Note: The upconversion threshold was measured for 5 mg/mL PbS with and without 3 mM TCA. This was because with thicker PbS (25 and 50 mg/mL), there was insufficient UC signal from the control (no TCA) samples to measure the threshold. The same samples (5 mg/mL with and without 3 mM TCA) were used to measure the TRUCPL.