Charge storage and memory effect in graphene quantum dots-PEG600 hybrid nanocomposite

We report an easy, one step, low cost method to obtain a hybrid composite material consisting in graphene quantum dots (GQDs) embedded in a polymeric - poly(ethylene glycol) bis (carboxymethyl) ether - matrix. Optical measurements show the excitation wavelength dependent photoluminescence of the GQDs - PEG(600). In comparison with self-passivated GQDs, the composite exhibits a blue shifted photoluminescence, as well as additional emission peaks in the range of 570-600 nm. These features are explained by the presence of new electronic surface states induced by the polymeric matrix as it was demonstrated by the electrochemical measurements. The transport properties consist in a large clockwise hysteresis presenting high and low resistance states, also two distinctive regions of negative differential resistance. The photocurrent decay and the transient currents indicate a large charge storage and confirm the existence of trap charge levels. The experimental findings suggest that the leading mechanism underling the transport is Simmons Verderber. We demonstrated the switching properties of GQDs - PEG600 for applications in nonvolatile memory by performing standard sequence memory tests. (C) 2013 Elsevier B.V. All rights reserved.