Fig. 1. Synthesis diagram of low-dimensional black phosphorus

Fig. 2. SEM image, TEM image, AFM image, and height statistics charts of 2D-BP sample. (a) SEM image; (b) TEM image; (c) AFM image; (d) height statistics charts of 2D-BP sample (vertical lines in figure indicate relative positions of peaks)

Fig. 3. TEM images, size statistics charts, lattice fringe patterns, AFM images, and height statistics charts of BP-QDs samples. (a) TEM images; (b) size statistics charts; (c) lattice fringe patterns; (d) AFM diagrams; (e) height statistics charts

Fig. 4. TEM images of BP-QDs prepared at different microwave annealing time. (a) 1 h; (b) 2 h; (c) 3 h; (d) 4 h

Fig. 5. Absorption spectra of 2D-BP and BP-QDs samples and fluorescence spectra of BP-QDs prepared at different temperatures. (a) Absorption spectra of 2D-BP and BP-QDs samples; (b)--(d) fluorescence spectra of BP-QDs prepared at different temperatures

Fig. 6. XPS diagrams of BP-QDs samples. (a) Full spectrum; (b) P2p peak fitted spectra

Fig. 7. XPS diagrams of 2D-BP samples annealed at different temperatures. (a) 150 ℃; (b) 200 ℃; (c) 250 ℃; (d) 300 ℃

Fig. 8. XPS diagrams of BP-QDs protected by Al₂O₃ films of different thickness. (a) 5 nm; (b) 10 nm; (c) 15 nm; (d) 20 nm