Peptide-Decorated\nTunable-Fluorescence Graphene Quantum Dots

Abstract

We\nreport here the synthesis of graphene quantum dots with tunable size,\nsurface chemistry, and fluorescence properties. In the size regime\n15–35 nm, these quantum dots maintain strong visible light\nfluorescence (mean quantum yield of 0.64) and a high two-photon absorption\n(TPA) cross section (6500 Göppert–Mayer units). Furthermore,\nthrough noncovalent tailoring of the chemistry of these quantum dots,\nwe obtain water-stable quantum dots. For example, quantum dots with\nlysine groups bind strongly to DNA in solution and inhibit polymerase-based\nDNA strand synthesis. Finally, by virtue of their mesoscopic size,\nthe quantum dots exhibit good cell permeability into living epithelial\ncells, but they do not enter the cell nucleus.