Characterization and in vitro biocompatibility evaluation of AIE probes. (a) Schematic illustrations of preparation of AIE probes through a nanoprecipitation method. (b) Fluorescence spectra of TTB molecules in THF solution with different water fractions (vol%). The inset shows plots of the AIE curves of TTB. (c) Dynamic light scattering data of the aqueous AIE probes. Inset: transmission electron microscopy image of water-dispersed AIE probes. (d) Fluorescence and absorption spectra of AIE probes. The red-shaded area shows the NIR-II emission wavelength of AIE probes from 1000 to 1350 nm and the maximum emission wavelength at 1050 nm. (e) The cytotoxicity analysis of the AIE probes by routine MTT assay. (f) Hemolysis analysis of red blood cells after exposure to AIE probes at 0 μg mL-1, 25 μg mL-1, 50 μg mL-1, 100 μg mL-1, 200 μg mL-1, and 400 μg mL-1. The inset shows digital photographs of AIE probe-treated red blood cells. The negative control group (-) and positive control group (+) are phosphoric acid buffer-treated red blood cells and deionized water-treated red blood cells, respectively.