Recently the increased interest of carbon-based materials decorated with metal nanoparticles (NPs) for sensors and energy applications has generated a huge development of the research in this field. Unfortunately, the immediate use of graphene in sensors or fuel cells applications is not yet possible since more effort must be performed to understand how NPs decorated graphene affect the selectivity and the sensitivity of the sensor and how surface radicals content influences the fuel cell performance.

In the present research, we developed a simple synthesis method of metal NPs on graphene layer and we investigated the optical properties and the surface radicals content of this system. Graphene layer have been produced on Cu foils by CVD method and transferred on different substrates to be characterized.1 The metal NPs were synthesized on the graphene layer using a well-established method used in our laboratory, based on a solution plasma process (SPP) system2,3, directly on the Cu foil covered with the graphene layer. The metal NPs were synthesized on the graphene surface through the reduction of the metal ion from the salt to the neutral form, or by the erosion of the electrode material. The graphene layer decorated with metal NPs was transferred on glass, Si/SiO2 substrate, Kapton scotch and carbon/Cu(Mo) grid surfaces to be analyzed by UV-vis spectroscopy, micro-Raman mapping spectroscopy, electron spin resonance (ESR), and transmission electron microscope (TEM) techniques, respectively. Micro-Raman mapping of 2D band at 2700 cm-1 (two photon double resonance band) which has higher intensity than G band at 1583 cm-1 (interlayer vibrations band of sp2-hybridized carbon) shows the quality and the uniformity of graphene layer on substrates. An enhanced Raman spectrum of graphene was detected when gold or silver NPs were adsorbed on the surface. The UV-vis spectra of graphene layer decorated with gold NPs which was transferred on a glass substrate, shows a week absorption band of surface plasmon resonance, at 520 nm, due to the thin layer of NPs on surface. The adsorbed metal NPs on graphene layers was observed by high resolution TEM analysis. The surface radicals content will be examined using ESR through calibration with stable free radicals compounds. The dependence of the surface radicals content of the graphene decorated with NPs on the size and shape of NPs will be discussed.

1 Xuesong Li, et al.,Science 2009, 324, 1312.

2 Takai, O. Pure Appl. Chem. 2008, 80, 2003 – 2011.

3 M.A. Bratescu, et al.,J. Phys. Chem., 2011, 115, 24569.