Figure 2. Micro⁵⁴⁰-UCPs are robustly photo-stable and respond rapidly to excitation light.

Kymographs generated from the time lapse imaging of (A) micro⁵⁴⁰-UCPs to demonstrate the emission photostability after a 45-min period of continuous irradiation with 1470 nm NIR light. For (A, B) this initial irradiation was followed by a 5 min off period, and then another 5 min NIR on period to show the emission intensity returns to the highest level with micro⁵⁴⁰-UCPs. (C, D) Kymograph and quantitative visible emission intensity analysis (average minus background) of the visible emission light generated over time for micro⁵⁴⁰-UCPs to demonstrate the visible light emission response speed to 2-min on and off pulses of 1470 nm irradiation. (A, C) The white dashed line indicates the approximate region used for plotting the kymographs. (A–D) The duration of NIR irradiation is indicated by the maroon bars on top of the kymographs. FIRE LUT used to indicate emission intensity. Scale bars (white = 10 µm) and (yellow = 2 min). Data represents mean ± standard error from n = 3 (A, B) or n = 5 (C, D) independent experiments. (E) Control, background signal quantification showing the lack of detectable emission intensity on the visible light sensitive camera upon excitation with increasing power levels of 1470 nm light through a 525 ± 25 nm emission filter in the absence of UCPs.