An investigation into the role of capping agents in optimizing the properties of ZnO nanostructures

Nowadays, capping agents are crucial for stabilizing nanostructures by preventing aggregation and refining surface properties, enhancing optical, electrical, and mechanical behavior in applications like sensors, energy storage, and piezoelectric devices. This study explores the use of polyvinyl alcohol (PVA) and polyvinyl pyrrolidone (PVP) as capping agents for stabilizing ZnO nanostructures (ZnO NSs), preventing aggregation and improving compatibility with systems such as polymer matrices and coatings. The wurtzite phase of ZnO, with a space group of P6₃mc, was confirmed through Rietveld refinement of X-ray diffraction (XRD) measurement. Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) demonstrate that PVA and PVP-capped ZnO NSs exhibit significantly reduced particle and grain sizes. Enhanced stability of the nanostructures is evident from their negative zeta potentials. Dielectric studies highlight the superior dispersion and polarization in PVA-capped ZnO NSs, resulting in an increased dielectric constant, while ferroelectric properties of ZnO, PVA–ZnO, and PVP–ZnO NSs demonstrate significant frequency dependence, with PVP–ZnO NSs exhibiting the highest remnant polarization and saturation polarization at both 50 and 100 Hz. These findings underscore the critical role of polyvinyl-based capping agents in optimizing the structural, dielectric, and ferroelectric properties of ZnO NSs, enhancing their potential in advanced applications such as electronic devices, optoelectronics, and energy storage, particularly in piezoelectric nanogenerators.