Green synthesis of curcumin-functionalized NiO/GO nanoparticles with dual role in plant growth and post-harvest fruit protection

Bio-inspired synthesis provides valuable potency in multifunctional applications. The post-harvest spoilage of fruits needs to be minimized through this approach. An eco-friendly and cost-effective bio-based synthesis of nickel oxide nanoparticles (NiO NPs) was successfully achieved using Illicium verum Hook.f. extract. To enhance multi-functionality, NiO NPs were further functionalized with graphene oxide (GO) and curcumin, resulting in Cur–GO–NiO. Three different ratios (1:1:0.5, 1:1:1, and 1:1:1.5) were prepared to investigate the concentration-dependent efficacy. The synthesized materials were extensively characterized using various analytical techniques such as UV-visible spectroscopy, X-ray diffraction (XRD) analysis, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy. UV-visible analysis revealed the hybrid formation of Cur–GO–NiO with the appearance of absorbance peaks at 240, 340 and 465 nm. X-ray diffraction pattern showed the high crystalline nature of composite. Fourier transform infrared analysis explicated the presence of C=O, C–O, O–H and Ni–O stretching vibrations. Scanning electron microscopy exposed the bulk rectangular, layered structure, spherical morphology of curcumin, GO and NiO NPs, respectively. Energy dispersive X-ray spectrum and mapping showed the existence of carbon, oxygen and nickel elements in Cur–GO–NiO composite. Functionally, Cur–GO–NiO (1:1:1.5) significantly enhanced the growth of Vigna radiata (L.) R.Wilczek at 20 and 40 ppm concentration within 10 days. Moreover, it provided effective post-harvest protection of tomatoes even in the lower 10 ppm dose maintaining zero decay up to 15 days. The high content of biosynthesized NiO NPs with curcumin and GO delivered the multifunctional performance, including post-harvest protection, biocompatibility and plant growth even in lower concentrations. These findings demonstrated that Cur–GO–NiO (1:1:1.5) can be used as a bio-based fungicide, specifically enhancing crop growth and extending post-harvest shelf life, making them highly valuable for sustainable agricultural applications.