Razi University

   Abstract: This doctoral dissertation comprises two main studies focusing on the design and development of piezoelectric nanogenerators based on polyvinylidene fluoride (PVDF)   anofibers enhanced with some nanomaterials. In the first study, the effects of incorporating nanorod perovskite structures (CoTiO?, NiTiO?, and MgTiO?) along with reduced graphene oxide (RGO) into PVDF nanofibers were investigated. Among the prepared composites, the PVDF–RGO–CoTiO? nanofiber exhibited the highest output voltage (Voc) and superior piezoelectric performance. The optimized nanogenerator demonstrated excellent energy-harvesting capabilities and was successfully applied as a self-powered sensor for human motion monitoring, achieving a remarkable power density and stable performance under repeated mechanical stress. In the second study, the influence of polyoxometalate Cs?H???PW??O?? (x= 0, 1, 2, 2.5, 3) compounds on the piezoelectric response of PVDF nanofibers was examined. The effect of adding RGO was also studied. The results revealed that the polyoxometalate itself can act as an efficient conductive particle, eliminating the need for additional RGO. The PVDF-Cs?.? composite nanofibers achieved the highest Voc and piezoelectric response. The fabricated nanogenerator effectively powered LEDs, stored energy in capacitors, and functioned as a sensitive motion-monitoring device, demonstrating its strong potential for energy harvesting and self-powered sensing applications. Overall, both studies highlight the significant role of material composition and nanostructure design in optimizing the piezoelectric and energy-harvesting performance of PVDF-based nanogenerators.