Nanostructured MnS-based thin films deposited from propylamine solutions of elemental sulfur and manganese

The exploration of novel methods for depositing MnS thin films is crucial due to their huge potential for optoelectronic, energy storage, and other advanced technological applications. This study proposes a novel solution-processing approach for the Mn–S-based nanostructured thin film fabrication using dissolved elemental Mn and S in propylamine-based solvents. The Mn/S ratio in the solution dictates the resulting film morphology, chemical composition, and molecular structure. Utilizing a 1/1 Mn/S ratio in propylamine and propylamine–methanol mixture solutions yielded nanoporous network structures formed mainly from Mn²⁺ sulfides and hydroxides. Conversely, using 1/5 Mn/S ratio solutions under the same solvent conditions resulted in ∼85 nm spherical nanoparticle films made from Mn²⁺/Mn⁴⁺ sulfides and hydroxides, polysulfides, and organic residues. Utilizing a propylamine–acetonitrile mixture, regardless of the Mn/S ratio, led to films formed from spherical/oval nanoparticles (∼126–136 nm). All nanoparticle-based films annealed at 300 °C exhibited photocatalytic activity, as evidenced by the methylene blue degradation under UV light illumination. Sulfur-rich films demonstrated the highest photocatalytic efficiency, indicating a promising route for tailored Mn–S photocatalysts.