Dual catalytic activity of hexagonal Mg–Sr codoped ZnO nanocrystals for the degradation of an industrial levafix olive reactive dye under sunlight and biosensing applications†
*a
Mounesh,
c
Abstract
Doping with alkaline earth metals has been found to be more efficient than doping with transition metals in lowering a semiconductor's photothreshold energy. The varied molar concentrations of Mg–Sr codoped ZnO catalysts were synthesized using a simple coprecipitation method and used for 5-fluorouracil (5-FU) detection as well as the degradation of Levafix olive (LO) reactive dye. As per our knowledge, studies on Mg–Sr codoped ZnO material are not present in the literature. X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS), high resolution-transmission electron microscopy (HR-TEM), Fourier transform infrared (FTIR) spectroscopy, UV-visible, photoluminescence (PL), Brunauer–Emmett–Teller (BET), X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS), zeta potential, and electrochemical (CV) studies were used to characterize the synthesized nanocrystals. According to XRD and XPS, Mg and Sr are found to be in the form of Mg+2 and Sr+2. Electrochemical impedance studies were used to perform electrochemical measurements on modifications made to the glassy carbon electrode (GCE) that was decorated with ZnO, Sr-ZnO, and Mg–Sr codoped ZnO. The as-synthesized nanocrystals were added to a carbon paste electrode to make it a chemical sensor for the detection of 5-FU. Due to an increase in the specific surface area and reduced rate of electron–hole recombination of Mg–Sr codoped ZnO nanocrystals, the 0.06 M Mg–Sr codoped ZnO catalyst showed enhanced photocatalytic degradation efficiency (99.42%) and degradation kinetic rates of LO (k = 0.02682 min−1) when compared to low-level Mg codoped Sr-ZnO, Sr-ZnO, and undoped ZnO catalysts under sunlight irradiation at 180 min. Different 0.06 M Mg–Sr codoped ZnO catalyst doses, various initial concentrations of LO, and variations in the pH of the LO solution on exposure to sunlight were all included in the evaluation of the photodegradation experiment. After four-cycle testing, the photostability and reusability of the 0.06 M Mg–Sr codoped ZnO catalyst were also evaluated, with a degradation efficiency of LO of about 88.51%. In the in situ capture investigation, the main species participating in the degradation of LO dye were determined to be hydroxyl radicals and electrons. The greater efficiency of 0.06 M Mg–Sr codoped ZnO at neutral pH under sunlight possesses a proposed mechanism. The Mg and Sr ion sites in the ZnO matrix may act as centers for electron and hole trapping, which would significantly increase the separation efficiency of photoinduced electrons and holes in the Mg–Sr codoped ZnO nanocrystals.
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