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 (MoS2 QDs). We found that the well-reported blue fluorescence of the so-called "MoS2 QDs" is mainly originated from the co-present carbon based dots rather than MoS2. Furthermore, the band gap of MoS2 is independent of the lateral size, and it is impossible to obtain luminescent MoS2 QDs by reducing the lateral size.