Graphene Surface Research Articles

Fe3O4 modified graphene epoxy composite materials via polyether amine reduction with enhanced microwave absorption performance

Abstract The increasing complexity of electromagnetic environments demands the development of advanced absorbers with superior performance. In this study, a novel magnetic Fe3O4-modified graphene-based absorber (FARGO) is synthesized via an in-situ reduction process using polyether amine. The resulting FARGO composite exhibits excellent microwave absorption properties. When the filling content of FARGO is 5 wt% in epoxy resin, the optimal reflection loss is -23.12 dB with a thickness of 4 mm and a broad absorption bandwidth of 5.6 GHz can be achieved as the thickness changes to 2 mm. Polyether amine efficiently reduces GO to rGO, significantly improving electrical conductivity. Simultaneously, it grafts amine groups onto the graphene surface, enhancing dispersion and reactivity within the epoxy resin matrix. These synergistic effects make it a promising candidate for high-performance microwave absorbing materials.

Compact and voltage-tunable surface plasmon polariton-based optical neural networks

Optical neural networks (ONNs) offer advantages in parallel processing, low power consumption, and high-speed operation. However, existing ONN designs face challenges in miniaturization, stability, tunability, and integration. This study proposes a graphene surface plasmon polariton (GSPP) waveguide switch array for all-optical neural networks. The design features a compact structure with a lateral area of only 0.045 . Numerical simulations show that within the 30.2 to 49.4 THz range, the transmission rate is tunable from 0 to 0.875, accurately simulating synaptic weights in ONNs. The compact switch array achieves a recognition accuracy of 93.83% on the CIFAR-10 dataset, demonstrating its potential for high-speed, low-power, and highly integrated neural network computing platforms.

Electronic and adsorption characteristics of hydrogen cyanide (HCN) and isocyanide (HNC) on intrinsic and doped phosphorene

Density functional theory calculations are performed to investigate the electronic properties of the phosphorene that is substituted with the non-metals in different patterns and concentrations and to study the adsorption of the toxic gases, hydrogen cyanide (HCN) and isocyanides (HNC), on the intrinsic and nitrogen-doped phosphorene adsorbents. It has been established previously that the number of valence electrons in the dopant atoms considerably affects the electronic characteristics of phosphorene. Doping with B, S, Si, and other non-metals has resulted in drastic changes in the direct bandgap characteristics of the semiconductor, resulting in the conversion of the semiconductor into an indirect bandgap material (boron-doped) or metallic (Si/S doped). Of all the doped surfaces, only nitrogen-doped phosphorene shows a direct bandgap. Therefore, adsorption studies are conducted to investigate the sensitivity of the toxic gases hydrogen cyanide (HCN) and isocyanide (HNC) on intrinsic and nitrogen-doped adsorbents. The adsorption results are compared to those on graphene and doped graphene surfaces. Pure phosphorene is a good candidate for the moderate adsorption of HCN and HNC due to its low adsorption energy and charge transfer. We have also found that intrinsic phosphorene is a better adsorbent for these gases than intrinsic graphene and doped graphene. In addition, N-doped phosphorene shows moderate reactivity toward HCN and HNC gases, suggesting it may be used as a metal-free catalyst for the adsorption of these adsorbates. The 2p orbitals on the nitrogen of HCN are found to play a significant role in the strong physisorption.

VG@nAu-based fluorescent biosensor for grading Alzheimer's disease by detecting P-tau181 protein in clinical samples.

Alzheimer's disease (AD) is a neurodegenerative disorder with a very long duration, posing a serious threat to people's life and health. To date, no medicine that can cure or reverse the disease has been developed or reported, so early diagnosis and timely intervention are essential. The concentration of Phosphorylated tau181 (P-tau181) in blood has been approved by FDA as a standard for assisting clinical diagnosis of AD. In this study, a fluorescence biosensor based on vertical graphene-modified nano-gold film (VG@nAu) was developed for the grading of AD diagnosis by detecting P-tau181 protein in the blood. The VG@nAu substrate that produces hundreds of times IR800 molecular compared with a glass substrate, which is prepared by sputtering nano-gold onto vertical graphene surface. The detection limit of this fluorescence biosensor for P-tau181 is 0.82pg/mL. The sensor also shows excellent selectivity and stability. Moreover, we analyzed the levels of P-tau181 in 16 clinical samples divided into four groups (HC group, SCD group, MCI group, and AD group) and found significant differences in P-tau181 levels. The grouping result based on the detection results using this biosensor is consistent with the grouping results of the clinical doctors. This study achieves ultrasensitive detection of P-tau181 protein by constructing a fluorescent biosensor, which validates the feasibility of the VG@nAu-based fluorescence biosensor for the grading of AD diagnosis. This research provides a promising tool for ultrasensitive detecting biomarkers in clinical samples, indicating significant potential for its use in related diagnosing disease.

Research on the flame retardancy properties and mechanism of modified epoxy resin with graphene‐based hybrid

AbstractThe inherent disadvantage of epoxy resin (EP) is that it is easy to burn, and a large number of toxic and harmful gases are generated in the combustion process, and there is a huge fire hazard. Graphene, a two‐dimensional‐layered material with physical barrier effects, is used by many researchers to enhance the fire safety of EP, but because of its easy aggregation, it is difficult to prepare high‐performance flame retardants. In our work, a high‐performance graphene flame retardant was prepared by grafting a hollow zirconium organic frame material onto the surface of graphene. First, zirconium‐based organic frame material (UiO66‐NH2) with different particle sizes was prepared by adjusting acetic acid, the hollow organic frame material was etched with sodium tungstate under acidic conditions, and then reacted with organophosphorus and graphene oxide, thus W‐UiO66‐DOPO‐RGO were obtained. The results show that the W‐UiO66‐3‐DOPO‐RGO/EP has enhanced smoke suppression and flame retardancy, the LOI value up to 33.5%, vertical combustion class up to UL‐94V‐0, PHRR and TSP reduced by up to 58% and 42%, respectively. Through the characterization of the condensed and gas phase of EP composites, the relevant flame retardancy mechanism was clarified, which were mainly the synergistic flame retardancy and smoke suppression mechanism among the adsorption of fractional pores of hollow bimetallic MOFs, catalytic carbonization of metals, condensed phase and gas phase interaction of phosphorus elements, and physical shielding of RGO.Highlights A high‐performance graphene‐based flame retardants were proposed. 3 wt% of W‐UiO66‐3‐DOPO‐RGO endows EP with excellent flame retardancy. The fire safety mechanism of W‐UiO66‐DOPO‐RGO/EP was proposed.

Porous Carbon Nanoparticle Composite Paper Fiber with Laser-Induced Graphene Surface Microstructure for Pressure Sensing.

In recent years, flexible pressure sensors have played an increasingly important role in human health monitoring. Inspired by traditional papermaking techniques, we have developed a highly flexible, low-cost, and ecofriendly flexible pressure sensor using shredded paper fibers as the substrate. By combining the properties of laser-induced graphene with the structure of paper fibers, we have improved the internal structure of pressure-sensitive paper and designed a conical surface microstructure, providing new insights into nanomaterial engineering. It features low resistance (424.44 Ω), low energy consumption of only 0.367 μW under a pressure of 1.96 kPa, high sensitivity (1.68 kPa-1), and a wide monitoring range (98 Pa-111.720 kPa). The pressure-sensitive paper with surface microstructure (MFTG) developed in this study has a total thickness comparable to A4 paper, is soft and bendable, can be cut into any shape like paper to fit the human body, and holds great potential for continuous monitoring of human activity status and physiological information.

Miniaturized Wearable Biosensors for Continuous Health Monitoring Fabricated Using the Femtosecond Laser-Induced Graphene Surface and Encapsulated Traces and Electrodes.

Wearable sensors are increasingly being used as biosensors for health monitoring. Current wearable devices are large, heavy, invasive, skin irritants, or not continuous. Miniaturization was chosen to address these issues, using a femtosecond laser-conversion technique to fabricate miniaturized laser-induced graphene (LIG) sensor arrays on and encapsulated within a polyimide substrate. The femtosecond laser-converted conductive traces can have a size of 20 to 2 μm compared to the traditionally larger CO2 laser dimensions of around 300 to 100 μm. This marks a 93-98% decrease in trace size when using a femtosecond laser. This miniaturization allows for the ability to process temperature, electrocardiography (ECG), electromyography (EMG), and glucose data in the same space that would have been occupied by a single sensor. The femtosecond laser-converted graphene (FSLIG) electrodes were modified to function as glucose sensors, and comprehensive electrochemical analyses using cyclic voltammetry (CV) and chronoamperometry (CA) were performed. These tests confirmed the capability of the sensors to detect glucose levels, showing a stability of 96.14%. Encapsulation of FSLIG within polyimide was achieved for the first time, demonstrating the ability to nondestructively create FSLIG electrodes within existing materials, thereby protecting them from external environmental factors. The encapsulated FSLIG shows potential as a method to produce LIG-coated Cu traces for improved multilayered printed circuit boards or layered circuits with complex geometries in polyamide to reduce size and increase functionality. Even sterile probes for use inside the body or under dermis polyamide injections and subsequent FSLIG circuit tattoos are possible. This study demonstrates the novel miniaturization and encapsulation capabilities enabled by the femtosecond laser, developing next-generation wearable biosensors focusing on miniaturization, flexibility, continuous monitoring, multifunctionality, and comfort.

Revealing the Water Structure at Neutral and Charged Graphene/Water Interfaces through Quantum Simulations of Sum Frequency Generation Spectra.

The structure and dynamics of water at charged graphene interfaces fundamentally influence molecular responses to electric fields with implications for applications in energy storage, catalysis, and surface chemistry. Leveraging the realism of the MB-pol data-driven many-body potential and advanced path-integral quantum dynamics, we analyze the vibrational sum frequency generation (vSFG) spectrum of graphene/water interfaces under varying surface charges. Our quantum simulations reveal a distinctive dangling OH peak in the vSFG spectrum at neutral graphene, consistent with recent experimental findings yet markedly different from those of earlier studies. As the graphene surface becomes positively charged, interfacial water molecules reorient, decreasing the intensity of the dangling OH peak as the OH groups turn away from the graphene. In contrast, water molecules orient their OH bonds toward negatively charged graphene, leading to a prominent dangling OH peak in the corresponding vSFG spectrum. This charge-induced reorganization generates a diverse range of hydrogen-bonding topologies at the interface driven by variations in the underlying electrostatic interactions. Importantly, these structural changes extend into deeper water layers, creating an unequal distribution of molecules with OH bonds pointing toward and away from the graphene sheet. This imbalance amplifies bulk spectral features, underscoring the complexity of many-body interactions that shape the molecular structure of water at charged graphene interfaces.

Combination of graphene plasmons and surface plasmons in a crystalline Ge2Sb1.5Bi0.5Te5 metasurface structure for laser mode-locking

Owing to the dynamic tunability and strong confinement, graphene plasmons (GPs) have emerged as an excellent candidate for the manipulation of light–matter interaction. Surface plasmons (SPs) have been admitted as another effective way allowing strong confinement of light at the nanoscale. The combination of GPs and SPs like localized surface plasmons (LSPs) and propagating surface plasmon polaritons (SPPs) will lead to a synergistic effect that could remarkably improve light–matter interactions, showing great potential for many applications for the improvement of solar cell efficiency, biosensor sensitivity, and the performance of photonic devices. In this study, the GPs were activated by placing graphene film onto a two-dimensional (2D) phase-changing crystalline Ge2Sb1.5Bi0.5Te5 (cGSBT) nanograting structure, which also acts as an original source generating LSPs. The SPPs originated by laying the above structure onto an Au mirror. The combined effects of GPs, LSPs, and SPPs are epitomized in such a simple Gr/2D cGSBT gratings/Au heterostructure, which allows easy realization of an ultrafast mode-locked laser quite stable working at 1550 nm range due to the strong nonlinear optical absorption capability. This approach overcomes the heat and energy loss in metallic gratings or a Gr-based heterostructure, exhibiting great potential for applications in the design and fabrication of photonic devices.

Understanding the Curvature Effect on the Structure and Bonding of MoCy Nanoparticles on Carbon Supports.

The interaction between molybdenum carbide (MoCy) nanoparticles and both flat and curved graphene surfaces, serving as models for carbon nanotubes, was investigated by means of density functional theory. A variety of MoCy nanoparticles with different sizes and stoichiometries have been used to explore different adsorption sites and modes across models with different curvature degrees. On flat graphene, off-stoichiometric MoCy featuring more low-coordinated Mo atoms exhibits stronger interaction and increased electron transfers from the carbide to the carbon substrate. This preferentially occurs through support C and Mo atoms leading to the formation of additional Mo-C bonds. Notably, the MoCy adsorption strength increases on concave surfaces and decreases on convex surfaces, showing a strong linear correlation with the surface curvature. This curvature-dependent behavior alters the charge state of the nanoparticles, making them more/less positively charged in concave/convex regions. The present results demonstrate that the interaction strength can be effectively tuned by manipulating the carbide stoichiometry, the substrate curvature, and the local concave/convex environments, providing valuable guidelines for the rational design of MoCy/C-based catalysts.

Enhanced Near-Infrared Fluorescence Emission near a Graphene-Metal Hybrid Structure.

Plasmon resonance plays an important role in improving the detection of biomolecules, and it is one of the focuses of research to use metal plasmon resonance to achieve fluorescence enhancement and to improve detection sensitivity. However, the problems of nondynamic tuning and fluorescence quenching of metal plasmon resonance need to be solved. Graphene surface plasmon resonance can be dynamically controlled, and the graphene adsorption of fluorescent molecules can avoid fluorescence quenching and greatly improve the fluorescence emission intensity. The graphene-metal hybrid structure designed in this work can solve the above two problems well, and the plasmon resonance can improve the fluorescence emission efficiency of molecules on the surface of graphene and improve the sensitivity of biological detection. At the same time, graphene nanoribbons in our hybrid structure do not require patterning, which greatly lowers the threshold for graphene application in biosensing.

Programmable Electromagnetic Wave Absorption via Tailored Metal Single Atom-Support Interactions.

Metal single atoms (SA)-support interactions inherently exhibit significant electrochemical activity, demonstrating potential in energy catalysis. However, leveraging these interactions to modulate electronic properties and extend application fields is a formidable challenge, demanding in-depth understanding and quantitative control of atomic-scale interactions. Herein, in situ, off-axis electron holography technique is utilized to directly visualize the interactions between SAs and the graphene surface. These interactions facilitate the formation of dispersed nanoscale regions with high charge density and are highly sensitive to external electromagnetic (EM) fields, resulting in controllable dynamic relaxation processes for charge accumulation and restoration. This leads to customized dielectric relaxation, which is difficult to achieve with current band engineering methods. Moreover, these electronic behaviors are insensitive to elevated temperatures, having characteristics distinct from those of typical metallic or semiconducting materials. Based on these results, programmable EM wave absorption properties are achieved by developing a library of SA-graphene materials and precisely controlling SA-support interactions to tailor their responses to EM waves in terms of frequency and intensity. This advancement addresses the customized anti-EM interference requirements of electronic components, greatly enhancing the development of integrated circuits and micro-nano chips. Future efforts will concentrate on manipulating atomic interactions in SA-support, potentially revolutionizing nanoelectronics and optoelectronics.

One‐Pot Synthesis of a Nitrogen‐ and Iodine‐Doped Graphene Composite for Energy Storage Applications

AbstractWith the growth of power generation, portable electronic devices are gaining more attention toward energy storage devices, preferably supercapacitors. In this, the surface of graphene was functionalized with conductive polymer by in situ polymerization of pyrrole (PPy) and doping of iodine via hydrothermal method. Doping iodine (potassium triiodide) and nitrogen (polypyrrole) from their respective precursors made GNI composition more suitable for energy storage applications. The synthesized GNI composite showed the maximum specific capacitance of 200 F g−1 at 1.0 Ag−1 with an efficient specific energy of 22.5 Wh kg−1 and specific power of 1800 W kg−1 in a symmetrically arranged two‐electrode Swagelok type cell. The durability of the synthesized composite was analyzed by cyclic stability at current density 10 Ag−1, retaining up to 85% of its initial capacitance after 10,000 repetitive charge‐discharge cycles. The in situ polymerization of pyrrole with the insertion of iodine makes graphene composition more conductive than control graphene, showing a specific capacitance of 111 F g−1 at 1.0 Ag−1. The one‐pot synthetic approach is a simple, easy, and efficient route toward supercapacitor applications. This approach will provide an easy way to introduce N and I to graphene compositions for various applications, including energy storage materials.

Cluster-like Mo2N anchored on reduced graphene oxide as an efficient and high-performance catalyst for deep-degree oxidative desulfurization

The cluster-like Mo2N catalyst, uniformly dispersed on the graphene surface, was successfully prepared. The resulting Mo2N/rGO-A catalyst exhibited plentiful accessible surface active sites, exhibiting efficient and high-performance for ODS.

Construction of advanced Nb9VO25 electrode material by introducing graphene quantum dot for high energy supercapacitors with exceptionally high diffusive capacitance

Unreasonable tunnel structure and low intrinsic conductivity limit practical applications of niobium oxide in high-performance supercapacitors. The study reports the construction of Nb9VO25 electrode material via coordination of Nb(V) and V(V) with histidine and serine-functionalized and boron-doped graphene quantum dot (HSBGQD) and subsequent annealing. The introduction of HSBGQD and rambutan peel leads to formation of small Nb9VO25 nanocrystal and low valent Nb and V species. The combination of small size and more reasonable tunnel structure accelerates the ion diffusion. The Nb(IV) and V(IV) double doping optimizes the tunnel structure, narrows the bandgap and creates new pathways for high-speed electron transfer. The integration of defect engineering with graphene surface modification enhance the intrinsic conductivity. The Nb9VO25 electrode shows exceptionally high specific capacitance of 2925.3 F/g, which is more than 142 times that of Nb2O5. The symmetrical supercapacitor with Nb9VO25 electrodes and PVA/Li2SO4 gel electrolyte offers high specific capacitance (263 F/g at 1 A/g), high-rage capacity (138 F/g at 50 A/g), cycling stability (capacitance retention of 99.4 % after 10000-cycle), energy density (146 W h Kg−1 at 996 W Kg−1 and 77 W h Kg−1 at 50181 W kg−1) and broad application prospect in wearable electronic devices.

Machine Learning Optimized Graphene and MXene-Based Surface Plasmon Resonance Biosensor Design for Cyanide Detection

Machine Learning Optimized Graphene and MXene-Based Surface Plasmon Resonance Biosensor Design for Cyanide Detection

Tuning the Electronic and Optical Properties of Graphene via Doping to Realize Nitrogen Dioxide Sensing: A Computational Study.

Recently, doped graphene has emerged as a promising material for gas sensing applications. In this study, we performed first-principles calculations to investigate the adsorption of nitrogen dioxide (NO2) on pristine, nitrogen (N)-doped, ruthenium (Ru)-doped, and N-Ru-co-doped graphene surfaces. The adsorption energies, Mulliken charge distributions, differential charge densities, electronic density of states, and optical properties of NO2 on the graphene surfaces were evaluated. The adsorption energies follow the order N-Ru-co-doped > Ru-doped > N-doped > pristine graphene, suggesting that doped graphene has higher sensitivity to NO2 gas molecules than pristine graphene. Analysis of the charge transfer and differential charge densities indicated weak physisorption of NO2 on pristine and N-doped graphene, whereas stronger chemisorption of NO2 occurred on Ru-doped and N-Ru-co-doped graphene because of the formation of chemical bonds between NO2 and the doped surfaces. The peak absorption and reflection coefficients of NO2 adsorbed on N-Ru-co-doped graphene are approximately 2.88 and 7.75 times higher, respectively, than those of NO2 adsorbed on pristine graphene. The substantial changes of the electronic and optical properties of N-Ru-co-doped graphene upon interaction with NO2 can be exploited for the development of highly sensitive and selective NO2 gas sensors.

Graphene Functionalization by O2, H2, and Ar Plasma Treatments for Improved NH3 Gas Sensing.

Graphene-based materials have gained attention for their promise in various applications owing to their two-dimensional structure. Functionalizing the graphene surface can help realize materials with noble properties. In this study, graphene was functionalized by plasma treatment in O2, H2, and Ar environments, and the effects on the NH3 gas-sensing performance were evaluated. The O2 plasma treatment induced oxidation of the graphene (i.e., graphoxide), while the H2 plasma treatment induced hydrogenation (i.e., graphane). Raman scattering spectroscopy suggested that graphoxide had vacancy-type defects and graphane had sp3-type defects, while Ar-treated graphene had both types of defects. Graphane had the highest sheet resistance followed by graphoxide, Ar-treated graphene, and pristine graphene, which can be attributed to the large bandgap of 3.0 eV for graphane. In contrast, graphoxide had the best NH3 gas-sensing performance, which indicates that NH3 gas interacts more strongly with vacancy-type defects than with sp3-type defects. The results showed that functionalizing the graphene structure generated noble materials with a superior NH3 gas-sensing performance compared with pristine graphene.

Atomic Layer Deposition of Platinum on the Oxygen-Pretreated Graphene Surface

Atomic Layer Deposition of Platinum on the Oxygen-Pretreated Graphene Surface

Inelastic Scattering in Weak Localization for Single‐Layer Graphene

Chemical‐vapor‐deposited graphene is used extensively to fabricate devices. However, the charge‐neutral point (CNP) of this material appears at a relatively high back‐gate voltage (VG) because of molecular adsorption and impurities on the graphene surface. In this study, a Ti‐cleaning process is used to remove contaminants from the transferred graphene. Two contributions to the magnetoresistance are investigated: weak localization (WL) and inhomogeneous charge transport near the Dirac point. One of the most important parameters for clarifying the quantum transport properties is the inelastic scattering time. Fitting of the experimental results with a theoretical WL expression is performed to investigate the temperature and VG dependence of the inelastic scattering and intervalley scattering rates. Small momentum transfer due to Nyquist scattering is dominant in the CNP region, while large momentum transfer processes of direct electron–electron interaction dominate the electron and hole‐transport regions.