Figure 16.

(A) Schematic of nanothermometer used to monitor the temperature profile created by heating a colloidal solution of NaYF₄:Er³⁺,Yb³⁺ UCNPs in water with a NIR diode laser (980 nm, pump beam) and scanned with a Ar⁺ laser (488 nm, probe beam). (B) Confocal image of all the visible upconverted luminescence under 980 nm excitation (Left). Thermal image of the spot created by the 980 nm pump beam (Right). (C) Optical transmission images of an individual HeLa cell at different temperatures and temperature-dependent property of the HeLa cell determined by UCNPs as a function of the applied voltage ¹¹³. The voltage determines the heating temperature of plate under the cells. Reproduced with permission from reference ¹¹³.