Cyperus scariosus– mediated synthesis of nickel-based nanomaterials for photocatalytic methylene blue degradation, antibacterial and antioxidant activities

was prepared in water and it was used for the synthesis of a nanomaterial based on nickel. The synthesized nanomaterial was tested for its photocatalytic, antibacterial and antioxidant properties. The maximum absorption wavelength obtained by the UV-visible analysis was ∼292 nm, with an apparent optical transition of ∼3.6 eV. The presence of crystalline features containing nickel and oxygen was confirmed by XRD, FTIR and EDX; however, unambiguous assignment of the reflection at 2θ = 32.58° was not possible and no phase purity was claimed. The image resolved features by SEM ranged from ca. 5-60 nm with a fitted distribution center of 33.5 ± 0.4 nm while the average hydrodynamic diameter by DLS was ca. 45 nm. The electrostatic colloidal stabilization was found to be limited with a zeta potential of around -14 mV. The material under sunlight irradiation resulted in about 96% of absorption reduction of methylene-blue in 50 min. The pseudo-first order rate constant was found to be 0.0153 min-1 at 298 K and 0.0286 min-1 at 343 K with an apparent activation energy of 12.04 kJ mol-1. After 5 reuses around 80% of degradation activity was maintained. An anti-bacterial and anti-oxidant response was also seen, and scavenger experiments indicated that more than one reactive species was involved, but did not identify a specific pathway. The results indicate that plant-based nickel-based materials could be used to treat dye-contaminated water, and suggest that more research is needed in this area. In the future, the mineralization, nickel release, ecotoxicity and performance of the system should be assessed in actual wastewater.