Magneto-Optical and Photocatalytic Properties of Magnetically Recyclable Mn x Zn1−x S(x = 0.0, 0.3, and 0.5) Nanocatalysts

Abstract

In this article, undoped and Mn-doped ZnS (MnxZn1−xS; x = 0.0, 0.3, and 0.5) nano photocatalysts were synthesized successfully by a facile microwave combustion method. Powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), energy dispersive X-ray (EDX), and selected area electron diffraction (SAED) patterns revealed the presence of material in well-crystalline single phase with average crystallite size of about 12 nm and the material remained cubic over the whole MnxZn1−xS solid solution range. Formation of ultrafine, spherical, and homogeneous dispersed nanoparticles (NPs) with size 14 nm was confirmed by high-resolution scanning electron microscopy (HR-SEM) and high-resolution transmission electron microscopy (HR-TEM) analyses. Vibrating sample magnetometer (VSM) results confirmed a weak superparamagnetic behavior of MnxZn1−xS nanocrystals, and the values of magnetization (Ms) gradually increased with increasing the concentration of Mn2+ cations, due to the higher magnetic moment of Mn2+ ions (5 μB) replaced the nonmagnetic nature of Zn2+ ions (0 μB) in ZnS. The band gap of the samples was increased with increasing the concentration of Mn2+ ions, due to decrease in the particle size. The room temperature photoluminescence (PL) spectra of Mn2+-doped ZnS NPs showed extra peaks in yellow–orange and red region in comparison of undoped ZnS NPs. Mn2+-induced PL spectra was suggested with the significant enhancement of the PL intensity in MnxZn1−xS NPs, due to Mn2+ incorporation. The present study leads to enhance the photocatalytic activity of MnxZn1−xS NPs, and TiO2 catalyst was added. As expected, MnxZn1−xS NP-sensitized TiO2 catalyst showed enhanced photocatalytic degradation (PCD) of 4-chlorophenol (4-CP) under visible light irradiation. The alteration of MnxZn1−xS–TiO2 nanocomposites (NCs) catalysts show higher adsorption with synergistic effect and enhanced the separation of photogenerated electron–hole pairs, important to higher PCD efficiency.