The effect of various capping agents on the surface modifications of sol–gel synthesised ZnO nanoparticles

Control of the nanostructure and optical properties of ZnO nanoparticles are studied by using various capping agents. The uncapped and capped ZnO nanoparticles were synthesised from sol–gel process by reacting zinc acetate dehydrate with NaOH in deionised water at 70 °C. Various capping agents such as Ethylene diamine tetra acetic acid (EDTA), Triethanolamine (TEA) and Tetraethylammonium Bromide (TEABr) were used as capping agents to control the size and morphology of the ZnO nanoparticles. The size and morphological changes of ZnO nanoparticles were investigated by using Transmission electron microscopy (TEM) and UV–Vis optical absorption spectroscopy. The XRD spectra of the synthesised samples confirmed that the synthesised products were ZnO nanoparticles with wurtzite structure. The presence of capping agents were analysed by Fourier transform infrared (FT-IR) spectroscopy. The morphology of the synthesised particles was changed with capping agents. Moreover, the capping mechanism is discussed based on the chemical reaction between the ZnO nanoparticles and the functional groups of the various capping agents.

► The effect of various capping agents on the growth of ZnO nanoparticles is studied.
► Clear changes in the morphology of the ZnO nanoparticles are observed by TEM.
► Capping mechanism for the morphological changes of ZnO nanoparticles are discussed.