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The stacking state of atomic layers critically determines the physical properties of twisted van der Waals materials. Unfortunately, precise characterization of the stacked interfaces remains a great challenge as they are buried internally. With conductive atomic force microscopy, we show that the moiré superlattice structure formed at the embedded interfaces of small-angle twisted multilayer graphene (tMLG) can noticeably regulate surface conductivity even when the twisted interfaces are 10 atomic layers beneath the surface. Assisted by molecular dynamics (MD) simulations, a theoretical model is proposed to correlate surface conductivity with the sequential stacking state of the graphene layers of tMLG. The theoretical model is then employed to extract the complex structure of a tMLG sample with crystalline defects. Probing and visualizing the internal stacking structures of twisted layered materials is essential for understanding their unique physical properties, and our work offers a powerful tool for this via simple surface conductivity mapping. [ABSTRACT FROM AUTHOR]

The coupling effects of surface plasmon resonance (SPR) from metamaterials induce variation in both the frequency and intensity of plasmonic modes. Here, we report an angular-dependent THz modulator with hybrid metal–graphene metastructures. The metastructures composed of the period gold split-rod arrays on top of a monolayer graphene, which show redshift modulation in the THz region with an increasing incident angle due to the strong out-of-plane magnetic flux introduced by the clockwise circular current at the oblique incidence. By utilizing graphene-based actively tunable conductor with ion-gel electrical gating, the THz transmission can be significantly modified. The modulation depth of the hybrid metal–graphene metastructure modulator can reach ~37.6% at 0.62 THz with a gate voltage of −3 V. The theoretical modeling of transmitted dependency on frequency and incident angle is demonstrated at different Fermi energies, which fits well with the experimental results. This hybrid device can offer a useful method for THz applications (such as angle sensors or angular-resolved spectroscopy), where angle-dependent modulation is needed. [ABSTRACT FROM AUTHOR]

Novel phenyl-modified magnetic graphene/mesoporous silica (MG-MS-Ph) composites with hierarchical bridge-pore structure were successfully synthesized. The magnetic graphene (MG) as bridge were obtained by one-step solvothermal approach and then phenyl-functionalized mesoporous silica (MS-Ph) as pore modified the MG surfaces through one-pot facile strategy. The resulting MG-MS-Ph exhibited large surface area (446.5 m 2 g −1 ), highly ordered mesopores with uniform pore size (2.8 nm) and pore volume (0.32 cm 3 g −1 ) and higher saturation magnetization (25 emu g −1 ). These wonderful features made MG-MS-Ph as a promising magnetic solid-phase extraction adsorbent for the removal of pesticides from wastewater. Batch adsorption studies indicated that the novel composites exhibited superior adsorption capacity of pesticides compared with other adsorbents including Activated carbon, Multi-walled carbon nanotube and Single-walled carbon nanotube. Therefore, MG-MS-Ph as a low cost and efficient adsorbents for the removal of toxic pesticides would be economically and technically feasible. [ABSTRACT FROM AUTHOR]

Multi-angle modulation properties of electrolyte gated graphene visible-infrared modulators with supercapacitor structures have been examined in both experiment and theory. Both transmission and reflection geometries have been studied, and the results show that all the modulations of these devices are gate voltage and wavelength dependent. Maximum modulation depths for transmission device ∼3% and reflection modulator ∼5% are obtained, which can be attributed to the electrolyte assistant considerable change of the Fermi energy with tunable gate voltage. Moreover, little incident angle dependency can be observed with a certain gate voltage. Theoretical analysis based on the different tangential and normal optical responses of the quartz/graphene/eletrolyte interface has been used to explain the phenomena, which indicated a common effect of p -polarized and s -polarized light. This work offers useful insight into a multi-angle application of the graphene-based optical modulator in visible-infrared region. [ABSTRACT FROM AUTHOR]

Multilayer graphene (MLG) grown by chemical vapor deposition (CVD) is a promising material for electronic and optoelectronic devices. Understanding the stacking configuration and interlayer coupling of MLGs is technologically relevant and of importance for the device applications. Here, we reported a kind of twisted MLGs (tMLGs), in which only one twist angle was revealed from the twist-related modes, R and R'. With increasing the total layer number of N (N > 2), the observed interlayer shear modes in the tMLG flake always follow those of AB-stacked (N-1)LG, while the observed interlayer breathing modes always follow those of AB-stacked NLG, independent of its twist angle. The tMLGs are identified as t(1+ n )LGs, which are formed by stacking one graphene monolayer on the top of AB-stacked n layer graphenes by rotating a certain angle between them. The layer breathing coupling of the t(1+ n )LGs is almost identical to that of mechanically-exfoliated tMLGs, which demonstrates the high quality of MLGs grown by CVD. This study provides an applicable approach to probe the stacking configuration and interlayer coupling of MLGs grown by CVD or related methods. This work also demonstrates the possibility to grow MLG flakes with a fixed stacking configuration, e . g ., t(1+ n )LG, by the CVD method. [ABSTRACT FROM AUTHOR]

The persistence of pharmaceutical and personal care products (PPCPs) such as norfloxacin (NFX) poses a serious threat to the water environment, and the development of efficient and cost-effective advanced oxidation catalysts is an important step toward resolving this issue. Herein, Fe and N co-doped graphene (FeNGO) was synthesized from graphene oxide (GO), urea, and iron salt via simple impregnation pyrolysis, and applied for activating peroxymonosulfate (PMS) to degrade NFX. FeNGO possessed a two-dimensional porous sheet structure and was rich in defects, nitrogen species, and active sites. Compared with the control catalyst doped with N or Fe alone, FeNGO/PMS system showed the best degradation performance with 97.7% removal of NFX after 30 min, the rate constant was 7.1 and 1.7 times than that for NGO and FeGO, respectively. Fe 3 N was the main active site of FeNGO, and it is confirmed that singlet oxygen (1O 2) and superoxide radical (O 2 •-) were the primary oxidation active species (ROS) during NFX degradation. The formation of 1O 2 came from the transformation of O 2 •- and PMS decomposition. FeNGO showed strong pH adaptability, and also exhibited stale degradation performance in saliferous water matrices. It is believed that this work will offer theoretical and practical guidance for PMS activation by non-radical pathways. [Display omitted] • The FeNGO was prepared and the Fe 3 N were the main active sites. • The FeNGO exhibited good pH flexibility and had low Fe leaching. • O 2.•- and 1O 2 were primary cause of norfloxacin degradation. • Possible degradation pathway of norfloxacin was proposed. [ABSTRACT FROM AUTHOR]

By employing dopamine as a nitrogen source and reducing agent, the block copolymer P123 as a pore forming agent, and graphene oxide as a carbon precursor, we present, for the first time, a convenient and controllable approach to the preparation of a novel uniformly nitrogen doped porous graphene (N-PGR) material. Using the prepared N-PGR as the supporting material, a novel nitrogen doped porous graphene/Pt nanoflower material (Pt/N-PGR) was obtained by a green and simple method. The characterization results of scanning electron microscopy (SEM), element mapping, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) demonstrate that Pt nanoflowers are uniformly dispersed on nitrogen doped porous graphene. Electrochemical measurements show that Pt/N-PGR-900/GCE exhibits improved electrocatalytic activity towards H2O2 reduction and glucose oxidation. Linear responses are found for H2O2 and glucose in the range of 0.5–40 326 μM and 0.5–133.5 mM with the detection limit (S/N = 3) of 0.2 μM and 0.05 mM, respectively. In addition, Pt/N-PGR-900/GCE exhibits high sensitivity and good anti-interference ability. The superior catalytic activity and selectivity make Pt/N-PGR a promising nanomaterial for application in electrochemical biosensing studies. [ABSTRACT FROM AUTHOR]

Three-dimensional graphene-supported mesoporous silica@Fe3O4 composites (mSiO2@Fe3O4-G) were prepared by modifying mesoporous SiO2-coated Fe3O4 onto hydrophobic graphene nanosheets through a simple adsorption co-condensation method. The obtained composites possess unique properties of large surface area (332.9 m2/g), pore volume (0.68 cm3/g), highly open pore structure with uniform pore size (31.1 nm), as well as good magnetic separation properties. The adsorbent (mSiO2@Fe3O4-G) was used for the magnetic solid-phase extraction of seven pesticides with benzene rings in different aqueous samples before high-performance liquid chromatography. The main parameters affecting the extraction such as adsorbent amount, volume of elution solvent, time of extraction and desorption, salt effect, oscillation rate were investigated. Under the optimal conditions, this method provided low limits of detection (S/N = 3, 0.525-3.30 μg/L) and good linearity (5.0-1000 μg/L, R2 > 0.9954). Method validation proved the feasibility of the developed adsorbent, which has a high extraction efficiency and excellent enhancement performance for pesticides in this study. The proposed method was successfully applied to real aqueous samples, and satisfactory recoveries ranging from 77.5 to 113.6% with relative standard deviations within 9.7% were obtained. [ABSTRACT FROM AUTHOR]

In this study microwave-assisted reduction (MrGO) and direct reduction of graphene oxide (rGO) by Ti powders were established, and the effect of the reaction conditions on the reduction were discussed. The results showed that GO can be effectively reduced by both methods, however, microwave assistance can greatly shorten the reduction time. The produced Ti ions from the reaction of Ti powder with GO were transferred to TiO 2 by hydrolysis and formed MrGO/TiO 2 and rGO/TiO 2 . They were used as adsorbents for the removal of methylene blue (MB). MrGO/TiO 2 showed a higher adsorption capacity ( q max , 845.6 mg/g) than rGO/TiO 2 ( q max , 467.6 mg/g). Investigation on the adsorption MB onto MrGO/TiO 2 was conducted and demonstrated that adsorption kinetics followed the pseudo second-order kinetics model and the adsorption isotherm was well described by the Langmuir isotherm model. The recycling of MrGO/TiO 2 was achieved by photocatalytic degradation of MB catalyzed by MrGO/TiO 2 itself. [ABSTRACT FROM AUTHOR]

A simple hard template method and hydrothermal process have been employed to fabricate a self-standing hierarchical porous MnO 2 /graphene film. Thus-constructed electrode materials for binder-free supercapacitors exhibit a high specific capacitance of 266.3 F g −1 at the density of 0.2 A g −1 . Moreover, the two-electrode device demonstrates an excellent rate capability and cycling stability with capacitance retention of 85.1% after 2000 charge–discharge cycles at a current density of 1 A g −1 . The porous nanostructured design can effectively improve the specific surface areas and account for the shorter relaxation time for the electrodes, resulting in a high electrochemical performance. [ABSTRACT FROM AUTHOR]

An electrochemical immunosensor for quantitative detection of α-fetoprotein (AFP) in human serum was developed using graphene sheets (GS) and thionine (TH) as electrode materials and mesoporous silica nanoparticles (MSNs) loaded with ferroferric oxide (Fe 3 O 4 ) nanoparticles and horseradish peroxidase (HRP) as labels for signal amplification. In this study, the compound of GS and TH (GS–TH) was used as a substrate for promoting electron transfer and immobilization of primary antibody of AFP (Ab 1 ). MSNs were used as a carrier for immobilization of secondary antibody of AFP (Ab 2 ), Fe 3 O 4 , and HRP. The synergistic effect occurred between Fe 3 O 4 and HRP and greatly improved the sensitivity of the immunosensor. This method could detect AFP over a wide concentration range from 0.01 to 25 ng ml −1 with a detection limit of 4 pg ml −1 . This strategy may find wide potential application in clinical analysis or detection of other tumor markers. [ABSTRACT FROM AUTHOR]

The morphology- and size-controlled synthesis of branched Pt nanostructures on graphene is highly favorable for enhancing the electrocatalytic activity and stability of Pt. Herein, a facile approach is developed for the efficient synthesis of well-dispersed Pt nanoflowers (PtNFs) on the surface of polydopamine (PDA)-modified reduced graphene oxide (PDRGO), denoted as PtNFs/PDRGO, in high yield. The synthesis was performed by a simple heating treatment of an aqueous solution that contained K2PtCl4 and PDA-modified graphene oxide (GO) without the need for any additional reducing agent, seed, surfactant, or organic solvent. The coated PDA serves not only as a reducing agent, but also as cross-linker to anchor and stabilize PtNFs on the PDRGO support. The as-prepared PtNFs/PDRGO hybrid, with spatially and locally separated PtNFs on PDRGO, exhibits superior electrocatalytic activity and stability toward both methanol oxidation reaction (MOR) and oxygen reduction reaction (ORR) in alkaline solutions. [ABSTRACT FROM AUTHOR]

Abstract: In the present work, using copper as an etching agent, a novel and easy method to prepare porous graphene nanosheet (P-GR) was reported. With a large number of pores, more acidic groups and edge defect sites (EDSs) compared with graphene (GR), the prepared P-GR was used as an electrochemical biosensing platform for the first time. Using voltammetry and amperometry as detection methods, some important electroactive compounds, including dopamine (DA), ascorbic acid (AA), uric acid (UA), epinephrine (EP), guanine (G), adenine (A), xanthine (XA), hypoxanthine (HX), hydrogen peroxide and β-nicotinamide adenine dinucleotide (NADH) were employed to study their electrochemical responses on P-GR modified glassy carbon electrode (P-GR/GCE). The results show that P-GR/GCE exhibits better electrochemical performance to these substances compared with GR modified glassy carbon electrode (GR/GCE) and edge plane pyrolitic graphite electrode (PGE). The remarkable electrochemical advantage of P-GR makes it a promising material in electrochemical biosensing field. [Copyright &y& Elsevier]

Abstract: The luminescent reduced graphene oxide small sheets (average diameter: 30–50nm) are prepared by using a simple and eco-friendly solvothermal process, and show an obvious excitation-dependent PL emission as the excitation wavelength varies from 300 to 500nm. In particular, under excitation at 340nm, a strongest blue emission occurs, whose quantum yield reaches ca. 3.2% as Rhodamine B is used as a reference. This offers a simple pathway to prepare the luminescent reduced graphene oxide small sheets. Furthermore, the emission exhibits a good resistance to the change of pH for the surroundings, which could be beneficial to the practical applications in the field of optoelectronics, and molecule detection. [Copyright &y& Elsevier]

Abstract: Incorporation of reduced graphene oxide (rGO) in Co3O4 matrix is systematically investigated through a chemical route for supercapacitors. The α-Co(OH)2 supported by graphene oxide is first fabricated by a chemical precipitation approach. Thermal decompositions of these precursors at the given temperature (150°C) lead to rGO/Co3O4 composites. Measurement results show that the morphology and electrochemical activity of the rGO/Co3O4 composites are influenced significantly by the mass ratios of rGO to Co3O4. When used as electrode materials in supercapacitors, the composite with mass ratio of 0.22:1 (rGO:Co3O4) achieves the specific capacitance as high as 291Fg−1 at 1Ag−1 in the potential range of −0.4 to 0.55V, as compared with each individual counterpart (56 and 161Fg−1 for rGO and Co3O4, respectively). In addition, the excellent rate capability and well cycling ability are observed in the composite electrodes. The enhanced electrochemical performance is indicative of a positive synergistic effect between rGO and Co3O4. These results suggest the importance and great potential of graphene based composites in the development of high-performance energy-storage systems. [Copyright &y& Elsevier]

Abstract: A hybrid material of graphene oxide (GO) sheets beaded with ZnO nanoparticles was prepared. The material extends over a few hundred square nanometers, in which the ZnO nanoparticles (average diameter (∼5nm)) are dispersed evenly on the GO sheet. Both the surface photovoltage or surface photocurrent intensity for the material are much stronger than for pure ZnO nanoparticles, meaning that the free charge carriers can effectively be transferred from ZnO nanoparticles to GO sheets, which can serve as a probe to monitor the electron transfer from excited ZnO to GO. Anchoring ZnO nanoparticles on two dimensional carbon nanostructures such as GO can pave a way towards the design of ordered nanostructure assemblies that can harvest light energy efficiently. [Copyright &y& Elsevier]

Abstract: In this work, a comparative study on the electrocatalytic activities of ordered mesoporous carbons (OMCs) and graphene (GR) is presented. Using voltammetry and amperometry as detection methods, four DNA bases, double-stranded DNA (dsDNA), six important electroactive compounds and various biomolecules were employed to investigate their electrochemical responses on OMC and GR modified glassy carbon electrodes (OMC/GCE and GR/GCE). The results show that OMC/GCE enhances the electron transfer kinetics of these compounds compared to GR/GCE. The discrepancy in electrochemical activities can be attributed to the different microstructures of OMC and GR, which were examined by transmission electron microscopy, X-ray photoelectron spectra, X-ray diffraction, Raman spectra and nitrogen adsorption–desorption. [Copyright &y& Elsevier]

Abstract: This work demonstrates a novel and facile route for preparing graphene-based composites comprising of metal oxide nanoparticles and graphene. A graphene nanosheet–bismuth oxide composite as electrode materials of supercapacitors was firstly synthesized by thermally treating the graphene–bismuth composite, which was obtained through simultaneous solvothermal reduction of the colloidal dispersions of negatively charged graphene oxide sheets in N,N-dimethyl formamide (DMF) solution of bismuth cations at 180°C. The morphology, composition, and microstructure of the composites together with pure graphite oxide, and graphene were characterized using powder X-ray diffraction (XRD), FT-IR, field emission scanning electron microscopy (FESEM), transmission electron microscope (TEM), thermogravimetry and differential thermogravimetry (TG–DTG). The electrochemical behaviors were measured by cyclic voltammogram (CV), galvanostatic charge–discharge and electrochemical impedance spectroscopy (EIS). The specific capacitance of 255Fg−1 (based on composite) is obtained at a specific current of 1Ag−1 as compared with 71Fg−1 for pure graphene. The loaded-bismuth oxide achieves a specific capacitance as high as 757Fg−1 even at 10Ag−1. In addition, the graphene nanosheet–bismuth oxide composite electrode exhibits the excellent rate capability and well reversibility. [Copyright &y& Elsevier]

Improving the catalytic performance of graphene for the electrochemical CO2 reduction reaction (CO2RR) has been a promising avenue to abate the concentration of greenhouse gas and develop a strategy of CO2 recyclable utilization. In this paper, we systematically investigate the catalytic performance of different active sites, both on the undoped and N‐doped graphene sheets, under non‐strained (0%) and 1%, 5% and 10% lattice strain (LS) via density functional theory calculations. The results uncover that N‐doping and LS synergistically modulate the electronic structures of graphene, enhancing the electrocatalytic reduction of CO2 to CO. Among all models in this work, the site with the highest catalytic activity toward CO2RR is shown to be the carbon atom at the ortho‐position (labeled as G2) relative to the nitrogen heteroatom (denoted by N1) on the graphene under 10% LS due to its lowest overpotential of 1.19 eV. Moreover, the projected density of states and the charge density differences of all systems are calculated to explore the mechanism for the enhancement of CO2 reduction performance. These analyses indicate that the localization of electron density on the G2 site makes it be the most active site on the N‐doped graphene sheet for CO2RR. Hence, our computations demonstrate that by both nitrogen doping and LS increasing on the graphene sheet is a promising way for positive modulating its catalytic activity of the CO2RR. [ABSTRACT FROM AUTHOR]

Adsorption and advanced oxidation technology are important means to remove organic pollutants, and the combination of adsorption and catalytic degradation to construct a multi-field coupled system can realize valid adsorption and degradation of organic contaminants. In this paper, CuBi 2 O 4 supported by a nonmetallic element-modified graphene hydrogel composite structure CuBi 2 O 4 /X-rGH (X = N, P, S, B) was synthesized and applied to the efficient removal of organic pollutants. We found that the doping of nonmetallic elements enhances the graphene conjugated large π-bond system, which not only improves the adsorption performance of pollutants but also increases the graphene conductivity and builds more carrier transport channels, which is beneficial to the photocatalytic Fenton synergistic degradation activity. Among them, CuBi 2 O 4 /P-rGH could achieve 90 % degradation of phenol (50 ppm) after 20 min of turning on the light, which was nearly 2 times more than the degradation activity of CuBi 2 O 4 /rGH. Electron paramagnetic resonance (EPR) and quenching experiments proved that ·OH was the main active species in the synergistic degradation process, and the mechanism of adsorption of nonmetallic modified graphene hydrogel hybrid catalysts and in situ photocatalytic Fenton degradation of pollutants was proposed. [ABSTRACT FROM AUTHOR]

Adsorption and advanced oxidation technology are important means to remove organic pollutants, and the combination of adsorption and catalytic degradation to construct a multi-field coupled system can realize valid adsorption and degradation of organic contaminants. In this paper, CuBi 2 O 4 supported by a nonmetallic element-modified graphene hydrogel composite structure CuBi 2 O 4 /X-rGH (X = N, P, S, B) was synthesized and applied to the efficient removal of organic pollutants. We found that the doping of nonmetallic elements enhances the graphene conjugated large π-bond system, which not only improves the adsorption performance of pollutants but also increases the graphene conductivity and builds more carrier transport channels, which is beneficial to the photocatalytic Fenton synergistic degradation activity. Among them, CuBi 2 O 4 /P-rGH could achieve 90 % degradation of phenol (50 ppm) after 20 min of turning on the light, which was nearly 2 times more than the degradation activity of CuBi 2 O 4 /rGH. Electron paramagnetic resonance (EPR) and quenching experiments proved that ·OH was the main active species in the synergistic degradation process, and the mechanism of adsorption of nonmetallic modified graphene hydrogel hybrid catalysts and in situ photocatalytic Fenton degradation of pollutants was proposed. [ABSTRACT FROM AUTHOR]

Abstract In this paper, we developed a simple and convenient method for incorporating graphene with anatase-rutile TiO 2 composite and applied it as photoanode to improve the photovoltaic performance of CdS QDSSCs. Our research indicated in a CdS QDSSC system, the photoelectric conversion efficiency (PCE) of anatase-rutile TiO 2 (TGr0) composite photoanode was 86% higher than that rutile TiO 2 NRs. We also found that the PCE increased first and then decreased with the change of graphene content after the graphene was introduced into the anatase-rutile TiO 2 photoanode. When the ratio of optimized graphene/anatase TiO 2 particles composite that spin-coated on rutile TiO 2 NRs photoanode was 5%, we attained a maximum PCE of 2.20%, which was 178% and 50% higher than that pure TiO 2 NRs (0.79%) and TGr0 (1.47%), respectively. Graphical abstract The structure of CdS sensitized graphene and anatase-rutile TiO 2 composite photoanode based on Cu 2 S CE. Image 1 Highlights • Incorporated the optimized graphene into anatase-rutile TiO 2 as photoanode. • The PCE of TGr0 photoanode was twice higher than that of pure rutile TiO 2 NRs. • The maximum PCE of 2.20% was 178% higher than that TGr0 photoanode. [ABSTRACT FROM AUTHOR]

Electrochemical carbon dioxide (CO2) reduction into value‐added products holds great promise in moving toward carbon neutrality but remains a grand challenge due to lack of efficient electrocatalysts. Herein, the nucleophilic substitution reaction is elaborately harnessed to synthesize carbon nanoplates with a FeN4O configuration anchored onto graphene substrate (FeN4OC/Gr) through covalent linkages. Density functional theory calculations demonstrate the unique configuration of FeN4O with one oxygen (O) atom in the axial direction not only suppresses the competing hydrogen evolution reaction, but also facilitates the desorption of *CO intermediate compared with the commonly planar single‐atomic Fe sites. The FeN4OC/Gr shows excellent performance in the electroreduction of CO2 into carbon monoxide (CO) with an impressive Faradaic efficiency of 98.3% at −0.7 V versus reversible hydrogen electrode (RHE) and a high turnover frequency of 3511 h−1. Furthermore, as a cathode catalyst in an aqueous zinc (Zn)‐CO2 battery, the FeN4OC/Gr achieves a high CO Faradaic efficiency (≈91%) at a discharge current density of 3 mA cm−2 and long‐term stability over 74 h. This work opens up a new route to simultaneously modulate the geometric and electronic structure of single‐atomic catalysts toward efficient CO2 conversion. [ABSTRACT FROM AUTHOR]

Graphene aerogel–mesoporous carbon (GA–MC) composites with three-dimensional (3D) hierarchical nanostructures were synthesized using a nanocasting technique. The honeycomb-like GA–MC composites exhibited very high surface areas (728.3 m2 g−1), and ultra large pore sizes (48 nm) and pore volumes (0.96 cm3 g−1) due to the synergistic combination of the advantages of both macro-porous graphene aerogels and the meso-pores of mesoporous carbon. These wonderful features made GA–MC a promising enrichment material for SPME fiber coating. Under the optimum conditions, the home-made fiber (GA–MC) was successfully applied to extract BFRs in real wastewater samples and ideal results were obtained with recoveries of 74.6–96.2%. The new fibers demonstrated excellent enrichment capabilities compared to commercial polydimethylsiloxane (PDMS) and polyacrylate (PA) fibers for six brominated flame retardants (BFRs). The ideal extraction performance of the novel graphene aerogel–mesoporous composites creates new opportunities for SPME applied in environmental analysis. [ABSTRACT FROM AUTHOR]

A CoO/3D graphene composite synthesized via hydrothermal method was used as an anode material for Li-ion batteries. X-ray diffraction, scanning electron microscopy, thermogravimetry, energy-dispersive X-ray spectroscopy, transmission electron microscope, cyclic voltammetry, electrochemical impedance spectroscopy, and charge/discharge measurement were conducted to evaluate the physical and electrochemical properties of the CoO/3D graphene composite. Results showed that the composite delivered high rate capacities of 1481.1, 657.7, 472.5, 423.8, and 391.2 mAh g −1 , at 50, 100, 200, 300, 400, and 500 mA g −1 , respectively. The capacity after 100 cycles was 860 mAh g −1 at 50 mA g −1 , thereby indicating excellent cycle stability. The excellent electrochemical performance was ascribed to 3D graphene sheets that were formed in the composite structure. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) graphene aerogels–mesoporous silica (GAs–MS) frameworks were successfully fabricated. The interconnected macropores were obtained from hydrothermally assembled 3D GAs, while the mesopores were generated by the silica uniformly grown on the surface of graphene. The resulting GAs–MS exhibited narrow mesopore size distribution (1.87 nm), high surface area (1000.80 m 2 g −1 ), and hierarchical macro- and mesoporous structures. These wonderful features made GAs–MS as a promising adsorbent for the removal of hazardous phenols from wastewater. The adsorption study implied that the novel materials exhibited superior adsorption capacity of phenols to such as phenol, catechol, resorcinol and hydroquinone, with removal efficiencies of 68.6%, 86.6%, 91.1% and 94.7%, respectively. [ABSTRACT FROM AUTHOR]

Gold nanoparticles (AuNPs) and reduced graphene oxide (graphene) composites were synthesized via a simple one-pot approach in the presence of polyvinylpyrrolidone (PVP). Further, the Au–PVP–graphene nanocomposite was used as a new sensing material for the electrochemical detection of butylated hydroxyanisole (BHA). Because of the greatly enlarged surface area, the enhanced electron transfer rate, and a stronger enrichment of BHA, the sensor based on Au–PVP–graphene modified glassy carbon electrode (GCE) displayed highly sensitive electrochemical responses to BHA. Applying linear sweep voltammetry, a good linear relationship of the oxidation peak current with respect to concentrations of BHA across the range of 0.2–100.0 µM and a detection limit of 0.04 µM was achieved. The practical analytical performance of the Au–PVP–graphene/GCE was examined by evaluating detection of BHA in soybean oil and the flour samples. Satisfactory results revealed that this work offered a new way for the sensitive and simple determination of BHA in complex samples. [ABSTRACT FROM AUTHOR]

A novel aptamer/graphene interdigitated gold electrode piezoelectric sensor was developed for the rapid and specific detection of Staphylococcus aureus ( S. aureus ) by employing S. aureus aptamer as a biological recognition element. 4-Mercaptobenzene-diazonium tetrafluoroborate (MBDT) salt was used as a molecular cross-linking agent to chemically bind graphene to interdigital gold electrodes (IDE) that are connected to a series electrode piezoelectric quartz crystal (SPQC). S. aureus aptamers were assembly immobilized onto graphene via the π – π stacking of DNA bases. Due to the specific binding between S. aureus and aptamer, when S. aureus is present, the DNA bases interacted with the aptamer, thereby dropping the aptamer from the surface of the graphene. The electric parameters of the electrode surface was changed and resulted in the change of oscillator frequency of the SPQC. This detection was completed within 60 min. The constructed sensor demonstrated a linear relationship between resonance frequency shifts with bacterial concentrations ranging from 4.1×10 1 −4.1×10 5 cfu/mL with a detection limit of 41 cfu/mL. The developed strategy can detect S. aureus rapidly and specifically for clinical diagnosis and food testing. [ABSTRACT FROM AUTHOR]

The effects of reinforced structure (three-dimensional braided preform and laminated plain woven fabric) and graphene nanoplatelet-reinforced hierarchical interface on the impact properties of carbon fabric composites after thermo-oxidative aging were investigated. The results indicated that the impact properties decreased with increasing aging time due to the degradation of the matrix and fiber–matrix interface. After exposure to 140℃ for 1200 h, the peak impact force and impact strength retention rates of 3D-braided graphene nanoplatelet-coated carbon fiber-reinforced composite were 13% and 8% higher than those of the laminated composite, respectively. One of the reasons was the graphene nanoplatelet-reinforced gradient interphase may provide an effective shield against interface oxidation, transfer the localized thermal stress, and restrict the movement of the different phase of the materials at the composites interface. Another reason was the integrated structure of the 3D-braided composite can make the fiber bear impact force together although the resin was damaged and the adhesive force between fiber bundles and resin decreased after thermo-oxidative aging. This synergetic reinforcing effect of 3D-braided structure and graphene nanoplatelet-reinforced hierarchical interface provides an easy and effective way to design and improve the thermo-oxidative stability of carbon fiber-reinforced composites. [ABSTRACT FROM AUTHOR]

In this study, nickel tailings were utilized to prepare electrothermal coatings composited with nano-graphite/multilayer graphene, and the effects of heat treatment temperature and time of nickel tailings on the performance of electrothermal coatings were investigated. The experimental results show that the addition of nickel tailings can significantly enhance the performance of the composite electrothermal coatings. Using nickel tailings treated at 60 °C for 2 h caused the temperature response time of the coatings to decrease by 57%, and the maximum temperature was 55.4 °C. However, as the treatment temperature was increased to 100 °C, a large amount of oxygen was introduced into the system, which led to a weakening of the ferric ion conduction in the ferromagnesian olivine, resulting in only a 28.6% reduction in the temperature response time at the maximum temperature of 45.4 °C. Meanwhile, it was established that the multidimensional stabilized conductive network formed by nickel tailings and nano-graphite/multilayer graphene enhanced the comprehensive performance of the coating. In addition, the study on the coating work stability revealed that the electrothermal coating prepared by adding nickel tailings treated at 60 °C for 2 h can maintain the maximum stable temperature above 55 °C for a long period of time, which is significantly better than the samples without nickel tailings and with nickel tailings heat-treated at 100 °C. This electrothermal composite coating is particularly suitable for low-pressure and low-power high-efficiency heating equipment, energy saving and environmental protection. Compared with the existing work, this experiment uses nickel tailings solid waste as auxiliary filler, which has the advantages of low cost, simple fabrication process, energy saving, environmental protection, low energy consumption, etc. It provides a more sustainable and eco-friendly solution for heating needs in a variety of fields. The material will be developed in the direction of higher conversion efficiency and higher temperature threshold in the future. It can be widely used in the fields of intelligent heating of houses, intelligent electric heating of clothes, and de-icing of wings of aircrafts. • Incorporation of waste nickel tailings into nano-graphite/multilayer graphene composite powders to improve the performance of composite electrothermal coatings. • Temperature response time of the electrothermal coating by 57%. • The fluctuation of each performance in the cycling stability test lasting 10 days was less than 1%. [ABSTRACT FROM AUTHOR]

• Novel graphene-like nanosheets stacked carbon nanotube structure was synthesized for the first time. • It was found for the first time that hydrogen peroxide has not only reducing property but also decomposing and stripping function. • Lamellar carbon nanotubes are bonded to transition metal alloys. • Large specific surface area plays a greater positive role in product transport and electron transport. • The novel structural catalyst is highly active in HER and OER. In this study, we prepared a novel graphene-like stacked carbon nanotube-supported Fe-Ni alloy nanometer composite material. The cubic structure of nickel dimethylglyoxime was synthesized as the base material. Under hydrothermal condition, FePc was adsorbed on the surface of the nickel dimethylglyoxime cube. In addition, hydrogen peroxide not only decomposes FePc into Pc and Fe2+, but also reduces Fe2+ to Fe. On the other hand, hydrogen peroxide was first found could decompose and peel the cube of nickel dimethylglyoxime into a novel type of nanotubes with graphene-like nanosheet stacking structure. After the final calcination, the Fe2+ and Ni2+ were converted to FeNi alloy, and the dimethylglyoxime carrier with its loaded Pc was converted to carbon material. The novel structure has a large BET, which is conducive to electron transport, product transport and provides a large active site for Fe-Ni3 alloy. The composite has high electro-catalysis performance for OER and ORR, which provides a new idea for the study of new energy reserves, energy conversion and reserve materials. This study provides a new idea for preparing novel carbon nanotube-loaded transition metal composites in the field of electrocatalysis. The reducing and weak oxidizing decomposition of hydrogen peroxide was first found could peel off the dimethylglyoxime cube to a new graphene-like nanolayer stacking structure carbon nanotube structure. The prepared materials have high electrocatalytic activity for oxygen evolution and oxygen reduction reactions. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: In the present study, a facile method is developed for the synthesis of graphene oxide-Ag nanocomposite (GOAg). The method involves the application of in situ photochemical deposition and growth processes under certain alkaline environments in the absence of chemical reductants and surfactants. Silver nanoparticles with monodisperse size are well dispersed on the surface of graphene oxide (GO). The roles of GO and NaOH in the formation of GOAg are discussed. A corresponding formation mechanism of GOAg is proposed. Fluorescence quenching and Raman enhancement are examined as well. [Copyright &y& Elsevier]

Graphene oxide (GO) is one of the promising two-dimensional nanomaterials for the development of fluorescent aptasensors. Its limitations are related to the inevitable negative effect of GO on the fluorescence. Here this challenge was explored and solved by ssDNA adsorption on GO and centrifugal separation of GO from the ensembled solution. On this basis, a fluorescent aptasensor was constructed for the detection of staphylococcal enterotoxin A (SEA), in which GO assisted the separation of free aptamers to achieve cDNA-induced structure-switching from SEA/aptamer complex to dsDNA, and GO was added again to separate free cDNA and reduce the background signal. SYBR Green I was inserted into dsDNA as the fluorescent signal to achieve the quantitative analysis. It displayed a wide linear range (1–8000 ng/mL), low detection limit (0.899 ng/mL), and satisfactory application in milk and milk powder. Notably, the method was low-cost, general, and instructive for other two-dimensional nanomaterials. [Display omitted] • A label-free, low-background fluorescent aptasensor for staphylococcal enterotoxin A. • Graphene oxide-assisted ssDNA separation to reduce the background and interference. • The cDNA-induced structure-switching formed dsDNA and amplified the signal. • The method was low-cost, general, and instructive for two-dimensional nanomaterials. [ABSTRACT FROM AUTHOR]

Sodium (Na) metal is the most promising alternative anode to metallic lithium for high‐energy batteries due to the low cost and high abundance of Na resources, but it suffers from severe dendritic/mossy growth at high current densities. Understanding Na nucleation/growth mechanism in different electrolyte systems is the key to tackling this issue but is complicated by the structural complexities of existing substrates for Na plating/stripping. Herein, well‐defined planar doped graphene substrates are synthesized as model plating platforms to unravel a binding energy dominant Na nucleation‐growth mode. The dopants (e.g., boron) in doped graphene and the regions close to the dopants possess high binding energies with Na atoms, providing abundant preferential nucleation sites and contributing to uniform Na plating/stripping. Accordingly, the boron‐doped graphene regulated Na anode exhibits long‐term stability at high current densities in both liquid and polymer electrolytes. The results enhance the understanding of Na nucleation/growth for stabilizing Na metal batteries. Planar doped graphene substrates are synthesized to unravel a binding energy dominant sodium (Na) nucleation‐growth mode. The boron (B) dopants in doped graphene and the regions close to the dopants possess high binding energies with Na atoms, providing abundant preferential nucleation sites. Accordingly, the boron‐doped graphene regulated Na anode exhibits long‐term stability at high current densities. [ABSTRACT FROM AUTHOR]

Summary: Ni electrode was modified with graphene by the electrodeposition (ED) method to prepare an anode (anode‐ED) for microbial fuel cell (MFC). Electrochemical and morphological characterizations of anode‐ED along with the effects of anode modification on the MFC performance were investigated. The graphene modification based on cyclic voltammetric electrodeposition resulted in the decrease of charge transfer resistance (Rct) and improved extracellular electron transfer efficiency of anode. The maximum power density obtained from the MFC equipped with anode‐ED was 25.83 and 17.86 times larger than those of MFCs equipped with bare Ni anode and anode modified with graphene by traditional hydrothermal treatment method (anode‐HT), respectively. The electrochemical impedance spectroscopy (EIS) analysis results indicated that the Rct of anode decreased significantly after inoculation during the MFC operation. The improvement in power density was attributed to the decreasing Rct and the biocompatibility of graphene modified on anode‐ED surface. This study presented an effective electrodeposition method to make graphene‐modified anodes, which could improve the MFC performance. [ABSTRACT FROM AUTHOR]

Abstract A novel label-free electrochemiluminescent (ECL) immunosensor based upon luminol functionalized platinum nanoparticles loaded on graphene sheets (Lu-Pt@GS) as sensing platform was fabricated for highly sensitive and selective determination of prostate specific antigen (PSA). In this work, for the first time luminol was employed as both ECL luminescence reagent and reductants to in-situ reduce H 2 PtCl 6 forming Pt NPs on surface of GS. A great deal of luminol could be attached onto the surface of Pt NPs within the reduction process, which can generate strong ECL emission. Pt NPs not only could enhance ECL signals of luminol but supply active sites for the immobilization of PSA antibodies with micro friendly environment. For preventing the consecutive reaction among luminol and H 2 O 2 , single-step cycle pulse was adopted, resulting in stable and strong ECL signals. Under optimized experimental conditions, the proposed ECL immunosensor acquired a wide linear range of 1 pg/mL to 10 ng/mL with a relatively low detection limit of 0.3 pg/mL for PSA. Furthermore, due to high sensitivity, simplicity and cost-effectiveness, the designed immunosensor provides a new method for detecting other important biomarkers in clinical analysis. Highlights • ECL immunosensor was designed based upon Lu-Pt@GS for PSA detection. • Luminol was employed as both ECL luminescence reagent and reductants of Pt NPs. • Single-step cycle pulse was adopted to get stable and strong ECL signals. [ABSTRACT FROM AUTHOR]

Abstract The development of high-performance noble metal-free electrochemical catalyst for effective water splitting is a key factor to achieve low-cost and sustainable renewable energy production. Herein, for the first time, highly dispersed cobalt nanoparticles decorated uniform nitrogen doped graphene (CoNPs-N-GR) was design synthesized. In the preparation procedure, graphene oxide (GO) was employed as supporting material, polydopamine as nitrogen source, location reagent as well as connecting agent for uploading cobalt metal ion, and then cobalt metal-organic frameworks (ZIF-67) in situ grew on GO. During the calcining process, GO reduction, nitrogen doping and cobalt nanoparticles forming were finished in one step. Scanning electron microscopy (SEM) images, transmission electron microscopy (TEM), energy-dispersive X-ray (EDS), X-ray photoelectron spectrometer (XPS) and X-ray diffraction (XRD) were applied to characterize the as-prepared CoNPs-N-GR. Moreover, owing to the presence of dopamine, high dispersed cobalt nanoparticles were obtained, leading to high electrocatalytic activity of CoNPs-N-GR for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline media. HER reaches 10 mA cm−2 at the over-potential of 0.453 V with a Tafel slope of 67 mV dec−1. OER reaches 10 mA cm−2 at the over-potential of 1.63 V with a Tafel slope of 65 mV dec−1. And the as-prepared CoNPs-N-GR shows excellent durability in the long-term stability for HER and OER. Graphical abstract Image 1 Highlights • Highly dispersed CoNPs decorated uniform nitrogen doped graphene was prepared. • Polydopamine as nitrogen source, location reagent as well as connecting agent. • In situ grow of cobalt metal-organic frameworks (ZIF-67) as cobalt precursor. • High electrocatalytic performance for both HER and OER in alkaline media. [ABSTRACT FROM AUTHOR]

Fe N4O C Nanoplates Covalently Bonding on Graphene for Efficient CO2 Electroreduction and Zn CO2 Batteries (Adv. Funct. Zn CO 2 battery, atomically dispersed Fe N 4O, axial coordinations, covalent interactions, electrochemical CO 2 reductions Keywords: Zn CO 2 battery; atomically dispersed Fe N 4O; axial coordinations; covalent interactions; electrochemical CO 2 reductions EN Zn CO 2 battery atomically dispersed Fe N 4O axial coordinations covalent interactions electrochemical CO 2 reductions 1 1 1 07/06/23 20230704 NES 230704 B Electrochemical CO SB 2 sb Reduction b In article number 2300801, Huan Wang and co-workers report a graphene-supported Fe-N SB 4 sb O-C nanoplates electrocatalyst that drives a rechargeable Zn-CO SB 2 sb battery with energy supply and highly efficient conversion of CO SB 2 sb into CO, an important one-carbon building block for the synthesis of long-chain compounds. [Extracted from the article]

Developing electrochemical biosensor, particularly for high sensitive recognizing and detecting tumor marker at low level under benign conditions, is highly desired, but still remains a severe challenge. In this communication, we report a dual-signaling ratiometric method for sensitive detection of carcinoembryonic antigen (CEA) based on gold nanoparticles (Au NPs) functionalized Cu 2 S-CuS/graphene composite (Au-Cu 2 S-CuS/graphene) as the matrix material and carboxyl-Au nanoparticles (Au-COOH) functionalized mesoporous CeO 2 nanoparticles (Au-CeO 2 ) supported toluidine blue (TB) complex as signal label. The oxidation peak current of Cu 2 S-CuS decreases with the increase of CEA concentration, while the oxidation peak current of TB increases. The change of dual signals “Δ I = Δ I TB + |Δ I Cu2S-CuS |” (Δ I TB and |Δ I Cu2S-CuS | are the change values of the oxidation peak currents of TB and Cu 2 S-CuS, respectively) is used as the response signal for quantitative determination of CEA. Notably, the linear range is 0.001 ∼ 100 ng/mL with a detection limit of 0.78 pg/mL (S/N = 3). The ratiometric electrochemical system provides an extremely simple strategy for detecting tumor markers in a reliable, facile, sensitive, and specific manner, which has a promising application for quantitative detection of other tumor markers in clinical diagnosis. [ABSTRACT FROM AUTHOR]

Purpose The aim of this paper is to synthesize graphene-modified titanium dioxide (GR-TiO2) nanorod arrays nanocomposite films, so that these can enhance the photocatalytic properties of titanium dioxide and overcome the problem of difficult separation and recovery of photocatalysts.Design/methodology/approach The GR-TiO2 nanocomposite films were synthesized via hydrothermal method and spin-coating. The obtained samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), ultraviolet–visible (UV-Vis) diffuse reflectance spectrum and Raman spectrum. The photocatalytic performance of the GR-TiO2 nanocomposite films for degrading Rhodamin B under ultraviolet (UV) was studied by a UV-Vis spectrophotometer. The photocatalytic enhancement mechanism of graphene was studied by photoelectrochemical analysis.Findings The introduction of graphene expanded the range of the optical response of TiO2 nanorod arrays, improving the separation efficiency of the photogenerated electron-hole pairs, and thus dramatically increasing its photocatalytic performance.Research limitations/implications A simple and novel way for synthesizing GR-TiO2 nanocomposite films has enhanced the photocatalytic performance of TiO2.Originality/value The photocatalyst synthesized is easy to separate and recycle in the process of photocatalytic reaction, so it is possible to achieve industrialization. [ABSTRACT FROM AUTHOR]

Abstract: Bimetallic palladium–silver nanoparticles (NPs) supported on reduced oxide graphene (RGO) with different Pd/Ag ratios (Pd–Ag/RGO) were prepared by an easy green method which did not use any additional reducing agents or a dispersing agent. During the process, simultaneous redox reactions between AgNO3, K2PdCl4 and graphene oxide (GO) led to bimetallic Pd–Ag NPs. The morphology and composition of the Pd–Ag/RGO were characterized by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, thermogravimetric analysis and Raman spectroscopy. Cyclic voltammetry and chronoamperometry were used to investigate the electrochemical activities and stabilities of these Pd–Ag/RGO catalysts for the electro-oxidation of methanol and ethanol in alkaline media. Among the different Pd/Ag ratios, the Pd–Ag (1:1)/RGO had the best catalytic activities and stability. So it is a promising catalyst for direct alcohol fuel cell applications. [Copyright &y& Elsevier]

• Graphene aerogel prepared at different freeze-casting temperatures yield unequal electromagnetic properties. • Modulate absorption/reflection shielding performance through the introduction of new skeleton. • Graphene aerogel with different pore structures reveal different mechanical properties. We report a comprehensive analysis of the Electromagnetic (EM) properties of graphene aerogel-based shielding materials prepared by freeze casting. Controlling the freeze casting temperature allows for tailoring the pore sizes of graphene aerogels, which further affects the permittivity and EM shielding properties. To protect the aerogel structures from collapsing during high temperature heat-treatment, we used Melamine sponge (MS) as a supporting strut. Through a comparison with bare aerogels, we find that the presence of MS can significantly modify both the reflection and absorption performances and that an absorption-dominated shielding material can be obtained. After heat-treatment at 1000 °C for two hours, the MS-supported aerogel sample (MS-aero) showed a shielding efficiency of 55.8 dB. Our work shows that the material composition and the microstructural architecture of aerogels crucially influence their electromagnetic shielding efficiency. [ABSTRACT FROM AUTHOR]

Abstract: A rapid, environmental friendly, and sensitive biosensor for detection of zearalenone (ZEN) was developed at glassy carbon electrode (GCE) using nanoporous bimetallic alloy as label of secondary antibody (Ab2). The biosensor was prepared by immobilizing nitrogen-doped graphene sheets (N-GS) captured primary antibody (Ab1) on GCE. The analytes were then bound to Ab1 for further capture of antibodies, labeled by the nanoporous bimetallic alloy, nanoporous PtCo alloy (NP-PtCo). NP-PtCo with three-dimensional bicontinuous spongy structures and various hollow channels was prepared by corrosion of PtCoAl alloy, and exhibited remarkably improved electrocatalytic activity toward H2O2. Within ZEN concentration range (0.005–25ngmL−1), the biosensor exhibited a highly sensitive response to ZEN with a detection limit of 2.1pgmL−1. Several factors that would affect the performance of the biosensor were studied, such as erosion time of NP-PtCo, concentration of NP-PtCo, pH of buffer solution, and concentration of N-GS. After H2O2 was injected into the buffer solution, the amperometric response of the biosensor can be used to detect ZEN by chronoamperometry. The developed biosensor shows good selectivity and sensitivity to ZEN and is promising in feed safety analysis. [Copyright &y& Elsevier]

Abstract: Reduced graphene oxide/cadmium sulfide (RGO/CdS) hybrid material was synthesized by a one-step solvothermal method, wherein graphene oxide (GO) was a supporting material on which CdS nanoparticles were distributed homogeneously, and cadmium acetate (Cd(Ac)2·2H2O) was used as the CdS precursor. The supporting material RGO for CdS nanoparticles effectively enhanced their photocatalytic activities for the photodegradation of methylene blue in the aqueous solution. The optimum weight ratio of the GO to CdS in the hybrid material was 5.0%, which exhibited an excellent photodegradation efficiency (94%) and a better removal efficiency of total organic carbon (TOC) (57%), about 2.5 times and 5.1 times higher than that of pure CdS nanoparticles, respectively, under visible light (VL) irradiation. This improved photodegradation efficiency could be attributed to the increased adsorbability for methylene blue molecules, light absorption levels located in visible region, high charge transfer and separation ability, due to the introduction of a two-dimensional RGO network. [Copyright &y& Elsevier]

Abstract: A novel hedgehog-like core/shell structure, consisting of a high density of vertically aligned graphene sheets and a thin graphene shell/a copper core (VGs-GS/CC), has been synthesized via a simple one-step synthesis route using radio-frequency plasma-enhanced chemical vapor deposition (RF-PECVD). Scanning and transmission electron microscopy investigations show that the morphology of this core/shell material could be controlled by deposition time. For a short deposition time, only multilayer graphene shell tightly surrounds the copper particle, while as the deposition time is relative long, graphene sheets extend from the surface of GS/CC. The GS can protect CC particles from oxidation. The growth mechanism for the obtained GS/CC and VGs-GS/CC has been revealed. Compared to VGs, VGs-GS/CC material exhibits a better electron field emission property. This investigation opens a possibility for designing a core/shell structure of different carbon–metal hybrid materials for a wide variety of practical applications. [Copyright &y& Elsevier]

Abstract: A label-free amperometric immunosensor for fast and sensitive assay of human serum chorionic gonadotropin (hCG) is presented. hCG was immobilized on nanoporous gold (NPG) foils and using hydroquinone (HQ) redox species as indicator. The variation of amperometric response to the concentration of hCG, the target antigen, was evaluated by cyclic voltammetry in phosphate-buffered solution. Taking advantage of dual-amplification effects of the NPG foils and graphene sheets (GSs), the immunosensor exhibited a specific response to hCG in the range of 0.5–40.00ngml−1 with a detection limit of 0.034ngml−1 under optimal conditions. It was demonstrated that our proposed method possesses good accuracy, acceptable precision, and reproducibility. The NPG showed a better sensitizing effect and stability as immobilization matrices. [Copyright &y& Elsevier]