The impact of gallium dopant on the structure, surface morphology, optical band gap and photoluminescence properties of ZnO-polystyrene nanocomposites

Abstract

The study details the synthesis of un-doped and gallium-doped zinc oxide (GZO) (2, 4, and 6) wt% nanoparticles (NPs) via hydrothermal approaches at a reaction temperature and novel reaction time of 160 °C and 5 h, respectively. Furthermore, ZnO-polystyrene (ZO-PS) and GZO-PS nanocomposite (NCs) films were fabricated using the casting method. X-ray diffraction results revealed that all synthesized nanocomposite films exhibit polycrystalline structures of the ZnO hexagonal wurtzite phase. A broad and low-intensity peak was observed at diffraction angles of approximately (15–23)° related to the semi-crystalline structure of polystyrene polymer. The crystallite size and the micro-strain were determined utilizing the Scherrer and Williamson-Hall methods, showing an increase (26–34) nm and (2.4–3.9) × 10^–3 and varied with the rise in Ga content. The presence of functional groups in polymer systems was confirmed through (FTIR) spectral analysis. The topographical characteristics of the prepared nanocomposite films indicated that the roughness and root mean square (r.m.s) roughness increased from 1.89 to 2.31 nm and from 1.54 to 1.87 nm, respectively, with an increase in Ga dopant content. The surface morphology of the prepared nanocomposites from FESEM images showed nanostructured grains formed by agglomerated particles, and the particle size is about 42 and 46 nm for ZnO-PS and GZO-PS nanocomposites respectively. The nanocomposite samples demonstrated that the particles are well dispersed within the PS polymeric compounds. The optical absorption edge of ZnO-PS red-shifted and the forbidden direct energy band gap was reduced from 4.4 eV to 3.74 eV at a Ga content of 6 wt %. Furthermore, photoluminescence studies of the produced nanocomposite films demonstrated bright blue light emission.

Graphical Abstract