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. 2023 Jun 17;23(12):5668.
doi: 10.3390/s23125668.

Fabrication of Carbon Nanofiber Incorporated with CuWO4 for Sensitive Electrochemical Detection of 4-Nitrotoluene in Water Samples

Ganesh Abinaya Meenakshi  1   2 , Subramanian Sakthinathan  1   2 , Te-Wei Chiu  1   2
Affiliations

Fabrication of Carbon Nanofiber Incorporated with CuWO4 for Sensitive Electrochemical Detection of 4-Nitrotoluene in Water Samples

Ganesh Abinaya Meenakshi et al. Sensors (Basel). .

Abstract

In the current work, copper tungsten oxide (CuWO4) nanoparticles are incorporated with carbon nanofiber (CNF) to form CNF/CuWO4 nanocomposite through a facile hydrothermal method. The prepared CNF/CuWO4 composite was applied to the electrochemical detection of hazardous organic pollutants of 4-nitrotoluene (4-NT). The well-defined CNF/CuWO4 nanocomposite is used as a modifier of glassy carbon electrode (GCE) to form CuWO4/CNF/GCE electrode for the detection of 4-NT. The physicochemical properties of CNF, CuWO4, and CNF/CuWO4 nanocomposite were examined by various characterization techniques, such as X-ray diffraction studies, field emission scanning electron microscopy, EDX-energy dispersive X-ray microanalysis, and high-resolution transmission electron microscopy. The electrochemical detection of 4-NT was evaluated using cyclic voltammetry (CV) the differential pulse voltammetry detection technique (DPV). The aforementioned CNF, CuWO4, and CNF/CuWO4 materials have better crystallinity with porous nature. The prepared CNF/CuWO4 nanocomposite has better electrocatalytic ability compared to other materials such as CNF, and CuWO4. The CuWO4/CNF/GCE electrode exhibited remarkable sensitivity of 7.258 μA μM-1 cm-2, a low limit of detection of 86.16 nM, and a long linear range of 0.2-100 μM. The CuWO4/CNF/GCE electrode exhibited distinguished selectivity, acceptable stability of about 90%, and well reproducibility. Meanwhile, the GCE/CNF/CuWO4 electrode has been applied to real sample analysis with better recovery results of 91.51 to 97.10%.

Keywords: 4-nitrotoluene; CNF; CuWO4; electrochemical sensor; real sample analysis.

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Conflict of interest statement

The authors declare no competing interest.

Figures

Figure 1
Figure 1
(a) XRD patterns of CuWO4 and CNF/CuWO4 nanocomposite. (b) Raman spectra of CuWO4, CNF, and CNF/CuWO4 nanocomposite.
Figure 2
Figure 2
FESEM analysis for (a) CuWO4, (b) CuWO4/CNF, (c) EDX color mapping for CuWO4/CNF, and (d) Cu, (e) W, (f) O, and (g) C elemental mapping (h) EDX spectra of CuWO4/CNF composite.
Figure 3
Figure 3
HR-TEM analysis of (a) CuWO4, (b) CNF, and (c,d) CuWO4/CNF nanocomposite.
Figure 4
Figure 4
(a) Cyclic voltammogram of bare GCE, CNF/GCE, CuWO4/GCE, CuWO4/CNF/GCE modified electrodes in 5 mM K3[Fe (CN)6]3−/4− 0.1 M KCl system at 10 mV/s. (vs. Ag/AgCl). (b) Bar diagram of redox currents for different electrodes. (c) CV profiles were recorded for CuWO4/CNF/GCE at scan rates of 20–240 mVs−1. Different colors peak mentioned different scan rates studies. (d) The linear plot for scan rate vs. peak current (Ip).
Figure 5
Figure 5
(a) Cyclic voltammetry detection of 4-NT using different electrodes (b) GCE, (c) CNF/GCE, (d) CuWO4/GCE, (e) CuWO4/CNF/GCE in 0.05 M PBS (pH = 7.0) with 100 µM 4-NT. (A) shows the CV response in the non-existence of 4-NT, (B) Bar diagram of different electrode peak currents.
Scheme 1
Scheme 1
The electrocatalytic reduction of 4-nitro toluene to 4-hydroxylamine toluene on the CuWO4/CNF/GCE electrode surface.
Figure 6
Figure 6
(a) Cyclic voltammetry response of CNF/CuWO4 at different concentrations of 4-NT from 10 μM to 100 μM in 0.05 M PBS (pH = 7.0) at the scan rate 50 mV/s. Different colors mentioned for different concentration. (b) Linear plot of 4-NT peak current vs. concentration.
Figure 7
Figure 7
(a) Cyclic voltammetry response of CuWO4/CNF modified electrode in different pH-3, 5, 7, 9 conditions with 100 µM at the scan rate of 50 mV/s. (b) Calibration plot of reduction peak current vs. different pH.
Figure 8
Figure 8
(a) Cyclic voltammetry response of CuWO4/CNF nanocomposite electrode in PBS with 100 µM of 4-NT at different scan rates. Different scan rates peaks mentioned in different colors. (b) Calibration plot of the reduction peak current vs. scan rate.
Figure 9
Figure 9
(a) DPV response of the CuWO4/CNF/GCE for consecutive addition of 4-NT in 0.05M PBS (pH = 7). Different concentration peaks mentioned in different colors. (b) The linear plot for cathodic current peak vs. concentration of 4-NT.
Figure 10
Figure 10
i–t response of reduction of 4-NT in the presence of various interfering ions anions such as (a) F−, (b) Cl−, (c) NO3−, (d) CO2−, (e) CO3−, (f) Cl−, and cations such as (g) Na+, (h) Cr2+, (i) Mg2+, (j) Zn+, (k) NH4+.
Figure 11
Figure 11
(a) Repetitive runs of a single GCE/CuWO4/CNF electrode. (b) Reproducibility of CuWO4/CNF/GCE electrode for five differently fabricated electrodes. (c) Cyclic stability of the CuWO4/CNF/GCE electrode in 0.05 M PBS with 100 µM at the scan rate of 50 mV/s for 100 cycles.
Figure 12
Figure 12
DPV voltammogram for various concentrations from 10 to 30 µM in water samples of (a) river water and (b) tap water.
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