Fig. 1

a TEM image of the CDs. Insets show the HRTEM image of the CDs. b XRD pattern of the CDs. c Raman spectroscopy of the CDs. d FTIR spectroscopy of the CDs. e Fluorescence variation of CDs after adding 0.5 M H₂O₂. Insets show photographs of CDs before (left) and after (right) adding the H₂O₂ under UV light. f Colorimetric variation of CDs after adding 0.5 M H₂O₂. Insets show photographs of CDs before (left) and after (right) adding the H₂O₂ under daylight