Fig. 1. Structural characteristics of SiQDs. (a) TEM image; (b) HR-TEM image; (c) EDS spectrum

Fig. 2. Simulation results of SHG electric field distribution. (a) SHG electric field distribution of SiQDs; (b) SHG electric field distribution of SiNP; (c) absorption spectra

Fig. 3. Diagram of SHG imaging device

Fig. 4. Imaging characteristics of PEG-coated SiQDs. (a) Fluorescence imaging; (b) SHG image; (c) fluorescence emission spectra at 280 nm and 322 nm single photon excitation; (d) SHG emission spectra; (e) relationship between SHG intensity and laser power

Fig. 5. Confocal images of HepG2 cells. (a)‒(c) SHG image, bright field image and superimposed image of HepG2 cells with SiQDs incubation; (d)‒(f) SHG image, bright field image and superimposed image of HepG2 cells without SiQDs incubation

Fig. 6. Comparison of SHG and TPL imaging in HepG2 cell. (a)‒(c) SHG image and corresponding bright field image and superimposed image; (d)‒(f) TPL image and corresponding bright field image and superimposed image; (g)‒(i) continuous SHG imaging; (j)‒(l) continuous TPL imaging; (m) SHG and TPL emission spectra