Controlled Biosynthesis of Zinc Oxide Nanoparticles Using Plant Extracts: A Box-Behnken Design for Size Optimization

This study employed a green and sustainable approach to biosynthesize zinc oxide nanoparticles (ZONPs) using a mixture of Anastatica hierochuntica L and Solenostemma argel plant extracts. The primary aim was to address the common challenges of uncontrolled nanoparticle size in biosynthesis and the inefficiencies of traditional optimization methods. To achieve this, the Box-Behnken design (BBD) of the response surface methodology (RSM) was utilized to systematically investigate the effects of three key synthesis parameters: zinc acetate concentration (ZA-C), reaction temperature (REA-T), and annealing temperature (AN-T) on ZONP size. The successful synthesis of pure ZONPs with a hexagonal crystal system and a band gap of 3.26 eV was confirmed through various characterization techniques including ultraviolet-visible spectroscopy (UV-Vis), fourier transform Infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive x-ray spectroscopy (EDX). The synthesized ZONPs exhibited spherical or slightly elongated shapes with sizes ranging from 66 nm to 32 nm. Statistical analysis validated the generated quadratic model, which accurately predicted and fit the experimental data, with a predicted R² of 95.42% and an adjusted R² of 97.93%. ANOVA results indicated that ZONPs size is significantly affected by all the investigated parameters as well as their interactions, except for the REA-T and AN-T interaction. Utilizing numerical optimization and the desirability function, the optimal conditions yielded a minimum size of 31 nm. This study successfully demonstrates the efficiency of RSM in controlling ZONPs size produced via the biosynthesis method, suggesting potential for future research to include additional parameters for further refinement of NPs size control.