Electrochemical detection of 4-nitrophenol on nanostructured CuBi2O4 with plausible mechanism supported by DFT calculations

Abstract

In this report, copper bismuth oxide (CuBi2O4), a ternary oxide is used for the electrochemical detection of 4-nitrophenol (4-NP). 4-NP is an organic pollutant which is extremely toxic and hazardous to environment. Herein, CuBi2O4 nanorods are prepared hydrothermally followed by electrode fabrication using drop casting method. Structural, morphological studies of CuBi2O4 and electrochemical characterizations pertaining to its performance for electrochemical detection of 4-NP are performed. The electrode has displayed the sensitivity of 56.16 μA μΜ−1 cm−2 with limit of detection (LoD) of 0.61 μM. It displayed high selectivity against several organic and inorganic interferences. The feasibility of CuBi2O4 modified electrode for real water samples is tested and obtained good recovery values. The detailed mechanism involved in the electrochemical detection of 4-NP is proposed and validated with computational studies. Density functional theory (DFT) calculations are performed on the optimized molecules involved in the electrochemical detection of 4-NP confirming CuBi2O4 acting as electron donor while 4-NP as electron acceptor. Further, natural bond orbital (NBO) calculations of 4-NP show a charge of − 0.251 a.u. on -NO2 group and + 0.251 a.u. on the rest of the molecule indicating 4-NP undergoes facile nucleophilic attack. The electrostatic potential (ESP) mapping of 4-NP blue shaded regions justifies its favorable behavior towards nucleophilic attack. Apart from this, UV-Vis spectroscopy is used to study the catalytic reduction of 4-NP using NaBH4. This study reveals that CuBi2O4 is promising material for the electrochemical detection of 4-NP. Also, further modifications of CuBi2O4 can be explored for electrochemical sensing and catalytic performance.