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The authors describe a nonenzymatic glucose sensor that was obtained by electrochemical deposition and oxidization of metallic nickel on the surface of nitrogen-doped reduced graphene oxide (N-RGO) placed on a glassy carbon electrode (GCE). An analysis of the morphology and chemical structure indicated the composite to possess a well-defined vermicular Ni(OH) nanorods combined with N-RGO. The electrochemical performance of the modified GCE with respect to the detection of glucose in 0.1 M NaOH was investigated by cyclic voltammetry and amperometry. The wrinkle and protuberance of N-RGO for loading of nanostructured Ni(OH) are found to increase electrical conductivity, surface area, electrocatalytical activity and stability. The modified GCE displays a high electrocatalytic activity towards the oxidation of glucose in 0.1 M NaOH solution. The lower detection limit is 0.12 μM at an applied potential of +0.45 V (vs Ag/AgCl) (S/N=3), and the sensitivity is 3214 μA mM cm. The modified GCE possesses long-term stability, good reproducibility and high selectivity over fructose, sucrose and lactose. [ABSTRACT FROM AUTHOR]

Ultrasensitive explosive sensors are significant in anti-terrorism and related environment issues. Herein, we proposed a novel boron-doped graphene (B-GE) modified glassy carbon electrode (GCE) applied as a simple, sensitive electrochemical high melting explosive (HMX) sensor. The morphology and structure features of B-GE were characterized. The electrochemical behaviors of HMX on the B-GE modified GCE were investigated by cyclic voltammetry (CV). Under the optimized conditions, CV was used for the quantitative detection of HMX, and the reduction peak current exhibited good linear dependence with the concentration of HMX in the ranges of 2 ∼ 20 μM and 20 ∼ 100 μM. The low detection limit (LOD) was calculated as 0.83 μM (245.81 ppb). Furthermore, the B-GE/GCE showed satisfactory repeatability, high selectivity and stability. The reduction reaction mechanism of HMX on B-GE modified electrode was explored by computational theoretical analysis. Additionally, the differences of the reduction mechanisms from nitroaromatic explosives were discussed. [ABSTRACT FROM AUTHOR]

A stable and well-distributed nitrogen-doped graphene (NGE) is prepared by a simple and efficient hydrothermal method with a reducing-doping reagent of vitamin B3. Compared with NGE reduced by urea, vitamin B3 reduced NGE (NGE-N) show superior catalysis towards the electrochemical reduction of imidacloprid. The pyridine-N oxide induced in graphene sheets is considered enhancing the interaction between NGE-N and imidacloprid molecules. The NGE-N modified electrode is used in fast determination of imidacloprid with a low detection limit of 0.55 μM. [ABSTRACT FROM AUTHOR]

Highlights: [•] A PEDOT/GO modified electrode was obtained via potentiostatic method using GO as a dopant. [•] The electrochemical behavior of acetaminophen (AP) showed highly reversibility. [•] An electrochemical sensor based on PEDOT/GO was developed for the detection of AP. [•] The sensor shows high sensitivity and selectivity to AP. [ABSTRACT FROM AUTHOR]

Abstract: Polycarbazole (PCz) and PCz/chemically reduced graphene oxide (PCz/CRGO) modified glassy carbon electrodes (GCEs) were fabricated by a simple procedure and characterized. The modified electrodes based on PCz or PCz/CRGO were used as sensing electrodes for the voltammetric investigation of imidacloprid (IMI) insecticides. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used as sensing techniques. Both of modified electrodes have good electrocatalytic activity toward the reduction of IMI. The presence of CRGO enhanced the electrochemical signal of the modified glassy carbon electrode (GCE), which increased the sensitivity of the sensor. The limit of detection (LOD) and the limit of quantitation (LOQ) values for CV are 0.22μM and 0.74μM, respectively; while those values for DPV are 0.44μM and 1.52μM, respectively. [Copyright &y& Elsevier]

Abstract: A novel poly(3,4-ethylenedioxy-thiophene) (PEDOT)/graphene oxide (GO) hybrid film was directly electrodeposited on a glassy carbon electrode. The SEM and TEM images of the as-obtained film revealed that PEDOT grew well on the surface of GO sheets with high affinity. The chemical structure of the composite was characterized by FT-IR, and the result conformed the formation of PEDOT doped by GO, leading to the enhanced electrochemical performance of the modified electrode. The composite modified electrode was utilized as an electrochemical sensor for the simultaneous detection of hydroquinone (HQ) and catechol (CT). It showed well electrocatalytic activity toward the redox of HQ and CT. Under the optimized condition, the response peak currents of the modified electrodes were linear over ranges from 2.5 to 200μM for HQ and from 2 to 400μM for CT. The sensor also exhibited good sensitivity with the detection limit of 1.6μM for both HQ and CT, and good stability. This study provides a new kind of composite modified electrode for electrochemical sensors. [Copyright &y& Elsevier]

Polycarbazole (PCZ)/nitrogen-doped graphene (N-GE) composite was prepared by electropolymerization of carbazole on the N-GE modified glass carbon electrode (N-GE/GCE) for fabricating a novel electrochemical sensor for 4-nitrophenol (4-NP). The PCZ/N-GE shows high conductivity and well-distributed nanostructure. The redox behavior of 4-NP at a PCZ/N-GE/GCE was investigated in acetate buffer solution by cyclic voltammetry (CV), compared with the bare GCE, reduced graphene oxide (RGO), N-GE and PCZ modified GCEs. The results indicate that all modified electrodes show the enhanced reduction peak currents. However, the PCZ/N-GE/GCE exhibits the highest peak current and most positive reduction potential of 4-NP, which reflects the PCZ/N-GE composite has the best electrocatalytic activity towards 4-NP. The enhanced electrochemical performance of PCZ/N-GE and the electrocatalytic activity to 4-NP are contributed to the synergic effect of PCZ and N-GE with highly conductivity and large surface area, which can greatly facilitate the electron-transfer processes between the electrolyte and electrode. An electrochemical sensor for 4-NP was developed based on the PCZ/N-GE modified electrode under the optimized conditions. The reduction peak current was linear with the concentration of 4-NP in the range of 8 × 10 -7 ∼2 × 10 -5 M. The low detection limit of the sensor was estimated to be 0.062 μM (S/N = 3). The sensor based on PCZ/N-GE/GCE was also applied to the detection of 4-NP in real water samples. [ABSTRACT FROM AUTHOR]

Abstract A rapid and sensitive, non-enzymatic electrochemical detection of hydrogen peroxide (H 2 O 2) is of utmost importance for diagnosis and treatment of related diseases in clinical purpose. To meet this requirement, we report a simple and robust microwave-assisted synthetical route via prepared Gd 2 O 3 nanoparticles decorated reduced graphene oxide nanocomposite (Gd 2 O 3 NPs@RGO) modified electrode for non-enzymatic H 2 O 2 detection. The composition and morphological formation were characterized by using XRD, FT-IR, XPS, FESEM, and HRTEM. The impedance and cyclic voltammetry exhibit tremendous electrocatalytic capability and superior performance toward H 2 O 2 reduction. A sensitive and reproducible amperometric H 2 O 2 sensor was fabricated which was able to detect concentration as low as 1.57 nM. The method worked well even in clinical and biological samples, which indicates the reliability of the method in real time analysis. [ABSTRACT FROM AUTHOR]

Nb2O5@carbon/reduced graphene oxide (M-Nb2O5@C/rGO) composites are fabricated by annealing the precursor of graphene oxide supported Nb-based metal organic frameworks for the first time. The lithium ion capacitor using M-Nb2O5@C/rGO as the anode and activated carbon as the cathode delivers a high energy density of 71.5 W h kg−1 and excellent cycling stability. [ABSTRACT FROM AUTHOR]

Highlights • Graphene oxide (GO) hydrogel was induced by synergistic effect of pyrrole and Co2+. • S and N are doped in graphene framework with doping/reducing agent of L -Cysteine. • 3D-sturctrue are obtained via evaporation induced drying without freeze-drying. • The 3D S/N-co-doped graphene show enhanced response for hydroquinone and catechol. Abstract Herein, a three-dimensional self-assembled hydrogel of graphene oxide sheets induced by pyrrole and Co2+ is described. Controlled shrinkage and sulfur/nitrogen co-doping occurred in the subsequent hydrothermal process. The obtained 3D sulfur/nitrogen co-doped graphene was further dried through direct evaporation, without freeze-drying. SEM images demonstrated a surface 3D structure with high roughness and composed of interconnected sheets. This newly fabricated 3D sulfur/nitrogen co-doped graphene was used in the simultaneous detection of catechol and hydroquinone with low detection limits of 0.28 and 0.15 μM, respectively. [ABSTRACT FROM AUTHOR]

Poly(3-methylthiophene)/reduced graphene oxide (P3MT/RGO) modified glassy carbon electrode (GCE) was fabricated via a facile procedure. P3MT was directly electrodeposited on the RGO coated electrode and employed for the electrochemical detection of paracetamol (PCT). The morphology of composite was characterized by scanning electron microscopy (SEM). Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used to investigate the electrochemical behaviors of PCT on P3MT/RGO/GCE. Experimental parameters, such as the scan rates, polymerization laps and the pH of buffer solution were optimized. Under the optimal conditions, the anodic peak current in DPVs varies linearly with the concentration of PCT, and the limit of detection was 0.025 μ M. Moreover, the proposed P3MT/RGO/GCE also exhibited superior stability and reproducibility. The poly (3-methylthiophene)/reduced graphene oxide (P3MT/RGO) material was firstly proposed for the fast, sensitive electrochemical determination of paracetamol (PCT). The RGO can efficiently provide abundant reaction sites and promote the electron transfer, while the P3MT was electrodeposited on the surface of RGO/GCE. The redox current response increased further and the reversibility of the redox reaction was improved. The developed sensor showed excellent stability, high selectivity, low detection limit and good applicability in real samples. [ABSTRACT FROM AUTHOR]

A newly fabricated nitrogen-doped graphene (NGE) supported hemin composite was prepared with facile one-pot method deriving from graphene oxide. Hemin was directly anchored on the surface of NGE during the N-doping process with doping-reducing agent of 2-aminopyridine. XPS results revealed the nitrogen doping of graphene and the integration of Hemin with NGE, and the hemin-N C (H-NGE) composite was characterized with TEM and SEM. The peroxidase-like activity of hemin maintained, displaying fast redox property. The H-NGE also exhibited remarkable electrocatalysis towards O 2 and H 2 O 2 reduction due to the high-speed charge-transfer between hemin and the modified electrode. The good electroactivity of NGE and the excellent synergic effect enables an enhanced electrochemical performance. Based on the well-designed H-NGE, the electrocatalytic H 2 O 2 determinations was monitored amperometrically with a low detection limit (0.092 μM). [ABSTRACT FROM AUTHOR]

Ultrafine CuS nanoparticles anchored on nitrogen-sulfur co-doped graphene nanosheets are synthesized by a simple-green solvothermal method, the composite has excellent electrochemical performance for CO 2 reduction. [Display omitted] • The CuS/N, S-rGO was synthesized via a facile and environmentally friendly method. • The co-doping of N and S on graphene can promote the activation and conversion of CO 2. • CuS/N, S-rGO exhibits outstanding formate selectivity for CO 2 RR. Electrochemical conversion of CO 2 into hydrocarbons can effectively alleviate the energy crisis and promote carbon cycle. Herein, we report that small-size CuS nanoparticles are confined in nitrogen and sulfur co-doped reduced graphene oxide (CuS/N,S-rGO) for electrochemically reducing CO 2 to formate. Specifically, the CuS/N,S-rGO electrode achieves maximum Faradaic efficiency of 82% for formate formation at −0.63 V versus the reversible hydrogen electrode (RHE). Moreover, this catalyst exhibits a stable performance during 20 h-electrolysis. Experiments demonstrate that the doping of nitrogen and sulfur can create an abundance of active sites on the graphene nanosheets to accelerate the CO 2 reduction reaction (CO 2 RR). The CuS/N,S-rGO electrode exhibits excellent performance for CO 2 RR is attributed to the synergistic effect between N,S-rGO and CuS, and graphene can improve stability of composite. This work provides an efficient electrocatalyst for CO 2 RR and offers a facile and environmental friendly approach to synthesize small-size Cu-based composites. [ABSTRACT FROM AUTHOR]

Metal oxides decorated carbon nanomaterials, as an electrode material have been well explored in the field of electrochemical sensor. However, instead of using the high concentration of graphene oxide (GO), we try to explore the influence of minimum quantity of GO in material synthesis. Here we demonstrate the hydrothermal synthesis of low-cost cerium (Ce)-doped tungsten oxide/graphene oxide (CeW/GO) composite for the precise electrochemical detection of antibiotic drug furazolidone (FUZ). For the synthesis of composite, 40 μg/mL concentration of GO has been utilized. Then, several physicochemical and electrochemical techniques were used to examine the morphological, structural, and electrochemical characteristics of the CeW/GO composite. Interestingly, the composite material has a porous-coral-like structure, which is being described here for the first time. The GO nanosheets cover the CeW and make the smooth surface and lead to the porous structure. Then we looked into the analytical behavior of CeW/GO composite modified glassy carbon electrode for the application towards the electrochemical detection of the FUZ using the voltammetric technique. The effect of experimental conditions, including loading concentration of active material, pH, scan rate, accumulation time, and concentration of FUZ, were analyzed with respect to the reduction peak current response of FUZ. At the optimum conditions, the fabricated sensor has a low detection limit (0.054 μM), appreciable sensitivity (2.5 μA μM−1 cm−2) with a wide linear range (1–260 μM), and the decent anti-interference ability for FUZ detection. Furthermore, the developed sensor was successfully used to assess the FUZ concentration in the human urine samples, yielding satisfactory results. [Display omitted] • porous-coral-like CeW/GO micro balls composite material was designed for the first time. • The CeW/GO composite was employed as a novel electrocatalyst to detect the furazolidone (antibiotic drug). • A detailed study was made on electrochemical performance of the developed sensor. • The performance of CeW/GO/GCE was comparable with the noble metals (Pt, Re, and Au) based modified electrodes. [ABSTRACT FROM AUTHOR]

• A sonochemical method was used to prepare the SnO 2 @rGO nanocomposites. • SnO 2 @GO/GCE shows an owing electrochemical activity towards Hg2+ ions detection. • The LOD 1.2 nM of mercury ion was established at SnO 2 @GO NPs/GCE. • SnO 2 @GO NPs/GCE shows the appreciable results in the real samples. In modern approaches for nanomaterials synthesis, ultrasonication plays an important role in providing the larger surface area and smaller crystalline size properties that are favorable to electrochemical techniques. Herein, we report the tin (IV) oxide on graphene oxide nanoparticles were synthesized (SnO 2 @GO NPs) by ultrasonic methodology (UZ SONOPULS HD 3400 Ultrasonic homogenizer) with the total power of 400 W and the (frequency of 20 kHz; 140 W/dm3). The formation of as-prepared SnO 2 @GO NPs and its surface morphology were scrutinized over XRD, XPS, TEM, and FESEM. Besides, the sonochemically prepared SnO 2 @GO NPs were employed for the determination of environmental hazardous mercury (Hg). As a result, the modified electrode acquired a very low-level detection limit of 1.2 nM with a wider range of 0.01–10.41-µM and 14.52–225.4-µM for the detection of Hg. Finally, the practical applicability of SnO 2 @GO NPs in spiked human blood serum and tuna fish samples shows appreciable found and recovery values.. [ABSTRACT FROM AUTHOR]

Mesoporous CuS nanospheres (CuS-NS) decorated reduced graphene oxide (rGO) aerogel composite (3D CuS-NS/rGO) was prepared by chemical reduction process and used for the synergistic removal of Cr(VI) and cationic dyes. The porosity of the as prepared samples was determined by Bruner-Emmet-Teller (BET) surface Area. Structural and morphological properties were studied by Scanning electron microscopy (SEM) and Transmission electron microscope (TEM). These analysis revealed that the as obtained hybrid CuS-NS/rGO composite with three dimensional (3D) structure was composed of mesoporous CuS nanospheres clearly induced onto the interconnected network of rGO sheets. The photocatalytic performance of 3D CuS-NS/rGO composites was studied against the reduction of Cr(VI) and degradation of cationic dyes (MB and RhB) under visible light spectrum. Excellent photocatalytic performance was observed with 3D CuS/rGO hybrid composites as compared to the as prepared CuS nanospheres. This high photocatalytic activity was attributed to the efficient charge transfer from the mesoporous CuS nanospheres to nanosheets of rGO, which was confirmed by UV–Vis spectrometry (UV–Vis). Electrical conductivity of the prepared samples was also investigated using electrochemical impedance spectroscopy (EIS). Additionally, the as prepared hybrid composites was easy to recycle by using simple tweezers and can be a best candidate for industrial applications. Image 1 • Preparation of 3D CuS/rGO aerogel by simple reduction process. • Photocatalytic activity of 3D CuS-NS/rGO investigated over Cr(VI) and cationic dyes. • Investigation of the catalyst concentration on photocatalytic performance. • High stability of 3D CuS-NS/rGO aerogel over five cycles. [ABSTRACT FROM AUTHOR]

• Hierarchical layered Fe 3 O 4 QDs@C/rGO array derived from MIL-100(Fe)/GO. • Graphene and mesoporous carbon act as conductive support for anchoring Fe 3 O 4 QDs. • Multi-porous channels increase interface contacts and facilitate ion transportation. • Synergetic effect in Fe 3 O 4 QDs@C/rGO array results in the enhanced LIB performance. Herein, a double-buffering strategy is presented to boost the lithium storage potential of Fe 3 O 4. Firstly, the skeleton of MIL-100 (Fe) MOF is grown on graphene oxide, as a self-assembled template via in-situ solvothermal approach, which transform into ultrafine, well-dispersed and mesoporous carbon coated Fe 3 O 4 QDs (4 nm) imbedded on reduced graphene oxide (Fe 3 O 4 QDs@C/rGO), by pyrolysis. Each component in such a well-designed porous hierarchical structure significantly contributes to the remarkable enhancement of lithium ion storage performance, leading to high reversible capability with excellent prolonged cyclic stability after 2000 cycles (505 mAh g−1 at 2.0 A g−1). Both, Graphene sheets and mesoporous carbon act as conductive support for anchoring uniform Fe 3 O 4 QDs with confined double buffering for cyclic volume flux. Multi-channels with uniform mesopores in the self-assembled array and 4 nm QDs of Fe 3 O 4 confined in conductive carbon shells were favorable to enhance the interfacial electron/ion transfer, leading to the excellent rate and cycling performance with released volume changes upon Li+ insertion/extraction. The present research work provides a promising outset design and synthesis strategies for metal oxide QDs based nanocomposites, which may also be extended to the other electrode material system. [ABSTRACT FROM AUTHOR]