The suitability of ZnO film-coated glassy carbon electrode for the sensitive detection of 4-nitrophenol in aqueous medium

The performance of a ZnO nanoparticle-based electrochemical sensor, fabricated by different treatments of ZnO on glassy carbon electrode, was evaluated for the determination of 4-nitrophenol (4-NP) in aqueous medium.</p

Ultra-sensitive 2-nitrophenol detection based on reduced graphene oxide/ZnO nanocomposites

Polyethylene glycol mediated reduced graphene oxide/zinc oxide (r-GO/ZnO) nanocomposites were synthesized by simple and cost-effective chemical reduction method using graphene oxide and zinc acetate as the precursors. The crystalline structure, morphology and thermal decomposition of the as-prepared r-GO/ZnO nanocomposites were characterized by X-ray diffraction, transmission electron microscopy and thermogravimetric analysis, respectively. Elemental composition was analyzed by energy dispersive spectra and mapping. A selective 2-nitrophenol (2-NP) sensor onto glassy carbon electrode (GCE) was fabricated with a thin-layer of synthesized r-GO/ZnO composites. Improved electrochemical responses with high sensitivity including large dynamic range and long-term stability towards the selective 2-NP were acquired using the fabricated r-GO/ZnO/GCE sensor. The calibration curve was found linear (r2: 0.9916) over a wide range of 2-NP concentrations (10.0 nM–10.0 mM). The detection limit and the sensitivity were calculated as 0.27 nM and 5.8 μA·mM− 1 cm− 2 respectively based on 3 N/S (Signal-to-Noise ratio). In this approach, 2-NP was detected by I-V method using r-GO/ZnO composites modified GCE electrode with very high sensitivity compared to various nanocomposites reported earlier. The synthesis of r-GO/ZnO composites using chemical reduction process is a good way of establishing sensor based r-GO/ZnO composites for toxic and carcinogenic chemicals. © 2017 Elsevier B.V.

Mercury meniscus on solid silver amalgam electrode as a sensitive electrochemical sensor for tetrachlorvinphos

The in-house prepared mercury meniscus modified solid silver amalgam electrode (m-AgSAE) was successfully applied for the detection of organophosphate pesticide tetrachlorvinphos in pH 7 buffer solution. The electrochemical performance of m-AgSAE for the reduction of tetrachlorvinphos was evaluated using cyclic voltammetry (CV), differential pulse voltammetry (DPV), and square wave voltammetry (SWV), respectively. The surface morphology of solid silver electrode (AgE), as-amalgamated solid silver amalgam electrode (AgSAE), and polished solid silver amalgam electrode (p-AgSAE) was examined by field emission scanning electron microscopy (FESEM). Among the applied techniques, DPV and SWV analysis showed a remarkable increase in the reduction peak current and provided a simple, fast, and sensitive method for the determination of tetrachlorvinphos. The electrochemical impedance spectroscopy (EIS) was used to correlate the electrocatalytic activity of AgSAE, p-AgSAE and m-AgSAE with their interfacial charge transport capabilities. Under the optimized experimental conditions, the DPV and SWV responses were linear over the 1–9 μM and 10–50 μM concentration ranges with a detection limit of 0.06 μM for DPV and 0.04 for SWV. The estimation of tetrachlorvinphos in the ground and waste water samples with the proposed method was in good agreement with that of the added amount. The proposed electrochemical method not only extends the application of non-toxic m-AgSAE, but also offers new possibilities for fast and sensitive analysis of tetrachlorvinphos and its structural analogs in environmental samples. Keywords: Organophosphate pesticide, Tetrachlorvinphos, Electrochemical sensor, Mercury meniscus modified solid silver amalgam electrode, Electrocatalytic reductio