Effect of nanocomposite partnering of g-C3N4 with Morinda pubescens leaf extract mediated Sr doped Ni/NiO on the photocatalytic dye detoxification: Confirmation by seed germination test

A carbonaceous 2D material g-C₃N₄ was added as the composite partner to Sr doped (Ni/NiO) to synthesize a green routed nanocomposite (Ni/NiO):Sr/g-C₃N₄ using the leaf extract of Morinda pubescens. The synthesized material was employed as a photocatalyst towards complete detoxification of synthetic toxic dyes methylene blue (MB-cationic) and rose bengal (RB- anionic) widely used in textile, leather and paper industries. The efficiency of the nanocomposite was compared with those of Ni/NiO and Ni/NiO:Sr samples. The composite formation was verified through XRD, SEM, TEM, EDAX, FTIR, UV–Vis-NIR and XPS analyses. The Sr doped (Ni/NiO)/g-C₃N₄ nanocomposite showed significant higher photocatalytic efficiency of 98 % for MB dye and 94 % for RB dye compared to (Ni/NiO):Sr (72 and 65 %) and (Ni/NiO) (83 % and 70 %) within 45 min of irradiation. The inclusion of g-C₃N₄ in the nanocomposite reduces the band gap (from 3.9 eV for Ni/NiO to 2.9 eV for (Ni/NiO):Sr/g-C₃N₄), enabling it to serve as visible light responsive photocatalyst. The stability of the material was confirmed by conducting re-cycle test. To find the role of active species involved in the photocatalysis, trapping test was conducted, the result of which showed that OH^⁎ radicals predominate over the other three species (e⁻, h⁺ and O₂⁻) in degrading the dye molecules. The attainment of complete detoxification of the test dye solutions was demonstrated by conducting seed germination test using Amaranthus viridis seeds. A superior seed germination was observed in the case of water sample treated by (Ni/NiO):Sr/g-C₃N₄ nanocomposite compared to all the other samples including the control. Thus, this eco-friendly nanocomposite synthesized using Morinda pubescens plant leaf extract shows its potential for efficient detoxification of organic dyes through photocatalytic process.