Electro-catalytic properties of graphene composites containing gold or silver nanoparticles

Abstract

Composite nanostructures based on few-layers graphene with encased gold or silver nanoparticles (denoted as Gr-Au and Gr-Ag, respectively) were separately prepared in a single-step synthesis by radio frequency catalytic chemical vapor deposition (RF-cCVD) over Aux/MgO and Agx/MgO catalytic system (where x=3wt.%), respectively. Their morphological properties were investigated by electron microscopy techniques (TEM/HRTEM), which demonstrated that the number of graphitic layers within the sheet varied between 2 and 7. Thorough TEM analysis also indicated that gold nanoparticles had a mean size of 22nm, while silver nanoparticles were found to be larger with a mean size of 35nm. X-ray powder diffraction proved that the crystallinity of the Gr-Au or Gr-Ag samples is less influenced by the type of metallic nanoparticles (silver or gold) encased between the graphitic layers. The mean value of the crystalline domain perpendicular to graphene (002) crystallographic plane was determined to be approximately 2.25nm (for Gr-Au sample) and 2.14nm (for Gr-Ag sample), both corresponding to 6 graphitic layers. Gr-Ag and Gr-Au nanostructures were used to modify platinum substrates and subsequently employed for the electrochemical analysis of carbamazepine. A significant decrease in the electrochemical oxidation potential of carbamazepine (150mV) was obtained with both modified electrodes. The detection limit (DL) was found to be 2.75×10−5M and 2.92×10−5M for the Pt/Gr-Ag and Pt/Gr-Au electrode, respectively.