Figure 4. Anti-Stokes luminescence stability and reproducibility.

(a) Evolution of luminescence monitored at 700 nm under continuous illumination with an incoherent LED (7.87 mW/cm²) operating at a wavelength of 800 nm. (b) Reproducibility of anti-Stokes luminescence generation during 17 on/off cycles over a period of 10000 s. Before measurements, effective optical charging of the probe can be done by UV-vis light for 5 min, the measurements were taken at the interval of 24 hours after charging.