Effect of polyethylene glycol on the particle size and photoluminescence emissions characteristics of chemically synthesized ZnO nanoparticles

ZnO nanoparticles have been prepared by a simple wet chemical approach at a low temperature of 75 °C by using polyethylene glycol (PEG) as capping agent. It is demonstrated that by varying the concentration of the PEG the particle size can be varied within 7.7 to 21 nm. The nanostructures of the samples are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Optical properties are measured by UV–Visible absorption spectrophotometer and photoluminescence (PL) spectroflourimeter. It is found that the uncapped sample emits strong UV light, whereas the capped samples exhibit strong and broad visible emission. An enhancement of green PL emission intensity by the factor of ~30 has been obtained, in a capped sample with the minimum particle size and thus with more defect centers, in comparison to that of uncapped one. Also some interesting results of enhanced green PL emissions as well as co-emission of light in blue and green wavelength region have been reported by excitation wavelength dependent PL emission measurements. These results might attract the attention of the researchers to use the synthesized materials as biomarkers, if the nontoxic nature of ZnO is coupled with the photoluminescence properties reported in this work.