Surface-tuned hierarchical ɤ-Fe2O3–N-rGO nanohydrogel for efficient catalytic removal and electrochemical sensing of toxic nitro compounds

4- Nitrophenol (4-NP) is a top rated hazardous environmental pollutant and secondary explosive chemicals. For the sake of ecology and environment safety, the catalytic reduction and detection of 4-NP is highly important. In this work, ɤ-Fe2O3-nitrogen doped rGO (ɤ-Fe2O3–N-rGO) nanohydrogel was synthesized by green hydrothermal method. The morphology and phase purity of prepared ɤ-Fe2O3–N-rGO nanohydrogel were confirmed by various analytical (SEM, TEM, XRD, and XPS) and electrochemical techniques. The morphological structure of ɤ-Fe2O3–N-rGO nanohydrogel confirmed that the nanocrystals are well covered over the 2D N-rGO layer. Further, ɤ-Fe2O3–N-rGO nanohydrogel was applied for the catalytic reduction and electrochemical detection of ecotoxic 4-NP. A low cost, ɤ-Fe2O3–N-rGO nanohydrogel displayed an excellent catalytic activity, high recyclability (>5 cycles) and high conversion efficiency of 4-NP to 4-Aminophenol (4-AP). In addition, ɤ-Fe2O3–N-rGO nanohydrogel modified GCE displayed a wide linear sensing range (0.1–1000 μM), and a low detection limit (LOD) of 0.1 μM with excellent sensitivity, high selectivity (<1.2%) and good stability (>4 weeks). The developed sensor electrode shows the low reduction potential of −0.3 V and −0.60 V for the determination of 4-NP. The proposed ɤ-Fe2O3–N-rGO nanohydrogel is promising catalyst for the detection and removal of toxic aromatic nitro compounds in real site applications.