Figure 3.

Profiling the toxicity of metal-based ENMs based on identified descriptors. Dashed line indicates the simplified (mutual) correlation between the descriptors. The descriptors are grouped as relating to the surface characteristics of ENMs or metal oxide, the activity of released ions, the bond breaking, ion and electron detachment, and the medium-related parameters. Molref, molar refractivity; M, molecular weight; ρ, density; N_A, Avogadro’s number; RI, refractive index; PZC, point of zero charge; E_v, valence band energy; E_c, conduction band energy; E_g, band gap; χ_oxide, electronegativity of metal oxide; χ_cation, electronegativity of cation; E_Amz, atomization energy; ∆H_L, lattice energy; ∆H_s, enthalpy of sublimation; ∆H_Me+, enthalpy of formation of a gaseous cation having the same oxidation state as that in the metal oxide structure; ∆H_f⁰, enthalpy of formation of metal oxide nanocluster representing a fragment of the surface; E_∆H⁰, energy associated with a single metal-oxygen bond in the metal oxide; PBS, phosphate buffered saline.