We present a simple method for modification of 2D materials by drop-casting of the organic molecule in solution on the 2D material under ambient conditions. Specifically, we investigated the adsorption of 6-(4,5-Dihydro-1H-imidazol-3-ium-2-yl)-2-(naphthalene-2-yl)benzothiazole methanesulfonate (L63MS) organic molecule on 2D MoS${}_2$. To better understand the effect of the organic molecule on the 2D material, we also investigated the impact of solvents alone on the materials’ properties. The MoS${}_2$ samples were synthesized using ambient pressure chemical vapor deposition. Atomic force microscopy, Raman spectroscopy, photoluminescence spectroscopy and optical microscopy were used to characterize the samples. The measurements were performed after synthesis, after the drop-casting of solvents and after the drop-casting of organic molecule solutions. Our results indicate that the used organic molecule effectively adsorbs on and prompts discernible changes in the (opto)electronic properties of the 2D material. These changes encompass variations in the Raman spectra shape, alterations in the photoluminescence (PL) signal characteristics and modifications in excitonic properties. Such alterations can be linked to various phenomena including doping, bandgap modifications, introduction or healing of defects and that the solvent plays a crucial role in the process. Our study provides insights into the modification of 2D materials under ambient conditions and highlights the importance of solvent selection in the process.

In this study, we investigate the real-time evolution of photoluminescence (PL) in MoS₂ samples modified with L63MS molecules during controlled thermal treatment, unveiling a unique laser-induced molecular agglomeration process. By integrating a heater into our microscopy setup, we monitored in situ changes and discovered that between 120 °C and 180 °C, focused laser irradiation induces the formation of molecular agglomerates with heights ranging from 5 to 20 nm (as confirmed by atomic force microscopy (AFM)). Notably, after subsequent heating to 320 °C, while non-agglomerated molecules desorb, these agglomerates remain stable. Raman spectroscopy reveals that the MoS₂ lattice beneath the agglomerates experiences minimal phonon mode shifts—demonstrating a protective effect—and PL measurements show a redshift in the exciton A peak due to localized strain and charge transfer effects. In contrast to previous studies on the real-time PL evolution of MoS₂, our work uniquely demonstrates that controlled agglomerate formation via laser exposure not only modulates optical properties but also provides a pathway for localized functionalization of MoS₂, opening new avenues for optoelectronic device engineering.