Conductive polymer and graphene oxide functionalized nanofiber based piezoelectric nanogenerators

Within the scope of this thesis, polyvinylchloride (PVDF) piezoelectric nanogenerators have been developed ,which can be used in their own energy generating systems and sensor technologies, containing reduced graphene oxide (rGO), polyaniline (PANI) and polyaniline functionalized reduced graphene oxide (rPANIGO). In the first part of the study, the conductive materials are doped into the piezoelectric nanofiber material. In the second part, the conductive materials were coated by spraying onto the nanofiber material. Piezoelectric performance of the materials was primarily measured. In addition, Fourier Transfer-Infrared Spectrophotometric (FT-IR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), mechanical test, contact angle test and UV-visible region (UV-VIS) spectrophotometric analysis were performed. In order to obtain flexible electrodes on nanogenerators, reduced graphene oxide(rGO) was sytnesized by improved Hummers method; polyaniline(PANI) was synthesized by in-situ polymerization of aniline; polyaniline functionalized reduced graphene oxide(rPANIGO) was produced by in situ polymerization of aniline presence of graphene oxide. These materials were dispersed separately in ethyl alcohol and the concentration of the dispersion was determined. PDVF nanofibers were produced in electrospinning machine as piezoelectric layer, decided amounts of organic conductive material was integrated into or sprayed onto the nanofibers. When the samples were dried, they were polarized under electrical field and piezoelectric tests were performed. β and γ crystalline phases of PVDF were observed in FT-IR analysis of produced nanofibers. β and γ crystalline phase peaks were not observed on PVDF powder form and it was determined that the polymer passed to piezoelectric β and γ crystalline phase in the electrospinning stage. In addition, it was determined that coating or doping processes affected the FT-IR spectra but did not play a role in the transition between the crystalline phases. As a result of piezoelectric measurements, output voltage decreased with incremention of coat thickness while incremention of doping amount was increasing the voltage. In addition, it was determined that the coating method was lacking in terms of signal intensity according to the doping method. Despite all these, both coating and doping processes provided higher ouput voltages than pure PVDF nanofiber's. The nanogenerator, which is consist of hybrid conductive coated PVDF nanofiber, yielded too high output voltage of 10,6 V, compared to other coated nanogenerators. A synergistic effect was observed between graphene and polyaniline. The nanogenerators, which are produced in thesis, will be able to used in self-powered systems, sensor technologies and waste energy recycling systems in the future.