Binary and Ternary Indium Chalcogenide Nanoplates Capped with 3-Mercaptopropionic Acid: Preparation, Structural and Optical Properties

This paper presents the synthesis and characterization of binary metal chalcogenide nanoplate semiconductors of type III–VI, specifically indium selenide (InSe) and ternary InSe 1− x S x , capped with 3-mercaptopropionic acid (3-MPA). The nanoplates were synthesized in an alkaline aqueous medium using the hydrothermal method. The structural and optical properties of the materials were extensively investigated using, infrared (IR) spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (HR-TEM), Raman spectroscopy, optical absorption, and X-ray photoelectron spectroscopy (XPS). XRD and TEM analyses confirmed the formation of crystalline nanoplates with well-defined morphologies with binary indium selenide indexed with a mixed phase of In 2 Se 3 and InSe. Meanwhile, the binary structure with 100% sulfur indexed with a cubic phase of In 5 S 4 . Raman and IR spectroscopies provided insights into the phonon of binary and ternary InSe 1− x S x along with the surface interactions introduced by 3-MPA capping. Optical absorption measurements showed a variation of bandgaps with sulfur substitution, while XPS analysis revealed the electronic structure and chemical composition, confirming effective capping with 3-MPA. The use of 3-MPA as a capping agent improved the stability and dispersibility of the nanoplates in aqueous media, making them suitable for optoelectronic and sensing applications. This work highlights the potential of hydrothermally synthesized InSe and InSe 1− x S x nanoplates capped with 3-MPA for use in advanced semiconductor devices.