Figure 1.

Morphology and optical properties of PCDs. a) TEM image, b) AFM image, and c) UV/Vis absorption spectra of SSFPCDs. d) Excitation–emission matrix of SSFPCDs in aqueous solutions with the concentration of 0.8 mg mL⁻¹. e) Photographs of the SSFPCDs in aqueous solution with different concentrations and the SSFPCDs powder under UV light. f) The normalized PL spectra of SSFPCDs solution with different concentrations and the SSFPCDs powder under the excitation wavelength of 365 nm. Insets: a) the size distributions of SSFPCDs. b) the height of most of the SSFPCDs is 2.5 nm. f) The inset numbers are their quantum yields.