Synthesis, characterization and photocatalytic dye degradation capability of Calliandra haematocephala-mediated zinc oxide nanoflowers

An environmentally sound approach towards the green synthesis of zinc oxide nanostructures has been achieved with an aqueous extract of Calliandra haematocephala leaves. The nanoparticles were characterized using various analytical techniques to substantiate the structural details. An absorption band at 358 nm corresponds to the formation of zinc oxide nanoparticles. Scanning electron microscopy revealed the nanoflower morphology of the nanoparticles. Energy dispersive spectral analysis portrayed the strong presence of zinc and oxygen, while X-ray diffraction showed the nanoparticles to conform to hexagonally-formed wurtzite structure. The crystallite size of the nanoflowers was estimated to be 19.45 nm. Vibrational frequencies, typical of zinc‑oxygen and other functional groups, were revealed using Fourier transform infrared spectroscopy. BET analysis revealed that the pores were of mesoporous nature with an estimated specific surface area of 9.18 m²/g. The photocatalytic nature of the nanoparticles was established by the degradation of methylene blue (MB) dye, under solar radiation. Up to 88% degradation was achieved in a duration of 270 min. Kinetic data from the studies proved that the reaction was compliant with first-order model, with rate constant as 0.01 min⁻¹. The study illustrated the synthesis of zinc oxide nanoparticles using a novel source, viz., the leaves of C. haematocephala.