results highlight the critical role of catalyst pretreatment in regulating nucleation behavior and microstructural evolution during plasma-assisted graphene growth.

Freestanding graphene exhibits exceptional mechanical flexibility and electrical conductivity, making it well suited for varying capacitance applications. For example, when suspended above a fixed electrode, graphene will move in response to an applied bias voltage, thereby forming a varactor or voltage-controlled capacitor. In this work, we present a very detailed and scalable fabrication process for building graphene-based variable capacitor device structures. Starting with commercially available 100 mm silicon wafers with a thick thermal oxide layer, we fabricate thousands of individually accessible freestanding graphene variable capacitors using standard semiconductor methods. The process begins with metal deposition to establish alignment crosshairs, then oxide etching to create trenches, a second metal deposition to form electrodes and bonding pads, followed by large-area graphene transfer, then patterning the graphene via oxygen plasma etching, critical point drying for suspension, and finally wire bonding our devices into a package. We use optical and atomic force microscopy characterization to confirm our design specifications were met. Electrical characterization confirms successful graphene suspension through voltage-dependent capacitance measurements. The procedure presented here successfully suspends both pure multilayer graphene as well as graphene with a thick layer of PMMA.

Anomalous Hall effect (AHE), occurring in materials with broken time-reversal symmetry, epitomizes the interplay between magnetic order and electron orbital motions1-4. In two-dimensional (2D) systems, AHE is coupled with out-of-plane orbital magnetization associated with in-plane chiral orbital motions. In three-dimensional (3D) systems, in which sample thickness far exceeds a vertical coherence-transport length lz, the AHE is effectively a thickness-averaged 2D counterpart4-still governed by out-of-plane orbital magnetization arising from in-plane orbital motions. Here we report the experimental observation of a fundamentally new type of AHE that couples both in-plane and out-of-plane orbital magnetizations in multilayer rhombohedral graphene, shown by pronounced Hall resistance hysteresis under both in-plane and out-of-plane magnetic fields. This state emerges from a peculiar metallic phase that spontaneously breaks time-reversal, mirror and rotational symmetries driven by electron-electron interactions. By measuring multiple devices spanning 3-15 layers, we find that this phenomenon emerges only within an intermediate thickness of 2-5 nm. Theoretical calculations show that carriers within this window can sustain coherent orbital motions both within and across the 2D plane. Together, these identify an uncharted 'transdimensional' regime between 2D and 3D, in which the sample thickness is much larger than atomic spacing yet remains comparable to lz, for the emergence of this new state of matter-transdimensional AHE. Our findings point to a distinct class of AHE, opening an unexplored model for correlated and topological physics in transdimensional landscapes.

Recent studies of rhombohedral multilayer graphene have revealed a variety of superconducting states that can be induced or enhanced by magnetic fields, reinforcing rhombohedral multilayer graphene as a powerful platform for investigating novel superconductivity. Here, we report an insulator-superconductor transition driven by in-plane magnetic fields B_{∥} in rhombohedral hexalayer graphene. The upper critical field of B_{∥} can reach 2T and an analysis based on isospin symmetry breaking supports a spin-polarized superconductor. At B_{∥}=0, such spin-polarized superconductor transitions into an insulator, exhibiting a thermally activated gap of Δ≈0.14 meV. In addition, we observe four superconducting states in the hole-doped regime, which violate the Pauli limit, as well as phases with magnetoelectric hysteresis near charge neutrality point. These findings substantially enrich the phase diagram of rhombohedral graphene and provide new insight into the microscopic mechanisms of superconductivity.

The electrical performance analysis of multilayer graphene nanoribbon based through silicon via in three-dimensional integrated circuits

ABSTRACT Coating engineering fibers with carbon nanostructures is used to develop smart textiles and electroconductive polymer composites. However, graphene derivatives still face challenges regarding dispersion and interfacial adhesion. To overcome these issues, multilayer graphene sheets (GSs) were chemically oxidized using a wet acid procedure. Chemical oxidation increased the surface density of hydroxyl, carbonyl, carboxyl, ester and epoxide groups on the surface of GSs, thereby enhancing their dispersion and chemical affinity with the surface of glass fibers. Such oxygen-containing groups improved the interfacial bonding between the oxidized GSs and the surface coating (sizing) of glass fibers, yielding a more homogeneous GS coating. The improved GS dispersion was further evidenced by the homogeneous electrical resistance maps of 160 mm × 100 mm GS-coated fibers, with electrical resistances on the order of a few hundred kΩ/m. The interfacial adhesion between GSs and glass fibers was quantified by measuring the relative GS-covered surface remaining after sequential peelings, using a novel image processing protocol. Results showed up to ~19.5% higher adhesion for oxidized GSs compared to as-received ones. The stronger GS/glass fiber interfacial bonding is explained through hydrogen bonding, dipole interactions, esterification reactions and physico-chemical interactions with the silanol group of the fiber sizing.

Rational design and preparation of a low-cost electromagnetic wave absorber are highly desired but remain a significant challenge. In this experiment involving the dimensionality engineering of carbon materials, multilayer graphene with gradient pores from nanometer to micrometer sizes were prepared by annealing carbon dots and nanocobalt powder. The heterogeneous interface between the gradient-pore multilayer graphene and the cobalt anchoring synergistically enhances interfacial polarization, while the multireflection within the porous architecture, combined with the intrinsic magnetic loss of nanocobalt, endows the composites with remarkable dielectric and magnetic loss capabilities. This cooperative dielectric-magnetic loss mechanism significantly promotes electromagnetic wave dissipation and optimizes the impedance matching of the material. As a result, the obtained nanocobalt-anchored gradient-pore multilayer graphene exhibits an exceptional minimum reflection loss of -56.0 dB, with an effective absorption bandwidth of 3.0 GHz, and it also achieves a minimum reflection loss of -38.5 dB and a broad effective absorption bandwidth of 5.1 GHz. This work reveals a dimensionality transition from zero-dimensional carbon dots to two-dimensional graphitic architectures, accompanied by pores emerging during the high temperature reaction. The insights provide a feasible strategy for designing high performance electromagnetic wave absorbers, ensuring that they are highly promising material candidates for addressing electromagnetic pollution challenges.

Excellent photoelectric properties and stability of CsPbBr3 single crystals mark broad prospects in the fields of photoelectrical detection. While attention to the contacts that have a huge influence on the figures of merit of the devices is relatively lacking, making an investigation into high-quality contacts a pressing need. Here, transparent multilayer graphene electrodes (MGE) are directly laminated to CsPbBr3 single crystals, forming a photoconductor-type photodetector. Benefiting from the optical transparency, mechanical flexibility, and chemical stability of multilayer graphene (MG) and its appropriate energy band alignment with CsPbBr3, the MG-contacted photoconductor exhibits significantly reduced dark current, enhanced photocurrent, and improved operational stability compared to its Au-contacted counterpart. Schottky barrier height at the MG-CsPbBr3 interface varies under different illuminations owing to the transparency of MG, enabling variable contact resistance (RC) over a wide range and thereby an approximately 2 orders of magnitude enhancement in the light-to-dark ratio of the MG-contacted photoconductor. Enhanced detectivity under weak illumination and an improved response rate are also achieved. Furthermore, the chemical inertness of carbon-based multilayer graphene electrodes brings about a pronounced suppression of photocurrent drift. The transparent MGE provides a method for achieving wide-range changes in contact resistance to realize photodetection and also offers a feasible approach for the assembly of efficient and stable perovskite optoelectronics.

Under the deformation potential model, the superconducting phenomenon in ABC-stacked multilayer graphene under a vertical electric field is investigated using linear combination operators and unitary transformation methods. Through the deformation potential model applied to a linear continuous medium, the effect of the external electric field is converted into the deformation potential energy of the crystal. Deformation potential phonons (LA phonons) act as propagators, generating electron-electron interactions. As the electric field increases, the ratio of the electric displacement vector to the dielectric function (D/ε) rises, leading to an increase in the electron ground-state energy, the opening of the band gap, and an enhancement of the attractive electron-electron interaction. With further increases in the external electric field, the deformation potential constant of the crystal (Dl) increases. When the phonon vibration frequency (ω) is around 8.5 THz, and the conditions are satisfied-where the wave vectors of different LA phonons are equal in magnitude and opposite in direction, and the electron spins are opposite-the attractive electron-electron interaction reaches its maximum (Heff), resulting in the emergence of superconductivity. Our study also provides a new perspective for understanding the unique quantum properties-such as strong correlations, superconductivity, and ferromagnetism-in different stacking configurations like AB, ABC, and ABCA.

Abstract Interlayer twisting provides a powerful geometric means to manipulate phonon-mediated heat transport in two-dimensional materials. However, its role under realistic substrate-supported conditions remains poorly understood. Here, we investigate thermal transport in twisted multilayer graphene by combining the neuroevolution potential (NEP) machine-learning framework with the homogeneous nonequilibrium molecular dynamics (HNEMD) method. The simulations reveal that interlayer twist strongly suppresses the contribution of out-of-plane phonons to thermal conductivity, with the suppression concentrated in the low-frequency regime below ~15 THz. This behavior originates from moiré-induced modulation of interlayer coupling, which enhances out-of-plane phonon scattering and disrupts long-wavelength coherence. Remarkably, the suppression persists even in the presence of substrate coupling, where out-of-plane phonons are already significantly damped. As a result, supported twisted graphene approaches its suspended thermal conductivity more rapidly with increasing layer number than untwisted counterparts. These findings elucidate the microscopic mechanism of twist–substrate interplay and establish interlayer twist as an effective structural degree of freedom for controlling phonon transport in van der Waals layered materials.

Non-Abelian Chern Band in Rhombohedral Graphene Multilayers

Designing electromagnetic wave absorbing (EWA) materials that simultaneously deliver strong attenuation and withstand harsh environments remains a major challenge due to long-standing trade-offs between dielectric performance and structural robustness. Here, we report a heterostructured diamond-graphene composite synthesized under moderate high-pressure and high-temperature conditions, in which multilayer graphene is embedded within a nanodiamond framework through covalently bonded interfaces. This architecture enables modulation of the sp3/sp2 hybridization ratios, yielding tunable dielectric responses, improved impedance matching, and multiple, synergistic energy-dissipation pathways. The optimized composite achieves a minimum reflection loss of -60 dB and an effective absorption bandwidth of 4.0 GHz. Simultaneously, the material exhibits exceptional environmental tolerance, including high thermal stability, reliable absorption at high temperatures, large fracture toughness, and enhanced corrosion resistance, which originates from the mechanically interlocked diamond/graphene networks and chemically stable carbon interfaces. Our results establish a scalable heterointerface-engineering strategy for constructing multifunctional carbon architectures that unify strong microwave attenuation with outstanding thermal, mechanical, and chemical durability, offering a promising platform for next-generation EWA materials suitable for harsh or demanding environments.

Triboelectric nanogenerators (TENGs) can effectively harvest mechanical energy from the environment, offering a promising solution for a sustainable power supply in wearable electronics. However, their widespread application is often hindered by expensive raw materials and complex fabrication processes. This study develops a simple and efficient integrated ultrasonic-shear process to exfoliate low-cost flake graphite (FG) into multi-layer flake graphite (MLFG), which is then embedded into polydimethylsiloxane (PDMS) to fabricate a novel composite triboelectric layer. The multi-layered structure of MLFG provides a larger specific surface area and more charge trapping sites, significantly enhancing capacitive behavior. The optimized 2 wt% MLFG-TENG achieved an open-circuit voltage of 90.3 V and a short-circuit current of 4.6 μA, which are 1.2 times and 1.6 times higher than those of the 3 wt% FG-TENG and 3.1 times and 4.2 times higher than those of the pure PDMS-TENG, respectively. This method delivers superior output performance with lower doping levels and maintains stable output after 20 000 cycles, demonstrating exceptional scalability. Furthermore, by integrating a rectifier circuit, the MLFG-TENGs successfully power small electronic devices such as LED arrays and electronic clocks. Concurrently, when integrated with machine learning, the MLFG-TENGs achieve 100% accurate recognition of five distinct hand motion patterns, highlighting their great potential in the fields of self-powered wearable devices and motion sensing.