Zinc oxide zno nanopowder

Zinc oxide (ZnO), nanopowder, particle size <100 nm, Sigma-Aldrich (Saint Louis, MO, USA); aniline (An, 99%, Morris Plains, NJ, USA) and ammonium persulfate (APS, (NH₄)₂S₂O₈, Morris Plains, NJ, USA) Acros Organics; and sulfuric acid (H₂SO₄, 96%, Kemika, Zagreb, Crioatia) and diethylene glycol (DEG, C₄H₁₀O₃, Kemika, Zagreb, Crioatia) were used to synthesize composite samples. Commercial organic dye C.I. Acid Blue 25 (AB25) Ciba-Geigy was used as the water pollutant. The chemicals were used as received, without any additional pre-treatment. All aqueous solutions were prepared with ultrapure water from the Merc Millipore Direct-Q3 UV water purification system (Merc KGaK, Darmstadt, Germany).
One of ZnO’s main drawbacks is a photocorrosion reaction under ultraviolet A (UVA) light, which can be presented by Equation (1) [34 (link),35 (link)]: $\mathrm{ZnO}+2{\mathrm{h}}^{+}+n{\mathrm{H}}_2\mathrm{O}\to \mathrm{Zn}{\left(\mathrm{OH}\right)}_n^{{\left(2-n\right)}^{+}}+1/2{\mathrm{O}}_2+n{\mathrm{H}}^{+}$ where n depends on the pH of the media and h⁺ is photo-induced hole (see, e.g., Section 3.8).
However, intense ZnO solubility in aqueous solutions also prevents its wider application.
In strong acid media: $\mathrm{ZnO}+2{\mathrm{H}}^{+}\to {\mathrm{Zn}}^{2+}+1/2{\mathrm{O}}_2$
$\mathrm{ZnO}+2{\mathrm{H}}^{+}\to {\mathrm{Zn}}^{2+}+{\mathrm{H}}_2\mathrm{O}$
In an alkaline medium: $\mathrm{ZnO}+{\mathrm{H}}_2\mathrm{O}+2{\mathrm{OH}}^{-}\to \mathrm{Zn}{\left(\mathrm{OH}\right)}_4^{2-}$
Upon UV irradiation: $2\mathrm{ZnO}+4{\mathrm{H}}_2\mathrm{O}+4{\mathrm{h}}^{+}\to 2\mathrm{Zn}{\left(\mathrm{OH}\right)}_2+{\mathrm{O}}_2+4{\mathrm{H}}^{+}$
Thus, both strongly acidic and alkaline conditions do not favor both the composite’s synthesis and photocatalytic process.