Diffuse reflectance spectra were collected by an Analytik Jena Specord ® S-600 UV/Vis 15 spectrophotometer (Analytik Jena AG, Germany), coupled with an integrating sphere, using 16 barium sulfate as the reflectance standard. The agar-well diffusion method was employed to 17 assess the toxicity of the as-synthesized FeCoNiCuZn powder, towards the Gram-negative 18 bacterium Escherichia coli (E. coli).