nanomaterials Article Graphene Oxide Layer-by-Layer Films for Sensors and Devices Ivan C. C. Assunção 1, Susana Sério 1 , Quirina Ferreira 2 , Nykola C. Jones 3 , Søren V. Hoffmann 3 , Paulo A. Ribeiro 1,* and Maria Raposo 1,* 1 Laboratory of Instrumentation, Biomedical Engineering and Radiation Physics (LIBPhys-UNL), Department of Physics, NOVA School of Science and Technology, NOVA University Lisbon, 2829-516 Caparica, Portugal;
[email protected] (I.C.C.A.);
[email protected] (S.S.) 2 Instituto de Telecomunicações, Avenida Rovisco Pais, 1, 1049-001 Lisboa, Portugal;
[email protected] 3 ISA, Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, 8000 Aarhus C, Denmark;
[email protected] (N.C.J.);
[email protected] (S.V.H.) * Correspondence:
[email protected] (P.A.R.);
[email protected] (M.R.) Abstract: Layer-by-layer films of poly (allylamine hydrochloride) (PAH) and graphene oxide (GO) were characterized, looking at growth with the number of bilayers, morphology, and electrical properties. The PAH/GO films revealed a linear increase in absorbance with the increase in the number of deposited bilayers, allowing the determination that 10.7 ± 0.1 mg m−2 of GO is adsorbed per unit of area of each bilayer. GO absorption bands at 146, 210, 247 and 299 nm, assigned to π-π* and n-π* transitions in the aromatic ring (phenol) and of the carboxylic group, respectively, were characterized by vacuum ultraviolet spectroscopy. The morphological characterization of these films demonstrated that they are not completely uniform, with a bilayer thickness of 10.5 ± 0.7 nm.