Figure 7.

Energy levels scheme of CD core electronic bands, CD surface states, and of Gr electronic bands at K point (Dirac cones) relative to the energy of the vacuum level. The elements of the CDs-Gr interaction described in the proposed model are reported. The laser light (green arrows) is absorbed by CDs and scattered by Gr, thus generating CD PL and Gr Raman signals (red arrows), respectively. In CDs, electrons are promoted from the core valence band (VB) to surface states, for which the energy distribution is between the energies of zinc and cobalt ions. The electron migrates from the surface states towards the conduction band (CB) of Gr by electron transfer (ET). Finally, after an ultrafast relaxation towards lower energy states, the states in the VB of Gr are populated, as attested by the increase of Fermi energy revealed by Raman signal.