GO Nanosheet-Wrapped\nZnS-Nanoplate-Based Highly Efficient\nWearable Piezoelectric Nanogenerator for Biomechanical Energy Harvesting,\nPortable Electronics, and Health Monitoring

In this work, we propose an easy, cost-effective, and\nefficient\napproach to wrap zinc sulfide (ZnS) nanostructures or other similar\nnanomaterials with graphene oxide (GO) nanosheets for energy harvesting.\nThe ZnS nanoplates were wrapped with different concentrations of GO\nnanosheets (5, 10, 15, 20, and 25 wt %) by using the hydrothermal\nmethod. Field-emission scanning electron microscopy and powder X-ray\ndiffraction were performed to study the surface morphology and crystal\nphase structure of each sample. The dielectric study revealed that\nthe wrapping gradually enhanced the polarization density of ZnS nanostructures.\nThen, GO<i>x</i>-ZnS nanostructures were loaded in a polydimethylsiloxane\n(PDMS) polymer matrix (GO<i>x</i>-ZnS@PDMS) to develop flexible\npiezoelectric nanogenerator (FPENG) devices. Among all fabricated\ndevices, the GO20-ZnS@PDMS-based FPENG device showed the highest electric\noutput of ∼27 V and 50.9 μWcm<sup>–2</sup>. The\nGO20-ZnS@PDMS-based FPENG device was used to develop a highly efficient\nself-charging green power system, which effectively charged a series\nof capacitors (1, 2.2, and 4.7 μF) up to ∼5.8, 4, and\n2.6 V, respectively. For practical implementation, wearable/portable\nelectronic gadgets were operated. The efficiency of the fabricated\nFPENG device was found to be ∼21.56%. Further, the FPENG device\nwas demonstrated for biomechanical energy harvesting, and it showed\nremarkable electrical output performance under various kinds of human\nbody motions. This indicates that the GO20-ZnS@PDMS-based FPENG device\ncan be used in futuristic real-time health monitoring applications.\nTherefore, the present work on a highly efficient wearable FPENG device\ncan be used in many daily life applications.