White-Light Emission from Unmodified Graphene Oxide Quantum Dots

We report herein the synthesis and characterization of unmodified graphene oxide quantum dots (GOQDs) with white-light-emitting properties, upon photoexcitation at 340 nm. The Commission International de lEclairage (CIE) 1931 chromaticity coordinates for GOQDs (x = 0.29, y = 0.34) suggest that highly pure white-light emission was achieved. A detailed mechanistic study was carried out utilizing UV-visible absorption, steady-state and time-resolved fluorescence spectroscopy, and dynamic light scattering (DLS) techniques to understand the origin of the white-light emission. The results taken together suggest that GOQDs could self-assemble in solution and thus transform the luminescence behavior. Furthermore, the results indicate that the pH of the medium also plays a crucial role in assisting the aggregation to generate the white-light emission. The concentration-dependent DLS measurements support a cooperative mechanism for the aggregation kinetics in the system. More importantly, the study suggests that white-light emission can be generated from unmodified graphene oxide quantum dots by tuning their nanoscopic aggregation properties.