Single-layer Graphene Research Articles

Trajectory-dependent highly charged ion-induced electron yield from single-layer graphene

Abstract We study the neutralisation dynamics of highly charged ions by transmission through a free-standing single layer of graphene in dependence of the particle trajectory. Both the secondary electron yield and the neutralisation of the ion increase for increasing scattering angles (smaller impact parameters). This supports the current understanding of highly charged ion deexcitation, according to which the presence of an interatomic deexcitation mechanism with improved efficiency in the proximity of neighbours is necessary in addition to intraatomic radiative- and non-radiative decay pathways.

An Overview on Single-Layer Graphene Production Methods with High Quality for Large-Scale Applications

An Overview on Single-Layer Graphene Production Methods with High Quality for Large-Scale Applications

Four-band tunable narrowband optical absorber built on surface plasmonically patterned square graphene

The square and ring-shaped graphite four-band ultra-narrow-band absorber in this paper achieve perfect absorption. Therefore, the four waves of perfect transmission in the middle infrared band have been achieved, and there are four common values at λ1 = 2471.33 nm, λ2 = 2553.81 nm, λ3 = 2588.4 nm and λ4 = 2661.9 nm. Their ultra-high reflectors are 99.95 %, 96.65 %, 92.87 %, and 97.65 %, respectively, and the average reflective rate is 96.78 %. This is achieved in the graphene array structure of the pattern. Single-layer graphene is due the near-field enhancement has achieved almost perfect absorption. From the characteristics of graphene, a single variable is used to compare the effects of each variable on the efficiency of the absorber. From the perspective of incident light, it can be understood that the absorber can work within a wide range of incident angle to achieve a high absorption rate. The results obtained from the changes in environmental refractive index are more interesting. The structural model in this chapter has a high FOM (Figure of Merit) and can act as a atmospheric refractive index sensor.

Graphene: Study in Electronic Structure, Superconductivity and Potential in Quantum Information Sciences

Graphene, a two-dimensional lattice of carbon atoms, exhibits remarkable electronic properties due to its Dirac-like electronic excitations. This paper reviews the elementary electronic properties of graphene, including the tight-binding model for single-layer graphene and the band structure formation. The tight-binding Hamiltonian provides a fundamental understanding of graphene’s linear energy dispersion near the Dirac points, leading to unique phenomena such as massless Dirac fermions and chiral tunneling. We explore the potential of superconductivity in graphene using BCS theory. We find that BCS theory cannot explain superconductivity in graphene and its forms. This is in contradiction with the discovery of unconventional superconductivity in twisted bilayer graphene (TBG). The study further explores the potential application of bilayer graphene quantum in quantum information sciences, highlighting the development of states with relaxation times exceeding 500 ms. These valley states, arising from the hexagonal lattice structure, can be used to encode information as robust valley qubits for fault-tolerant quantum computing

Exploring structural and electronic properties of topological insulator/graphene nano-heterostructures

There is great interest in the study of topological insulator-based heterostructures due to expected emerging phenomena. However, a challenge of topological insulator (TI) research is the contribution of bulk conduction to the TI surface states. Both strain engineering and thickness control routes, which have been proposed to compensate for bulk doping, can be accessed through the use of nano-heterostructures consisting of topological insulator nanostructures grown on 2D materials. In this work, we report the synthesis of TI/graphene nano-heterostructures based on Bi2Te3 and Sb2Te3 nanoplatelets (NPs) grown on single-layer graphene. Various techniques were used to characterize this system in terms of morphology, thickness, composition, and crystal quality. We found that most of the obtained NPs are mainly <30 nm thick with thickness-dependent crystal quality, observed by Raman measurements. Thinner NPs (1 or 2 quintuple layers ) tend to replicate the topography of the underlying single-layer graphene, according to roughness analysis. Finally, we show preliminary studies of their band structure obtained by Low Temperature Scanning Tunneling Microscopy, Scanning Tunneling Spectroscopy, and by Density Functional Theory. We observe a highly negative ED value which can be attributed to the presence of defects.

Ultrasensitive Detection of Chemokines in Clinical Samples with Graphene-Based Field-Effect Transistors.

Due to their ultra-high sensitivity, solution-gated graphene-based field-effect transistors (SG-GFET) have been proposed for applications in bio-sensing. However, challenges regarding the functionalization of GFETs have prevented their applications in clinical diagnostics so far. Here GFET sensors based on van der Waals (vdW) heterostructures of single-layer graphene layered with a molecular ≈1nm thick carbon nanomembrane (CNM) are presented. The CNM acts as an ultrathin molecular interposer between the graphene channel and the analyte and allows bio-functionalization without impairing the graphene properties including its charge carrier mobility. To achieve specificity and reliability in the detection of biomarkers in real patient samples, the functionalization incorporates biostable aptamers in the non-natural l-configuration and hydrophilic polyethylene glycol for avoiding non-specific adsorption. A rapid (≈5min) detection of the clinically relevant inflammatory mediator CXCL8/IL-8 within the concentration range of 0.5 - 500 pM (5 - 5000 pgml-1) is demonstrated in nasal swab samples collected from patients with respiratory tract infections. This detection range may aid in diagnostics of early-stage infectious diseases making the reported approach promising for the development of future medical tools.

An Optimized Graphene-Based Surface Plasmon Resonance Biosensor for Detecting SARS-CoV-2

Graphene-enhanced surface plasmon resonance (SPR) biosensors offer promising advancements in viral detection, particularly for SARS-CoV-2. This study presents the design and optimization of a multilayer SPR biosensor incorporating silver, silicon nitride, single-layer graphene, and thiol-tethered ssDNA to achieve high sensitivity and specificity. Key metrics, including SPR angle shift (Δθ), sensitivity (S), detection accuracy (DA), and figure of merit (FoM), were assessed across SARS-CoV-2 concentrations from 150 to 525 mM. The optimized biosensor achieved a sensitivity of 315.91°/RIU at 275 mM and a maximum Δθ of 4.2° at 400 mM, demonstrating strong responsiveness to virus binding. The sensor maintained optimal accuracy and figure of merit at lower concentrations, with a linear sensitivity response up to 400 mM, after which surface saturation limited further responsiveness. These results highlight the suitability of the optimized biosensor for real-time, point-of-care SARS-CoV-2 detection, particularly at low viral loads, supporting its potential in early diagnostics and epidemiological monitoring.

Exfoliation and optical properties of S = 1 triangular lattice antiferromagnet NiGa2S4

Two-dimensional (2D) van der Waals (vdW) materials have been an exciting area of research ever since scientists first isolated a single layer of graphene. Single layer magnetic materials can provide a pathway for vdW heterostructures with magnetic properties. While most of the magnetic vdW materials exhibit ordering transitions in the bulk, here we report a successful exfoliation of a triangular lattice S = 1 antiferromagnet NiGa\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document}S\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_4$$\\end{document}, which already demonstrates exotic magnetism in the bulk material. We establish the number of layers of the material by atomic force microscopy (AFM) and detail a careful characterization using Raman and optical spectroscopy to demonstrate how the optical, electronic, and structural properties of NiGa\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document}S\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_4$$\\end{document} change as a function of sample thickness. Optical measurements and electronic structure calculations of bulk versus monolayer NiGa\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document}S\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_4$$\\end{document} confirm the material to be a Mott insulator with an electronic gap of about 1.5 eV, which slightly increases for layers below 10 L. We conclude with a theoretical analysis of the possibility of doping monolayer NiGa\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document}S\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_4$$\\end{document} by proximity to a metal.

Single/Multi-band graphene-based disk THz absorbers with single graphene layer: conceptual design

Single/Multi-band graphene-based disk THz absorbers with single graphene layer: conceptual design

Improving thermal conductivity of butylpyridine latex‐based composites by modified single‐layer graphene

AbstractChelated titanate (CT) modified single‐layer graphene (CTMSG), exhibiting much better static and dynamic stability due to the synergy of physical and chemical bonds, was mixed with butadiene‐vinylpyridine latex (BL) to prepare composite (CTMSG‐BL) film to enhance its thermal conductivity. Furthermore, CTMSG‐BL was complexed with polyethylene terephthalate (PET) fabric to promote the thermal conductivity of the composite (CTMSG‐BL/PET). Compared with the samples without CTMSG, the thermal conductivity of CTMSG‐BL (CTMSG content: 0.2 wt%) and CTMSG‐BL/PET increased from 3.52 to 4.35 W/(m·K) and from 1.91 to 2.56 W/(m·K), improved by 19.1% and 34.0%. This benefits from the excellent orientation alignment of single‐layer graphene (SG) in BL film and the highly efficient construction of the thermal conductivity pathway. The CTMSG‐BL emulsion is suitable for preparing heat‐resistant thermal conductive film with a thickness of micro‐nano meter (~0.6 μm) by impregnation process because of the low viscosity of the CTMSG‐BL emulsion (3.61 mPa·s) and the good heat resistance of the pyridine groups of BL with average pyrolysis temperature about 444 °C. The CTMSG‐BL film and CTMSG‐BL/PET composites have excellent heat conduction and dissipation properties, exhibiting broad application prospects in thermal interface materials, aerospace, and transport.Highlights The static and dynamic stability of the CTMSG was significantly improved. Low viscosity CTMSG‐BL is suitable for preparing thermally conductive films. With the addition of CTMSG, the thermal conductivity of BL improved by 19.0%. With addition of CTMSG, the thermal conductivity of BL/PET improved by 34%.

Transferred single-layer graphene on pre-patterned metal electrode: comparison of thermoelectric and electric properties

Transferred single-layer graphene on pre-patterned metal electrode: comparison of thermoelectric and electric properties

Hydrodynamic heat conduction based on eigenvalues and eigenvectors of the normal collision operator

Abstract Although the Guyer-Krumhansl equations has opened up the study of phonon hydrodynamics in ultra-low temperature and low dimensional non-metallic crystals, it still cannot explain the high thermal conductivity of low dimensional non-metallic materials in adiabatic environments. In this work, the analytical solution of the linear Boltzmann transport equation with the Callaway approximation is obtained by expanding the nonequilibrium distribution function into a series of the orthogonal eigenvectors of the normal-process collision operator. By assuming the normal scatterings dominate the heat conduction in an anisotropic non-metallic crystal allowing the different branches of the phonon frequency spectrum having different group velocity, the macroscopic energy and momentum balance equations are developed for describing the phonon hydrodynamic transport. For an isotropic and dispersionless system, these balance equations reduce to the improved Guyer-Krumhansl equations. The thermal conductivity in these balance equations includes not only the contribution of the resistive scatterings, but also the contribution of the normal scatterings. Therefore, the improved Guyer-Krumhansl equations is capable for explaining the high thermal conductivity of suspended graphene, which is validated by the experimental results. Finally, the improved Guyer-Krumhansl equations is employed to derive the occurrence condition of the second sound in suspended single-layer graphene.

Enhanced SERS signal in the hybrid substrate through electronic modulation of CVD grown single-layer graphene

The ever-growing demand for sensitive and reliable detection of hazardous material in the food chain and trace detection of chemical entities in a variety of field attracted advanced Surface Enhanced Raman Spectroscopy (SERS) active materials such as graphene-based hybrid SERS. The graphene silver nanostructures (AgNS) based hybrid SERS substrates are explored to understand the critical role of pristine graphene grown by chemical vapor deposition (CVD) on SERS signal and its possible mechanism. A lithography-free fabrication process has been developed for growth of uniform array of AgNS with varying both particle sizes and inter-particle gaps. The optimal AgNS with average feature size ∼40 nm and average inter-particle spacing of ∼13 nm demonstrated the maximum SERS enhancement with rhodamine 6G (R6G). The single-layer graphene (SLG) grown by CVD with the aid of controlling the reaction geometry with growth under a free molecular regime leads to the highest quality graphene with I2D/IG ratio of ∼3.58 and ID/IG ratio of ∼0.154. The flow regime-controlled CVD-grown SLG integrated with AgNS and its SERS enhancement mechanism is explored for trace detection of R6G. The graphene with its ability to modulate the electronic structure and tune it relative to the highest occupied molecular orbital-lowest occupied molecular orbital (HOMO-LUMO) levels of R6G molecules resulted in improved SERS signal by about an order for graphene-AgNS hybrid structure as compared to bare AgNS. The obtained findings paved the way for the futuristic and reliable hybrid SERS substrate for trace-level detection of a wide range of chemical entities.

Realizing single-layer graphene by simultaneous crystallization and top-down etching of amorphous graphene-like carbon obtained via CVD

Continuous large-area graphene can be obtained on copper by utilizing solid polymer carbon sources (SPCS). However, the detailed conversion process and related mechanisms have been rarely reported. Here, a low-temperature chemical vapor deposition (CVD) combined with high-temperature hydrogen annealing (HTHA) method is designed to investigate the intricate evolution process from SPCS to amorphous graphene-like carbon (AGLC), and subsequently to single-layer graphene (SLG). During low-temperature CVD process, under catalysis of copper and auxiliary catalysis of hydrogen, the pyrolysis products of SPCS undergo nucleation and growth on copper, resulting in the formation of AGLC at 500 °C. During subsequent HTHA process above 1000 °C, the conversion of AGLC to continuous SLG can be achieved through simultaneous catalytic crystallization of copper and top-down etching of hydrogen, which sequentially undergoes coexistence stage of AGLC/few-layer graphene (FLG), followed by FLG formation stage. Under different stage and conditions, there exists a synergistic-competitive relationship between catalytic effect of copper and etching effect of hydrogen. The proposed conversion mechanism can provide fundamental insights into SLG synthesis via SPCS, which could facilitate further advancements in large-scale industrial applications of graphene.

Tunable Graphene‐Based Absorber Using Nanoscale Grooved Metal Film at Telecommunication Wavelengths

Graphene‐based absorbers have various modern applications across industries due to their exceptional properties. Some common applications include: thermal management and energy storage. Herein, the design and simulation of a broadband tunable absorber based on graphene with perfect absorption spectra in the near‐infrared region are reported. The proposed structure consists of an MgF2 layer and golden disc surrounded by L‐shaped golden arms placed on single layer of graphene. The structure guarantees polarization‐insensitive (PI) performance under normal incident due to the symmetrical design. The investigation of the PI of the structure reveals almost similar absorption for oblique incident angles up to 55° for TM and up to 60° for TE polarization. The desirable resonance wavelength is achievable by tuning the geometrical parameters. By changing the chemical potential of graphene, the absorption and bandwidth of absorber are controllable. A full width at half maximum of 330 nm is another superiority of this absorber. These considerable aspects of the proposed structure make it practical for varieties of applications such as cloaking, sensing, switching, and so on.

Growth Kinetics of Graphene on Cu(111) Foils from Methane, Ethyne, Ethylene, and Ethane

AbstractChemical vapor deposition of carbon precursors on Cu‐based substrates at temperatures exceeding 1000 °C is currently a typical route for the scalable synthesis of large‐area high‐quality single‐layer graphene (SLG) films. Using molecules with higher activities than CH4 may afford lower growth temperatures that might yield fold‐ and wrinkle‐free graphene. The kinetics of growth of graphene using hydrocarbons other than CH4 are of interest to the scientific and industrial communities. We measured the growth rates of graphene islands on Cu(111) foils by using C2H2, C2H4, C2H6 and CH4, respectively (each mixed with H2). From such kinetics data we obtain the activation enthalpy (ΔH≠) of graphene growth as shown in parentheses (C2H2 (0.93±0.09 eV); C2H4 (2.05±0.19 eV); C2H6 (2.50±0.11 eV); CH4 (4.59±0.26 eV)); C2Hy (y=2, 4, 6) show similar growth behavior but CH4 is different. Computational fluid dynamics and density functional theory simulations suggest that C2Hy differs from CH4 due to different values of adsorption energy and the lifetime of relevant carbon precursors on the Cu(111) surface. Combining experimental and simulation results, we find that the rate determining step (RDS) is the dissociation of the first C−H bond of CH4 molecules in the gas phase, while the RDS using C2Hy is the first dehydrogenation of adsorbed C2Hy that happens with assistance of H atoms adsorbed on the Cu(111) surface. By using C2H2 as the carbon precursor, high‐quality single‐crystal adlayer‐free SLG films are achieved on Cu(111) foils at 900 °C.

Growth Kinetics of Graphene on Cu(111) Foils from Methane, Ethyne, Ethylene, and Ethane.

Chemical vapor deposition of carbon precursors on Cu-based substrates at temperatures exceeding 1000 °C is currently a typical route for the scalable synthesis of large-area high-quality single-layer graphene (SLG) films. Using molecules with higher activities than CH4 may afford lower growth temperatures that might yield fold- and wrinkle-free graphene. The kinetics of growth of graphene using hydrocarbons other than CH4 are of interest to the scientific and industrial communities. We measured the growth rates of graphene islands on Cu(111) foils by using C2H2, C2H4, C2H6 and CH4, respectively (each mixed with H2). From such kinetics data we obtain the activation enthalpy (ΔH≠) of graphene growth as shown in parentheses (C2H2 (0.93±0.09 eV); C2H4 (2.05±0.19 eV); C2H6 (2.50±0.11 eV); CH4 (4.59±0.26 eV)); C2Hy (y=2, 4, 6) show similar growth behavior but CH4 is different. Computational fluid dynamics and density functional theory simulations suggest that C2Hy differs from CH4 due to different values of adsorption energy and the lifetime of relevant carbon precursors on the Cu(111) surface. Combining experimental and simulation results, we find that the rate determining step (RDS) is the dissociation of the first C-H bond of CH4 molecules in the gas phase, while the RDS using C2Hy is the first dehydrogenation of adsorbed C2Hy that happens with assistance of H atoms adsorbed on the Cu(111) surface. By using C2H2 as the carbon precursor, high-quality single-crystal adlayer-free SLG films are achieved on Cu(111) foils at 900 °C.

Ballistic transport enhanced heat convection at nanoscale hotspots

Along with device miniaturization, severe heat accumulation at unexpected nanoscale hotspots attracts wide attentions and urges efficient thermal management. Heat convection is one of the important heat dissipating paths at nanoscale hotspots but its mechanism is still unclear. Here shows the first experimental investigation of the convective heat transfer coefficient at size-controllable nanoscale hotspots. A specially designed structure of a single-layer graphene supported by gold-nanorod array is proposed, in which the gold nanorods generate hundreds of nanometers heating sources under laser irradiation and the graphene layer works as a temperature probe in Raman thermometry. The determined convective heat transfer coefficient (1928+155 −147 W m−2 K−1 for the 330 nm hotspot and 1793+157 −159 W m−2 K−1 for the 240 nm hotspot) is about three orders of magnitude higher than that of nature convection, when the simultaneous interfacial heat conduction and radiation are carefully evaluated. Heat convection, thus, accounts to more than half of the total energy transferred across the graphene/gold nanorods interface. Both the plasmon induced nanoscale hotspots and ballistic convection of air molecules contribute to the enhanced heat convection. This work reveals the importance of heat convection at nanoscale hotspots to the accurate thermal design of miniaturized electronics and further offers a new way to evaluate the convective heat transfer coefficient at nanoscale hotspots.

Single-layer graphene oxide nanosheets induce proliferation and Osteogenesis of single-cell hBMSCs encapsulated in Alginate Microgels

Microfluidics cell encapsulation offers a way to mimic a 3D microenvironment that supports cell growth and proliferation, while also protecting cells from environmental stress. This technique has found extensive applications in tissue engineering and cell therapies. Several studies have demonstrated the advantages of graphene oxide (GO) as an osteogenic inducer; however, the significance of GO on stem cell fate in the single-cell state is still unclear. Here, a microfluidics-based approach is developed for continuous encapsulation of mesenchymal stem cells (MSCs) at the single-cell level using alginate microgels. So, single-layer graphene oxide (slGO) nanosheet is used to be encapsulated inside the alginate droplets. The results of AFM and SEM show that slGO can increase the roughness and reduce the stiffness of alginate hydrogels. The Young’s modulus of the alginate and alginate-slGO was obtained as 1414 kPa and 985.9 kPa, respectively. Live/dead assay and fluorescence microscopy images illustrate that slGO can maintain the viability and proliferation of microencapsulated hBMSCs. The obtained results show that slGO increases the mineralization of the encapsulated hBMSCs, so that microgels containing hBMSCs gradually became opaque during 21 days of culture. RT-qPCR results indicate that the expression of OCN, Runx2, and ALP in the alginate-slGO microgels is significantly higher than in the alginate microgels. The expression of OCN and Runx2 in the alginate-slGO microgels is 4.27 and 5.87-fold higher than in the alginate microgels, respectively. It can be concluded that low doses of slGO nanosheets have the potential to be utilized in the development of tissue engineering and bone regeneration. This finding offers a new method for creating injectable tissue transplants that are minimally invasive.

Graphene Phase Modulators Operating in the Transparency Regime.

Next-generation data networks need to support Tb/s rates. In-phase and quadrature (IQ) modulation combine phase and intensity information to increase the density of encoded data, reduce overall power consumption by minimizing the number of channels, and increase noise tolerance. To reduce errors when decoding the received signal, intersymbol interference must be minimized. This is achieved with pure phase modulation, where the phase of the optical signal is controlled without changing its intensity. Phase modulators are characterized by the voltage required to achieve a π phase shift, Vπ, the device length, L, and their product, VπL. To reduce power consumption, IQ modulators are needed with <1 V drive voltages and compact (sub-cm) dimensions, which translate in VπL < 1Vcm. Si and LiNbO3 (LN) IQ modulators do not currently meet these requirements because VπL > 1Vcm. Here, we report a double single-layer graphene (SLG) Mach-Zehnder modulator (MZM) with pure phase modulation in the transparency regime, where optical losses are minimized and remain constant with increasing voltage. Our device has VπL ∼ 0.3Vcm, matching state-of-the-art SLG-based MZMs and plasmonic LN MZMs, but with pure phase modulation and low insertion loss (∼5 dB), essential for IQ modulation. Our VπL is ∼5 times lower than the lowest thin-film LN MZMs and ∼3 times lower than the lowest Si MZMs. This enables devices with complementary metal-oxide semiconductor compatible VπL (<1Vcm) and smaller footprint than LN or Si MZMs, improving circuit density and reducing power consumption by 1 order of magnitude.