No abstract

Production of a ZnO–rGO composite, using a novel one-pot method consisting in continuously flowing argon into a GO aqueous suspension heated at 80 °C, in the presence of galvanized iron steel scrap is presented. FTIR shows the complete disappearance of GO functional groups and only the C=C band remained, indicating extensive GO reduction. Raman spectra indicated sp2 character increase after reaction and the presence of the E2h mode of ZnO. SEM showed submicron crystals identified by XRD as ZnO in the hexagonal phase, while TEM images indicate ZnO nanoparticles decorate mainly the rGO borders. Optical band gap of 3.5 eV corresponding to ZnO, and optical transitions at 4.1 and 5.5 eV related with n → π and π → π* were observed. Electrochemical characterization by cyclic voltammetry shows an specific capacitance of 4.7 F g−1 at a scan rate of 5 mVs−1, which drops to ca. 0.8 F g−1 at 200 mVs−1. By electrochemical impedance spectroscopy, the relaxation time was ca. 5 ms. The proposed mechanism for the materials‘ synthesis includes Zn dissolution from scrap, galvanic displacement of oxygen moieties at the GO sheet, Zn deposition onto the carbon surface, and further oxidation and growth of ZnO nanocrystals.

The local atomic structure of multilayer films of graphene oxide, cadmium sulfide, and cadmium sulfide−selenide was analyzed by Xray absorption fine structure spectroscopy. The films were prepared by sequential electrophoretic deposition and successive ion layer adsorption and reaction onto F-doped SnO 2 substrates. The obtained films were characterized by scanning electron microscopy, energy dispersive spectroscopy, Raman spectroscopy, UV−vis spectroscopy, and step-potential photocurrent response. From the transmittance data analysis, a direct band gap ranging from 2.13 to 2.3 eV was deduced. From photocurrent measurements, we conclude that films of CdS and CdSSe have photovoltaic properties suitable for utilization as an active layer in multilayer thin film hybrid solar cells. X-ray absorption near-edge structure spectra show a difference in amplitude between CdS/GO and CdSSe/GO samples, ascribed to a change in the local electronic structure around S. Extended X-ray absorption fine structure spectra show a direct C−S bond between the CdS/CdSSe nanoparticles and the graphene oxide layer. Band diagrams for the CdS/GO and CdSSe/GO electrolyte interfaces are proposed.

No abstract