<![CDATA[Green synthesis has emerged as an alternative approach for preparing zinc oxide (ZnO) nanoparticles using plant-derived compounds. This study aimed to synthesize ZnO nanoparticles using aqueous Orthosiphon aristatus leaf extract and characterize their crystalline structure and phase characteristics using X-ray diffraction (XRD). The leaf extract was prepared by heating 10 g of powdered leaves in 100 mL of distilled water at 60 °C for 1 h. A zinc nitrate hexahydrate solution was mixed with the extract at a precursor-to-extract ratio of 1:10, and the mixture was adjusted to approximately pH 7 using NaOH. The reaction was maintained at 70 °C for 4 h, followed by drying at 50 °C for 14 h and calcination at 450 °C for 4 h. The XRD pattern exhibited prominent reflections at 2θ values of 31.740°, 34.397°, and 36.225°, corresponding to the (100), (002), and (101) planes, respectively, consistent with the hexagonal wurtzite structure of ZnO. Based on these reflections, the lattice parameters were estimated to be a ≈ 3.253 Å and c ≈ 5.210 Å, with a c/a ratio of approximately 1.602. These values are consistent with the characteristic crystallographic features of Wurtzite ZnO. However, the available diffraction results alone are insufficient to establish phase purity conclusively. The findings demonstrate the feasibility of preparing ZnO with a wurtzite-type crystalline structure using O. aristatus leaf extract. Further phase analysis and direct antibacterial assays are required to establish phase purity and evaluate the material's potential antibacterial performance.]]>
