Optical and morpho-structural properties of ZnO nanostructured particles synthesized at low temperature via air-assisted USP method

Abstract

Here, we report on the ZnO nanoparticles processing employing low-temperature (500 °C) ultrasonic spray pyrolysis (USP) method, using different Zn nitrate precursor solution concentrations (0.01, 0.1 and 1.0 M). Particle structural, morphological and luminescence characteristics were studied based on X-ray powder diffractometry, Fourier transform infrared spectroscopy, transmission electron microscopy (TEM/HRTEM), thermal analysis, UV–Vis diffuse reflectance spectra and photoluminescence measurements (PL). The generated so-called secondary particles have a hexagonal ZnO wurtzite-type crystalline structure with preferred orientation of (101) plane and quasi-spherical in shape. It was shown that such particle structural and morphological features are independent on the precursor solution concentrations used. All the PL spectra illustrate a strong green-yellow typical emission band exhibiting the corresponding redshift and variation of direct band gap from 3.22 to 3.12 eV with the increase in precursor concentration. The thermal analysis confirmed high thermal nanoparticles stability. The results proved that USP method successfully produces ZnO nanoparticles using neither dispersing agents nor post-heating treatments at high temperature, which allows rapid, continuous, single-step preparation, demonstrating a high potential for industrial applications.