False luminescence of molybdenum disulfide quantum dots from carbon dots.

For the first time, a systematical investigation has been carried out to verify luminescent molybdenum disulfide quantum dots (MoS 2 QDs). We found that the well-reported blue fluorescence of the so-called "MoS 2 QDs" is mainly originated from the co-present carbon based dots rather than MoS 2 . Furthermore, the band gap of MoS 2 is independent of the lateral size, and it is impossible to obtain luminescent MoS 2 QDs by reducing the lateral size.