Enhancement of the electrochemical behavior of CuO nanoleaves on MWCNTs/GC composite film modified electrode for determination of norfloxacin
Graphical abstract
Highlights
► A novel and single step method for the synthesis of PDDA stabilized CuO nanoleaves. ► The CuO nanoleaves were fabricated on MWCNTs/GC modified electrode for the electrochemical oxidation of norfloxacin. ► The obtained CuO/MWCNTs/GC modified electrode exhibits excellent electrochemical activity for the determination of norfloxacin at low operating potential of +0.91 V.
Introduction
Norfloxacin [1-ethyl-6-fluoro-1,4-dihydro-4-oxo-7-(1-piperazinyl)-3-quinolonecarboxylic acid] belongs to fluoroquinolone class of synthetic antibiotics which exhibits broad activity against gram-negative bacteria and marginal activity against gram-positive bacteria [1]. Norfloxacin is used effectively in both human and veterinary therapeutic medicines for the treatment of a wide variety of diseases caused by urinary, respiratory and gastrointestinal tract infections [2], [3]. Norfloxacin has been associated with rare cases of sensory or sensorimotor axonal polyneuropathy resulting in paresthesias, hypoesthesias, dysesthesias, and weakness [4]. In clinical trials, norfloxacin related adverse effects have been minimal, while these effects were mild and included disturbances of the gastrointestinal tract and in the central nervous system resulting in tremors, restlessness, nervousness, hallucinations, paranoia, depression, insomnia, and rarely suicidal thoughts or acts [5]. The most commonly reported side effects include nausea, vomiting, anorexia, dizziness, headache, drowsiness, depression, and a bitter taste in the mouth [6]. Therefore, it is necessary to develop a sensitive analytical method for the determination of norfloxacin in biological samples and in pharmaceutical formulations. There have been numerous techniques reported in the literature such as UV–vis spectrophotometry [7], spectrofluoriometry [8], HPLC [9], capillary electrophoresis [10] and electro chemiluminescence [11] for the determination of norfloxacin. However, in many such techniques certain disadvantages include: time consuming, tedious sample pretreatment and involvement of expensive reagents are subject to interferences. To overcome these disadvantages, there is a need for fast sensitive and cost effective method for the successful determination of pharmaceutical drugs arises.
In this context, electrochemical methods have received considerable interest because of the high sensitivity, selectivity and their ability to minimize the interferences. The electrochemical oxidation of norfloxacin usually involves a large overpotential at the surface of the bare electrodes, and therefore, the determination of norfloxacin tends to suffer interferences from other oxidizable compounds. In order to circumvent these interferences, chemically modified electrodes have attracted immense importance because of fast electron rate transfer, decrease in overpotential with minimal surface fouling and reduce the overpotential of the oxidizing species. Recently, Ghoneim et al. [12] investigated the electrochemical behavior of norfloxacin on GC electrode at its oxidation peak, +0.95 V. Goyal et al. [13] reported the electrochemical oxidation of norfloxacin on edge plane and basal plane pyrolytic graphite electrode with oxidation peak at +0.95 V. Xie et al. [14] have recently reported a poly(methyl red) film modified GC for the oxidation of norfloxacin at +1.12 V, which is attributed to the overlapping of interfering species on the bare electrodes. To overcome these difficulties, electrodes modified with nanocomposites have been explored [15], [16]. Among the most promising designs, those involving the fabrication of carbon nanotubes along with metal oxide nanoparticles are especially exhibit remarkable electrocatalytic properties by enhancing the electrode conductivity, facilitating the electron transfer and the anti-fouling capability reduce the overpotential at the modified electrode [17], [18].
Recently, considerable efforts have been developed toward the synthesis of CuO nanoparticles to enhance their existing applications in batteries [19], gas sensors [20], magnetic storage media [21], solar cells [22] and biosensors [23]. The synthesis of CuO nanostructures with well-defined shapes and sizes (nanorods, nanowires, nanotubes, nanosheets, nanowhiskers, nanoshuttles, nanoneedles and nanoleaves) by a simple and inexpensive route remains a great challenge [24]. There are numerous methods reported in the literature for the synthesis of CuO nanoleaves. Xu et al. [25] reported a transition process for the synthesis of 2D CuO nanoleaves from 1D Cu(OH)2 nanowires, Xiang and coworkers [26] were reported the self-assembled synthesis of various hierarchical CuO morphologies at various pH values. Recently, Zhao et al. [27] synthesized 2D CuO nanoleaves using surfactant in aqueous medium at room temperature. Even though, there is a need for the development of a facile and desirable method for the synthesis of CuO nanostructures. In this context, PDDA stabilized nanostructures (can act as both stabilizing and reducing agent) have significant advantage such as single step, low temperature and cost effective method for the synthesis of desired nanostructures compared to other methods reported. Metallic Cu nanoparticles are not enough stable for the electrochemical determination because it can be easily oxidized in aqueous medium. Herein, the modification of an electrode by CuO nanostructures is an essential way to enhance the selectivity and sensitivity of the electrochemical method [28]. To the best of our knowledge, the study involving the fabrication of copper oxide nanostructures modified electrode for electrochemical determination of norfloxacin are not reported in literature.
Therefore, in this paper considerable effort has been taken toward the fabrication of PDDA stabilized CuO nanoleaves incorporated MWCNTs/GC nanocomposite film modified electrode for electrochemical oxidation of norfloxacin. The methods of cyclic voltammetry and differential pulse voltammetry of the CuO/MWCNTs/GC modified electrode for the electrochemical determination of norfloxacin are described. The obtained CuO/MWCNTs/GC modified electrode exhibits excellent electrochemical activity for the determination of norfloxacin.
Section snippets
Chemicals and reagents
Poly(diallyldimethyl)ammonium chloride (PDDA) (Mw = 5000–20,000, 25 wt% in water), copper chloride (CuCl2) anhydrous, multiwalled carbon nanotubes (MWCNTs), and sodium hydroxide (NaOH) pellets were purchased from Sigma–Aldrich. Phosphate buffer (0.1 M, pH 7.2) solution (PBS) prepared with Na2HPO4 and NaH2PO4 were used as supporting electrolyte. All chemicals and reagents used in the experiments were of analytical grade and used without further purification. All the solutions were prepared by using
Results and discussion
In order to investigate the band gap structure of the CuO nanoleaves, the optical band gap energy (Eg) is estimated using the following Eq. (1):where, α is the absorption coefficient, Ephoton is the discrete photon energy, K is a constant, and Eg is the band gap energy. The plot of (αEphoton)2 vs. Ephoton based on the direct transition are shown in Fig. 1A. The extrapolated value (the straight lines to the x axis) of Ephoton at α = 0 gives absorption edge energies
Conclusion
In conclusion, we have successfully synthesized CuO nanoleaves with single step and facile method. The morphology of the synthesized CuO nanostructures revealed leaf like structure. The XRD pattern reveals the monoclinic phase of CuO nanostructures. The CuO/MWCNTs/GC modified electrode exhibited good electrocatalytic oxidation of norfloxacin with an operating potential at +0.91 V in physiological conditions. The sensitivity (0.028 μA/μM), detection limit (3.21 × 10−7 M) and linear response range
Acknowledgements
The authors gratefully acknowledge Department of Science and Technology (DST-PURSE) for the financial support and National Centre for Nanoscience and Nanotechnology (NCNSNT) for HRTEM and XPS measurements.
References (39)
- et al.
Int. J. Antimicrob. Agents
(1998) - et al.
Talanta
(2009) - et al.
Anal. Chim. Acta
(2008) - et al.
J. Pharm. Biomed. Anal.
(2001) - et al.
Bioelectrochemistry
(2012) - et al.
Anal. Chim. Acta
(2008) - et al.
Talanta
(2007) - et al.
Electrochim. Acta
(2011) - et al.
J. Power Sources
(2010) - et al.
Electroanalysis
(2011)