Abstract
Graphene: zinc oxide nanocomposite (GN:ZnO NC) platform was tried for the sensitive determination of para-nitrophenol (p-NP) through the electrochemical method. ZnO nanoparticles (NPs) were synthesized by the modified wet-chemical method where in potassium hydroxide and zinc nitrate were used as precursors and starch as a stabilizing agent. A green and facile approach was applied to synthesize GN:ZnO NC in which glucose was employed as a reductant to reduce graphene-oxide to graphene in the presence of ZnO NPs. The synthesized NC was characterized using scanning and high-resolution transmission electron microscopy, energy dispersive x-ray analysis, X-ray diffraction and Raman spectroscopic techniques to examine the crystal phase, crystallinity, morphology, chemical composition and phase structure. GN:ZnO NC layer deposited over the glassy carbon electrode (GCE) was initially probed for its electrochemical performance using the standard 1 mM K3[Fe(CN)6] model complex. GN:ZnO NC modified GCE was monitored based on p-NP concentration. An enhanced current response was observed in 0.1 M phosphate buffer of pH 6.8 for the determination of p-NP in a linear working range of 0.09 × 10–6 to 21.80 × 10–6 M with a lower detection limit of 8.8 × 10–9 M employing square wave adsorptive stripping voltammetric technique at a deposition-potential and deposition-time of − 1.0 V and 300 s, respectively. This electrochemical sensor displayed very high specificity for p-NP with no observed interference from some other possible interfering substances such as 2, 4-di-NP, ortho-NP, and meta-NP. The developed strategy was useful for sensitive detection of p-NP quantity in canals/rivers and ground H2O samples with good recoveries.
Highlights
Graphene: zinc oxide nanocomposite (GN:ZnO NC) platform was tried for the sensitive determination of para-nitrophenol (p-NP) through the electrochemical method
The size of ZnO-NPs was calculated with the help of “Debye–Scherrer formula, d = 0.89λ/ βcosθ”[54,55], where, 0.89 is Scherer’s factor, λ is wavelength of x-ray used, ‘θ’ the “Bragg diffraction angle”, and ‘β’ a constant known as the “full width at half-maximum (FWHM)” of a particular diffraction angle
A new diffraction peak characteristic of GN at 26.52° with inter-layer spacing (d-spacing) of 0.35 nm was observed in the XRD outline of GN:ZnO NC composite
Summary
Graphene: zinc oxide nanocomposite (GN:ZnO NC) platform was tried for the sensitive determination of para-nitrophenol (p-NP) through the electrochemical method. ZnO NPs directly synthesized on the graphene surface have been reported as good electrode material for supercapacitors[41,49,50]. The synergistic effect of GN:ZnO NC improved electrochemical detection of p-NP and enabled its sensitive determination in presence of o-nitrophenol using voltammetric techniques.
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