Fabrication of All-Liquid and Convertible Solid-State White Light-Emitting Diodes via Sequential and Parallel Energy Transfers between Carbon Dots, Fluorescein Dye, and Gold Nanoclusters: An In-Depth Spectroscopic Study

This paper reports the simple fabrication of all-liquid white light-emitting diodes (WLEDs) using carbon dots (CDs)-fluorescein (FS)-gold nanoclusters (AuNCs) for the first time. All-liquid WLED from the CDs-FS-AuNC system has been realized from a sequential Förster resonance energy transfer (FRET) mechanism via the CDs-FS and FS-AuNCs paths in conjunction with a parallel FRET process directly from the CDs to the AuNCs. The chromaticity parameters of the as-fabricated system in aqueous solution can be easily tuned from cyan to white by simply changing the concentrations of the individual components. For practical applications in optoelectronic devices, a CDs-FS-AuNCs white light (WL)-emitting gel in an agarose medium was coated on a commercial UV-LED chip to produce bright WL under UV excitation, thereby opening its applications in solid-state lighting devices.