Inorganic Chemistry in a Nanoreactor: Doped ZnO Nanostructures by Miniemulsion

Doped M:ZnO nanoparticles (Zn:M=50:1 or 20:1, with M= Ag(I), Co(II), Cu(II), Eu(III), Mg(II), Mn(II)) were produced by an easy, reproducible and fast inverse miniemulsion approach, enabling the co-precipitation of the oxide in a confined space. Unexpectedly, the formation of crystalline materials took place already at room temperature. Suspensions were characterized by Dynamic Light Scattering (DLS) and UV-Vis Spectroscopy, whereas precipitated powders were characterized by the combined use of several techniques, i.e. X-Ray Photoelectron Spectroscopy (XPS), X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), Inductively Coupled Plasma Atomic Emission Spectrometry (ICP- AES) and Thermogravimetric Analysis (TGA). The obtained particles showed a preferential growth along the [0002] direction, with a size of 70 nm, whereas along the other directions an average size between 26 and 33 nm is determined. The outcomes of the employed techniques confirmed a successful doping in all cases but one: in fact, the Ag doped sample corresponded to a nanocomposite consisting of metallic silver clusters dispersed in the ZnO matrix. A red emission for the ZnO:Eu sample is evidenced upon excitation around 465 nm.