Monolayer Graphene Research Articles

Observation of different Li intercalation states and local doping in epitaxial mono- and bilayer graphene on SiC(0001).

Li intercalation is commonly used to enhance the carrier density in epitaxial graphene and mitigate coupling to the substrate. So far, the understanding of the intercalation process, particularly how Li penetrates different layers above the substrate, and its impact on electron transport remains incomplete. Here, we report different phases of Li intercalation and their kinetic processes in epitaxial mono- and bilayer graphene grown on SiC. The distinct doping effects of each intercalation phase are characterized using scanning tunneling spectroscopy. Furthermore, changes in the local conduction regimes are directly mapped by scanning tunneling potentiometry and attributed to different charge transfer states of the intercalated Li. The stable intercalation marked by the formation of Li-Si bonds leads to a significant 56% reduction in sheet resistance of the resulting quasi-free bilayer graphene, as compared to the pristine monolayer graphene.

Resonant Raman scattering on graphene: SERS and gap-mode TERS.

Nanoscale deformations and corrugations occur in graphene-like two-dimensional materials during their incorporation into hybrid structures and real devices, such as sensors based on surface-enhanced Raman scattering (SERS-based sensors). The structural features mentioned above are known to affect the electronic properties of graphene, thus highly sensitive and high-resolution techniques are required to reveal and characterize arising local defects, mechanical deformations, and phase transformations. In this study, we demonstrate that gap-mode tip-enhanced Raman Scattering (gm-TERS), which offers the benefits of structural and chemical analytical methods, allows variations in the structure and mechanical state of a two-dimensional material to be probed with nanoscale spatial resolution. In this work, we demonstrate locally enhanced gm-TERS on a monolayer graphene film placed on a plasmonic substrate with specific diameter gold nanodisks. SERS measurements are employed to determine the optimal disk diameter and excitation wavelength for further realization of gm-TERS. A significant local plasmonic enhancement of the main vibrational modes in graphene by a factor of 100 and a high spatial resolution of 10 nm are achieved in the gm-TERS experiment, making gm-TERS chemical mapping possible. By analyzing the gm-TERS spectra of the graphene film in the local area of a nanodisk, the local tensile mechanical strain in graphene was detected, resulting in a split of the G mode into two components, G+ and G-. Using the frequency split in the positions of G+ and G- modes in the TERS spectra, the stress was estimated to be up to 1.5%. The results demonstrate that gap-mode TERS mapping allows rapid and precise characterization of local structural defects in two-dimensional materials on the nanoscale.

Ultra-thin proton conducting carrier layers for scalable integration of atomically thin 2D materials with proton exchange polymers for next-generation PEMs.

Scalable approaches for synthesis and integration of proton selective atomically thin 2D materials with proton conducting polymers can enable next-generation proton exchange membranes (PEMs) with minimal crossover of reactants or undesired species while maintaining adequately high proton conductance for practical applications. Here, we systematically investigate facile and scalable approaches to interface monolayer graphene synthesized via scalable chemical vapor deposition (CVD) on Cu foil with the most widely used proton exchange polymer Nafion 211 (N211, ∼25 μm thick film) via (i) spin-coating a ∼700 nm thin Nafion carrier layer to transfer graphene (spin + scoop), (ii) casting a Nafion film and cold pressing (cold press), and (iii) hot pressing (hot press) while minimizing micron-scale defects to <0.3% area. Interfacing CVD graphene on Cu with N211 via cold press or hot press and subsequent removal of Cu via etching results in ∼50% lower areal proton conductance compared to membranes fabricated via the spin + scoop method. Notably, the areal proton conductance can be recovered by soaking the hot and cold press membranes in 0.1 M HCl, without significant damage to graphene. We rationalize our finding by the significantly smaller reservoir for cation uptake from Cu etching for the ∼700 nm thin carrier Nafion layer used for spin + scoop transfer compared to the ∼25 μm thick N211 film for hot and cold pressing. Finally, we demonstrate performance in H2 fuel cells with power densities of ∼0.23 W cm-2 and up to ∼41-54% reduction in H2 crossover for the N211|G|N211 sandwich membranes compared to the control N211|N211 indicating potential for our approach in enabling advanced PEMs for fuel cells, redox-flow batteries, isotope separations and beyond.

Emergent fermion dynamical symmetry for monolayer graphene in a strong magnetic field

Emergent fermion dynamical symmetry for monolayer graphene in a strong magnetic field

Experimental observation and characterization of amorphous carbon generated in graphene on gold nanoparticles.

The interaction of graphene with gold nanoparticles is investigated using transmission electron microscopy. We observe gold-nanoparticle-mediated etching of graphene flakes, often leading to hole formation. Further, using a combination of high-angle annular dark field imaging and electron energy loss spectroscopy, we highlight that the catalytic effects of gold nanoparticles on graphene lead to the formation of amorphous carbon layers. From the extracted diffractograms, we observe regions with diffraction halos as well as some regions with a weak tetrahedral motif. Using independently performed Raman measurements, we confirm the presence of tetrahedral amorphous carbon as well as mixed graphitic-amorphous regions. For the amorphous carbon regions with mixed sp2-sp3 states, the Raman G peak is red-shifted to 1564 cm-1 and an I D/I G ratio of 0.63 indicates less than 20% sp3 content. For the tetrahedral amorphous carbon regions, we observe that the Raman G peak is at 1580 cm-1, close to that of monolayer graphene. However, there is no Raman D peak, i.e., I D/I G = 0, which indicates close to 100% sp3 content. The translation of the Raman G peak location and the I D/I G ratios is on par with the amorphization trajectory analysis of Ferrari and Robertson (Phys. Rev. B: Condens. Matter Mater. Phys., 2000, 61, 14095) and validates the conversion route of graphite to amorphous carbon to tetrahedral amorphous carbon. The presented method provides a promising pathway for creating defect-induced amorphous carbon at room temperature, which has a broader impact on the electronics and semiconductor industries.

Tunable multiband circular dichroism and asymmetric transmission enabled by chiral quasi-BICs in dielectric metasurfaces covered with graphene

High-Q chiral resonances have attracted great interest recently due to their practical photonic applications. For generating such resonances, chiral quasi-bound states in the continuum (quasi-BICs) have recently been proposed and experimentally demonstrated by many researchers, while their dynamic tunability has still not been discussed. In this work, we show multiband circular dichroism and asymmetric transmission based on high-Q chiral quasi-BICs in dielectric metasurfaces, which are dynamically tunable in the mid-infrared range by using graphene monolayers covering the metasurfaces. By changing the Fermi energy, the surface conductivity of graphene is tunable in a wide range, resulting in tunable chiroptical responses of the metasurfaces. Since the metasurfaces exhibit high-Q resonances with narrow linewidths, tuning the metasurfaces results in large modulation depths of circular dichroism and asymmetric transmission, which is of great importance for photonic applications, including tunable polarization manipulation and polarization-dependent detection.

Sensing and slow light applications of graphene plasmonic terahertz structure

In this work, Ansys FDTD is used to design and simulate a terahertz metamaterial structure based on periodic continuous pattern graphene monolayer, and the high-quality PIT phenomena are obtained by continuously adjusting structural parameters. To validate the designed structure, the simulated transmission curve (reflection curve) obtained is compared with the theoretical transmission curve (reflection curve) derived from coupled-mode theory. It is observed that these two results exhibit a remarkably high degree of overlap. The resonant frequency and Fermi energy reveals a perfect linear correlation between them with the resonant frequency increasing proportionally with Fermi energy increasing. Dynamic tuning of PIT can be realized by adjusting the Fermi energy of graphene. For a more in-depth study of its sensing characteristics, the structure is placed in different environments. As the refractive index of the detection medium increases, the resonant frequency gradually decreases, demonstrating a redshift phenomenon. By manipulating the resonant frequency of the PIT sensor, the selective detection of specific target can berealized. After analyzing the sensitivity and FOM values of the structure, it is found that the maximum sensitivity is 1.457 THz/RIU. At a resonant frequency of 6.8174 THz, FOM reaches 30.5652. In summary, the sensor structure designed in this work has dual frequency sensing characteristics and can be used for dual frequency detection. Moreover, compared with other sensor structures, it demonstrates superior sensing performance. Additionally, in studying the slow light effect of the structure, it is found that as the Fermi energy increases, the group index and phase shift at the transparency window continue to increase. At the Fermi energy of 1.2 eV, the group index reaches a high value of 584. This is because in the PIT phenomenon, transparent peaks are formed due to multimodal coupling. This coupling will significantly improve the dispersion characteristics near the transparent peak, resulting in a large group index near the transparent peak. Furthermore, with the increase of carrier mobility, the group index and phase shift of the structure also gradually increase. At a carrier mobility of 0.75 m²/(V·s), the group refractive index is 456, and reaches 1010 at 2.0 m²/(V·s). In this study, the slow-light performance of graphene structure can be optimized through jointly adjusting the Fermi energy and carrier mobility. This research provides theoretical support and methods for designing advanced graphene-based sensors and devices for slow-light applications.

Broadband THz graphene absorber with graphene and sensing of trimethylglycine concentration

This paper proposes a tunable broadband terahertz absorber based on metamaterial graphene. The absorber consists of a monolayer of graphene, a dielectric layer, and a metal reflection backing. By adjusting the applied bias voltage, the unique properties of graphene are utilized to control its Fermi level. Simulation results indicate that the absorber has an absorption rate exceeding 70% between 4.2–4.8 THz, with a maximum absorption rate reaching 99.99%, and a sensitivity of 740 GHz/RIU. Compared to similar studies, this structure has significant advantages in sensitivity. Due to the symmetry of the unit structure, the absorber is insensitive to the incident angle. We applied the absorber to trimethylglycine concentration. Experimental results show that the designed absorber can accurately identify the concentration of trimethylglycine solution, detecting concentrations as low as 0.5%.

Actively modulating near-infrared absorption of monolayer graphene in a compound grating-coupled waveguide structure

In this work, we numerically study the tunable light absorption of monolayer graphene at the near-infrared region by the guided mode resonance in a compound grating-coupled waveguide structure. A biased graphene capacitor is placed below the coupled waveguides. The electromagnetically induced transparency phenomenon is demonstrated by the resonant coupling of guided modes. The light absorption of monolayer graphene at the transparency window can be dynamically tuned by shifting the Fermi energy of graphene in capacitor. The absorption modulation depth of monolayer graphene at the transparency window can vary quickly from zero to nearly 100 % around the interband transition of graphene in capacitor. These results have potential applications in the active photodetectors and photoconductive devices.

Vertical Graphene/Pentacene Single Crystal/Graphene Transistors for Self‐Powered Weak Light Detection and High‐Speed Imaging

AbstractOrganic semiconductors are promising candidates for next‐generation photodetectors owing to their unique properties including large absorption coefficient and intrinsic mechanical flexibility. However, limited by high defect density, large exciton binding energy, and short exciton diffusion length, many challenges remain for fabricating high‐performance organic photodetectors, especially for scenarios where weak light sensing and high‐speed imaging are required. Herein, by coupling single‐crystal pentacene with monolayer graphene, a vertical organic phototransistor with excellent zero‐bias photon detecting capacity is demonstrated. Under self‐powered weak light condition, the responsivity and specific detectivity are 2.86 AW−1 and 3.3 × 1011 Jones (based on experiment spectral noise density), respectively. It is demonstrated that weak light down to 25 nWcm−2 can be detected. When operating with an external bias, the responsivity of the device increases dramatically (up to 105 AW−1), and a better 3 dB bandwidth (≈74 kHz) is obtained. Finally, imaging functionality is demonstrated by employing this vertical transistor as a single‐sensing pixel. This work suggests organic single crystals exhibit enormous potential in advanced optoelectronic systems, and may provide a viable route for weak light detecting and high‐speed imaging.

A Micromechanical Study of Interactions of Cyanate Ester Monomer with Graphene or Boron Nitride Monolayer.

Polymer composites, hailed for their ultra-strength and lightweight attributes, stand out as promising materials for the upcoming era of space vehicles. The selection of the polymer matrix plays a pivotal role in material design, given its significant impact on bulk-level properties through the reinforcement/polymer interface. To aid in the systematic design of such composite systems, molecular-level calculations are employed to establish the relationship between interfacial characteristics and mechanical response, specifically stiffness. This study focuses on the interaction of fluorinated and non-fluorinated cyanate ester monomers with graphene or a BN monolayer, representing non-polymerized ester composites. Utilizing micromechanics and the density functional theory method to analyze interaction energy, charge density, and stiffness, our findings reveal that the fluorinated cyanate-ester monomer demonstrates lower interaction energy, reduced pull-apart force, and a higher separation point compared to the non-fluorinated counterpart. This behavior is attributed to the steric hindrance caused by fluorine atoms. Furthermore, the BN monolayer exhibits enhanced transverse stiffness due to increased interfacial strength, stemming from the polar nature of B-N bonds on the surface, as opposed to the C-C bonds of graphene. These molecular-level results are intended to inform the design of next-generation composites incorporating cyanate esters, specifically for structural applications.

Characteristic analysis and simulation of a Cu-graphene hybrid nanointerconnect under different Drude models

It is well known that the ultra thin barrier layer around the Cu nanointerconnect has a great impact on its performance. Currently, graphene is the thinnest two-dimensional material. Cu-graphene hybrid nanointerconnects can significantly advance the potential of integrated cirCuit technology. In this article, we put a monolayer graphene on the top, left and right sides of a Cu nanointerconnect. graraphene adopts three Drude models, namely, the Drude model obtained by simplified Kubo formula, the Drude-Lorentz model, and the Drude model derived from Boltzmann equation. We use cst to simulate the voltage-current variation and propagation delay characteristics of a Cu-graphene hybrid nanointerconnect are observed under three Drude models and compared with a Cu nanointerconnect. Finally, the Drude model of graphene which is derived from the Boltzmann transport equation can minimize the voltage of the Cu nanointerconnect and reduce the propagation delay of the two ports of the Cu nanointerconnect.

Thermal conductivity and nonreciprocity in wrinkled monolayer graphene ring

We explore an external tunable approach to produce thermal nonreciprocity, by means of controlling wrinkle characteristics in graphene rings. The wrinkling formation and evolution law of graphene rings under torsional deformation is studied. Results show that wrinkle patterns of monolayer graphene can be flexibly tuned by controlling mechanical torsion. We further study the dependence of graphene rings’ thermal conductivity on sizes, temperatures and torsional angles, and reveal the influential mechanism by phonon density of states. Specifically, the thermal conductivity is reduced by 20.4 % when the torsional angle increases from θ=0∘ to θ=10.3∘. Finally, nonreciprocal conductive heat transfer is demonstrated in torsion-wrinkled graphene rings. It is found that thermal nonreciprocity effect is dependent on both torsional angles and temperature differences, i.e., the thermal nonreciprocity factor increase from 1.9 % to 4.5 % as temperature difference varies from 100 K to 400 K under torsional angle θ=6.9∘. Our work paves new avenues for the design and implementation of thermal metadevices by mechanical tuning approach.

A Novel and Large-Scale Rapid Green Synthesis of Few-Layer and Multi-Layer Graphene

Mono-layer graphene has shown path-breaking potential in almost all areas that are useful to humankind. However, research in the last decade indicated that few-layer graphene (FLG) (3-10 layers) and multi-layer graphene (MLG) (>10 layers) could also be utilized for a wide range of applications. The synthesis of mono-layer graphene at a large scale is quite complex. Producing FLG and MLG at a kilogram scale is equally challenging. A vast amount of literature on different routes to prepare FLG and MLG is available. However, most of the preparation routes involve the use of hazardous chemicals, copious amounts of water, and thermal treatments and are time taking. Also, these processes need bigger machinery to convert the lab-scale methods into continuous large-scale production. On the contrary, in this work we report a novel process of producing FLG and MLG along with trace quantities of graphene (< 3 layers) developed using a kitchen mixer and a modified mixing jar (3 litres). The highlights of this process include the use of no hazardous chemicals/solvents, no washing or thermal treatment needed, much less time (30 minutes), and large quantity (250-500 grams) per batch. Our study successfully converted natural graphite flakes (NGF) into FLG and MLG by carrying out rapid liquid phase shear mixing using a green solvent. The shear mixing and the green solvent convert the NGF into FLG and MLG. The quantity of FLG and MLG getting produced is time-dependent. It has been optimized by thoroughly characterizing FLG and MLG using techniques like particle size analyser, X-ray diffraction, Raman spectroscopy, and electron microscopy. The conversion of NGF to FLG and MLG is also affirmed by studying changes in properties using tools like thermogravimetry, BET, and UV-visible spectroscopy. The developed process is rapid, efficient, economical, scalable, continuous, and, most importantly, chemical free.The graphenaceous powder produced unlike graphite can be easily coated on different substrates using appropriate binders and thus makes it useable for energy storage applications. Also the fine particle size of graphite makes is an ideal material to be used as lubricant, both in solid and liquid mediums. The developed material can be explored for its applications in several other areas which require FLG/MLG.

Effects of electron irradiation on graphene drums

Using a scanning electron microscope, we irradiate graphene drums with electrons at an energy of 20 keV and a dosage of about 1.58 × 1017 electrons/cm2. The drums consist of graphene exfoliated in ambient air over holes having a diameter of 4.6 μm and etched into an SiO2 substrate. After irradiation, we observe that the drum’s suspended monolayer (ML) region has a ratio of the Raman D peak height, ID, to the Raman G peak height, IG, as high as 6.3. In contrast, the supported ML on the SiO2 substrate has an ID/IG ratio of 0.49. Previous studies have shown that graphene drums containing air can leak in a vacuum at a low rate. We attribute the high ID/IG ratio of the suspended ML to the air that may be in the drums. We propose that the air produces much adsorbed water on the ML, resulting in a high average defect density during irradiation. We present Raman maps of the full-width-at-half maximum, position, and height of the G, 2D, D, and D’ peaks before and after irradiation and maps of ID/IG and ID/ID’. We anneal the drums at temperatures from 50 to 215 °C and find that ID/IG significantly reduces to 0.42. The annealing data are analyzed using an Arrhenius plot. We also find that ID/ID’ depends on annealing temperature and has values ≥8, in the range expected for sp3 defects, for ID/IG ≤ 3.9. This irradiation method may help achieve high average defect densities in ML graphene, imparting novel and potentially valuable properties.

(Invited) Enabling High Quality Dielectric Passivation on Monolayer WS2 Using a Sacrificial Graphene Oxide Template

Two-dimensional transition metal dichalcogenides (2D TMDC’s) hold a wide variety of applications, among which microelectronic devices. 2D TMDC’s are promising alternatives for today’s silicon-based technology but suffer from various integration challenges. Among others, direct dielectric growth on the 2D surface occurs poorly due to their self-passivated surfaces resulting in island-like growth initiated at defect sites. This work focuses on enabling uniform high-k dielectric nucleation and growth on 2D TMDC’s via a sacrificial, graphene oxide-based buffer layer. Essentially, the role of the sacrificial graphene buffer layer is twofold: 1) serve as a passivation layer, protecting the underlying 2D TMDC (i.e., WS2) during processing and 2) act as a nucleation layer, enabling uniform atomic layer deposition (ALD) high-k dielectric (i.e,. HfO2) growth. A graphene layer is transferred on monolayer WS2, after which polymeric transfer residues are cleaned via a combination of wet treatments and a dry hydrogen downstream plasma exposure. The cleaned graphene is functionalized via a dry UV/O3 oxidative treatment, which enriches its basal plane with carbon-oxygen single bond functionalities by sacrificing its π-network. This way, the graphene carbon lattice itself remains intact and retains its passivation properties. Moreover, a substrate dependency is observed where graphene transferred on WS2 requires longer UV/O3 exposure to ensure functionalization compared to a SiO2 substrate and can be explained by UV-light induced, ultrafast charge transfer between the graphene and WS2 monolayer. The carbon-oxygen groups formed on graphene’s basal plane act as nucleation sites during a subsequent HfO2 ALD process. A constant roughness is noted for the HfO2 film grown on the graphene oxide capped WS2, indicating uniform material deposition even in the early stages of the ALD process. This is in sharp contrast when HfO2 is directly grown on the WS2 monolayer, whose roughness stabilizes only after many ALD cycles (up to 256), demonstrating the poor, island-like growth mechanism. In addition, a similar hafnium areal density is measured for the graphene oxide capped WS2 compared bare SiO2, which was selected to represent a well-functionalized surface and thus confirming the efficiency of the graphene oxide-based nucleation layer. For devices incorporating the graphene oxide buffer layer concept, a crucial question is to what extent the graphene oxide layer gives rise to leakage currents by providing a conductive path between source and drain. Electrical evaluation of a GFET by means of I-V measurements reveal a significant shift in Dirac point towards positive gate voltage for transferred graphene, which is typically associated with p-type doping originating from the polymeric transfer residues still present on the surface. The Dirac point shifts towards 0-point voltage after final hydrogen downstream plasma cleaning, confirming the effectiveness of the established cleaning protocol. Moreover, Graphene’s conductivity is suppressed after UV/O3 to the nA range, as caused by the formation of carbon-oxygen functionalities and associated sacrifice of its π-network. The residual current may be further suppressed by extending the UV/O3 treatment, but nevertheless demonstrates that the graphene oxide buffer layer will not give rise to significant leakage currents.

Bipolar Electrochemistry for Functionalization of 2D Materials

After the isolation of graphene monolayer graphene 2D materials have garnered great attention for their theoretically predicted exceptional properties. Covalent functionalization strategies are used to further finetune and improve these properties, which allow to integrate these materials into a wide range of applications. However, these strategies need highly reactive conditions, which do not guarantee a control over the degree and homogeneity of functionalization of the surface. Moreover, existing methods do not allow the functionalization of non-conductive surfaces and not much work has been done on 2D materials besides graphene. Additionally, there is a need in obtaining these 2D materials in a scalable fashion to be viable for industrial application. In this work we propose a scalable, low cost, facile method to achieve both exfoliation and functionalization in one-pot using bipolar electrochemistry for the production of 2D material in dispersions. Bipolar electrochemistry applies a high voltage to the electrolyte cell, and a gradient of the electric field occurs over the cell which induces the polarization of material placed between two electrodes. The polarization drives simultaneous reduction and oxidation reactions at the opposite poles of the placed material. This opens possibilities of functionalization of inert and semiconductor materials. The material is characterized with a range of techniques including Raman, AFM and TEM. References Line Koefoed, Kyoko Shimizu, Steen Uttrup Pedersen, Kim Daasbjerg, Alexander Kuhn and Dodzi Zigah, RSC Advances, 6 (2016), 3882–3887Yong Wang, Carmen C. Mayorga-Martinez, Xinyi Chia, Zdeněk Sofer and Martin Pumera, Nanoscale, 10 (2018), 7298-7303Line Koefoed, Emil Bjerglund Pedersen, Lena Thyssen, Jesper Vinther, Thomas Kristiansen, Steen U. Pedersen, and Kim Daasbjerg, Langmuir, 32(25), 6289–6296 Figure 1

Influence of ‘period four’ transition metal doping in graphene on adsorption and transduction characteristics for CO gas- A detailed ab-initio perspective

This work analyses the comparative effects of period-four transition metal (TM) dopants for CO molecular adsorption on the monolayer Graphene (Gr) supercell using the density functional theory (DFT) based ab initio method for the first time. Ten different TM dopant species (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cr, Zn) have been incorporated and extensively studied in the context of Carbon Monoxide (CO) adsorption. The study elaborates on the effects of metallic doping in Gr on structural stability, electronic properties, adsorption strength, transduction efficacy, and CO recovery time. The study reveals that introducing each period-four TM dopant in the Gr lattice changes the semi-metallic nature, wherein distinct modulations in the energy band structure and the total density of state profiles can be observed after CO adsorption in each doped Gr matrix. The C atom of the polar CO molecule preferentially adsorbed on the doped TM, forming physical C-X (X: metal) bonds and resulting in slight vertical displacement of the dopant towards adsorbed CO. The results exhibit that depending on the strength of CO adsorption, the metallic dopants can be placed in the following order: Ti > V > Cr > Mn > Fe > Co > Ni > Cu > Zn > Sc, with a significant improvement in charge transfer during CO adsorption after Sc, Co, Ni, V, and Zn doping in Gr. Specifically, the Ni, Zn, and Sc-doped Gr ensures an efficient trade-off between adsorption stability and recovery time with high selectivity in CO2 and N2 environments.

Emission and coherent control of Levitons in graphene

Flying qubits encode quantum information in propagating modes instead of stationary discrete states. Although photonic flying qubits are available, the weak interaction between photons limits the efficiency of conditional quantum gates. Conversely, electronic flying qubits can use Coulomb interactions, but the weaker quantum coherence in conventional semiconductors has hindered their realization. In this work, we engineered on-demand injection of a single electronic flying qubit state and its manipulation over the Bloch sphere. The flying qubit is a Leviton propagating in quantum Hall edge channels of a high-mobility graphene monolayer. Although single-shot qubit readout and two-qubit operations are still needed for a viable manipulation of flying qubits, the coherent manipulation of an itinerant electronic state at the single-electron level presents a highly promising alternative to conventional qubits.

A Point-of-Care Testing Device Utilizing Graphene-Enhanced Fiber Optic SPR Sensor for Real-Time Detection of Infectious Pathogens.

Timely detection of highly infectious pathogens is essential for preventing and controlling public health risks. However, most traditional testing instruments require multiple tedious steps and ultimately testing in hospitals and third-party laboratories. The sample transfer process significantly prolongs the time to obtain test results. To tackle this aspect, a portable fiber optic surface plasmon resonance (FO-SPR) device was developed for the real-time detection of infectious pathogens. The portable device innovatively integrated a compact FO-SPR sensing component, a signal acquisition and processing system, and an embedded power supply unit. A gold-plated fiber is used as the FO-SPR sensing probe. Compared with traditional SPR sensing systems, the device is smaller size, lighter weight, and higher convenience. To enhance the detection capacity of pathogens, a monolayer graphene was coated on the sensing region of the FO-SPR sensing probe. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was used to evaluate the performance of the portable device. The device can accurately detect the SARS-CoV-2 spike S1 protein in phosphate-buffered saline (PBS) and artificial saliva within just 20 min, and the device successfully detected cultured SARS-CoV-2 virus. Furthermore, the FO-SPR probe has long-term stability, remaining stable for up to 8 days. It could distinguish between the SARS-CoV-2 spike protein and the MERS-CoV spike protein. Hence, this FO-SPR device provides reliable, rapid, and portable access to test results. It provides a promising point-of-care testing (POCT) tool for on-site screening of infectious pathogens.