The downscale of transitional metal dichalcogenides (TMDCs) from bulk to few-layer flakes (2D) and quantum dots (0D) brings up new properties, including visible-range photoluminescence, and provides an application in such areas as photocatalysis, sensing, and bioimaging. In this work, we successfully dispersed MoS2 in aqueous solutions of deoxyadenosine monophosphate (dAMP), deoxyguanosine monophosphate (dGMP), deoxycytidine monophosphate (dCMP), and uridine monophosphate (UMP) by ultrasound-assisted liquid-phase exfoliation. The photoluminescence (PL) attributed to MoS2 quantum dots (MoS2 QDs) was registered for all MoS2 suspensions. The comparison of the PL band intensity, the peak position, and the spectral width suggests the essential role of MoS2-nucleic base interaction for MoS2 exfoliation, colloidal stabilization, and the production of emissive QDs. Notably, the MoS2-dAMP suspension displayed the highest PL intensity and the relative quantum yield. By means of UV–Vis and Raman spectroscopy, we also show that consecutive use of two sonication methods followed by several stages of centrifugation provides separation of 2D MoS2 nanoflakes from MoS2 QDs accompanied by improved emission properties. Analysis of the PL band allowed us to suggest that the main emission was due to defect-induced extrinsic states, however, a high-energy component of the band observed in the spectrum was attributed to emission from the intrinsic states of the MoS2 QDs. Temporal observations of the PL from MoS2 QDs showed the high stability of the emission over long periods of time, despite gradual growth of the contribution of the defect-related emission.
Курносов et al. (Thu,) studied this question.