Experimental Study on the Synthesis of Molybdenum Disulfide Quantum Dots by Ultrasonic, Solvent-Thermal, and Atmospheric Plasma-Assisted Exfoliation

Molybdenum disulfide quantum dots (MoS2 QDs) were synthesized using ultrasonic (US), solvent-thermal (ST), and atmospheric plasma-assisted (PA) top-down exfoliation. Energy analysis shows PA exfoliation is remarkably more energy-efficient and faster due to direct plasma-precursor contact. High-resolution transmission electron microscopy (HR-TEM) indicated average particle sizes of 4.95 nm (ST), 5.59 nm (US), and 8.69 nm (PA). All samples exhibited strong UV-blue and broad red-to-NIR absorption. The QDs displayed excitation-dependent photoluminescence, with PA samples showing twice the emission intensity of US and ST versions. Across all methods, functional performance was comparable: an 808 nm laser-induced photothermal heating in water to 47 °C within 5 min, while UV irradiation triggered >50% methyl orange photocatalytic degradation within 40 min. This indicates that functional behavior is inherently governed by the QDs rather than the synthesis route. Consequently, highly efficient PA exfoliation offers a promising, scalable pathway for producing multifunctional MoS2 QDs.