Fig. 4

Two-color fluorescence imaging of a tumor in the NIR-II window. a Wide-field fluorescence imaging of a mouse inoculated with a 4T1 tumor through collection of fluorescence emitting from p-FE above 1300 nm with exposure time of 5 ms and variation of T/NT signal ratio as a function of time (n = 3). b High-magnification fluorescence imaging of a mouse inoculated with a 4T1 tumor using two colors in the NIR-II window. c Confocal imaging of a tumor using two colors in the NIR-II window. 740 µm  × 740 µm × 220 µm area, step size: 2 µm along x and y directions, 5.4 µm along z direction. Laser power ~30 mW, PMT voltage: 500 V for p-FE channel and 600 V for laser CNT channel, scanning speed 15 min/frame. Pin hole: 150 µm for p-FE and 300 µm for laser CNT channel. Wavelength range: 1100–1300 nm for p-FE channel and 1500–1700 nm for laser CNT channel. Scale bars in Figs 1a and 2b represent 2 cm and 6 mm, respectively. Error bars correspond to standard deviation