title: Time-Resolved Emission Reveals Ensemble of Emissive States as the Origin of Multicolor Fluorescence in Carbon Dots.
abstract: The origin of photoluminescence in carbon dots has baffled scientists since its discovery. We show that the photoluminescence spectra of carbon dots are inhomogeneously broadened due to the slower relaxation of the solvent molecules around it. This gives rise to excitation-dependent fluorescence that violates the Kasha-Vavilov rule. The time-resolved experiment shows significant energy redistribution, relaxation among the emitting states, and spectral migration of fluorescence spectra in the nanosecond time scale. The excitation-dependent multicolor emission in time-integrated spectra is typically governed by the relative population of these emitting states.
authors.affiliation: School of Basic Sciences, Indian Institute of Technology Mandi , Himachal Pradesh 175001, India.
authors.forename: Syamantak
authors.initials: S
authors.lastname: Khan
authors.affiliation: School of Basic Sciences, Indian Institute of Technology Mandi , Himachal Pradesh 175001, India.
authors.forename: Abhishek
authors.initials: A
authors.lastname: Gupta
authors.affiliation: School of Basic Sciences, Indian Institute of Technology Mandi , Himachal Pradesh 175001, India.
authors.forename: Navneet C
authors.initials: NC
authors.lastname: Verma
authors.affiliation: School of Basic Sciences, Indian Institute of Technology Mandi , Himachal Pradesh 175001, India.
authors.forename: Chayan K
authors.initials: CK
authors.lastname: Nandi
keywords: Carbon dots; inhomogeneous broadening; red-edge effect; solvent relaxation; spectral migration; time-resolved fluorescence emission