Spin-resolved negative magnetoresistance in polycrystalline CVD graphene

Thermoacoustics of CVD graphene

Angstrom‐scale proton‐selective pores in atomically thin 2D materials present fundamentally new opportunities for advancing proton exchange membranes (PEMs). Vanadium Redox Flow Batteries (VRFBs) for grid‐scale energy storage require PEMs with high areal proton conductance (>1 S cm−2) and minimal vanadium ion (VO2+) crossover. However, state‐of‐the‐art Nafion 212 membranes (N212 ≈50 µm thick), suffer from persistent VO2+ crossover reducing performance and efficiency. Here, a layered PEM is demonstrated, comprising monolayer CVD graphene with Angstrom‐scale proton‐selective pores introduced via Ar plasma, integrated with an ultra‐thin ≈300 nm polybenzimidazole (PBI) layer and sandwiched between two Nafion 211 (25 µm thick) layers. The layered architecture facilitates scalable membrane fabrication by mitigating defects while processing and facile stacking of graphene layers allows stochastic non‐selective defect isolation enabling exceptionally low VO2+ crossover (selectivity (H+ areal conductance / VO2+ permeability) ≈6709 × 106 S min cm−4), with proton conductance >8 S cm−2. Systematic transport experiments supported by resistance‐based transport modelling elucidate the role of defect size, defect isolation, and sealing, as well as layering/stacking, to enable orders of magnitude (>671× over N212) improvements in selectivity, along with areal proton conductance >8 S cm−2. This work highlights the potential of atomic‐scale proton‐selective defect engineering in 2D materials, in conjunction with facile stacking and layering of materials as strategies for scalable, high‐performance advances in PEMs for energy, electrochemical, and separation applications beyond VRFBs.

This work introduces a high-performance graphene-silver hybrid metasurface biosensor for the fast and precise detection of COVID-19. Through parametric optimization with COMSOL Multiphysics, the sensor achieves a sensitivity of 400GHz/RIU, a figure of merit (FOM) of 5.000 RIU⁻¹, and a Q factor of 12.7 within the refractive index range of 1.334-1.355 RIU. A machine learning framework enhances predictive reliability across different refractive indices, as reflected by a coefficient of determination (R²) of 0.90. The fabrication strategy-combining CVD graphene growth, electron beam lithography, and silver deposition-ensures scalability and practical realization. The novelty of this study lies in the synergistic integration of a graphene-silver metasurface platform with machine learning-based predictive modeling, enabling rapid, label-free, and highly accurate COVID-19 detection. Unlike conventional RT-PCR and antigen-based tests, which suffer from delays, high costs, or reduced sensitivity in asymptomatic cases, the proposed sensor achieves superior balance between sensitivity, figure of merit, and predictive accuracy, thereby surpassing state-of-the-art optical and terahertz biosensors. This positions the device as a novel, portable, and cost-effective diagnostic tool for next-generation pandemic preparedness.

A new decoupling strategy for strain and doping in wrinkled CVD graphene with total effective strain evaluation

High-precision and rapid detection of complex defects in transferred CVD graphene enabled by machine learning algorithms

Introducing multiple functionalities to contact lenses (CLs) are achieved by additives such as nanomaterials, pigments, and dyes. CLs with graphene have been used in electromagnetic interference (EMI) shielding, drug delivery and sensing. Generally, CVD graphene or graphene nanocomposites are used during the manufacturing stage of CLs. In this work, we incorporate graphene into commercial CLs through three post processing techniques: the breath in - breath out (BIBO) technique, immersion of CLs in graphene ink, and 3D printing of graphene hydrogel composite. Graphene ink was used as the aqueous solution in BIBO cycles. The BIBO cycles were repeated to obtain the necessary attachment without losing transparency. In the immersion technique, immersion time controlled the concentration of graphene. In the third method, graphene ink was dispersed in hydroxyethyl methacrylate (HEMA) resin to 3D print patterns onto the CLs. Scanning Electron Microscopy (SEM) was used to observe graphene dispersion within CLs. The UV-Vis spectroscopy of the CLs indicated steady absorption throughout the visible region as a tinting additive, suggesting uses such as broad-spectrum absorbers. These methods could be used to quickly synthesize large amount of functionalized CLs for different applications. The lenses exhibited both anti-bacterial and exceptional biocompatibility properties.

Plasma processes have been proposed as an efficient and environmentally friendly approach for modifying graphene to tailor its properties for advanced applications, including those in electrochemistry. However, certain modifications, such as sulfurization, can be constrained by the choice of plasmagen gas. To address this, a plasma-based process for sulfur-graphene generation has been developed and thoroughly characterized. Drawing inspiration from ampoule reactions, the process involves placing solid sulfur (S₈) and CVD graphene (transferred onto SiO₂/Si) within a silica tube, where a microwave (MW) discharge is initiated by a surfatron in 10 Torr argon. The process works by utilizing plasma collisions to heat the gas, vaporize the sulfur, and create reactive radical sulfur species (S and S2) capable of functionalizing the graphene. A detailed study of the argon plasma was conducted using high-resolution and ultra-high-resolution optical emission spectroscopy and imaging. Gas temperature was determined through the resonant and Van der Waals broadening of argon emission lines (826 and 840 nm) under varying experimental conditions. This temperature enabled the estimation of sulfur vapor pressure, a critical parameter for generating reactive sulfur species. Monolayer CVD graphene was functionalized with sulfur in the spatial post-discharge region to avoid plasma-induced etching, while Highly Ordered Pyrolytic Graphite (HOPG) exposed directly to the sulfur plasma showed significant etching. The resulting sulfur-functionalized graphene was characterized using Hyperspectral Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). Raman spectroscopy provided insights into defect generation and doping effects, as indicated by shifts and intensity changes in the D, G, and 2D bands, while XPS confirmed the incorporation of sulfur species into the graphene structure. This novel plasma-based process for sulfur-functionalized graphene presents exciting opportunities for advanced materials, particularly in electrochemical applications such as energy storage, catalysis, and sensors. Sulfur-modified graphene holds great potential for enhancing performance for Li-Sulfur batteries.

2D materials offer a unique opportunity to achieve new device functionality and realize novel quantum states. Synthesizing high-purity starting materials is key to achieving these goals. Our synthesis efforts focus on (1) growing ultra-pure crystals of transition metal dichalcogenides (TMDs), and identifying the different types of point defects within these crystals; and (2) new strategies for graphene CVD synthesis that dramatically improve speed, reproducibility, and quality. These improvements in quality lead to dramatically improved performance and open the door to applications in quantum devices. In particular, we are exploring the use of 2D materials for compact qubit architectures in which a single heterostructure can act as a capacitor and Josephson junction.

High-Temperature Ultrasensitive FET-Based CVD Graphene Hall Probes

Encapsulation is crucial for protecting graphene devices, but traditional whole-package encapsulations usually add bulky structures and reduce their flexibility. Hexagonal boron nitride (h-BN) holds potential for graphene encapsulation, but faces challenges in large-area acquisition and conformal coverage due to limitations in exfoliation and transfer techniques. Graphene-skinned glass fiber fabric (GGFF), made via graphene CVD growth on each fiber of a glass fiber fabric, consists of a hierarchical conductive network, but pressure/deformation-induced inter-fiber contact resistance fluctuations destabilize its electrical conduction. Whole-package encapsulation cannot resolve this, as fails to insulate inter-fiber contacts. Herein, thick, high-quality h-BN films are CVD-grown on each fiber in GGFF, achieving conformal encapsulation. This unlocks conductive network in GGFF, stabilizing electrical conduction while preserving structure stability and flexibility. This also improves GGFF’s resistance to doping and oxidation, extending its service life. This encapsulation strategy is broadly applicable to other two-dimensional materials and complex device structures, promoting reliable nanoelectronics in demanding environments.

Genetic algorithm designed multilayered Si3N4 nanowire membranes hybridized by dielectric wide-range tunable CVD graphene skin for broadband microwave absorption

We employ ultrabroadband terahertz (THz) spectroscopy to expose the high-frequency transport properties of Dirac fermions in monolayer graphene. By controlling the carrier concentration via tunable electrical gating, both equilibrium and transient optical conductivities are obtained for a range of Fermi levels. The frequency-dependent equilibrium response is determined through a combination of time-domain THz and Fourier-transform infrared spectroscopy for energies up to the near-infrared, which also provides a measure of the gate-voltage dependent Fermi level. Transient changes in the real and imaginary parts of the graphene conductivity are electro-optically resolved for frequencies up to 15 THz after near-infrared femtosecond excitation, both at the charge-neutral point and for higher electrostatic-doping levels. Modeling of the THz response provides insight into changes of the carrier spectral weights and scattering rates, and reveals an additional broad-frequency ( 8 THz) component to the photo-induced response, which we attribute to the zero-momentum mode of quantum-critical transport observed here in large-area CVD graphene.

Quantum transport transition from quantum interference to Coulomb blockade in suspended CVD graphene nanoribbons with reduced ribbon widths

Controlling the number of layers of Mo-grown CVD graphene through the catalyst thickness

Polymethylmethacrylate (PMMA) is commonly used as a support material in graphene transfer. Heat treatment exceeding 250 °C is required to remove the PMMA after the transfer process. However, the transparent flexible substrates conventionally used for graphene transfer generally exhibit low heat resistance. This hinders the complete removal of the PMMA, resulting in low electrical conductivity of graphene. Therefore, we focused on developing heat-resistant transparent polyimide (TPI) films as substrates for graphene transfer. The interactions between the TPI substrates and chemical vapor deposition graphene were systematically investigated. The effects of the TPI surface roughness, chemical composition, and chemical structure of the TPI, and doping effects of the substrate were examined, and a silane coupling agent (SCA) was coated to bring the TPI surface properties closer to those of a quartz glass substrate. Three-layer stacked graphene (3LG) on TPI, in which the -CF3group in TPI is replaced with -CH3, exhibited the highest carrier mobility of 3610 cm2Vs-1at a constant carrier density after annealing. The sheet resistance of the 3LG on TPI annealed after vapor phase deposition of the SCA was lower than that of the standard TPI and decreased to 82 Ω/sq. after doping with bis(trifluoromethanesulphonyl)amide. This is comparable to the electrical properties of graphene on a quartz glass substrate. Furthermore, after doping, the 3LG/TPI maintained a high optical transmittance of 88.8% at a wavelength of 550 nm. The knowledge obtained from this study will allow graphene flexible transparent conductive films to be transferred onto TPI for use in transparent heaters and solar cells as well as to control the electrical properties for various device applications by modifying the roughness, chemical structure, and coating layers on the surface of the TPI substrate.

SnO2/GO co-supported transfer of CVD graphene for high-performance ammonia detection

OLEDs with CVD graphene anodes on cellulose substrates demonstrate an alternative for environmentally friendly, transparent and flexible devices.

To expand the possible applications, chemical vapor deposition grown graphene needs to be transferred to appropriate substrates such as a silicon wafer. Although enormous efforts have been devoted to transfer graphene to various substrates using many different methods, the quality of the final product is still insufficient. We develop a new process named semi-dry transfer, which combines wet etching and dry transfer to obtain graphene with a clean interface with the substrate. For this purpose, an adhesive tape is attached to a sacrificial polymer deposited on the synthesized graphene, which allows the graphene to be easily manipulated so that it can be carefully cleaned before being precisely transferred onto target substrates, here silicon (Si) surfaces. We used this technique to transfer up to 4 × 4 cm2 of graphene onto SiO2/Si substrates. Using various analysis techniques such as low energy electron diffraction, scanning electron microscopy, scanning tunneling microscopy/spectroscopy, Raman, Auger electron and X-ray photoelectron spectroscopies, we demonstrate that our transferred graphene on Si is continuous, clean and that it is very promising for device fabrication. Graphene transistors show transport properties comparable with the state-of-the-art.

Graphene exhibits promise in gas detection applications despite its limited selectivity. Functionalization with fluorine atoms offers a potential solution to enhance selectivity, particularly towards ammonia (NH+) molecules. This article presents a study on electron-beam fluorinated graphene (FG) and its integration into gas sensor platforms. We begin by characterizing the thermal stability of fluorographene, demonstrating its resilience up to 450 °C. Subsequently, we investigate the nature of NH3interaction with FG, exploring distinct adsorption energies to address preferential adsorption concerns. Notably, we introduce an innovative approach utilizing x-ray photoelectron spectroscopy cartography for simultaneous analysis of fluorinated and pristine graphene, offering enhanced insights into their properties and interactions. This study contributes to advancing the understanding and application of FG in gas sensing technologies.