Tunable Color in 2,6-Diaminopyridine-Functionalized Graphene Oxide

Graphene oxide (GO) is functionalized by 2,6-diaminopyridine (DAP) to invoke a superior optical property. Temperature-dependent photoluminescence has been carried out to elucidate the hybridized energy levels generated due to functionalization of GO. In addition to a blue color at 300 K, a new peak in the wavelength region of 500-700 nm is observed as the temperature decreases to 78 K. Density functional theory calculations are carried out to estimate the hybridized energy levels arising due to functionalization. This tunable color in functionalized graphene oxide is very useful in designing light-emitting devices. A light-emitting diode is fabricated using this DAP-functionalized graphene oxide (DAP-fGO) as an emissive material. Tunable electroluminescence in the visible range (red to green) with increasing bias voltage and finally white emission are obtained from the device at an operating voltage above 8 V.