Laser fragmentation of MoS 2 in ethanol: MoO 3− x coatings, oxygen vacancies, and photoluminescence with NIR heating

Two-dimensional transition metal dichalcogenides such as MoS 2 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 MoS 2 target in ethanol followed by laser-induced colloidal fragmentation. HRTEM shows that the ablation step initially yields 2H-MoS 2 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 MoS 2 core and an amorphous/poorly crystalline molybdenum oxide shell. Raman spectroscopy provides evidence consistent with the coexistence of 2H-MoS 2 and sub-stoichiometric molybdenum oxide (MoO 3− 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 MoS 2 domains together with defect–related states associated with oxygen-deficient MoO 3− 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 MoS 2 /MoO 3− 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.