Light Emission from/on Graphene

Graphene is a 2D material with atomic thickness and possesses unusual thermal, electrical, and mechanical properties. Most of current research has been focused on synthesis of graphene and applications to enhance electrical and mechanical properties. However, graphene quantum dots (GQDs), simply making graphene typically under 10 nm, and the change of emission behavior from known fluorescents on graphene draws huge interest for potential applications to display, lighting, and optoelectronic devices. GQD could be a new class of optical material with useful properties of tunable luminescence, superior photo-stability, and chemical resistance. Here, we demonstrate the first GQD light-emitting diodes (GQD-LEDs) in which GQDs are incorporated into polymeric host layers in a multilayer electroluminescent (EL) device that irradiates blue (~400 nm) emission exceeding 1,000 cd/m2. The GQD-LEDs are possible because our novel and simple synthesis method creates high-quality GQDs with minimal, or controlled, oxidation. More recent study of PL origin from GQDs suggests the oxidation control is a key to form intact graphitic subdomains in the GQD that possess discrete bandgap. Besides the direct emission from graphene, when conjugated fluorescent materials (i.e. Pt-porphyrin) interact with the conjugated plane of graphene, interesting PL shifts and emission enhancements are observed. The potential mechanism of the unusual behaviors will be explained with some experiment evidences. Finally, if time allows, some of recent optical 3D nanopatterning work will be presented.