The efficacy of carbon quantum dots decorated magnetic metal ferrite nanocomposites in reducing of 4-nitrophenol

Abstract

Removing organic contaminants from aqueous environments through chemical reduction reactions using transition metal-based nanocatalysts and in the presence of NaBH4 as an electron donor has become a consistent approach in recent years. In this study, we fabricated economical, non-toxic, environmentally friendly and, convenient MFe2O4(M = Zn, Mn) and NiZnFeO4 nanoparticles (NPs) via one-pot hydrothermal techniques and magnetic nanocomposites of ferrite NPs/carbon quantum dots (CQDs) via co-precipitation method using reflux setup. Then, the obtained magnetic nanocatalysts were employed to reduce 4-nitrophenol (4-NP) using sodium borohydride as a reducing agent. FT-IR, XRD, SEM, EDAX, VSM, PL, DRS, and BET analyses were employed to investigate the synthesized NPs and nanocomposites. The SEM pictures of the catalysts indicated a mix of spherical and granular shapes. Also, the new nanocomposites have represented a remarkable reduction in energy bands compared to the corresponding magnetic metal oxides. The band gap (Eg) was calculated as 1.87, 2.35 and 2.45 eV for NiZnFeO4/CQDs, MnFe2O4/CQDs and ZnFe2O4/CQDs, respectively, where NiZnFeO4/CQDs showed the smaller band gap and rapid release of electrons. The catalytic activity of the magnetic NPs and nanocomposites was investigated via UV–Vis spectroscopy in the range of 250 and 500 nm in the absence and presence of the catalysts, with NaBH4 to reduce 4-NP to 4-aminophenol in an aqueous medium. The NiZnFeO4/CQDs as a novel nanocatalyst represented exceptional activity in the reduction of 4-NP, with a constant rate, k’, time and conversion up to 1.94 × 10−1(s−1), 6.92 × 10−3(s−1 mg −1), 20 s and 96.5 %, respectively, which was superior to other reported templates.