Fig. 4: Optical properties of ensemble and single-particle CDs.
From: Electron–phonon coupling-assisted universal red luminescence of o-phenylenediamine-based carbon dots
a Normalized absorption (black) and photoluminescence (PL) spectra of ensemble (blue) CDs and the representative single-particle CD (red) PL spectra. b, c are the distributions of the maximum emission peak and spectral band separation, respectively. The dotted curves in b, c are the distributions fitted with Gaussian functions; fluorescence images of single-particle CDs placed on a PVA film (inset). PL spectra of the ensemble CDs (d) and the single-particle CDs (e) at different temperatures from 77 to 298 K. f PL spectra of single R-CDs at 77 K. Black circles represent the measured data; red curves correspond to the total fits that contain four Lorentzian functions. g Distributions of the spectral band separation of dozens of single-particle CDs at 77 K
