Synthesis and characterization of pristine and strontium-doped zinc oxide nanoparticles for methyl green photo-degradation application

Abstract

Herein we describe an effective route for the degradation of methyl green (MG) dye under visible light illumination by pristine and strontium (Sr)-doped zinc oxide (ZnO) photocatalysts (synthesized by the simple chemical precipitation method). The x-ray diffraction structural analysis has confirmed that both photocatalysts exhibit the hexagonal wurtzite structure; without any additional phase formation in Sr-doped ZnO, in particular. The optical properties of the synthesized photocatalysts have been investigated using UV–vis absorption spectroscopy in the wavelength range of 250–800 nm. Through Tauc’s plot, the slight decrease from 3.3 to 3.2 eV in band gap energy has been elucidated (in the case of Sr-doped ZnO), which has been further confirmed by the quenching in the intensity of Photoluminescence (PL) emission spectrum. This may be due to sub-band level formation between valence and conduction band, caused by the impregnation of Sr2+ ions into ZnO host. The morphological study has also been performed using Field Emission Scanning Electron Microscope, which indicates nanoparticles (NPs) based surface texture for both photocatalysts. During the photocatalytic activity study, after 30 min irradiation of visible light, ∼65.7% and ∼84.8% photocatalytic degradation of MG dye has been achieved for pristine and Sr-doped (2 wt%) ZnO photocatalysts, respectively. The rate of photocatalytic reaction (K) has been observed to be ∼0.06399 min−1 for Sr-doped (2 wt%), whereas nearly half magnitude ∼0.03403 min−1 has been observed for pristine ZnO, respectively. The significantly improved photodegradation activity may be ascribed to the relatively broader optical absorption capability, surface defects and the enhanced charge separation efficiency of the Sr-doped ZnO photocatalyst.

Testing of Sr-Doped ZnO/CNT Photocatalysts for Hydrogen Evolution from Water Splitting under Atmospheric Dielectric Barrier Plasma Exposure

“…This decrease in the band gap is attributed to the synergistic effect between graphene and Sr-doped ZnO, as shown in Figure b–d. The relation of Kubelka–Munk (α h ν = A ( h ν – E g ) n /2 ) was utilized for the calculation of band gap energies of S 10 ZC 2 , S 20 ZC 2 , and S 25 ZC 2 photocatalysts as 2.27, 2.22, and 1.94 eV, respectively …”

“…The relation of Kubelka−Munk (αhν = A(hν − E g ) n/2 ) was utilized for the calculation of band gap energies of S 10 ZC 2 , S 20 ZC 2 , and S 25 ZC 2 photocatalysts as 2.27, 2.22, and 1.94 eV, respectively. 31 The photoluminescence (PL) technique is used to study the transfer capability and recombination efficiency of charge carriers in the catalyst. 32 A high photoemission intensity usually indicates strong recombination of charge carriers.…”

Dielectric Barrier Discharge Plasma Processing and Sr-Doped ZnO/CNT Photocatalyst Decoration of Cotton Fabrics for Self-Cleaning Application

“…Figure b–d provides a relation of Kubelka–Munk [α h ν = A ·( h ν – E g ) n /2 ] used for the estimation of the optical band gap energy of the photocatalysts. The S 10 ZC 2 , S 15 ZC 2 , and S 20 ZC 2 photocatalysts showed a band gap energy of 2.85, 2.78, and 2.5 eV, respectively …”

Structural, Optical, and Magnetic Properties of Pure and Ni–Fe-Codoped Zinc Oxide Nanoparticles Synthesized by a Sol–Gel Autocombustion Method

“…Major properties that distinguish ZnO among others are the wide and direct band gap of 3.39 eV and its piezoelectricity . Due to these remarkable properties, it has several applications in different fields such as optoelectronics, electromechanical devices, light-emitting diodes, photocatalysis, piezoelectricity, nanogenerators, solar cells, smart windows, transistors, gas sensors, and much more. − It is a multifunctional semiconductor that can also be used as a magnetic storage device or optical/electrical switching device. ,− ZnO is low cost, abundant, biosafe, and biocompatible, thereby it is used in various medical applications . Interestingly, the optical and electrical properties of ZnO can be easily tuned by transition metal doping and specifically by varying the dopant concentrations.…”

“…Interestingly, the optical and electrical properties of ZnO can be easily tuned by transition metal doping and specifically by varying the dopant concentrations. As a result, doped ZnO nanoparticles (NPs) have gained huge interest in the past decade. − Significantly improved magnetic, electrical, optical, and structural properties have been reported by many researchers. − Fabrication of transition metal-doped ZnO can be achieved by several different techniques, − microemulsion process, − microwave hydrothermal process, sol–gel synthesis, precipitation method, chemical vapor, solvothermal synthesis, , chemical method, , and autocombustion method . The autocombustion method, however, is a short, time-saving, and homogeneous method.…”