Paddy-Straw-Derived Graphene Quantum Dots Reinforced Vertical Aligned Zinc Oxide Nanosheet-Based Flexible Triboelectric Nanogenerator for Self-Powered UV Sensors and Tribotronics Application

Herein, we report the paddy-straw-derived graphene quantum dots (GQDs)-reinforced vertical-aligned two-dimensional (2D) ZnO nanosheet-based flexible triboelectric nanogenerator (FTNG) for scavenging mechanical energy for the first time. The GQDs (diameter ∼5–7 nm) and ZnO nanosheets were grown using a hydrothermal method and seed-assisted chemical route, respectively. The X-ray diffraction and electron microscopy results confirmed the formation of a hexagonal wurtzite crystal structure and vertical-aligned morphology of 2D ZnO nanosheets. The GQD-reinforced ZnO-nanosheet-based FTNG device generated an output voltage of 40 V and current density of 2 μA/cm2, respectively, whereas pristine vertical-aligned ZnO-nanosheet-based device produced an output voltage of only 16 V and a current density of 0.36 μA/cm2, respectively. The performance of the GQD-ZnO nanosheet FTNG device was also measured under illumination of the UV light, and a drastic increase in the output voltage is observed as compared to a pristine ZnO-nanosheet-based device. The GQD-reinforced ZnO nanosheets exhibited very high dielectric constant of 40 at low frequency side. The current finding suggested a novel approach to efficiently harvest mechanical energy and a novel method to fabricate the self-powered UV sensors and tribotronics devices using agrowaste-derived GQDs and ZnO nanosheets.