(color online) (a) Various values of (F₀ − F)/F₀ of WS₂ QDs solution in the absence and presence of 200-μM interfering substances (K⁺, Na⁺, Ca²⁺, Ba²⁺, Al³⁺, Fe³⁺, Ni²⁺, Ag⁺, Hg²⁺, Zn²⁺, , Cl⁻, NO³⁻) under 365-nm excitation wavelength. (b) Effect of WS₂ on the viability of HepG2 cells. The cells are cultured for 12 h and then incubated with 160-μg·ml⁻¹ WS₂ for 6, 12, 24, and 48 h. Cell viability was determined by an MTT assay.