Optimisation of green synthesis of MnO nanoparticles via utilising response surface methodology.

This study concerns the optimisation of green synthesis of manganese oxide nanoparticles (MnO NPs) with Dittrichia graveolens (L.) extract via response surface methodology (RSM). Central composite design was used to evaluate the effect of pH, time, and the extract to the metal ratio on the synthesised nanoparticles (NPs). Nine runs were designed to investigate the effect of each parameter while NPs were synthesised under different conditions. Considering the p-values (p-value < 0.05), it is indicated that the extract to the metal ratio was the most effective parameter. The synthesised NPs were characterised using UV-vis. Synthesis of the NPs by polyphenolic compounds of green reducing agent and their stabilisation by curcumin was confirmed by Fourier transform infrared spectra and the surface morphology of the spherical MnO NPs was studied by field-emission scanning electron microscopy and transmission electron microscope techniques. The present researchers claimed the optimal condition as follows: time = 56.7 min, pH = 7.2, and the extract to the metal ratio = 87.9 v/v. MnO NPs at optimum condition were then employed for degradation of industrial dyes and they showed high dye degradation activity against Rhodamine B and light green dye. The average size of the synthesised MnO NPs at optimal condition was claimed to be nearly 38 nm.