The present article reports a facile approach to fabrication of mesoporous octahedron-shaped tricobalt tetroxide nanoparticles (Co₃O₄ NPs) with a very narrow size distribution for eco-friendly remediation of toxic dyes. Co₃O₄ NPs were fabricated by a sol–gel process using cobalt chloride hexahydrate (CoCl₂·6H₂O) and monosodium succinate (C₄H₅O₄Na) as a chelating/structure-directing agent and sodium dodecyl sulfate as a surfactant. Moreover, the phase structure, elemental composition, and thermal and morphological facets of Co₃O₄ NPs were investigated using XRD, FT-IR, EDS, Raman, XPS, TGA, SEM, and TEM techniques. The face-centered cubic spinel crystalline structure of the Co₃O₄ NPs was confirmed by XRD and SEM, and TEM analysis revealed their octahedron morphology with a smooth surface. Moreover, the narrow pore size distribution and the mesoporous nature of the Co₃O₄ NPs were confirmed by Brunauer–Emmett–Teller measurements. The photocatalytic activity of Co₃O₄ NPs for degradation of methyl red (MR), Eriochrome Black-T (EBT), bromophenol blue (BPB), and malachite green (MG) was examined under visible light irradiation, and the kinetics of the dye degradation was pseudo-zero-order with the rate constant in the order of MR > EBT > MG > BPB. Furthermore, the mechanism of photo-disintegration mechanism of the dye was examined by a scavenging test using liquid chromatography–mass chromatography, and its excellent photodegradation activities were attributed to the photogenerated holes (h⁺), superoxide (O₂^–) anions, and hydroxyl (^·OH) radicals. Finally, the synergistic effect of the nano-interconnected channels with octahedron geometry, mesoporous nature, and charge transfer properties along with photogenerated charge separations leads to an enhanced Co₃O₄ photocatalytic activity.

The ever-growing resistance of pathogens to antibiotics and crop disease due to pest has triggered severe health concerns in recent years. Consequently, there is a need of powerful and protective materials for the eradication of diseases. Metal/metal oxide nanoparticles (M/MO NPs) are powerful agents due to their therapeutic effects in microbial infections. In this context, the present review article discusses the toxicity, fate, effects and applications of M/MO NPs. This review starts with an introduction, followed by toxicity aspects, antibacterial and testing methods and mechanism. In addition, discussion on the impact of different M/MO NPs and their characteristics such as size, shape, particle dissolution on their induced toxicity on food and plants, as well as applications in pesticides. Finally, prospective on current and future issues are presented.