The effect of PEGylation on optical and structural properties of ZnO nanostructures for photocatalyst and photodynamic applications

In this paper, bare and pegylated ZnO nanoparticles with different ratios of polyethylene glycol 1000 to zinc acetate are successfully synthesized using the sol-gel method, and the effects of pegylation on the optical and structural properties of the ZnO NPs are investigated. The results show that ZnO molecules are formed in bare and pegylated nanoparticles. Also, ZnO nanorods are formed in non-pegylated conditions, while pegylation generally changes the morphology and no nanorods are observed in pegylated ZnO structures with different zinc acetate to PEG ratios. Furthermore, pegylation leads to a decrease in the NPs sizes significantly. The XRD results show the formation of the wurtzite ZnO phase and the absence of other oxide phases in the synthesized structure. Pegylation affects the optical properties of ZnO NPs significantly and the reflectance of PEG ZnO nanostructures in the Vis-NIR which is much higher than bare ZnO and it reaches approximately 100% at wavelengths greater than 400 nm. So, the PEG ZnO NPs can be established as strong reflectors in a wide range of optical applications. Furthermore, bandgap energies of the NPs experience a blue shift by pegylation. The zeta potential of bare ZnO NPs is more negative than PEG one. Also, the effect of pegylation on the photocatalytic activities of two selected ZnO NPs is studied using photodegradation of methylene blue (MB) dye under exposure LED light (power=20 W, central wavelength=380 nm, and full width at half maximum=13.2 nm) in normal and acidic solutions (pH=5.4 and 7.4). The results declare that pegylation of ZnO leads to more appreciable photodegradation of MB dye in the acidic solution than bare ZnO NPs. The kinetics of photocatalytic degradation of MB reactive dye under irradiated bare and pegylated ZnO NPs is also investigated in the paper.