Influence of ascorbic acid as modifier on the particle size and the optical properties of ZnO nanoparticles

In this work, zinc oxide nanoparticles (ZnO-NPs) were synthesized by a chemical precipitation method. A precursor zinc nitrate hexahydrate, polyvinylpyrrolidone (PVP), as a surfactant stabilizing agent and ascorbic acid (AA) as a reducing agent were used. Molar ratios of ascorbic acid to zinc nitrate hexahydrate were changed from 1 to 4 during preparation processes and under the same conditions. Morphology, crystallinity, and particle sizes calculations were studied using Transmission electron microscopy (TEM) and X-ray diffraction. The particle sizes were estimated at 57 nm, 66 nm, 53 nm, 47 nm, and 33 nm and crystalline sizes at 30.05 nm, 26.26 nm, 26.38 nm, 26.53 nm, and 20.80 nm when the ratio of (AA:Zn) was 1, 1.5, 3, 3.5, and 4, respectively. The difference between the particle and crystalline size values because of particle size consist of several crystalline. The results illustrated the effect of different concentrations of (AA:Zn) on the formation and agglomeration of (ZnO - NPs). Fourier transform infrared spectroscopy results showed that the characteristic transmittance bands of (ZnO - NPs) are closer to 455 cm(-1). UV - vis spectra results show the absorption band seen at 368nm; 374nm; 364nm; 358 nm; and 352nm and optical band gap calculated at 3:64 eV; 3:58 eV; 3:70 eV; 3:74 eV; and 3:69 eV when the ratio of (AA:Zn) was 1, 1.5, 3, 3.5, and 4, respectively. These results clarified the effect of quantum sizes effect on the optical band gap of (ZnO - NPs).