Nuclear-targeted of TAT peptide-conjugated carbon dots for both one-and two-photon fluorescence imaging.

•Carbon dots (CDs) with fluorescence quantum yield of 58% were prepared by hydrothermal method.•Tryptophan was selected as CDs precursor after screening from seventeen amino acids.•The CDs can be used for both one- and two-photon fluorescence cellular imaging.•The CDs conjugating with TAT peptide showed good capability in nuclear-targeted imaging.