Synthesis, characterization and photocatalytic behavior of mesoporous ZnS nanoparticles prepared by hybrid salt extraction and structure directing agent method

Mesoporous ZnS nanoparticles have been synthesized using hybrid salt extraction and surfactant assisted approach. Synthesis procedures were conducted in ethanol media under ultrasonic irradiation. As a by-product of the synthesis reaction, NaNO3, has a very low solubility in ethanol and acts as a template for porosity formation in the final solid structure. In addition, various structure directing agents, namely, CTAB, DDA, F127 and SDS have been used as soft templates for further porosity formation. Characterization of the synthesized specimens was performed using Transmission Electron Microscopy (TEM), X-ray diffraction (XRD), N2-physisorption, Furrier Transformation Infrared Spectroscopy (FTIR) and Diffuse Reflectance Spectroscopy (DRS). Results show that the by-product has the major contribution on the specific surface area of the obtained samples. It was found that MP-ZnS synthesized by DDA surfactant has the highest values of surface area (261m2g−1), pore volume (0.43cm3g−1) and average pore diameter amongst all of the samples under study. Studies on adsorption efficiency and photocatalytic behavior of the synthesized specimens were conducted for methylene blue removal from aqueous solution. Results revealed that the MP-ZnS sample synthesized using CTAB surfactant has the best total degradation efficiency amongst the samples under study. Findings were explained using optical band gap energy values (deduced from DRS spectra), the intensity of C-H bond vibrations in FTIR spectra, water droplet contact angle, average pore volume and diameter and also specific surface area from N2-physisorption data. At the end a simple mechanism was proposed in order to explain the main phenomena leading to photocatalytic removal of MB from aqueous solutions.