Chlorella vulgaris-mediated synthesis and physicochemical properties of ZnO nanoparticles with toxicity assessment using Artemia salina

• Chlorella vulgaris extract was used for eco-friendly ZnO nanoparticle synthesis. • Green and sol–gel routes produced spherical ZnO NP with nanoscale size. • Algal-derived ZnO NP showed smaller crystallite size and distinct FTIR features. • Toxicity against Artemia salina indicated LC₅₀ ≈ 132.56 ppm for algal ZnO NP. • Results highlight sustainable synthesis with comparable physicochemical quality. Green synthesis using microalgae is a sustainable process to produce a metal oxide nanomaterial. This study aims to synthesize ZnO nanoparticles (ZnO NP) using Chlorella vulgaris and compare the physicochemical characteristics and toxicity responses in Artemia salina . The synthesis method was conducted by extracting C.vulgaris using ethanol, then reacting it with zinc acetate dihydrate, subsequently calcining it at 400 °C for 2 h. Physicochemical properties of ZnO NP were analyzed by scanning electron microscopy coupled with energy-dispersive X-ray, UV–Visible spectroscopy, X-ray diffraction, and Fourier-transform infrared spectroscopy. In addition, the toxicity was assessed using A.salina as a bioassay model. UV–Visible spectroscopy revealed the highest absorption at peak of ∼300 nm, representing a significant blue-shift compared to the typical 370–400 nm range for ZnO NP, while energy-dispersive X-ray confirmed the Zn element with a signal at 1.2 keV. All ZnO NP exhibited a spherical morphology. The algal-mediated ZnO NP had the smallest crystallite size (40.5 ± 13.5 nm) and particle size of 57 ± 13 nm, followed by the sol–gel sample (45.4 ± 2.9 nm; 54 ± 10.8 nm) and the commercial ZnO NP (57.7 ± 3.9 nm; 50 ± 7.5 nm). The algal-mediated ZnO NP exhibited the highest LC₅₀ (132.56 ppm), suggesting lower acute toxicity compared to the sol–gel (123.89 ppm) and commercial (130.42 ppm) counterparts. However, the differences among LC₅₀ values were not statistically significant ( p > 0.05). These findings suggest that the C. vulgaris -mediated synthesis route produces smaller ZnO NP that display a clear time-dependent toxicological response toward A.salina .