Remarkable enhancement in adsorption capacity of methylene blue by hydrothermally processed MoSe₂ nanosheets for environmental application

In the present study, we have developed molybdenum diselenide (MoSe₂) nanosheets via an effective hydrothermal process by varying synthesis temperatures in a high-yield production. XRD results illustrate that all the products indexed to a hexagonal crystal phase of MoSe₂ (2H-MoSe₂) with crystallite sizes around 7 nm. TEM and HRTEM images confirmed a high-quality crystalline feature of MoSe₂ nanosheets. Interestingly, the identified interplanar spacing of 0.61 nm corresponds to a well-organized atomic-scale arrangement with (hkil: 0002) plane of 2H-MoSe₂ crystal. Additionally, Moire´ fringes of different periodicities are clearly visible in some crystalline regions suggesting that MoSe₂ nanosheets are well crystallized. The selected area electron diffraction patterns elucidate ring-like diffraction patterns indicating the polycrystalline nature of all the prepared MoSe₂ nanosheets. UV-Vis absorption spectra scrutinize the mechanism for photo-response phenomenon and the observed excitonic peaks evidently demonstrate that the synthesized MoSe₂ is in a semiconducting 2H phase with an optical bandgap ranging from 1.78 to 1.93 eV. Moreover, MoSe₂ nanosheets possess a prominent methylene blue (MB) dye adsorption capacity of 50-70% and 54-83% in lower and higher adsorption times, respectively. In a nutshell, this study reveals the potential environmental application in the adsorption of organic dye MB in wastewater of hydrothermally produced MoSe₂ nanosheets with structural and optical properties. (author)