Fig. 3. Confocal luminescence imaging and ratiometric luminescence imaging (λ _ex = 405 nm) of HepG2 cells incubated with the FP-Pdots (10 μg mL^–1) at 21% or 2.5% O₂ concentrations. In luminescence imaging, the emission channels at wavelengths of 420–460 nm and 630–680 nm were collected. In ratiometric imaging, the ratio of emission intensity at 630–680 nm to that at 420–460 nm was chosen as the detected signal.