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In this study, we report the determination of dopamine (DA) and acetaminophen (AC) using activated graphene-Nafion modified glassy carbon electrode (AG-NA/GCE). The AG was prepared by simple and facile method of thermal activation of graphene oxide (GO) with potassium hydroxide (KOH) to enhance the pore volume and specific surface area. The surface morphology and pore structure of AG were characterized by field-emission scanning electron microscope, transmission electron microscopy, Raman spectroscopy and nitrogen isothermal adsorption-desorption technique. The electrochemical characterization of AG-NA/GCE was examined with cyclic voltammetry analysis of potassium ferricyanide. The electroanalytical performance of AG-NA/GCE toward the oxidation of DA and AC was analyzed via cyclic voltammetry and differential pulse voltammetry. The result showed excellent selectivity and sensitivity toward analysis of DA and AC with low detection limit values of 0.33 and 0.031 μM (S/N = 3) for DA and AC, respectively. As for the examination and evaluation of electrochemical activities in real samples, the determination of DA and AC was examined with AG-NA/GCE in diluted human urine samples. [ABSTRACT FROM AUTHOR]

We report an analytical assessment of an iron oxide (Fe 2 O 3 )/graphene (G) nanocomposite electrode used in combination with in situ plated bismuth (Bi) working as an electrochemical sensor for the determination of trace Zn 2+ , Cd 2+ , and Pb 2+ . The as-synthesized nanocomposites were characterized by transmission electron microscopy, scanning electron microscopy, thermo-gravimetric analyzer, and X-ray diffraction. The electrochemical properties of the Fe 2 O 3 /G/Bi composite modified electrode were investigated. Differential pulse anodic stripping voltammetry was applied for the detection of metal ions. Due to the synergetic effect between graphene and the Fe 2 O 3 nanoparticles, the modified electrode showed improved electrochemical catalytic activity high sensitivity toward trace heavy metal ions. Several parameters such as the preconcentration potential, bismuth concentration, preconcentration time, and pH were carefully optimized to determine the target metal ions. Under optimized conditions, the linear range of the electrode was 1–100 μg L −1 for Zn 2+ , Cd 2+ , and Pb 2+ , and the detection limits were 0.11 μg L −1 , 0.08 μg L −1 , and 0.07 μg L −1 , respectively (S/N =3). Repeatability (% RSD) was found to be 1.68% for Zn 2+ , 0.92% for Cd 2+ , and 1.69% for Pb 2+ for single sensor with 10 measurements and 0.89% for Zn 2+ , 1.15% for Cd 2+ , and 0.91% for Pb 2+ for 5 different electrodes. The Fe 2 O 3 /G/Bi composite electrode was successfully applied to the analysis of trace metal ions in real samples. The solventless thermal decomposition method applied to the simple and easy synthesis of nanocomposite electrode materials can be extended to the synthesis of nanocomposites and promising electrode materials for the determination of heavy metal ions. [ABSTRACT FROM AUTHOR]

We report a facile strategy of graphene/gold nanocomposite based electrochemical biosensor that exhibit good sensitivity and high reproducibility. The graphene/gold nanocomposites were prepared by using sodium hydroxide acting as an accelerator for the reduction of gold ions. The graphene oxide was reduced by chemical and thermal methods after deposition of gold nanoparticles. The composition of the resulting materials was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and thermogravimetric analysis (TGA). Also, transmission electron microscope (TEM) was employed to demonstrate the successful deposition of gold nanoparticles on the surface of graphene sheets. The electrochemical behavior of dopamine (DA) on the surface of the graphene/gold nanocomposite modified electrode was investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). In comparison to the reduced graphene oxide (rGO) modified electrode, the graphene/gold nanocomposite modified electrode shows good performance for the selective determination of DA. The nanocomposite modified electrode showed a low detection limit (0.095 μM), an enhanced electrochemical oxidation current for DA, and a good separation of potential of DA and ascorbic acid (AA). [ABSTRACT FROM AUTHOR]

A novel electrochemically deposited graphene (EG)/bismuth (Bi) nanocomposite film-modified glassy carbon electrode (GCE) was prepared through successive electrodeposition of exfoliated graphene oxide (GO) and in situ plating bismuth film. Experimental variables, including deposition potential and bismuth concentration, were carefully optimized to determine trace zinc, cadmium, and lead ions by using the EG/Bi electrode as an electrochemical-sensing platform. The linear calibration curves ranged from 1 to 100 μg L − 1 for Zn 2 + , Cd 2 + , and Pb 2 + . The detection limits were 1.80 μg L − 1 for Zn 2 + , 0.18 μg L − 1 for Cd 2 + , and 0.11 μg L − 1 for Pb 2 + (S/N = 3). The EG/Bi nanocomposite film electrode was successfully applied to the analysis of trace metals in real environments. [ABSTRACT FROM AUTHOR]

In this study, we report the first example of a bismuth film electrode plated in situ using activated graphene (AG). The AG was prepared through of process of chemical activation of graphene oxide (GO) with KOH to create pores. The composite electrode was enhanced as an electrochemical sensing platform to determine trace Zn 2+ , Cd 2+ , and Pb 2+ using differential pulse anodic stripping voltammetry. The surface morphology of the AG-NA/Bi composite film modified electrode was investigated by scanning electron microscopy and transmission electron microscopy. The electrochemical properties of the AG-NA/Bi composite electrode were evaluated to examine the effects of experimental variables, such as deposition potential, deposition time, bismuth concentration, and stirring speed during pre-concentration, on the determination of trace metals in 0.1 M acetate buffer solution (pH 4.5). Linear calibration curves ranged from 5 to 100 μg L −1 for trace heavy metal ions. The detection limits were 0.57 μg L −1 for Zn 2+ , 0.07 μg L −1 for Cd 2+ , and 0.05 μg L −1 for Pb 2+ (S/N = 3). The limits of detection achieved are much lower than the guideline for drinking water quality provided by the World Health Organization (WHO). The AG-NA/Bi composite film electrodes were successfully applied to analysis trace metals in real samples. [ABSTRACT FROM AUTHOR]

In recent times, 2D materials-based heterostructures are extensively studied for fabricating different nanodevices. Among these materials, transition metal dichalcogenides (TMDC), hexagonal boron nitride (hBN), and graphene (Gr) are widely used in these devices. Optoelectronic memory devices based on 2D materials are among the recently studied devices for structural flexibility and device size miniaturization. In this study, a non-volatile optoelectronic memory device has been fabricated using tungsten diselenide (WSe 2), and hBN-encapsulated Gr-based heterostructures. This device can be easily controlled with UV light and an electric field. Two points were focused on in this study; first, the doping state was changed partially i.e., by illuminating a part of the WSe 2 layer by UV light and a p-n homo-junction was created. This phenomenon occurs due to the unique structure of Wse 2 /hBN and the p-n junction could be created in one layer. Secondly, Gr has been used as a floating gate to increase the retention time as Gr is acting as a charge trapping layer. The retention time is further increased due to the thickness of hBN because the defect states keep increasing the charges together. [Display omitted] • Fabrication of an optoelectronic memory device using WSe 2 , and hBN encapsulated Gr-based heterostructures • Memory device can be easily controlled with UV light and an electric field. • Graphene used as a floating gate to increase the retention time as Gr is acting as a charge trapping layer. • The retention time improvement with the thickness of hBN because the defect states keep increasing the charges together. [ABSTRACT FROM AUTHOR]