Laser fragmentation of MoS2 in ethanol: MoO3- x coatings, oxygen vacancies, and photoluminescence with NIR heating.

Two-dimensional transition metal dichalcogenides such as MoS2 are attractive optical nanomaterials because they can exhibit photoluminescence and light-to-heat conversion within the same colloidal system. Here, we synthesize surfactant-free Mo-based nanocolloids by picosecond pulsed laser ablation of a bulk MoS2 target in ethanol followed by laser-induced colloidal fragmentation. HRTEM shows that the ablation step initially yields 2H-MoS2 nanosheets with an interplanar spacing of 0.274 nm (assigned to the (100) planes), while subsequent fragmentation produces 12.3 ± 1.7 nm fullerene-like core-shell nanoparticles comprising a curved MoS2 core and an amorphous/poorly crystalline molybdenum oxide shell. Raman spectroscopy provides evidence consistent with the coexistence of 2H-MoS2 and sub-stoichiometric molybdenum oxide (MoO3- x ). UV-vis spectra analyzed via Tauc plots yield an apparent optical bandgap of E g ≈ 1.94 eV, suggesting size/curvature-related modifications of the electronic structure. Under 260 nm excitation, the nanocolloids display intense blue-violet photoluminescence with bands centered at 401, 425, and 452 nm. The emission is consistent with contributions from confined/curved MoS2 domains together with defect-related states associated with oxygen-deficient MoO3- x . Finally, irradiation with a 270 W near-infrared lamp produces a temperature rise of ~11 °C in 10 min for the nanocolloids, compared with ~6 °C for ethanol alone, indicating an enhanced photothermal heating response. These results highlight picosecond laser processing in liquids as a straightforward route to MoS2/MoO3- x fullerene-like nanostructures in which heating is obtained under broadband, spatially distributed irradiation rather than focused laser excitation, a configuration of interest for photothermal applications, where the local power densities delivered by focused sources are a recognised constraint.