Synthesis of Mixed Ceramic MgxZn1–xO Nanofibers via Mg2+ Doping Using Sol–Gel Electrospinning

Abstract

We report on the synthesis of tuned energy band gap Mg(x)Zn(1-x)O nanofibers (NFs) with different Mg(2+) content via the sol-gel electrospinning (ES) technique wherein the addition of the doping material affects not only the morphologies of as-spun ZnAc/PVA and MgAc/ZnAc/PVA nanofibers but also the crystal microstructure and optical properties of calcined ZnO and Mg(x)Zn(1-x)O nanofibers. Following an appropriate aqueous solution preparation of magnesium acetate (MgAc) and zinc acetate (ZnAc) with poly(vinyl alcohol) (PVA), electrospinning is performed and then as-spun nanofibers are calcined in an air atmosphere at 600 °C for 3 h. As-spun and calcined nanofiber diameters and morphologies are evaluated with scanning (SEM) and transmission (TEM) electron microscopies, whereas crystalline microstructural interpretations of ZnO and Mg(x)Zn(1-x)O are conducted with wide-angle X-ray diffraction spectra (XRD). Surface chemical composition and elemental evaluation of calcined nanofibers are examined with X-ray photoelectron spectroscopy (XPS), and optical properties and crystal defect analyses of the calcined nanofibers are conducted with photoluminescence spectra (PL). We observe a sharp reduction in fiber diameter upon calcination as a result of the removal of organic species from the fibers and conversion of ceramic precursors into ceramic nanofibers, and the appearance of a range of fiber morphologies from "bead in a string" to "sesame seed" coverage depending on fiber composition. Because Zn(2+) and Mg(2+) have similar ionicity and atomic radii, some Zn(2+) atoms are replaced by Mg(2+) atoms in the crystals, leading to a change in the properties of crystal lattices. The band gap energy of the calcined fibers increases significantly with addition of Mg(2+) along with an increase in the ultraviolet (UV) photoluminescence emission of the fibers.