Why ionic liquids coated ZnO nanocomposites emerging as environmental remediates: Enhanced photo-oxidation of 4-nitroaniline and encouraged antibacterial behavior

Abstract

In this paper, benzimidazole based ionic liquid (IL)was prepared, and then coated on ZnO to yield ZnO@ILwhich was then characterized systematically by different analytical methods such as X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and X-ray Photoelectron Spectroscopy (XPS) before exploring as a photo-catalyst for the oxidation of 4-nitroaniline (4-NA). In XRD, for ZnO@IL, the plane [100] has been shifted to higher angle at 64° in 2θ due to the influence of IL on the ZnO surface. The intensity and shape of the XPS peaks (appearing between 404 and 398 eV) originated from the IL's imidazole nitrogens indicate the existence of a sizable photoemission due to the interaction of NHCs with the electrophilic surface of ZnO. The catalytic oxidation of 4-NA (0.1 M) by ZnO@IL under UV light reveals a considerable degradation, which follows a first order kinetics. The formation of intermediates was analyzed by HPLC-MS, and proposed a possible mechanism for the oxidation. At lowpH=4, a greater oxidation rate (k=2.01 × 10−4mM.s−1) was obtained than that observed in higher pH of 10 (k = 0.26 × 10−4 mM.s−1). Additionally, ZnO@IL shows an antibacterial behavior exhibiting a significant microbial inhibition about 45%, and observed a considerable decrease in the cell growth if ZnO@IL presents in the culture medium.