Optical Characterization of Polyvinyl Alcohol–Zinc Oxide Nanocomposite Films Fabricated via Spray Coating and Enhanced Through Plasma Modification: A Comprehensive Study

Abstract

Polyvinyl alcohol (PVA) and zinc oxide (ZnO) nanocomposite films were synthesized and characterized in this study through a spray method with varying concentration of ZnO nanoparticles incorporated within the polymer. The XRD patterns exhibit significant peak broadening, indicative of a high-purity wurtzite hexagonal structure in the nanoparticles, and exhibit notably higher intensity peaks after argon (Ar) plasma treatment which may be due to increase in crystallinity of the ZnO nanoparticles. The AFM analysis of PVA samples with varying ZnO nanoparticle concentrations reveals a clear increase in surface roughness as the ZnO content rises. The mean roughness (Sa) increases from 0.90598 nm at 0 wt % ZnO to 1.18807 nm, 1.46771 nm, 1.84988 nm, and 2.60792 nm at 1 wt %, 3 wt %, 5 wt %, and 10 wt % ZnO, respectively. FESEM images show the change in morphology with the addition of ZnO nanoparticles where the round and clustered particles noted indicate a clustered distribution on the surface, and after plasma treatment, the surface gets etched or eroded. These films were then subjected to DC glow discharge plasma with Ar gases for functioning minutes starting from 15 min to 25 min. In order to study the change in the surface chemistry of PVA and PVA–ZnO nanocomposite films, the FTIR spectroscopy test was conducted. In the FTIR spectra, typical absorption bands of monoclinic phase of nano-ZnO were present and thus it can be said that Ar plasma treatment could slightly affect the chemical functional groups present on the surface. For plasma-treated materials, UV-Vis absorption spectra indicated that optical absorption increased with ZnO concentration and shifted to longer wavelengths. The calculated refractive index values for the samples, which fall within the visible range of the spectrum, ranged from 1.356 to 1.891. The extinction coefficient was found to increase for both untreated and Ar plasma–treated samples with longer treatment times. This work focuses on application of plasma technology, namely, DC glow discharge plasma, for surface treatment that can be a promising technology to improve properties of material.