ABSTRACT
Graphene sheets of nanometer size emit light in the visible regions of the spectrum due to opening the gap. This clearly evident effect of quantum confining stimulated the attribution of nanosize sheets to quantum dots and then to graphene quantum dots (GQDs). An important feature of the GQDs photoluminescence (PL) is the variation in a wide range of its quantum yield; furthermore, this variation is associated not only with different ways of GQD production but is typical of the samples prepared by the same procedure; the PL quantum yield varies with time after synthesis. The GQD concept evidently implies a dispersed state of a number of nanosize reduced graphene oxide fragments. The main distinguishing GQD characteristic is surely its open-shell electronic system that is responsible for unique features related to GQDs not only in photonics, but in chemistry biochemistry biomedicine, and so forth.
