OPTIMISATION OF THE GREEN SYNTHESIS PROCESS OF COPPER NANOPARTICLES USING LIME (Citrus aurantifolia) EXTRACT USING RESPONSE SURFACE METHODOLOGY WITH THE BOX-BEHNKEN MODEL

Abstract

This study presents a green synthesis method for copper nanoparticles (CuNPs) using lime extract (LE) as a reducing agent. The optimisation process was conducted through single-factor experiments and response surface methodology (RSM) with a Box-Behnken design, identifying the optimal conditions: temperature of 50.77 °C, pH 7.68, LE/H₂O ratio of 1.45, Cu²⁺concentration of 3.0 mM, Polyvinyl alcohol (PVA) concentration of 0.6 g/L, and reaction time of 90 minutes. TEM images revealed that the synthesized CuNPs exhibited a uniform cubic morphology. The particle size determined by dynamic light scattering (DLS) was 21.432 nm, while the crystallite size calculated from X-ray diffraction (XRD) was 21.276 nm. XRD analysis confirmed a face-centered cubic (FCC) crystal structure, consistent with the TEM images and the standard copper reference (JCPDS Card No. 04-0836). The difference in particle sizes measured by DLS and XRD arises from their distinct measurement principles: XRD determines crystallite size, while DLS measures hydrodynamic size. With significantly small particle sizes, the synthesized CuNPs exhibit superior physicochemical properties, offering promising applications in electronics, biomedicine, and agriculture.