Fig. 2

Morphological and optical characterizations of Phellodendri Chinensis Cortex-based carbon dots (PCC-CDs) prepared at 400 ℃. a Transmission electron microscopy (TEM) images. b Particle size distribution histogram. c High-resolution transmission electron microscopy (HRTEM). Inset: magnification figure. d Ultraviolet and visible spectrum, e Fluorescence spectra and f Fluorescence spectra of PCC-CDs with different excitation wavelengths