Nanoheating and in-situ temperature sensing of GNR-FNDs in cells. (a-c) Colocalization studies of internalized GNR-FNDs with lysosomes in HeLa cells by confocal fluorescence microscopy. The cells were fluorescently labeled with Hoechst 33342 (a), LysoTracker Green (b), and FND (c) markers. (d) Merged bright-field and fluorescence images of the cells. Yellow-coloured spots correspond to the colocalization of FNDs (red) with lysosomes (green). (e) Power-dependent temperature rises of two GNR-FND particles irradiated by an 808 nm laser with its power increasing from 0 to 0.8 mW in a HeLa cell.