Optimization and characterization of Sida acuta mediated synthesis of nickeloxide nanoparticles using Taguchi–Grey method

This study presents the optimization of nickel oxide nanoparticles (NiO NPs) synthesized through an environmentally benign route using Sida acuta (SA) leaf extract as a reducing and capping agent. Taguchi-Grey Relational Analysis (TGRA) was employed to optimize the hydrodynamic diameter (HDD) and polydispersity index (PDI) of the synthesized NiO NPs. Key synthesis parameters (extract concentration, reaction temperature, and reaction time) were varied within an L9 orthogonal array. Using Grey Relational Analysis (GRA), a regression-based model was developed to predict the grey relational grade (GRG) for multi-response optimization. The optimal synthesis conditions (60 mg/mL extract concentration, 70 °C reaction temperature, and 120 min reaction time) produced NiO NPs with an HDD of 62.72 nm and a PDI of 0.232. ANOVA identified temperature as the dominant factor governing the size and distribution of the NPs. UV-Vis spectroscopy showed a characteristic absorption peak at 284 nm, and XRD confirmed a face-centered cubic crystalline structure with an average crystallite size of 5.99 nm. SEM, EDS, and TEM analyses indicated well-dispersed polycrystalline NPs with 80% purity. The synthesized NiO NPs possess physicochemical characteristics that position them as promising candidates for catalytic, sensing, and energy-storage applications. This work demonstrates a statistical-experimental framework for tuning nanoparticle properties through sustainable synthesis routes, highlighting a scalable strategy for precision nanomaterial design.