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A promising electrochemical sensing platform for the detection of ponceau 4R in food has been fabricated based on the carboxylated graphene oxide (GO-COOH), metal–organic framework (MOF) UIO-66-NH2, and poly (3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). To this end GO-COOH was covalently coupled with UIO-66-NH2 through amide reaction, endowing the material (GO-CONH-UIO-66) unique hierarchical pores and high chemical stability and as a result improving the conductivity of MOF and the dispersion of GO. After the addition of PEDOT:PSS into GO-CONH-UIO-66, the continuity and conductivity of the composite (PEDOT:PSS/GO-CONH-UIO-66) have been further enhanced, due to the high conductivity, favorable film-forming, and hydrophilic properties of PEDOT:PSS. Systematic electrochemical experiments confirm that the PEDOT:PSS/GO-CONH-UIO-66/GCE shows satisfactory electrochemical sensing properties towards the detection of ponceau 4R, with a wide linear detection range of 0.01–30 μM, a low limit of detection of 3.33 nM, and a high sensitivity of 0.606 μA μM−1 cm−2. The PEDOT:PSS/GO-CONH-UIO-66 sensing platform was successfully used to detect ponceau 4R in beverage, and the detection results were compared with high-performance liquid chromatography. As a result, the PEDOT:PSS/GO-CONH-UIO-66 composite shows a promising application prospect for rapid detection of ponceau 4R in food and will play significant role in food safety detection and supervision. [ABSTRACT FROM AUTHOR]

In this work, a two-dimensional leaf-like framework-L embedded electrochemically reduced graphene oxide (ERGO@ZIF-L) was proposed as an outstanding electrode material for the sensitive electrochemical sensing of benomyl (BM). ZIF-L is surrounded by ERGO, which could effectively ensure the stability and dispersion of ZIF-L. With this unique combination, the prepared ERGO@ZIF-L displayed excellent synergistic characteristics with a large surface area, excellent conductivity, plentiful active sites, and high electrocatalytic properties, thus endowing it with high sensitivity for BM determination. The experimental parameters, such as solution pH, material volume, and accumulation time, were optimized. Under optimal conditions, the BM sensor showed a wide linear range (0.009–10.0 μM) and low-limit detection (3.0 nM). Moreover, the sensor displayed excellent stability, repeatability, and reproducibility, and good anti-interference capability. The method was successfully applied to detect BM in real-world samples. [ABSTRACT FROM AUTHOR]

Herein, Ti3C2Tx MXene/N-doped reduced graphene oxide (MXene/N-rGO) composite was employed as the electrocatalyst to construct a new electrochemical sensing platform for the determination of adrenaline (AD). The MXene/N-rGO was synthesized via a facile one-step hydrothermal method, where ethylenediamine acted as a reducing agent and N source. The doped N in rGO served as a bridge between MXene and rGO through tight hydrogen bonds. Scanning electron microscopy showed that large numbers of MXenes with accordion-like morphology were distributed on the surface of the N-rGO. The MXene/N-rGO composite displayed a synergetic catalytic effect for oxidizing AD, originating from the unique catalytic activity of N-rGO and the large surface area and satisfactory conductivity of MXene. These characteristics of composite material led to a remarkable effect on signal amplification for the detection of AD, with a wide linear range from 10.0 nM to 90.0 μM and a low detection limit of 3.0 nM based on a signal to noise ratio of 3. Moreover, the MXene/N-rGO electrode displayed good stability, repeatability, and reproducibility. Additionally, the proposed sensor was successfully applied for voltammetric sensing of AD in urine with recoveries from 97.75% to 103.0%. [ABSTRACT FROM AUTHOR]

Electrochemically reduced graphene oxide (ERGO) based voltammetric sensors have drawn considerable attentions due to their simple preparation process and outstanding electrochemical properties. While quite a lot of work suffers from problems in terms of sensitivity and cycling stability. Here, we demonstrate that the reduction extent of ERGO displays a crucial role in enhancing sensitivity and preventing electrode fouling. To illustrate this, partially reduced and relatively complete reduced ERGO films were prepared via the electrochemical method. The reduction extent was controlled by performing cyclic voltammetry with varieties of reduction cycle numbers. Results indicated that partially reduced ERGO film with 5 reduction cycle numbers (ERGO 5 ) showed the highest sensitivity towards electrochemical oxidation of isoniazid (INZ) among all the ERGO films with different reduction extents, and acquired better electrode stability as compared with ERGO 15 . Under the optimal conditions, the peak currents on ERGO 5 modified electrode increased linearly with the concentrations of INZ in the range of 0.09–100 μM. The detection limit of INZ reached 15 nM (S/N = 3). The present work has a guidance meaning in developing ERGO based sensors for detecting other electroactive analytes. [ABSTRACT FROM AUTHOR]

Herein, a sensitive voltammetric method for the determination of diethylstilbestrol (DES), illegally used as a growth promoter in animal husbandry, was developed using electrochemically reduced graphene oxide–multiwalled carbon nanotubes (ERGO–MWCNTs) modified electrode. The incorporated multiwalled carbon nanotubes (MWCNTs) served as electrical conducting wires, which could facilitate the electrochemical reduction of graphene oxide (GO). Compared to either electrochemically reduced graphene oxide (ERGO) or MWCNTs, integrating these nanostructures resulted in a strong synergistic effect between the two materials consequently leading to a superior hybrid material with higher activity for the electro-oxidation of DES. The electron transfer coefficient ( α ), the standard rate constant ( k s ), electrochemically effective surface area ( A ) and the saturating absorption capacity ( Г s ) were calculated. Under the optimized conditions, ERGO–MWCNTs modified electrode exhibited better linearity than either ERGO or MWCNTs over ranges from 0.01 to 40 μM with the detection limit of 3 nM ( S / N = 3). Moreover, the proposed method was successfully applied to determine DES in real sample and satisfactory results were obtained. The results showed that the modified electrode exhibits an excellent catalytic activity, good sensitivity and reproducibility. [ABSTRACT FROM AUTHOR]

Highlights: [•] Three carbon nanomaterials modified electrodes were successfully fabricated for the sensitive determination of niclosamide (NA) by differential pulse anodic stripping voltammetry. [•] A possible working mechanism for the electrochemical detection of NA was proposed. [•] Electrochemically reduced graphene oxide modified electrode is much more suitable for practical application than carbon nanotubes modified electrode. [ABSTRACT FROM AUTHOR]

[Display omitted] • Pd/PANI-rGO catalyst was prepared by in-situ redox reaction. • Lamellar PANI-modified rGO offers abundant attachment sites for Pd. • Pd/PANI-rGO exhibits superior electrocatalytic properties for EGOR and EOR. • The theoretical reference for PANI used as anode catalyst support was provided. Design and preparation of catalysts with lower cost and higher catalytic efficiency are still important strategy to promote the wide application of alkaline direct alcohol fuel cells (ADAFCs). In this study, a novel anode catalyst for ADAFCs has been easily synthesized based on polyaniline (PANI)-modified wrinkled reduced graphene oxide (rGO) and Pd nanoparticles (Pd NPs). Morphology and structure characterization confirm the modified lamellar structure and composition of the Pd/PANI-rGO composite, and X-ray photoelectron spectroscopy (XPS) demonstrates the electron transfer from PANI-rGO to Pd NPs. For ethylene glycol and ethanol oxidation reactions (EGOR/EOR) in alkaline media, the Pd/PANI-rGO exhibits promising electrocatalytic properties with mass activity as 4342.5 and 2220.4 mA mg Pd -1, specific activity as 26.6 and 13.6 mA cm-2 and intrinsic activity as 5.7 and 2.5 s-1, respectively. Moreover, the Pd/PANI-rGO shows significantly enhanced anti-poisoning ability and durability as compared with contrast samples due to the well dispersion of Pd NPs on PANI-rGO and the synergistic interaction between PANI-rGO and Pd NPs producing electron-rich Pd and more active sites for EGOR and EOR. This work is expected to provide theoretical foundation for designing low-cost and high-efficiency ADAFCs anode catalysts. [ABSTRACT FROM AUTHOR]

A sensitive Pb(II) sensor was fabricated based on Co 3 O 4 /reduced graphene oxide/chitosan (Co 3 O 4 /rGO/chitosan) nanocomposite modified glassy carbon electrode (GCE). The Co 3 O 4 /rGO material was synthesized through in situ growth of Co 3 O 4 nanoparticles (NPs) on GO and subsequent hydrazine reduction process. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) show that Co 3 O 4 NPs with a diameter of around 100 nm are attached on rGO sheets. The structures and compositions of Co 3 O 4 /rGO were further characterized by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). Many experimental parameters, such as pH value, deposition time and deposition potential were optimized. Under optimal conditions, the calibration plot for Pb(II), with data acquired at − 0.556 V ( vs . SCE) is linear in the concentration range from 1.0 to 200.0 nM. Combining the good conductivity and high surface area of rGO, strong Pb(II) adsorption ability of Co 3 O 4 NPs, and excellent Pb(II) complex-forming ability of chitosan, the nanocompsite provides a sensitive Pb(II) senor with a detection limit of 0.35 nM. Moreover, the positively charged chitosan can interact with the negatively charged rGO to increase the stability of Co 3 O 4 /rGO nanocomposite. The hybrid nanocomposite Pb(II) senor provides new opportunity for vegetable analysis. [ABSTRACT FROM AUTHOR]

Herein, an electrochemical sensor was developed for detecting heavy metal ions by using a carboimidazole grafted reduced graphene oxide (reduced graphene oxide-NH-carboimidazole, abbreviated as RGO-NH-Ci) modified electrode. The morphology of RGO-NH-Ci material was characterized by scanning electron microscopy (SEM). The electrochemical behaviors of the RGO-NH-Ci modified electrode toward heavy metal ions, including Hg 2 + and Pb 2 + , were investigated with differential pulse anodic stripping voltammetry (DPASV). Compared with pure reduced graphene oxide (RGO), RGO-NH-Ci modified electrode showed improved analytical performance in detecting the two metal ions owing to the strong complexing capacity of Ci and the presence of the amino groups. The detection limits were estimated to be 0.2 nM and 3.0 nM for Hg 2 + and Pb 2 + , respectively, under the optimized conditions. The developed method was also employed to detect the Hg 2 + and Pb 2 + in real water samples, and satisfactory results were obtained. [ABSTRACT FROM AUTHOR]

Abstracts Development of selective methods for the detection of mercury (Hg 2+ ) has received tremendous attention in modern chemical research due to its health hazard and persistence in environment. In this paper, the electrochemical determination of Hg 2+ at trace level based on poly(3,4-ethylenedioxythiophene) nanorods/graphene oxide nanocomposite modified glassy carbon electrode (PEDOT/GO/GCE) is reported. PEDOT/GO nanocomposite has been proposed via a simple liquid–liquid interfacial polymerization approach. Scanning electron microscopy (SEM) and transmission electron microscope (TEM) were employed to characterize the morphology and structure of the as-prepared PEDOT/GO. The results revealed that PEDOT with a nanorods-like structure anchored on the surface of GO nanosheets, which could enhance the electro-active sites of the nanocomposite. Differential pulse stripping voltammetry (DPSV) was applied to determine low concentrations of Hg 2+ on PEDOT/GO/GCE. Experimental conditions, including accumulation time, pH values and deposition potential were optimized. In optimal conditions, a good linear relationship was found between peak currents and the concentration of Hg 2+ in 10.0 nM-3.0 μM range. The detection limit was estimated to be 2.78 nM at a signal-to-noise ratio of 3. Finally, the applicability for Hg 2+ determination in tap water samples was successfully demonstrated. [ABSTRACT FROM AUTHOR]

Hierarchical nanocomposites of poly(3,4-ethylenedioxythiophene) nanorods array on graphene oxide nanosheets (PEDOT/GO) were synthesized via a liquid–liquid interfacial polymerization method. The synthesized composites were characterized by using Fourier transform infrared (FTIR) and Raman spectroscopic studies, and their morphology was analyzed by transmission electron microscopy (TEM). Characterization and surface morphology results indicated that PEDOT with a nanorods-like structure successfully anchored on the surface of GO sheets, which could enhance the electro-active sites of the nanocomposites. Then the obtained PEDOT/GO nanocomposites were utilized to modify glassy carbon electrode and designed for the trace level sensing of rutin. Electrochemical results revealed that the PEDOT/GO nanocomposites modified electrode exhibited larger oxidation peak currents of rutin than pure PEDOT and GO owing to the synergistic effect of GO and PEDOT nanorods. Under optimized conditions, the anodic peak current was linear to the concentration of rutin in the range from 0.004 to 60 μM with the detection limit of 0.00125 μM. To further validate its possible application, the proposed method was successfully used for the determination of rutin in pharmaceutical formulations with satisfactory results. [ABSTRACT FROM AUTHOR]

Highlights: [•] The necklace-like GO-MWCNTs nanohybrid was facilely synthesized by ultrasonication. [•] The nanocomposites can be effectively used for the detection of Azithromycin. [•] Low detection limit with wide linear range could be obtained. [•] The method was applied to determine Azi in real samples. [ABSTRACT FROM AUTHOR]

• PEDOT: PSS/rGO fibers are prepared by easily-accessible hydrothermal confinement reaction. • PEDOT:PSS/rGO fiber with simultaneously enhanced capacitance and mechanical properties can be obtained. • The fiber-shaped supercapacitor shows a high specific energy density of 10.68 Wh•kg−1 at the power density of 81.25 W kg−1. Implantable, flexible and easily reconfigurable supercapacitors with high power and energy densities are considered necessary for the development of portable and wearable electronics. However, obtaining a fiber-incorporating high electrochemical performance and fracture elongation remains a huge challenge. Here, we prepare a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid)/reduced graphene oxide (PEDOT:PSS/rGO) fiber (PGF) with high-quality electrodes for supercapacitors by easily-accessible hydrothermal confinement reaction. The optimized P 3 G 7 F exhibits improved electrochemical performance including a high specific capacitance (C s) of 249.5 F g −1 at 0.5 A g −1 and good cycling stability. Moreover, after introducing the PEDOT:PSS, the elongation at break of the P 3 G 7 F is doubled to 13.9%. A symmetric supercapacitor (SSC) based on the P 3 G 7 F displays a high specific energy density of 10.68 Wh kg−1 at a specific power density of 81.25 W kg−1. The improved performance of the fabricated composite fiber is attributed to the unique structures of the rGO and PEDOT:PSS and their synergistic effect. This study introduces an opportunity for the development of next-generation flexible and wearable devices. PEDOT:PSS/rGO fibers are prepared via easily-accessible hydrothermal confinement method and the PEDOT:PSS/rGO fibers exhibit good capacitance and mechanical properties. Image, graphical abstract [ABSTRACT FROM AUTHOR]

• Few-layered crumpled porous N-doped graphene was prepared using nitroaromatic molecules as N sources. • Nitroaromatic molecules effectively suppressed the aggregation of N-doped graphene. • As-obtained 5-NIGN had high specific capacitance of 457.4 F g−1 and long cycle life. Nitroaromatic pollutants with unusually strong adsorption affinity are highly attractive candidates for creating 2D molecular assemblies on the surface of graphene, which is crucial to prepare high-quality N-doped graphene by post-treatment. Herein, the few-layered crumpled N-doped graphene (5-NIGN) with high N content is successfully prepared by mixing 5-nitroindole (5-NI), ammonia, and graphene oxide (GO) and using a simple hydrothermal method followed by the post-treatment process of vacuum freeze-drying and annealing. It is found that the rapid assembly of 5-NI effectively suppresses the aggregation of the products in the reduction process of GO, so that the thickness of as-prepared 5-NIGN is 4.21 nm, very close to that of GO (4.01 nm). Compared with the N-doped graphene (GN) derived from the system of GO containing ammonia (341 F g−1), 5-NIGN exhibits higher capacitance of 457.4 F g−1 at 1 A g−1 and prominent long-term life (115% of capacitance maintenance upon 10,000 cycles) within the voltage window of 1.0 V. Furthermore, the supercapacitor assembled by 5-NIGN electrodes can deliver the energy density of 15.5 Wh kg−1~18.5 Wh kg−1 at the power density of 8000 W kg−1~800 W kg−1. These results indicate that the 5-NIGN material will have potential advantages in the realm of electrochemical energy storage. Image, graphical abstract [ABSTRACT FROM AUTHOR]