Rapid one pot syntheses of magnetic Zn_1-xFe_xS nanostructures: Enhancing properties of ZnS material for effective photocatalytic application

Here in the present work, simple, eco-friendly and economical method of synthesis has been approached known as hydrothermal synthesis that allowed easy doping of Fe ions into the ZnS host lattice. A unique approach was adopted for the first time to prepare ZnS material where thioglycolic acid (TGA) was used as a source for sulfur in addition to a reducing and capping agent. Properties of the nanostructures were explored using different techniques. The X-ray diffraction (XRD) results indicated formation of single phase hexagonal ZnS material where inclusion of Fe²⁺ ions into the ZnS lattice have no influence on the crystal phase of the material. Probably almost identical sizes of Zn²⁺ and Fe²⁺ ions made this possible that indicated Fe²⁺ ions take Zn²⁺ vacant sites by substitution of Zn²⁺ ions by Fe²⁺ ions. Chemical analysis (X-ray photoelectron spectroscopy) performed discovered that Zn and Fe ions were present in +2 oxidation states whereas S is in −2 state. Anisotropic growth of the nanostructures is reported where irregular shaped nanostructures of varying dimensions were formed that agglomerated as doping concentration was increased to form spherical microstructures. Inclusion of Fe ions into the host material modified magnetic behavior of the nanostructures converting diamagnetic ZnS into a ferromagnetic material. Optical properties were also influence by the doping resulting in photon absorption at different wavelengths. The band gap got reduced from 3.2 eV to 2.7 eV making the ZnS nanostructures visible light active. The nanostructures with band gap 2.7 eV exhibited good photocatalytic activity against methylene blue (MB) dye under visible light illumination degrading 94% of the dye in just 2 h. The scavenging experiments performed showed hydroxyl free radicals play an active role in mineralizing the dye. Reusability and post photocatalytic properties of the photocatalysts determined their stability and potential ability for possible commercialization.