Multilayered reduced graphene oxide decorated homogenously with Platinum nanoparticles (rGO/Pt) was confirmed by Transmission Electron Microscopy and X-ray diffraction. It was found that the rGO/Pt flakes were suitable for adsorbing biomolecules in one step with the use of carbon disulfide (CS2) based compound. In this context, the adsorption-interaction of CS2 and Human Serum Albumin biomolecules on rGO/Pt (forming Platinum dithiocarbamate complexes) was confirmed by X-ray photoelectron spectroscopy and cyclic voltammetry techniques in neutral conditions. As a proof of concept, this nanocomposite was used as a transducer in Back-gated Field Effect Transistor (GFET) based nanobiosensors. The fabrication of GFET devices, at the level of 2-inch wafer, was conducted by conventional photolithography. The CS2, rGO/Pt and protein G that detects IgG, were locally deposited by using a commercial microplotter instrument. The experiments demonstrated that the homogenous decoration with Platinum nanoparticles as surface could permit the detection of biomolecules by using non-uniform graphene flakes functionalized with CS2, for rapid elaboration of electrochemical and electrical-nanobiosensors.