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• Surface plasmon polarization waveguide based on graphene sense trace gases. • The interface between graphene and gas stimulate surface plasmon polarization. • Effective refractive index of waveguide can be changed to modify the emergent light. To improve the selectivity of carbon nanotubes for gas sensors, we design a surface plasmon polarization waveguide based on graphene that can sense trace gases. In addition, a gas concentration measurement system was designed for a sensor based on optical cavity ring-down spectroscopy. The gas concentration measurement system was composed of two loops, which were combined with the minimum mean square error algorithm to achieve an amplified spontaneous emission noise filter. The experimental results show that the gas concentration measurement error was significantly improved after CO filtering. The slope of the logarithmic ring-down curve and the ring-down time decreased with the increasing gas concentration. The gas concentration and ring-down time showed an improved linear relationship. The design system can detect trace gases as a single gas or a variety of toxic gases in special environments. The device provided a wide range of sensors and measurements. Moreover, the proposed device is relatively simple and easy to implement, with high detection sensitivity. [ABSTRACT FROM AUTHOR]

This study investigates a Fermi-level-reconfigurable terahertz wavefront modulator composed of a hybrid material comprising graphene, silver metal, and silicon dioxide. Through theoretical simulation, analysis, and experimental investigations, it is found that graphene plays a crucial role in enhancing the performance of the modulator. Specifically, the presence of graphene increases the limiting factor of the modulator by 0.281, reduces the normalized modal field area by 0.15, decreases the transmission loss, and lowers the gain threshold by 30097 cm−1, thereby improving the efficiency, reliability, and stability of the device. The silicon dioxide and silver metal in the structure act as the primary reflective materials, achieving the effect of a metallic lens and validating the modulator's capability for efficient defocusing. Further investigations reveal that the carrier concentration of graphene can be easily controlled, allowing for manipulation of its physical properties through Fermi-level modulation. When incident light passes through the graphene array, it induces phase variations, altering the transmission path of light and thereby affecting the position of the defocused focal point, enabling dynamic adjustability. Under low Fermi-level control, the modulator achieves a 2 π phase adjustment range with an average reflectivity of 75%. Thus, this provides potential for practical applications of more dynamic and tunable microdevices, particularly in the field of laser cutting technology and etching processes. [ABSTRACT FROM AUTHOR]

• As a multi-frequency optical switch. For the "on/off" state at 5.35 THz, the MD and IL are 95.6% and 0.315 dB. • Make band optical switch. The structures all maintain MD > 90% and IL < 0.35 dB in the 5.28–5.48 THz band. • The transmission plunge can exhibit a high refractive index sensitivity of 0.7 THz/RIU. A periodic metamaterial comprising three graphene-strips and four C-type graphene square-ring is proposed herein to realize plasmon-induced transparency (PIT). Based on the characteristics of graphene dynamic modulation, we effectively broaden of the transparent window the relative bandwidth to realize the broadband PIT. The influence of the polarized light angle on PIT is investigated, demonstrating that the polarization angle affects PIT significantly, the dynamic change from multiple plasma-induced transparency to single-PIT can be realized. By tuning the Fermi levels in the graphene, our proposed metamaterial structure allows preparing not only a multi-frequency optical switch with modulation degrees of the amplitude (MDA) up to 95.6% and insertion loss (IL) down to 0.315 dB at 5.35 THz but also preparing optical switches with MDA > 90% and IL < 0.35 dB in bands ranging from 5.28 to 5.48 THz. The refractive index sensitivity of metamaterials is also investigated, and the simulation results show that a sensitivity of 0.7 THz/RIU is achieved, meaning an excellent sensors can be prepared. Thus, the proposed structure provides a new idea for the design of terahertz multi-frequency switches and refractive index sensors. [ABSTRACT FROM AUTHOR]

Graphene has potential to replace germanium as compound semiconductor for high-performance devices because of its unique optoelectronic properties and availability of existing integrated circuit manufacturing technology. This study investigates surface plasmon polariton (SPP) waveguide-based interaction between CdS nanowires and graphene nanobelts to determine shortcomings of the existing technology. The structure uses MgF 2 as cladding, which symmetrically covers CdS nanowires and graphene nanobelts. An air gap of same width is etched in middle of CdS nanowires and graphene nanobelts. SPP is optically excited. Gain compensation is obtained through coupling effect of nanowires, capacitance-enhanced effect of air gap and GaAs semiconductor material, and low refractive index of buffer layer to reduce transmission loss. The structure can achieve strong photon localization and easily implement low threshold for nanometer laser. Experiments on characteristics of SPP show that increasing air gap width of structure reduces transmission loss and increases limiting factors. Limiting factor of waveguide structure is less than 0.15, which indicates ultra-deep subwavelength constraints. SPP waveguide can be integrated with various nanophotonic and electronic devices and has broad application prospects in optical sensing, optical communication, and other fields. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) graphene aerogel and its composite with interconnected pores have aroused continuous interests in energy storage field owning to its large surface area and hierarchical pore structure. Herein, we reported the preparation of 3D nitrogen-doped graphene/polyaniline (N-GE/PANI) composite foam for supercapacitive material with greatly improved electrochemical performance. The 3D porous structure can allow the penetration and diffusion of electrolyte, the incorporation of nitrogen doping can enhance the wettability of the active material and the number of active sites with electrolyte, and both the N-GE and PANI can ensure the high electrical conductivity of total electrode. Moreover, the synergistic effect between N-GE and PANI materials also play an important role on the electrochemical performance of electrode. Therefore, the as-prepared composite foam could deliver a high specific capacitance of 528 F g −1 at 0.1 A g −1 and a high cyclic stability with 95.9% capacitance retention after 5000 charge-discharge cycles. This study provides a new idea on improving the energy storage capacity of supercapacitors by using 3D graphene-based psedocapacitive electrode materials. [ABSTRACT FROM AUTHOR]

Graphene has attracted strong attention due to its unique mechanical, electrical, thermal and magnetic properties. In this work, we investigate the effect of low temperature oxygen plasma treatment on microstructure and adhesion force of single-layer graphene (SLG). Low temperature oxygen plasma is used to treat SLG grown by chemical vapor deposition through varying the exposure time. Raman spectroscopy, X-ray photoelectron spectroscopy and atomic force microscopy are utilized to identify changes before and after treatment. Raman spectra of treated graphene reveal that peak intensity of the characteristic D and D’ peaks increase. Meanwhile, degradation of the G and 2D peaks in X-ray photoelectron spectroscopy indicates that abundant C OH and C O functional groups are introduced into graphene after treatment. AFM investigation shows that surface roughness and adhesion force of treated graphene increase significantly firstly and then slowly. Therefore, this work would offer a practical route to improve the performance of graphene-based devices. [ABSTRACT FROM AUTHOR]

The field of plasmonics has experience a renaissance in recent years by providing a large variety of new physical effects and applications. Surface plasmon polaritons (SPPs), i.e. the collective electron oscillations at the interface of a metal/dielectric, may bridge the gap between electronic and photonic devices, provided a fast switching mechanism is identified. Here, we design folds graphene waveguide excited SPPs and full compensation structures with periodic array by graphene material. Theoretically, we analyzed the loss of the way by periodic array gain full compensation is analyzed. By the results of theoretically analysis, we discover period fold structure not only excites SPPs, which also we can control device parameters using SPPs wave relations. In addition, periodic array compensation can significantly increase the propagation distance of SPPs. Simulation results we further find by simulation results: structure of our design has the advantage of strong localized and subwavelength waveguide size; periodic array compensation can significantly improve the electric field strength of nanocavity; structure of graphene waveguide expresses high levels of population inversion and low spontaneous emission noise disturbance. The graphene waveguide devices which we design can be the key device for the micro-nano optics, photonic sensing and measurement. [ABSTRACT FROM AUTHOR]

Abstract: Platinum nanoparticles (Pt-NPs) were deposited onto N-(trimethoxy-silylpropyl) ethylenediamine triacetic acid (EDTA-silane) modified reduced graphene oxide (EDTA-RGO). The EDTA-RGO/Pt-NPs were coated onto a glass carbon electrode and characterized using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Raman spectra, and electrochemical tests. The chelating groups create a micro-environment that is suitable for the catalytic behavior of Pt-NPs. Compared with traditional carbon-based Pt catalysts, EDTA-RGO/Pt-NPs exhibit great tolerance towards poisoning by CO. Graphene-supported Pt nanoparticles can be used for the fabrication of fuel cell electrodes and other catalytic devices. [Copyright &y& Elsevier]

[Display omitted] Multiscale microscopy spanning the atomistic, moiré, and meso scales has enabled engineering the equilibrium structure of graphene. However, temporal restrictions on in-operando imaging techniques make the moiré scale the finest accessible spatial resolution, thereby limiting our understanding of atomistic mechanisms of non-equilibrium processes in graphene. In order to include atomic scale features with in-operando microscopy, we develop a moiré metrology theory that infers the atomic scale structure from the moiré scale, creating a bridge to in-operando microscopy. The theory is based on atomic scale models that govern the atomistic structure and are promoted to the moiré scale by simulation. We introduce this through a relevant application: nuclei coalescence of graphene during chemical vapor deposition. We develop two mechanistic atomic scale models that govern the propagation and structure of grain boundaries, illuminating how edge dislocations, disconnections, and grain boundaries form from the attachment of individual dimers. The atomistic models are brought to the moiré scale through bond convolution simulations and the resultant moiré metrology theory is tested on results from in-operando scanning tunneling microscopy. By showing that we can identify atomic scale defects from moiré patterns, we highlight how moiré metrology can enable decision making during growth from in-operando observation of graphene structure, paving the way for the design of graphene atomistic structure under scalable synthesis conditions. [ABSTRACT FROM AUTHOR]

• The absorber could achieve a spectral absorption of 97.4% in the 1.259–1.504 THz band. • The absorption rates under TE/TM incidence could both reach 90%. • The proposed absorber exhibits a wide-band advantage and good insensitivity. The applications of terahertz waves and metamaterials in electromagnetic wave absorbers are one of the key focus areas of current interdisciplinary scientific research. In this study, we propose a metamaterial absorber composed of graphene double-open rectangular ring and graphene strip cross structures. The experiment uses numerical analysis software to study the proposed absorber. Transverse electric waves were normally incident on the absorber from the plane port, where resonance coupling was achieved. With an increase in the incidence angle alpha , the trough in the middle of the absorption spectrum continued to deepen. The bandwidth that the spectral absorption maintains above 0.9 is 2.88 GHz (1.260–1.548 THz). The maximum spectral absorption has reached 99.9%, which is approximately perfect absorption. The absorber under transverse magnetic wave incidence also exhibited a bandwidth advantage. As the Fermi energy continued to increase, the absorption bandwidth first increased and then decreased, and reached the maximum at ef = 0.5 eV. Simultaneously, the relative absorption bandwidth also reached its maximum. By adjusting the Fermi level of graphene, dynamic tuning of the metamaterial absorber could be achieved. Adjustment of the Fermi level shifted the absorption range and absorption bandwidth, and helped in controlling the increase in the relative absorption bandwidth. The findings of this study can be of theoretical and engineering significance in the domains of thermal photovoltaics, solar cells, and sensors, among others. [ABSTRACT FROM AUTHOR]

Highlights: [•] Reduction of GO to rGO was accelerated by 20kHz ultrasound irradiation. [•] High power ultrasound and long pulse mode enhanced the rate of rGO formation. [•] High temperature, high pH and large amount of l-AA enhanced the rate of rGO formation. [•] Pseudo rate and activation energy of rGO formation were measured. [•] Physicochemical effects during acoustic cavitation enhanced the reduction of GO with l-AA. [Copyright &y& Elsevier]

Highlights: [•] The Cu2O–rGO composites have been synthesised by a one-step sonochemical route. [•] The morphology and composition of Cu2O–rGO could be well controlled. [•] The Cu2O–rGO composites displayed superior photocatalytic activity. [ABSTRACT FROM AUTHOR]

Designing of cost-effective electrocatalysts for efficient oxygen evolution reaction (OER) is highly desired for the practical production of clean hydrogen energy. Herein, reduced graphene oxide (RGO) supported N-doped porous carbon-coated NiFe alloy composite (NiFe@NC/RGO) was synthesized via a facile pyrolysis route. The introduction of RGO effectively protects the active NiFe component from agglomeration and largely promotes charge transfer. Meanwhile, the formation of porous N-doped carbon shell provides sufficient contact between active species and electrolyte, thus exposing plenty of accessible active sites. Specifically, the optimized NiFe@NC/RGO composite shows superior electrocatalytic performance, delivering an overpotential as low as 223 mV at current density of 10 mA cm−2, and a small Tafel slope of 48.7 mV dec−1 in 1 M KOH solution, which outperforms commercial precious metal oxide catalysts such as RuO 2 and a vast majority of electrocatalysts reported so far. Long-term cycling test demonstrates that the overpotential at current density of 10 mA cm−2 has almost no change after 1000 cycles at a scan rate of 50 mV s−1, indicating its quite good stability. The low-cost and high-performance electrocatalyst developed in this work shows great potential for practical hydrogen production from electrolysis of water. Unlabelled Image • Graphene supported N-doped carbon-coated NiFe alloy was prepared by a facile pyrolysis route. • The NiFe@NC/RGO exhibits excellent electrocatalytic activity for oxygen evolution reaction. • It delivers an overpotential of 223 mV at 10 mA cm−2 with a Tafel slope of 48.7 mV dec−1 in 1 M KOH. • It outperforms commercial noble metal-based catalyst of RuO 2 and most catalysts reported so far. • The outstanding OER activity is ascribed to the core-shell structure and the introduction of RGO. [ABSTRACT FROM AUTHOR]

Electrogenerated chemiluminescence (ECL) behaviors of luminol were comparatively studied at CdS quantum dos, graphene, and CdS/graphene (CdS/GR) nanocomposites modified gold electrodes in neutral condition. The most intense anodic ECL signal was obtained at the CdS/GR nanocomposites modified gold electrode (CdS/GR/GE). The anodic ECL of luminol (ECL-1) located at ~ 0.50 V (vs SCE) was increased nearly 50-times compared with the bare gold electrode. Besides, two stronger anodic ECL peaks (ECL-2 and ECL-3) were observed at 1.0 V and 1.4 V (vs SCE), respectively. The fluorescence and the UV–vis absorption spectra revealed that resonance energy transfer between luminol and CdS/GR nanocomposites was possible. The ECL spectra further demonstrated the occurrence of ECL resonance energy transfer (ECL-RET), which resulted in strong ECL-2 and ECL-3. Cytochrome C could significantly inhibit the intensities of the anodic ECL peaks, and could be sensitively detected. [ABSTRACT FROM AUTHOR]

Abstract: An ultrasensitive electrochemical immunoassay was developed for rapid detection of interleukin-6 (IL-6) and matrix metallopeptidase-9 (MMP-9); the method utilized PS@PDA-metal nanocomposites based on graphene nanoribbon (GNR)-modified heated screen-printed carbon electrode (HSPCE). Because of the good hydrophilicity and low toxicity, GNRs were used to immobilize antibodies (Ab) and amplify the electrochemical signal. PS@PDA-metal was used to label antibodies and generate a strong electrochemical signal in acetic buffer. A sandwich strategy was adopted to achieve simultaneous detection of MMP-9 and IL-6 based on HSPCE without cross-talk between adjacent electrodes in the range of 10−5 to 103 ngmL−1 with detection limits of 5fgmL−1 and 0.1pgmL−1 (S/N=3), respectively. The proposed method showed wide detection range, low detection limit, acceptable stability and good reproducibility. Satisfactory results were also obtained in the practical samples, thus showing this is a promising technique for simultaneous clinical detection of biocomponent proteins. [Copyright &y& Elsevier]

Abstract: A new electrochemical immunosensor was developed for ultrasensitive detection of matrix metalloproteinase-2 (MMP-2), which is one of the key biomarkers in blood. In our approach, an effective assembly of well-defined gold nanoparticles on nitrogen-doped graphene sheets was demonstrated. The composite facilitated robust immobilization of antibodies, promoted electron transfer and exhibited excellent electrochemical activity, which are suitable for biosensing. The design of the immunosensor also involved a polydopamine functionalized graphene oxide hybrid conjugated to horseradish peroxidase-secondary antibodies by covalent bonds as a multi-labeled and biocompatible probe to increase the electrochemical response. This novel signal amplification strategy with a sandwich-type immunoreaction significantly enhanced the sensitivity of detection of biomarkers. The proposed immunosensor displayed excellent analytical performance in the detection of MMP-2 ranging from 0.0005 to 50ngmL−1, with a detection limit of 0.11pgmL−1. Furthermore, it not only exhibited good stability with adequate reproducibility and accuracy, but also demonstrated efficiency in the detection of MMP-2 in real samples. [Copyright &y& Elsevier]

Abstract: Here we demonstrate the fabrication of an effective cytosensor using carboxymethyl chitosan-functionalized graphene (CMC-G) prepared through chemical reduction of graphene oxide. The CMC-G hybrid was further characterized with UV–vis spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis, transmission electron microscopy and atomic force microscopy. Layer-by-layer assembly of CMC-G with polyethyleneimine and folic acid enabled the fabrication of a label-free electrochemical impedance spectroscopy cytosensor with high stability and biocompatibility. The proposed cytosensor exhibited good electrochemical behavior and cell-capture ability for HL-60 cells, and showed a wide linear range and low detection limit for quantification. [Copyright &y& Elsevier]

Abstract: Reduced graphene oxide–lead tellurium (RGO–PbTe) composites were fabricated via sonoelectrochemical technique. The crystalline structure, composition and morphology of the products were characterized by X-ray powder diffraction (XRD), energy dispersive X-ray spectrometer (EDS), transmission electron microscopy (TEM), respectively. The results showed that the PbTe nanoparticles (NPs) were uniformly decorated on the RGO sheets. The formation mechanism of RGO–PbTe nanocomposite was proposed. Ultrasonic played an important role in the formation of PbTe NPs. The composites were further used as supports for immobilization of hemoglobin (Hb) to fabricate a novel electrochemical biosensor, which had good thermal stability, conductivity and biocompatibility and enhanced direct electron transfer. This biosensor showed excellent electrocatalytic activity towards H2O2 with a linear range from 0.5 to 30μM and low detection limit as 0.13μM. [Copyright &y& Elsevier]

Abstract: A sensitive label-free amperometric immunosensor was developed based on the amine-functionalized graphene (GR-NH2) and gold nanoparticles (AuNPs) composite modified carbon ionic liquid electrode (CILE). CILE was fabricated by using an ionic liquid of 1-octyl-3-methylimidazolium hexafluorophosphate as binder. The nanocomposite AuNPs/GR-NH2 had prominent biocompatibility, good electron transfer ability, large specific surface area, and primarily excellent adsorption. The negatively charged AuNPs could be adsorbed on the positively charged GR-NH2 modified CILE surface by electrostatic adsorption, and then to immobilize α-fetoprotein antibody (anti-AFP) for the assay of α-fetoprotein (AFP). The fabricated procedures and electrochemical behaviors of the immunosensor were characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The anti-AFP/AuNPs/GR-NH2 modified CILE was sensitive to AFP in linear relation between 1 and 250ngmL−1 with the correlation coefficient of 0.995, and the detection limit (S/N =3) was 0.1ngmL−1 under the optimal conditions. In addition, the proposed immunosensor exhibited good sensitivity, selectivity, stability and long-term maintenance of bioactivity and it may be used to immobilize other biomoleculars to develop biosensor for the detection of other antigens or biocompounds. [Copyright &y& Elsevier]

Abstract: A sensitive electrochemical immunosensor with graphene-assisted signal amplification has been developed. In order to construct the base of the immunosensor, a novel hybrid architecture was initially fabricated by combining poly (diallyldimethylammonium chloride) functionalized graphene nanosheets (PDDA-G) and gold nanoparticles (AuNPs) via a simple sonication-induced assembly. The formed hybrid architecture provided an effective matrix for antibody immobilization with good stability and bioactivity. Subsequently, a smart, multilabel, and graphene-based nanoprobe that contains gold nanoparticles functionalized exfoliated graphene oxide and horseradish peroxidase-secondary antibodies was designed for constructing a novel sandwiched electrochemical immunosensor. Enhanced sensitivity was obtained by combining the advantages of high-binding capability and excellent electrical conductivity of hybrid architecture with the multilabel signal amplification. On the basis of the dual signal amplification strategy of graphene-based architecture and the multilabel, the immunosensor displayed excellent analytical performance for the detection of human IgG (HIgG) range from 0.1 to 200ng/mL with a detection limit of 0.05ng/mL at 3σ. Moreover, the proposed method showed good precision, acceptable stability and reproducibility, and could be used for the detection of HIgG in real samples. Therefore, the present strategy definitely paves a way for the wide application of graphene in clinical research. [Copyright &y& Elsevier]

Abstract: The functionalized graphene nanosheets (PDDA-G) with poly(diallyldimethylammonium chloride) (PDDA) were synthesized and used to combine with room temperature ionic liquid (RTIL). The resulting RTIL/PDDA-G composite displayed an enhanced capability for the immobilization of hemoglobin to realize its direct electrochemistry. Moreover, the RTIL/PDDA-G based biosensor exhibited excellent electrocatalytic activity for the detection of nitrate with a wide linear range from 0.2 to 32.6μM and a low detection limit of 0.04μM at 3σ. This work opens a new way to functionalized graphene nanosheets with good biocompatibility and solubility in biosensors. [Copyright &y& Elsevier]

Sn-based materials as potential anode materials have triggered significant research interests for lithium storage owing to their high theoretical capacity and low cost. However, the practical applications of Sn-based materials are hindered by low capacity release and fast capacity fading due to large volume expansion and structural pulverization of the electrodes during cycling. Herein, we demonstrate an efficient strategy to alleviate/resolve the above issues by introducing highly conductive inactive metal to alloy with Sn and then loading the Sn-based alloy particles onto two-dimensional (2D) graphene matrix. The graphene supported Fe–Sn nanoalloy composites (FeSn 2 /FeSn/Fe-rGO) are synthesized via a facile bimetallic metal-organic framework precursor route, in which Sn 3 [Fe(CN) 6 ] 4 nanocubes are grown in-situ on reduced graphene oxide (rGO) sheets, followed by thermal decomposition of the Sn 3 [Fe(CN) 6 ] 4 /rGO precursor in an Ar/H 2 atmosphere. As a result, the lithium-ion batteries based on FeSn 2 /FeSn/Fe-rGO composites exhibit outstanding lithium storage performance with a remarkable reversible capacity of 1274 mAh g−1 at 0.2 A g−1 after 200 cycles, a great rate capability of 665 mAh g−1 at 5.0 A g−1, and excellent high-rate cycling stability with a capacity decay of only 0.025% per cycle within 1200 cycles at 2.0 A g−1. The excellent electrochemical performance of FeSn 2 /FeSn/Fe-rGO can be ascribed to its unique three-order buffer structures: the Fe atoms in FeSn 2 and FeSn acting as tough buffer, metal Fe as framework buffer for cubic nanoparticles, and rGO as 2D elastic matrix buffer, which effectively alleviate the volume expansion and structural pulverization of the electrode during lithiation, synergistically enhance the lithium storage performance. Image 1 • Graphene supported Fe-Sn nanoalloy composites were prepared via a facile metal-organic framework precursor route. • The FeSn 2 /FeSn/Fe-rGO anode exhibits high reversible capacities, great rate capability, and excellent cycle stability. • Fe species in the composites effectively alleviated the volume expansion and structural pulverization of the electrode. • The graphene matrix accommodated the large volume change and prevented Fe–Sn alloy particles aggregation. [ABSTRACT FROM AUTHOR]