Cinnamon-bark-assisted synthesis of calcined Cu-Ni mixed metals nanostructures: HepG2 cytotoxicity, DPPH scavenging and visible-light BTB decolorization

Cinnamon bark extract was evaluated as a plant-derived reagent for preparing Cu-Ni nanomaterial. A broad visible absorption centred near 450 nm was observed; this optical feature is supportive. The FTIR band at 445.56 cm -1 is assigned conservatively to metal-oxygen vibrations. XRD reflections were provisionally indexed mainly to overlapping NiO- and CuO-related phases, with a Scherrer equation estimate of approximately 29 nm. SEM-EDX detected Cu (32.39 wt.%), Ni (19.08 wt.%), O (11.08 wt.%), and C (37.45 wt.%), while HR-TEM showed predominantly rounded primary particles with a reported diameter of 9.7 ± 4.7 nm and polycrystalline SAED rings. In HepG2 cells, viability decreased from 95.60% in the untreated control to 26.34% at 1000 µg mL -1 (reported IC 50 = 77.6 µg mL -1 ; n = 4). DPPH scavenging increased from 30.2% at 10 µg mL -1 to 88.43% at 100 µg mL -1 , compared with 35.72-98.22% for ascorbic acid. Following 30 min dark equilibration, the catalyst-dye suspension showed 82.55% apparent bromothymol blue (BTB) decolorization after 180 min of visible-light exposure and retained 72.67% decolorization in the fifth reuse cycle. Calculation from the tabulated absorbance values gave k app = 0.0097 min -1 and R 2 = 0.985, indicating a single pseudo-first-order model. These findings represent preliminary environmental and biological screening results. Dye mineralization, catalyst-specific activity, the cytotoxic mechanism, cancer selectivity, and biosafety remain unconfirmed and require TOC or intermediate analysis, appropriate photocatalytic controls, mechanistic cellular assays, and comparative normal-cell testing