N-substituted CQDs impregnated by Fe3O4 heterostructure: Bifunctional catalyst for electro-catalytic and photo-catalytic detection of an environmental hazardous organic pollutant.

ortho-Nitroaniline (o-NA) compounds are deemed to be a strongly toxic pollutant in nature and potentially carcinogenic; however, they are frequently utilized to synthesize dyes, pesticides, medicines, fungicides, pigments, and other organic chemicals. Their detection in an aqueous medium is fundamentally required to avoid the potential hazardous being created by these compounds. In this study, a novel sensor based on an Iron oxide (Fe3O4) containing highly dispersed nitrogen-doped carbon quantum dots (N-CQDs@Fe3O4 NFs) was demonstrated for the electrochemical detection of o-NA using differential pulse voltammetry (DPV) and cyclic voltammetry (CV) techniques. N-CQDs@Fe3O4 NFs were synthesized by hydrothermal method and studied by various analytical and spectroscopy techniques, which collectively reveal that the as-prepared composite has superior physical and chemical properties. The DPV study indicated that the o-NA sensor had a good limit of detection, linear range, and sensitivity in the range of 1.2 nm, 0.03-386.84 μM, and 36.5575 μA μM-1 cm-2, respectively, along with the sensor showed superior sensitivity when compared to the previously reported modified electrodes. Further, N-CQD/Fe3O4 NFs worked as heterogeneous catalysts for the photocatalytic reduction of o-NA to o-phenylenediamine (o-PD) in an aqueous medium. The reaction was examined under UV-Visible spectroscopy, and the complete photocatalytic reduction was observed for the N-CQD/Fe3O4 NFs in about 6 min with 96% as compared to other control samples; thus, authenticating the superiority of the synthesized composite in rendering the real-time applications.