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Graphene oxide coating was prepared on the surface of pure titanium via using 3-aminopropyltriethoxysiiane. Scanning electron microscopy, raman spectroscopy) X-ray energy spectrometer and X-ray photoelectron spectroscopy were adopted to characterize the morphology > structure and composition of the coating. The biological activity of titanium sheets in different treatment groups was evaluated via in vitro cytotoxicity test; acute hemolysis test and SBF simulated body fluid immersion test. The results showed that the graphene oxide coating was prepared on the surface of pure titanium by silane coupling agent. The invitro cytotoxicity test and acute hemolysis test preliminarily confirmed that the composite coating had good biocompatibility. The SBF simulated body fluid immersion experiment showed that the graphene oxide coating could improve the ability of hydroxyapatite deposition on the surface of pure titanium. [ABSTRACT FROM AUTHOR]

Low flux and membrane fouling are major challenges in membrane distillation (MD) for treating concentrated wastewater. This study compared the performance of GO composite membranes with different interlayer distances, by covalently bonding the terminal amine groups of ethylenediamine (EDA) and 1,12-diaminododecane (DADD) with the carboxyl groups present on the GO sheets. The results indicated that the GO-DADD/PTFE membrane, with longer carbon chain cross-linking, achieved the highest flux and antifouling properties. At 70 °C, the pure water flux reached 68.5 kg/m2·h, and the fluxes for treating NaCl, HA containing NaCl, and BSA containing NaCl were 29.8 %, 37.1 %, and 38.5 % higher than the uncrosslinked GO/PTFE, and 95.7 %, 121.2 %, and 146.9 % higher than the PTFE membrane, respectively. Through mathematical models for mass and heat transfer, the study identified the key to this enhancement as the increased d-spacing within the GO layer due to cross-linking, which weakened the Kelvin effect and enhanced the vapor partial pressure on the hot side. The unique surface structure and electrostatic interactions induced by long-chain cross-linking further boosted the antifouling effect. These modifications not only overcome the typical trade-off between retention rates and flux but also offer a scalable and efficient solution for advanced membrane distillation applications. [Display omitted] • GO-DADD/PTFE membrane has the biggest d-spacing and highest flux. • The increase of flux mainly attributes to the alleviation of Kelvin effect. • D-spacing variation has little impact on GO layer desalination performance. • Crosslinking agents with longer carbon chains contribute to anti-fouling property. [ABSTRACT FROM AUTHOR]

A novel Al@reduced graphene oxide (Al@RGO) composite was designed and synthesized by a one-step hydrothermal method. We investigated the effect of the graphene on the microwave absorbing properties and infrared emissivity of composites. The crystal structure, microscopic morphology, infrared emissivity and electromagnetic parameters of the prepared samples were characterized by XRD, FESEM, TEM, XPS, dual band infrared emissometer and vector network analyzer. TEM and SEM show that the thin Al sheet is uniformly wrapped by RGO with a crumpled surface. Functionalized RGO and surface cation-modified Al sheets are tightly compounded through an electrostatic interaction. The oxygen content and defect from RGO as polarization center endows the material with enhanced molecular polarization and dipole polarization effect. The Al sheet is well coated with RGO, enhancing interface polarization and impedance matching. The minimum reflection loss (RL) of optimized Al@RGO composites is − 46.11 dB at 13.68 GHz under the coating thickness of only 2 mm. The bandwidth below − 10 dB can reach 4.88 GHz (11.52–16.4 GHz). Al sheet is a suitable base material for both microwave absorption and infrared stealth. The Al@RGO composites exhibit excellent infrared stealth ability, and their lowest infrared emissivity is 0.62. Thus, Al@RGO composites show potential application for both electromagnetic wave absorption and infrared stealth. [ABSTRACT FROM AUTHOR]

Various Cu nanoparticles dispersedly load on the sheet-like pyridoxine modification graphene oxide (GO-VB 6 -Cu) materials were successfully and systematically synthesized through a simple and facile approach, which reveal superior catalytic activity, i.e. low overpotential (0.140 V) for ethanol formation and high Faradaic efficiency of ethanol with 56.3% at the potential of −0.250 V vs. the reversible hydrogen electrode. This work may shed light on the design and preparation of novel functionalized carbon materials for efficient CO 2 electrochemical reduction. • GO-VB 6 -Cu exhibits high activity, selectivity and stability for electroreduction of CO 2. • The Cu loading used in GO-VB 6 -Cu can lower the EtOH formation overpotential and improve the EtOH formation efficiency. • The enhanced activity is attributed to the large ECSA, enhanced CO 2 adsorption, and low electron transfer resistance. Efficient electrochemical reduction of CO 2 to ethanol is a promising approach for obtaining high-density renewable energy storage and relieving environment stress. In this paper, we report the highly efficient electrochemical reduction of CO 2 to ethanol by using Cu nanoparticles decorated on pyridoxine modification graphene oxide sheets (GO-VB 6 -Cu) as robust electrocatalysts. CO 2 was efficiently reduced to ethanol in 0.1 M KHCO 3 solution by using GO-VB 6 -Cu-2 catalyst at an overpotential as low as 0.140 V. The maximum Faradaic efficiency for ethanol formation of 56.3% was obtained at the potential of −0.250 V vs. the reversible hydrogen electrode. The resultant nanocomposite presented no degradation after approximately 24 h of continuous operation, demonstrating the pronounced stability of the electrode. The notable reactivity toward CO 2 reduction achieved here can be ascribed to large electrochemically active surface area, enhanced CO 2 adsorption, and low electron transfer resistance. [ABSTRACT FROM AUTHOR]

We prepared transparent conducting composite electrodes composed of silver nanowires (Ag NWs) and reduced graphene oxide (r-GO). We present a simple approach to welding the cross-positions of the Ag NWs by applying pressure at a relatively low temperature (100°C). We examined the Ag NWs/r-GO composite films in terms of their transmission, conductivity, and stability. The plasmonic features of the Ag NWs were used to assist the ultraviolet (UV) light-induced reduction of the GO coating. The r-GO coatings used to form Ag NWs/r-GO composite structures increased the conductivity of the film by providing more efficient electron conductive pathways. The G/D intensity ratios of the GO and r-GO produced by the UV light-induced method without and with Ag NWs were 0.95, 1.01, and 1.04, respectively. The lowest sheet resistance of the composite films was 7 ohm/sq with approximately 82% transparency in the visible spectrum region. No degradation of the films was observed after 2 months. This excellent environmental stability might facilitate applications of Ag NWs/r-GO composite films in optoelectronic devices. [ABSTRACT FROM AUTHOR]

A controllable flower-like Pt-graphene oxide (PtNF-GO) architecture was synthesized through layer-by-layer electrostatic self-assembly. Hexadecyltrimethylammonium chloride (CTAC) micelles were employed as the template and Pt nanoflowers with different sizes were selectively synthesized by controlling the dissolved K2PtCl4 precursor and CTAC amounts in the reaction system. The prepared PtNF-GO was applied for DNA damage biomarker 8-hydroxy-2′-deoxyguanosine (8-OHdG) biosensing research. With the distinctive flower-like morphology of PtNFs and high electrical conductivity of GO, the PtNF-GO architecture shows excellent electrochemical biosensing performance towards the oxidation of 8-OHdG. A very low detection limit of 0.025 nM is obtained. Moreover, the fabricated PtNF-GO was used for the detection of 8-OHdG generated from the damaged DNA sample, which can be used to evaluate and confirm the mechanism of DNA damage, and it is of great importance in gene diagnosis, clinical and life sciences. [ABSTRACT FROM AUTHOR]

We firstly investigate the generation of terahertz (THz) wave from reduced graphene oxide (RGO) illuminated with femtosecond near-infrared laser pulse. Experiment results show that the THz generation from RGO can be enhanced by increasing the reduction degree and reducing the film thickness. The former can be attributed to the increase of sp 2 carbon region, which has much smaller band gap and graphene-like photoelectric properties. The latter is due to the suppression of the light-induced lateral currents in the surface of RGO layers. The linear dependency of the THz electrical field on the pump power confirms that the THz emission from RGO is governed by second-order nonlinear properties. When exciting laser irradiates from opposite sample sides, π phase shift of the generated THz wave has been observed, suggesting the transient photocurrent related to THz emission is induced by the photon drag effect. The conclusion has been further confirmed by the well fitting of the experiment and theoretical calculation based on the symmetry of RGO. This work makes it clear the THz generation mechanism of RGO and paves a way for developing new THz sources. [ABSTRACT FROM AUTHOR]

Reduced graphene oxide (rGO) wrapped n -type BiOI hybrids for enhanced photoelectrocatalytic (PEC) degradation of organic pollutants is reported. The Scanning Electron Microscope (SEM) images showed that the rGO was homogeneously coated on the surface of BiOI, forming a core@shell structure. Raman spectra, Fourier transform infrared (FT-IR) spectra, and X-ray photoelectron spectroscopy (XPS) analyses showed that an intense interaction was formed between rGO and BiOI, which could highly promote the photo-generated charge transfer rate and photoelectric conversion efficiency. It was experimentally demonstrated that the degradation efficiency of organic pollutants for PEC process was 40.6% and 62.7% higher than that of photocatalytic (PC) and electrocatalytic (EC) processes, respectively. Further analyses indicated that the improvement in PEC degradation of organic pollutants benefited from: (1) a strong interaction and a wide range of conjugation were formed in the hybrid system; (2) negative shifts for the flat band potential in case of BiOI@rGO composites. [ABSTRACT FROM AUTHOR]

An effective electromagnetic interference (EMI) shielding cyanate ester (CE) composite has been fabricated with a combination of graphene nanosheets (GNSs) and nickel ferrite (NiFe2O particles. NiFe2O4 particles were loaded on the reduced graphene oxide (RGO) to improve the dispersibility while the composites were synthesized via solution blending method. Scanning electron micrographs (SEM) showed good dispersion of GNSs and RGO-NiFe2O4 in CE. Electromagnetic properties and EMI shielding effectiveness (SE) of the nanocomposites were determined over X-bands (8.2-12.4GHz). It was observed that the EMI shielding performance of composites was improved by increasing the filler loading of composites and absorption was found to be the dominant shielding mechanism. The total EMI SE is almost reaching 50dB for samples with thicknesses of 2.7mm, which suggests that the GNSs/RGO-NiFe2O4/CE could be good candidates for highly efficient EMI shielding materials in the whole X-band. This work provides promising EMI-shielding polymer composites by incorporating both GNSs and RGO-NiFe2O4 into CE matrix. It was found that the shielding mechanism of this composite was dominated by absorption. The average SE total of the composites was found to be substantially improved due to the increased electrical conductivity, reaching almost 50 dB for samples with thicknesses of ∼2.7mm, which suggests the GNSs/RGO-NiFe2O4/CE could be good candidates for highly efficient EMI-shielding materials in the whole X-band. [ABSTRACT FROM AUTHOR]

A reduced graphene oxide (rGO) wrapped Bi 2 WO 6 (Bi 2 WO 6 @rGO) hybrid as photoelectrode for enhanced photoelectrocatalytic (PEC) degradation of organic pollutants is reported, which exhibited excellent charge separation and photoconversion efficiency. The core@shell structured Bi 2 WO 6 @rGO photoelectrode yielded a pronounced 1.56-fold and 23.8-fold photocurrent density at 1.0 V vs. saturated calomel electrode (SCE), than that of loading structured Bi 2 WO 6 -rGO and pure Bi 2 WO 6 . The Bi 2 WO 6 @rGO hybrid exhibited enhanced photoelectrocatalytic efficiency for degradation of Rhodamine B (RhB), which was 43.0% and 65.6% higher than that of photocatalytic (PC) and electrocatalytic (EC) processes, respectively. The enhancement in PEC degradation of RhB benefited from: (1) a strong interaction and a wide range of conjugation were formed in the core@shell system; (2) a 0.26 V of flat band potential was negatively shifted in case of Bi 2 WO 6 @rGO composite; (3) the photogenerated electrons and holes could be spatially separated by external electric potentials. [ABSTRACT FROM AUTHOR]

In this work, the assembly between one-dimensional (1D) nanomaterials and two-dimensional (2D) nanomaterials was achieved by a simple method. Cuprous oxide nanowires decorated graphene oxide nanosheets (Cu 2 O@GO) nanocomposites were synthesized for the first time by a simple electrostatic self-assembly process. The nanostructure was well confirmed by scanning electron microscope (SEM) and transmission electron microscope (TEM) images. Taking advantages of good electrocatalytic activity and high specific surface area of Cu 2 O@GO nanocomposites, a label-free electrochemical immunosensor was developed by employing Cu 2 O@GO as signal amplification platform for the quantitative detection of alpha fetoprotein (AFP). In addition, toluidine blue (TB) was used as the electron transfer mediator to provide the electrochemical signal, which was adsorbed on graphene oxide nanosheets (GO NSs) by electrostatic attraction. The detection mechanism was based on the monitoring of the electrochemical current response change of TB by the square wave voltammetry (SWV) when immunoreaction occurred on the surface of electrode. Under optimal conditions, the proposed immunosensor displayed a high sensitivity and a low detection limit. This designed method may provide an effective method in the clinical diagnosis of AFP and other tumor markers. [ABSTRACT FROM AUTHOR]

In this work, an ultrasensitive electrochemical sensor was developed for detection of Hg 2+ . Gold nanoparticles decorated bovine serum albumin reduction of graphene oxide (AuNP-BSA-rGO) were used as subsurface material for the immobilization of triple-helix DNA. The triple-helix DNA containing a thiol labelled single-stranded DNA (sDNA) and a thymine-rich DNA (T-rich DNA), which could be unwinded in the present of Hg 2+ to form more stable thymine–Hg 2+ –thymine (T–Hg 2+ –T) complex. T–Hg 2+ –T complex was then removed and the sDNA was left on the electrode. At this time, gold nanoparticle carrying thiol labelled cytosine-rich complementary DNA (cDNA-AuNP) could bind with the free sDNA. Meanwhile, the other free cDNA on AuNP could bind with each other in the present of Ag + to form the stable cytosine–Ag + –cytosine (C–Ag + –C) complex and circle amplification. Plenty of C–Ag + –C could form silver nanoclusters by electrochemical reduction and the striping signal of Ag could be measured for purpose of the final electrochemical detection of Hg 2+ . This sensor could detect Hg 2+ over a wide concentration range from 0.1 to 130 nM with a detection limit of 0.03 nM. [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]

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]

Simultaneous redox reactions between K 2 PdCl 4, HAuCl 4, AgNO 3 , and graphene oxide (GO) are used to prepare Pd-Au-Ag nanoparticles (NPs) supported on reduced graphene oxide (RGO) by a facile method. The GO serves as the reducing agent, the stabilizing agent and the support. The morphology and composition of the Pd-Au-Ag(1:1:1)/RGO NPs are characterized by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, thermo-gravimetric analysis, Raman spectroscopy and electrochemical measurements. The prepared Pd-Au-Ag(1:1:1)/RGO has good electrocatalytic activity and stability for the oxidation of methanol and ethanol in alkaline media. This prepared Pd-Au-Ag(1:1:1)/RGO catalyst should have great potential for use in direct alcohol fuel cell. [ABSTRACT FROM AUTHOR]

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]

We report a novel composite graphene oxide (GO)/NiFe 2 O 4 /TiO 2 nanorod arrays (NRAs) prepared by calcinating and dipping, TiO 2 NRAs were prepared via hydrothermal method. XRD, SEM, XPS, and PL, show that GO/NiFe 2 O 4 /TiO 2 NRAs have been successfully synthesized having enhanced photocatalytic performance. Furthermore, the optimal degradation conditions of unsymmetrical dimethylhydrazine (UDMH) using the catalyst were obtained by orthogonal and single-factor experiment. Moreover, the possible photocatalytic mechanism is briefly discussed; under visible light, electrons and holes excited from NiFe 2 O 4 can be effectively separated due to the band energy matching between NiFe 2 O 4 and TiO 2. In addition, photogenerated electrons can quickly migrate to GO owing to the conduction band, as the position of NiFe 2 O 4 is more negative than the Fermi level of GO. The electrons and holes were well separated so that they can efficiently participate in the degradation of UDMH, resulting in enhancement of photocatalytic activity. • AA novel composite catalyst GO/NiFe 2 O 4 /TiO 2 NRAs was prepared for the first time. • It exhibits enhanced photocatalytic activity in degradation of UDMH, due to the efficient separation of carriers. • The optimal degradation conditions of UDMH under this catalyst are also achieved. [ABSTRACT FROM AUTHOR]

To develop iron-based materials for energy storage is an important issue because of their low cost, abundant storage and high theoretical specific capacitances. Fe(OH) 3 colloids stabilized by FeCl 3 are used as the precursor to fabricate with carbon from glucose and graphene oxide (GO) to prepare superparamagnetic iron oxide/carbon/rGO (reduced graphene oxide) composite for enhanced energy storage performance. Glucose or graphene oxide cannot avoid the aggregation of iron oxides when they are used separately; however, the simultaneous addition of glucose and graphene oxide can supress the aggregation of iron oxide nanoparticles, which is beneficial for energy storage. The characterization results of Fe 2 O 3 -based composites, including XRD, TEM and XPS, reveal that iron oxide nanocrystals in the composites are γ-Fe 2 O 3. The simultaneous utilization of GO and glucose leads to higher saturation magnetizations of iron oxide than GO or glucose does, and the saturation magnetization of iron oxide in the iron oxide/carbon/rGO composite can be up to 83 emu g−1. More importantly, the iron oxide/carbon/rGO composites have much higher energy storage performance than that of iron oxide/carbon or iron oxide/rGO samples. The specific capacitance of the composites can reach 400 F g−1 and the retention can remain 92% after 2500 cycles. Image 1 • Carbon and graphene oxide can induce the prodution of superparamagnetic iron oxide nanoparticles from Fe(OH) 3 colloids. • The structure of iron oxide/carbon/rGO can avoid the growth and aggregation of iron oxide nanoparticles. • The Fe 2 O 3 /carbon/rGO composite has better energy storage performance than that of Fe 2 O 3 /carbon and Fe 2 O 3 /rGO. [ABSTRACT FROM AUTHOR]

A novel hybrid structure sensor based on cobalt carbonate hydroxide hydrate (CCHH) and reduced graphene oxide (RGO) was designed for room temperature NH3 detection. This hybrid structure consisted of CCHH and RGO (synthesized by a one-step hydrothermal method), in which RGO uniformly dispersed in CCHH, being used as the gas sensing film. The resistivity of the hybrid structure was highly sensitive to the changes on NH3 concentration. CCHH in the hybrid structure was the sensing material and RGO was the conductive channel material. The hybrid structure could improve signal-to-noise ratio (SNR) and the sensitivity by obtaining the optimal mass proportion of RGO, since the proportion of RGO was directly related to sensitivity. The gas sensor with 0.4 wt% RGO showed the highest gas sensing response reach to 9% to 1 ppm NH3. Compared to a conventional gas sensor, the proposed sensor not only showed high gas sensing response at room temperature but also was easy to achieve large-scale production due to the good stability and simple synthesis process. [ABSTRACT FROM AUTHOR]

Co-doped CeO 2 /reduced graphene oxide (RGO) nanocomposites were prepared successfully by a simple solvothermal method using cobalt nitrate, cerium nitrate, and graphene oxide. The structure, micromorphology, material composition, and electromagnetic properties of the nanocomposites were investigated by X-ray Power diffraction, X-ray photoelectron spectroscope, transmission electron microscope, and vector network analyzer. The microwave absorption performance of nanocomposite in 2–18 GHz was calculated in accordance with transmission line theory. These results suggest that Co-doped CeO 2 /RGO composites do not influence the cubic fluorite structure of CeO 2 and that Co-doped CeO 2 nanoparticles were densely attached onto the RGO sheets (GSs). The Co-doped CeO 2 /RGO composites also enhanced microwave absorption properties owing to the synergetic effect between the Co-doped CeO 2 nanoparticles and GSs and the unique structure of CeO 2 . When the added molar ratio of Co(NO 3 ) 2 ·6H 2 O and Ce(NO 3 ) 3 ·6H 2 O was 1:6, the composites attained the optimal microwave absorption of −53.66 dB at 6.4 GHz under the coating thickness of 3.5 mm. By contrast, frequency bandwidths below −10 and −20 dB were 4 and 1.28 GHz, respectively, under the coating thickness of 2.0 mm. [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]

What is essential to solving energy scarcity problems is that develop the high activity, durable and non-noble metal-based dual-functional electrocatalysts for hydrogen evolution reactions (HER) and oxygen evolution reactions (OER). In this work, a series of core-shell structure M@Fe–Cu-GR nanocubes (NCs) are prepared. In the prepared process, the bimetallic FeCu prussian blue analogues (PBA) is used as precursor, transition metals ions Co2+ and Ni2+ are introduced into the FeCu-PBA using the exchange of potassium ions with other metal ions, and then the FeCu-PBA are successfully loaded on the graphene oxide (GO) employed the attraction of opposite charges between polydiallyldimethylammonium chloride (PDDA) and GO. Electrochemical tests show that the Tafel slope of Co–Ni@Fe–Cu–GR NCs for HER and OER are 60 and 82 mV dec−1, respectively, and Co–Ni@Fe–Cu–GR NCs shows excellent performance in long-term stability test. • Core-shell structure M@Fe–Cu–GR nanocubes (M = Co, Ni) were prepared. • Introduction the metals into the PBA by the exchange of potassium-tannic acid. • The opposite charge attraction was employed to anchor MOFs on the GO. • The formation of core-shell structure and graphene were realized in one step. • High electrocatalytic performance for both HER and OER. [ABSTRACT FROM AUTHOR]

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]

Graphical abstract Highlights • Ultrasensitive electrochemical aptasensor was developed for detecting Pb2+. • Au@p-rGO was applied as support for immobilizing the aptamer. • Au NPs@GO as signal probe exhibited high electrocatalytic activity towards H 2 O 2. • The aptasensor displayed low detection limit of 1.67 pmol/L for Pb2+. Abstract A sensitive electrochemical aptasensor was designed based on gold modified graphene nanocomposite with different morphologies for the detection of lead ion (Pb2+). Specifically, a sulfydryl-labeled substrate strand (Apt1) and a sulfydryl-labeled catalytic strand (Apt2) were devised in fabricating the electrochemical aptasensor. Gold modified porous reduced graphene oxide (Au@p-rGO) was synthesized and applied as support for immobilizing the Apt1. And gold modified graphene oxide (Au NPs@GO) was employed as signal probe and connected with Apt2 to realize the immobilization of it on the electrode by means of the principle of complementary base pairing. The current signal can be obtained by recording the electrocatalytic conditions toward H 2 O 2. The Pb2+-dependent DNAzyme could play a role when Pb2+ existed. With the increase of the concentration of Pb2+, the current response revealed a diminishing signal, thus realizing the sensitive detection of Pb2+. Under the optimal conditions, the fabricated electrochemical aptasensor exhibited a linear response toward Pb2+ ranging from 5 pmol/L to 1 μmol/L, together with a low limit of detection of 1.67 pmol/L. Moreover, the prepared aptasensor displayed outstanding selectivity, acceptable stability and superior reproducibility for detecting Pb2+. This proposed tactics may provide reference and potential applications for detecting some other heavy metal ions. [ABSTRACT FROM AUTHOR]

Exploring metal-free catalysts for electroreduction of CO 2 into value-added fuels has been a crucial challenge in nowadays society. Herein we report some metal-free electrocatalysts for electrocatalytic reduction of CO 2 to liquid products, such as ethanol and acetone. We develop functionalized graphene oxide (GO) surfaces with five pyridine derivatives: pyridoxine, 4-hydroxypyridine, 4-aminopyridine, 8-hydroxyquionline, and 5-amino-1,10-phenanthroline. Remarkably, pyridoxine modified on GO sheets with the pyridinic N content of 2.32% shows the optimum catalytic ability for electrochemical reduction of CO 2 , and the overall faradaic efficiency reaches up to 45.8%. Besides, other four pyridine derivatives functionalized GO exhibit various abilities for CO 2 reduction to ethanol and acetone. The experimental results show that N-doping can alter the electronic properties of GO for enhancing the catalytic active for CO 2 electroreduction, which is closely associated with the content of modified pyridinic N and the special structure of modified pyridine derivatives. Our work may provide inventive thought to design metal-free electrocatalysts for CO 2 reduction to useful chemical fuels. [ABSTRACT FROM AUTHOR]

A novel electrochemiluminescence (ECL) signal-off strategy based on CuS in situ grown on reduced graphene oxide (CuS-rGO) quenching luminol/H 2 O 2 system was firstly proposed. Luminol was grafted on the surface of Au@Fe 3 O 4 -Cu 3 (PO 4 ) 2 nanoflowers (Luminol-Au@Fe 3 O 4 -Cu 3 (PO 4 ) 2 ) which exhibited excellent catalytic effect towards the reduction of H 2 O 2 to enhance the ECL intensity of luminol. Cu 3 (PO 4 ) 2 nanoflowers showed large surface area which can immobilize more Fe 3 O 4 and Au nanoparticles. The quenching mechanism of CuS-rGO was due to ECL resonance energy transfer (RET). The spectral overlap between fluorescence spectrum of Luminol-Au@Fe 3 O 4 -Cu 3 (PO 4 ) 2 and UV–vis absorption spectrum of CuS-rGO revealed that resonance energy transfer was possible. Au nanoparticles were immobilized on the surface of CuS-rGO to capture secondary antibodies. After a sandwich-type immunoreaction, a remarkable decrease of ECL signal was observed. Under the optimal conditions, the immunosensor showed excellent performance for N-terminal pro-brain natriuretic peptide (NT-proBNP) detection with a wide detection range from 0.5 pg mL −1 to 20 ng mL −1 and a low detection limit of 0.12 pg mL −1 (S/N = 3). The prepared NT-proBNP immunosensor displayed high sensitivity, excellent stability and good specificity. [ABSTRACT FROM AUTHOR]

The RGO/AuNPs/CS/ZnTCPP nanocomposites were successfully prepared with reduced graphene oxide (RGO) loaded with Au nanoparticles (AuNPs) existed in chitosan (CS) and water-soluble zinc meso-tetra (4-carboxylphenyl) porphyrin (ZnTCPP) by π-π nanoassembly method and were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), 1 H NMR spectra and UV–vis absorption spectroscopy. The most important advantage of the RGO/AuNPs/CS/ZnTCPP nanocomposites was environmentally friendly. Indium tin oxide (ITO) electrode surface was modified with the RGO/AuNPs/CS/ZnTCPP nanocomposites exhibited a good photocurrent response at −0.2 V under whitelight of Xenon lamp illumination. The photocurrent response could be greatly increased by adding hydroquinone (HQ) to the solution. Electrons of ZnTCPP were excited from HOMO to LUMO by irradiating light. The photoexcited electrons injected into the RGO, and then transferred to AuNPs further to the ITO. Addition of HQ resulted in the enhanced photocurrent signal by acting as a sacrificial electron donor; Thereby scavenged the photogenerated holes of the excited ZnTCPP and oxidized to benzoquinone (BQ). Based on the above interaction, detection of HQ was developed by a novel photoelectrochemical (PEC) sensor (S/N = 3) with a linear range from 5 to 300 nmol/L (r = 0.997) and detection limit of 0.5 nmol/L. Proposed biosensor is simple, rapid and this was successfully applied for the quantification HQ in the real sample matrices. [ABSTRACT FROM AUTHOR]

An original electrochemiluminescent (ECL) luminophore porphyrin nanosphere–graphene oxide composite (TCPP NS-GO) was prepared. The TCPP NS-GO could produce greatly enhanced ECL in buffer with potassium peroxydisulfate (K 2 S 2 O 8 ) as the co-reactant. The enhancement ECL mechanism of TCPP NS-GO/K 2 S 2 O 8 system was investigated in detail. Moreover, The TCPP NS-GO composite had an abundant surface functional group to expand its application, which exhibited high sensitivity and selectivity to Fe 3+ . The wide linear relationship between ECL intensity and Fe 3+ concentration from 0.002 to 5.128 μmol L −1 (R 2 = 0.998) was found with the detection limit as low as 1 nmol L −1 . The ECL quenching mechanism of Fe 3+ was proved by UV-vis absorption spectroscopy, Fluorescence emission spectroscopy (FL) and Fourier transform infrared spectroscopy (FT-IR) analysis technology. [ABSTRACT FROM AUTHOR]

Fabrication of low-cost and efficient electrocatalyst for oxygen reduction reaction (ORR) is highly desirable. Herein, Zinc ferrite/reduced graphene oxide (ZnFe 2 O 4 /rGO) is prepared by a quite simple and environmentally benign approach and applied as a high performance ORR electrocatalyst for the first time. The surface morphology and chemical composition of ZnFe 2 O 4 /rGO are characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, thermogravimetric analysis and Fourier transform infrared spectroscopy. Cyclic voltammetry, linear sweep voltammetry and chronoamperometry are used to evaluate the electrochemical activities and stabilities of ZnFe 2 O 4 /rGO catalysts in alkaline media. Among ZnFe 2 O 4 /rGO with different mass ratios, the catalyst with 69.8 wt% ZnFe 2 O 4 (called ZnFe 2 O 4 /rGO (3)) has the best catalytic activities and it shows much superior methanol tolerance and better durability than the commercial Pt/C catalyst. Due to the synergistic effect, the ZnFe 2 O 4 /rGO (3) nanohybrid exhibits high ORR catalytic performance and durability, which follows a desirable four electron transfer mechanism in alkaline media. Therefore, it may be a highly competitive catalyst for fuel cells and metal-air batteries. [ABSTRACT FROM AUTHOR]

Generally, the photoanodic photoelectrochemical (PEC) immunoassay method has an outstanding photocurrent and low detection limit, but its poor anti-interference ability in the detection of real samples restricts its performance. The photocathode immunoassay method has an excellent ability to see interference in actual sample detection, but it has its own defect in that the photocurrent is not obvious. Here, a promising new cathodic PEC immunosensing platform is reported, which integrates a photocathode and photoanode. The photoanode and photocathode are WO 3 /Mn:CdS composite modified and reduced graphene oxide (RGO) modified indium tin oxide (ITO) electrodes, respectively. In addition to an excellent PEC response, the immunosensor constructed by the integrating the photoanode and photocathode also has good anti-interference ability in actual sample analysis. The constructed immunosensor achieves accurate detection of NSE with a range from 5.0 pg/mL to 20 ng/mL, and the limit of detection (LOD) is 1.2 pg/mL. The proposed immunoassay method has good stability, selectivity and reproducibility. Moreover, it introduces new ideas for the construction of PEC immunosensors. [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]

[Display omitted] • A self-adhesive tannin–graphene supramolecular pH-sensitive material is proposed. • The material adheres well to various solid and soft substrates. • The sensor exhibits reversible, Nernstian and selective pH responses. • The material can be printed directly to fabricate a wearable sensor for sweat pH monitoring. The pH of sweat is the most common biochemical parameter monitored by integrated wearable devices. A crucial factor in sensing materials for wearable applications is strong contact both with the skin and with the electrode substrate. Currently, the deposition of many sensitive materials on a substrate relies on mixing a small amount of binder, which raises the issue of biocompatibility and the risk of detachment. Herein, we report self-adhesive tannin–graphene supramolecular aggregates for use in wearable potentiometric pH sensors. The abundant phenolic hydroxyl groups in tannin (TA) result in strong adhesion and are also the pH response sites. The graphene (reduced graphene oxide, RGO) induces the supramolecular formation of TA and promotes electron transfer based on the π-π conjugation interaction. The pH sensor has a reversible and Nernstian response, and is not affected by potentially interfering ions. Owing to the strong adhesion of TA–RGO, a wearable pH device was directly fabricated using a dispensing printing technique. The sensor has been shown to be successful in monitoring the pH of sweat in real time. This work emphasizes the importance of the adhesion of sensing materials for use in wearable electrochemical sensors. [ABSTRACT FROM AUTHOR]

Abstract: A green and efficient approach for the synthesis of graphene decorated with silver nanoparticles is demonstrated by simultaneously reducing both graphene oxide (GO) sheets and silver ions with glucose as the reducing agent and poly(N-vinyl-2-pyrrolidone) (PVP) as the surface modifier. Different silver-containing materials are obtained by changing the synthesis temperature. The oxygen-containing groups of the substrate influence its decoration with the in situ formed silver nanoparticles. The combination of glucose and a silver–ammonia solution, as well as maintaining a good dispersion of GO by using PVP are crucial for the decoration of graphene with silver nanoparticles. The materials exhibit a distinct surface-enhanced Raman scattering effect. [Copyright &y& Elsevier]

• Manganese-eumelanin coordination nanocomposites quenched ECL behavior of luminol. • Luminol was anchored on PtCo and CuFe 2 O 4 nanoparticles decorated with rGO. • Quenching mechanism maybe inhibit electrooxidation of H 2 O 2 and ECL energy transfer. • The sandwich quenching ECL immunosensor was used to detect procalcitonin. Herein, a facile one-pot intrapolymerization strategy to synthesize manganese-eumelanin coordination nanocomposites (Mn-Eu) was introduced to quench the electrochemiluminescence (ECL) behavior of luminol/H 2 O 2 system. Bimetallic PtCo and CuFe 2 O 4 nanoparticles decorated with reduced graphene oxide was prepared to combine with luminol via electrostatic attractions (Lu-PtCo-CuFe 2 O 4 -rGO) which possessed excellent ECL signals. PtCo-CuFe 2 O 4 -rGO not only exhibited well electrocatalytic activity toward the electrooxidation reactions of luminol and H 2 O 2 , but also facilitated the electroreduction of H 2 O 2 producing more reactive oxygen species (ROSs) which can further enhance the ECL intensity of luminol. To sensitively detect procalcitonin, Mn-Eu labeled-secondary antibodies were employed to specific recognize antigen which incubated with primary antibodies/Lu-PtCo-CuFe 2 O 4 -rGO. The quenching mechanism may be via the synergistic effect between Mn-Eu inhibiting the electrooxidation of H 2 O 2 and ECL resonance energy transfer (ECL-RET) from ECL donor luminol to ECL acceptor Mn-Eu. Under optimal experiments, the ECL immunosensor for detecting procalcitonin with a wider linear range from 0.005 pg/mL to 100 pg/mL and a detection limit of 0.0021 pg/mL (S/N = 3) was obtained. The suggested strategy possessed great potential in bioanalysis and will broaden the application of Mn-Eu. [ABSTRACT FROM AUTHOR]

An electrochemical biosensor was fabricated for reliable and highly sensitive microRNA-21 assay by catalytic hairpin assembly and Pd nanoparticles-DNA layered nanoreticulation, providing a new way in the biochemical assay for detecting microRNA-21 in early disease diagnosis. • The sensitive biosensor was constructed for the detection of miR-21 based on CHA and Pd NPs-DNA LNR. • This biosensor shows low limit of detection and wide dynamic correlation of miR-21, providing a powerful platform for detecting miR-21. • The proposed method was enzyme-free, PCR-free, and convenient without the requirement of any additional separation steps. Herein, a Pd nanoparticles-DNA layered nanoreticulation (Pd NPs-DNA LNR) sensor was assembled to a graphene oxide (GO)-modified electrode by catalytic hairpin assembly (CHA) and a self-assembly process. In this process, GO was modified on the electrode surface to provide -COOH sites for DNA bonding. Moreover, with the CHA circular amplification strategy, many single DNA1 were exposed to be able to be bound with Pd-DNA2 for the formation of the Pd NPs-DNA LNR, which enabled the ultrasensitive detection of microRNA-21 (miR-21) with a low limit of detection 63.1 aM. This strategy combines the amplification technology of CHA and Pd NPs-DNA LNR with Pd NPs. Such a layered nanoreticulation material can support abundant Pd NPs to avoid aggregation and obtain enhanced electrochemical signals. Significantly, this method can be successfully applied in tumor cell lysates and provides a neoteric channel for early disease diagnosis. [ABSTRACT FROM AUTHOR]

To explore a green, low-cost, and efficient strategy to synthesis reduced graphene oxide (RGO), the process and mechanism of the graphene oxide (GO) reduction by a model electrochemically active bacteria (EAB), Geobacter sulfurreducens PCA, were studied. In this work, up to 1.0 mg mL−1 of GO was reduced by G. sulfurreducens within 0.5–8 days. I D /I G ratio in reduced product was similar to chemically RGO. After microbial reduction, the peak which corresponded to the reflection of graphene oxide (001) disappeared, while another peak considered as graphite spacing (002) appeared. The peak intensity of typical oxygen function groups, such as carboxyl C–O and >O (epoxide) groups, diminished in bacterially induced RGO comparing to initial GO. Besides, we observed the doping of nitrogen and phosphorus elements in bacterially induced RGO. In a good agreement with that, better electrochemical performance was noticed after GO reduction. As confirmed with differential pulse voltammetry (DPV) and cyclic voltammetry (CV) analysis, the maximum value of peak currents of bacterially induced RGO were significantly higher than those of GO. Our results showed the electron transfer at microbial cell/GO interface promoted the GO reduction, suggesting a broader application of EAB in biological mediated production of RGO. Image 1 • Provided a green chemistry strategy for the biological production of reduced graphene oxide (RGO) by Geobacter. • Bacterially induced RGO by Geobacter exhibited a good performance in electrochemical conductivity. • The doping of nitrogen and phosphorus elements were observed in the bacterially induced RGO by Geobacter. • Extracellular electron transfer at microbial cell/GO interface promoted the graphene oxide (GO) reduction of Geobacter. [ABSTRACT FROM AUTHOR]

The synthesis and development of catalyst with efficient electrocatalytic activity and long-term operation stability was a critical of hydrogen production for water splitting, however it is still a challenging step. Herein, a series of different proportion bimetallic uploaded nitrogen-doped graphene materials (Fe 2 O 3 -Co NPs-N-GR) were successfully synthesized through a simple, green and cost-effective method for efficient hydrogen evolution reaction (HER). All of the materials we used were earth-abundant and inexpensive. In this work, employing the interaction between DA and metal ions, Co2+ and iron (II) phthalocyanine (FePC) were loaded on the graphene oxide (GO). Moreover, the doping of N, reduction of GO and forming of Fe 2 O 3 NPs, Co NPs were realized by one-step calcination method. Among the series of catalysts we synthesized, Fe 2 O 3(1) -Co (1) NPs-N-GR exhibits better HER performance than other catalysts that we synthesized. Fe 2 O 3(1) -Co (1) NPs-N-GR exhibits significant catalytic activity and excellent durability for HER in a wide pH range. The electrocatalytic performance of Fe 2 O 3(1) -Co (1) NPs-N-GR toward HER is better in acidic solution (0.5 M H 2 SO 4) than in alkaline solution (1.0 M NaOH), the onset overpotential is 0.36 V, Tafel slope is 66 mV dec−1 and current densities of 10 mA cm−2 at overpotential is 0.39 V. The excellent HER catalytic performance of Fe 2 O 3(1) -Co (1) NPs-N-GR stem from its unique composition and structural properties by combining Fe 2 O 3 -Co nanoparticles and N co-doped graphene. This work provides a new valuable idea for the design of highly active bimetallic N-doped graphene electrocatalyst for HER. Unlabelled Image • A series of Fe 2 O 3 and Co bimetallic N-doped graphene materials were synthesized. • Achieving the uniformity loading of Co and Fe 2 O 3 used the localization of PDA. • The doping of N, reduction of GO were realized by one-step calcination method. • Fe 2 O 3(1) -Co (1) NPs-N-GR shows high electrocatalytic activity toward HER. [ABSTRACT FROM AUTHOR]