Sonication-assisted ion-intercalation exfoliation of MoS₂ quantum dots

Synthesis of MoS2 quantum dots (QDs) by a sonication-assisted ion-intercalation process where sodium hydroxide (NaOH) is used as sodium (Na+) and hydroxyl (OH-) ions source for the intercalation purpose is reported. The exfoliation method results in well-exfoliated mono- to few-layered QDs as illustrated by the atomic force microscopy (AFM) measurements, showing a thickness of < 1.6 nm, and confirmed by X-ray diffraction (XRD) studies where the characteristic peak at 2 theta = 14.4 degrees of bulk 2H-MoS2 disappears. The Raman spectroscopy measurements of the QDs show a frequency difference of 19.8 cm(-1) between the E and A(1g) vibration modes and are in good agreement with the AFM and XRD results. The reported exfoliation technique resulted in an improvement of similar to 7% in production yield with a total production yield of similar to 20%, higher than the previous reports. The QDs have average lateral size of 3.7 +/- 1.0 nm as determined from the HRTEM images.