Electrochemical Sensor Detects 4-Nitrophenol in Water Sample

Well known organic contaminant para nitrophenol, sometimes referred to as 4-nitrophenol (4NP), is widely released into the environment and presents a number of health risks to people. A novel electrochemical sensor based on Ni@CuO/rGO/PtE has been developed for the sensitive and selective screening of 4-NP. The Ni@CuO/rGO nanocomposite's outstanding crystalline structure and average size of 47.3 nm were shown by the XRD investigation. Evaluation of the effective integration of Ni and CuO into the GO sheets was conducted using SEM and HR-TEM characterisation. The remarkable purity and % elemental composition of the produced nanocomposite were validated by the EDX analysis. Ni@CuO/rGO was uniformly deposited across the surface of bare PtE as a result of the prepared material being cast on it using the drop-casting method. Under optimal conditions, such as scan rate 110 mV/s, acidic pH -5 PBS electrolyte, and potential window between -0.3 and -1.2 v, the constructed sensor Ni@CuO/rGO/PtE demonstrated outstanding response for 4-NP. A linear calibration curve of 4-NP was obtained by optimizing a wide linear concentration range, ranging from 0.09 to 105 μM. The estimated LOD and LOQ of the suggested approach are 0.0054 μM and 0.018 μM, respectively, which are nearly as low as the reported 4-NP sensor. Ni@CuO/rGO/PtE's analytical applicability was evaluated using samples of river and tap water. The suggested sensor's strong dependability in actual samples was demonstrated by the manufactured sensor, which demonstrated respectable recoveries for 4-NP in water samples.

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4-Nitrophenol (4-NP), a notorious organic pollutant, poses significant health risks as it is widely released into the environment. Addressing this concern, a cutting-edge electrochemical sensor has been developed for the sensitive and selective screening of 4-NP. The sensor, based on Ni@CuO/rGO/PtE, exhibits promising results for real-world applications.

Material Characterization

Extensive analysis, including X-ray diffraction (XRD), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HR-TEM), confirmed the excellent crystalline structure of the Ni@CuO/rGO nanocomposite. The nanocomposite, with an average size of 47.3 nm, successfully integrated Ni and CuO into graphene oxide (GO) sheets, as validated by energy-dispersive X-ray spectroscopy (EDX) analysis.

Sensor Fabrication and Optimization

Utilizing a drop-casting method, the prepared nanocomposite was uniformly deposited on bare PtE. The fabricated sensor, Ni@CuO/rGO/PtE, exhibited outstanding responsiveness to 4-NP under optimized conditions—scan rate 110 mV/s, phosphate-buffered saline (PBS) electrolyte at acidic pH -5, and a potential window between (−0.3 to −1.2 V). A broad linear concentration range from 0.09 to 105 μM resulted in a linear calibration curve for 4-NP.

Performance Metrics

The proposed sensor showcased remarkable sensitivity with a low limit of detection (LOD) and limit of quantification (LOQ) of 0.0054 μM and 0.018 μM, respectively—outperforming existing 4-NP sensors. The sensor's analytical applicability was successfully tested in tap water and river water samples, demonstrating its reliability and efficiency in real-world scenarios.

Chemicals and Reagents

The study employed high-quality analytical-grade chemicals, including graphite powder, NiCl2, CuCl2.5H2O, KMnO₄, NaNO3, bisphenol-S (BPS), bisphenol-A (BPA), isoproturon (ISP), trichlorophenol (TCP), pentachlorophenol (PCP), nitric acid (HNO3), hydrogen peroxide (H2O2), sulfuric acid (H2SO4), hydrochloric acid (HCl), and 4-nitrophenol.


In conclusion, the integration of Ni@CuO/rGO/PtE into electrochemical sensors showcases significant potential in the detection and measurement of 4-NP in water samples. The modified PtE not only enhances sensitivity and selectivity but also exhibits an excellent anti-interference profile. Electrochemical characterization through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) further supports the sensor's conductive nature and charge capabilities. This breakthrough offers a promising solution for environmental monitoring and pollution control.

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